---
title: Build a receiver
linkTitle: Receivers
weight: 100
aliases:
  - /docs/collector/trace-receiver
  - /docs/collector/building/receiver
# prettier-ignore
cSpell:ignore: backendsystem crand debugexporter mapstructure pcommon pdata ptrace rcvr resourcespans struct structs tailtracer telemetrygen uber
---

<!-- markdownlint-disable heading-increment no-duplicate-heading -->

OpenTelemetry defines
[distributed tracing](/docs/concepts/glossary/#distributed-tracing) as:

> Traces that track the progression of a single request, known as a trace, as it
> is handled by services that make up an application. The request may be
> initiated by a user or an application. Distributed tracing is a form of
> tracing that traverses process, network, and security boundaries.

Although distributed traces are defined in an application-centric way, you can
think of them as a timeline for _any_ request that moves through your system.
Each distributed trace shows how long a request took from start to finish and
breaks down the steps taken to complete it.

If your system generates tracing telemetry, you can configure your
[OpenTelemetry Collector](/docs/collector/) with a trace receiver designed to
receive and convert that telemetry. The receiver converts your data from its
original format into the OpenTelemetry trace model so the Collector can process
it.

To implement a trace receiver, you need the following:

- A `Config` implementation so the trace receiver can gather and validate its
  configurations in the Collector config.yaml.

- A `receiver.Factory` implementation so the Collector can properly instantiate
  the trace receiver component.

- A `receiver.Traces` implementation that collects the telemetry, converts it to
  the internal trace representation, and passes the telemetry to the next
  consumer in the pipeline.

This tutorial shows you how to create a trace receiver called `tailtracer` that
simulates a pull operation and generates traces as an outcome of that operation.

## Setting up receiver development and testing environment

First, use the [Building a Custom Collector](/docs/collector/extend/ocb/)
tutorial to create a Collector instance named `otelcol-dev`; all you need is to
copy the `builder-config.yaml` described in
[Configure the OpenTelemetry Collector Builder](/docs/collector/extend/ocb/#configure-the-opentelemetry-collector-builder)
and run the builder. As an outcome, you should now have a folder structure like
this:

```text
.
├── builder-config.yaml
├── ocb
└── otelcol-dev
    ├── components.go
    ├── components_test.go
    ├── go.mod
    ├── go.sum
    ├── main.go
    ├── main_others.go
    ├── main_windows.go
    └── otelcol-dev
```

To properly test your trace receiver, you may need a distributed tracing backend
so the Collector can send the telemetry to it. We will be using
[Jaeger](https://www.jaegertracing.io/docs/latest/getting-started/). If you
don't have a `Jaeger` instance running, you can easily start one using Docker
with the following command:

```sh
docker run -d --name jaeger \
  -p 16686:16686 \
  -p 14317:4317 \
  -p 14318:4318 \
  jaegertracing/jaeger:latest
```

Once the container is up and running, you can access Jaeger UI via this URL:
<http://localhost:16686/>

Now, create a Collector config file named `config.yaml` to set up the Collector
components and pipelines.

```sh
touch config.yaml
```

For now, you just need a basic traces pipeline with the `otlp` receiver and the
`otlp` and `debug` exporters. Here is what your `config.yaml` file should look
like:

> config.yaml

```yaml
receivers:
  otlp:
    protocols:
      grpc:
        endpoint: 0.0.0.0:4317

exporters:
  debug:
    verbosity: detailed
  otlp/jaeger:
    endpoint: localhost:14317
    tls:
      insecure: true
    sending_queue:
      batch:

service:
  pipelines:
    traces:
      receivers: [otlp]
      exporters: [otlp/jaeger, debug]
  telemetry:
    logs:
      level: debug
```

> [!NOTE]
>
> Here, we use the `insecure` flag in the `otlp` exporter config for simplicity;
> you should use TLS certificates for secure communication or mTLS for mutual
> authentication when running the Collector in production, by following this
> [guide](/docs/collector/configuration/#setting-up-certificates).

To verify that the Collector is properly set up, run this command:

```sh
./otelcol-dev/otelcol-dev --config config.yaml
```

The output may look like this:

```log
2023-11-08T18:38:37.183+0800	info	service@v0.88.0/telemetry.go:84	Setting up own telemetry...
2023-11-08T18:38:37.185+0800	info	service@v0.88.0/telemetry.go:201	Serving Prometheus metrics	{"address": ":8888", "level": "Basic"}
2023-11-08T18:38:37.185+0800	debug	exporter@v0.88.0/exporter.go:273	Stable component.	{"kind": "exporter", "data_type": "traces", "name": "otlp/jaeger"}
2023-11-08T18:38:37.186+0800	info	exporter@v0.88.0/exporter.go:275	Development component. May change in the future.	{"kind": "exporter", "data_type": "traces", "name": "debug"}
2023-11-08T18:38:37.186+0800	debug	receiver@v0.88.0/receiver.go:294	Stable component.	{"kind": "receiver", "name": "otlp", "data_type": "traces"}
2023-11-08T18:38:37.186+0800	info	service@v0.88.0/service.go:143	Starting otelcol-dev...	{"Version": "1.0.0", "NumCPU": 10}

<OMITTED>

2023-11-08T18:38:37.189+0800	info	service@v0.88.0/service.go:169	Everything is ready. Begin running and processing data.
2023-11-08T18:38:37.189+0800	info	zapgrpc/zapgrpc.go:178	[core] [Server #3 ListenSocket #4] ListenSocket created	{"grpc_log": true}
2023-11-08T18:38:37.195+0800	info	zapgrpc/zapgrpc.go:178	[core] [Channel #1 SubChannel #2] Subchannel Connectivity change to READY	{"grpc_log": true}
2023-11-08T18:38:37.195+0800	info	zapgrpc/zapgrpc.go:178	[core] [pick-first-lb 0x140005efdd0] Received SubConn state update: 0x140005eff80, {ConnectivityState:READY ConnectionError:<nil>}	{"grpc_log": true}
2023-11-08T18:38:37.195+0800	info	zapgrpc/zapgrpc.go:178	[core] [Channel #1] Channel Connectivity change to READY	{"grpc_log": true}
```

If everything went well, the Collector instance should be up and running.

You may use the
[telemetrygen](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/cmd/telemetrygen)
to further verify the setup. For example, open another console and run the
following commands:

```sh
go install github.com/open-telemetry/opentelemetry-collector-contrib/cmd/telemetrygen@latest

telemetrygen traces --otlp-insecure --traces 1
```

You should be able to see detailed logs in the console and the traces in Jaeger
UI via this URL: <http://localhost:16686/>.

Press <kbd>Ctrl + C</kbd> to stop the Collector instance in the Collector
console.

## Setting up Go module

Every Collector component should be created as a Go module. Let's create a
`tailtracer` folder to host our receiver project and initialize it as Go module.

```sh
mkdir tailtracer
cd tailtracer
go mod init github.com/open-telemetry/opentelemetry-tutorials/trace-receiver/tailtracer
```

> [!NOTE]
>
> The module path above is a mock path, which can be your desired private or
> public path. See the
> [initial trace-receiver code](https://github.com/rquedas/otel4devs/tree/main/collector/receiver/trace-receiver).

It is recommended to enable Go
[Workspaces](https://go.dev/doc/tutorial/workspaces) since we're going to manage
multiple Go modules: the `otelcol-dev` and `tailtracer`, and possibly more
components over time.

```sh
cd ..
go work init
go work use otelcol-dev
go work use tailtracer
```

## Designing and validating receiver settings

A receiver may have some configurable settings, which can be set via the
Collector config file.

The `tailtracer` receiver will have the following settings:

- `interval`: a string representing the time interval (in minutes) between
  telemetry pull operations.
- `number_of_traces`: the number of mock traces generated for each interval.

Here is what the `tailtracer` receiver settings will look like:

```yaml
receivers:
  tailtracer: # this line represents the ID of your receiver
    interval: 1m
    number_of_traces: 1
```

Create a file named `config.go` under the folder `tailtracer` where you will
write all the code to support your receiver settings.

```sh
touch tailtracer/config.go
```

To implement the configuration aspects of a receiver, you need to create a
`Config` struct. Add the following code to your `config.go` file:

```go
package tailtracer

type Config struct{

}
```

To be able to give your receiver access to its settings, the `Config` struct
must have a field for each of the receiver's settings.

Here is what the `config.go` file should look like after you implemented the
requirements above:

> tailtracer/config.go

```go
package tailtracer

// Config represents the receiver config settings in the Collector config.yaml
type Config struct {
   Interval    string `mapstructure:"interval"`
   NumberOfTraces int `mapstructure:"number_of_traces"`
}
```

> [!NOTE] Check your work
>
> - Added the `Interval` and the `NumberOfTraces` fields to properly have access
>   to their values from the config.yaml.

Now that you have access to the settings, you can provide any kind of validation
needed for those values by implementing the `Validate` method according to the
optional
[ConfigValidator](https://github.com/open-telemetry/opentelemetry-collector/blob/677b87e3ab5c615bc3f93b8f99bb1fa5be951751/component/config.go#L28)
interface.

In this case, the `interval` value will be optional (we will look at generating
default values later). But when defined, it should be at least 1 minute (1m) and
the `number_of_traces` will be a mandatory value. Here is what the config.go
looks like after implementing the `Validate` method:

> tailtracer/config.go

```go
package tailtracer

import (
	"fmt"
	"time"
)

// Config represents the receiver config settings in the Collector config.yaml
type Config struct {
	Interval       string `mapstructure:"interval"`
	NumberOfTraces int    `mapstructure:"number_of_traces"`
}

// Validate checks if the receiver configuration is valid
func (cfg *Config) Validate() error {
	interval, _ := time.ParseDuration(cfg.Interval)
	if interval.Minutes() < 1 {
		return fmt.Errorf("when defined, the interval has to be set to at least 1 minute (1m)")
	}

	if cfg.NumberOfTraces < 1 {
		return fmt.Errorf("number_of_traces must be greater or equal to 1")
	}
	return nil
}
```

> [!NOTE] Check your work
>
> - Imported the `fmt` package to properly format print error messages.
> - Added the `Validate` method to the Config struct to check if the `interval`
>   setting value is at least 1 minute (1m), and if the `number_of_traces`
>   setting value is greater or equal to 1. If that is not true, the Collector
>   will generate an error during its startup process and display the message
>   accordingly.

If you want to take a closer look at the structs and interfaces involved in the
configuration aspects of a component, refer to the
[component/config.go](<https://github.com/open-telemetry/opentelemetry-collector/blob/v{{% param vers %}}/component/config.go>)
file inside the Collector GitHub project.

## Implementing the receiver.Factory interface

The `tailtracer` receiver must provide a `receiver.Factory` implementation.
Although the `receiver.Factory` interface is defined in the
[receiver/receiver.go](<https://github.com/open-telemetry/opentelemetry-collector/blob/v{{% param vers %}}/receiver/receiver.go#L58>)
file within the Collector project, the right way to implement it is by using the
functions available in the `go.opentelemetry.io/collector/receiver` package.

Create a file named `factory.go`:

```sh
touch tailtracer/factory.go
```

Now, let's follow the convention and add a function named `NewFactory()` that
will be responsible for instantiating the `tailtracer` factory. Go ahead and add
the following code to your `factory.go` file:

```go
package tailtracer

import (
	"go.opentelemetry.io/collector/receiver"
)

// NewFactory creates a factory for tailtracer receiver.
func NewFactory() receiver.Factory {
	return nil
}
```

To instantiate your `tailtracer` receiver factory, you will use the following
function from the `receiver` package:

```go
func NewFactory(cfgType component.Type, createDefaultConfig component.CreateDefaultConfigFunc, options ...FactoryOption) Factory
```

The `receiver.NewFactory()` instantiates and returns a `receiver.Factory` and it
requires the following parameters:

- `component.Type`: a unique string identifier for your receiver across all
  Collector components.

- `component.CreateDefaultConfigFunc`: a reference to a function that returns
  the `component.Config` instance for your receiver.

- `...FactoryOption`: the slice of `receiver.FactoryOption`s that will determine
  what type of signal your receiver is capable of processing.

Let's now implement the code to support all the parameters required by
`receiver.NewFactory()`.

## Identifying and providing default settings

Previously, we mentioned that the `interval` setting for the `tailtracer`
receiver would be optional. You will need to provide a default value for it so
it can be used as part of the default settings.

Go ahead and add the following code to your `factory.go` file:

```go
var (
	typeStr         = component.MustNewType("tailtracer")
)

const (
	defaultInterval = 1 * time.Minute
)
```

As for default settings, you just need to add a function that returns a
`component.Config` holding the default configurations for the `tailtracer`
receiver.

To accomplish that, go ahead and add the following code to your `factory.go`
file:

```go
func createDefaultConfig() component.Config {
	return &Config{
		Interval: string(defaultInterval),
	}
}
```

After these two changes you will notice a few imports are missing, so here is
what your `factory.go` file should look like with the proper imports:

> tailtracer/factory.go

```go
package tailtracer

import (
	"time"

	"go.opentelemetry.io/collector/component"
	"go.opentelemetry.io/collector/receiver"
)

var (
	typeStr         = component.MustNewType("tailtracer")
)

const (
	defaultInterval = 1 * time.Minute
)

func createDefaultConfig() component.Config {
	return &Config{
		Interval: string(defaultInterval),
	}
}

// NewFactory creates a factory for tailtracer receiver.
func NewFactory() receiver.Factory {
	return nil
}
```

> [!NOTE] Check your work
>
> - Imported the `time` package to support the time.Duration type for the
>   defaultInterval.
> - Imported the `go.opentelemetry.io/collector/component` package, which is
>   where `component.Config` is declared.
> - Imported the `go.opentelemetry.io/collector/receiver` package, which is
>   where `receiver.Factory` is declared.
> - Added a `time.Duration` constant called `defaultInterval` to represent the
>   default value for our receiver's `Interval` setting. We will be setting the
>   default value for 1 minute, hence the assignment of `1 * time.Minute` as its
>   value.
> - Added a function named `createDefaultConfig`, which is responsible for
>   returning a `component.Config` implementation, which in this case is going
>   to be an instance of our `tailtracer.Config` struct.
> - The `tailtracer.Config.Interval` field was initialized with the
>   `defaultInterval` constant.

## Specifying the receiver's capabilities

A receiver component can process traces, metrics, and logs. The receiver's
factory is responsible for specifying the capabilities that the receiver would
provide.

Given that tracing is the subject of this tutorial, we will enable the
`tailtracer` receiver to work with traces only. The `receiver` package provides
the following function and type to help the factory describe the trace
processing capabilities:

```go
func WithTraces(createTracesReceiver CreateTracesFunc, sl component.StabilityLevel) FactoryOption
```

The `receiver.WithTraces()` instantiates and returns a `receiver.FactoryOption`
and it requires the following parameters:

- `createTracesReceiver`: A reference to a function that matches the
  `receiver.CreateTracesFunc` type. The `receiver.CreateTracesFunc` type is a
  pointer to a function that is responsible for instantiating and returning a
  `receiver.Traces` instance, and it requires the following parameters:
  - `context.Context`: the reference to the Collector `context.Context`, so your
    trace receiver can properly manage its execution context.
  - `receiver.Settings`: the reference to some of the Collector settings under
    which your receiver is created.
  - `component.Config`: the reference for the receiver config settings passed by
    the Collector to the factory so it can properly read its settings from the
    Collector config.
  - `consumer.Traces`: the reference to the next `consumer.Traces` in the
    pipeline, which is where received traces will go. This is either a processor
    or an exporter.

Start by adding the bootstrap code to properly implement the
`receiver.CreateTracesFunc` function pointer. Go ahead and add the following
code to your `factory.go` file:

```go
func createTracesReceiver(_ context.Context, params receiver.Settings, baseCfg component.Config, consumer consumer.Traces) (receiver.Traces, error) {
	return nil, nil
}
```

You now have all the necessary components to successfully instantiate your
receiver factory using the `receiver.NewFactory` function. Go ahead and update
your `NewFactory()` function in the `factory.go` file as follows:

```go
// NewFactory creates a factory for tailtracer receiver.
func NewFactory() receiver.Factory {
	return receiver.NewFactory(
		typeStr,
		createDefaultConfig,
		receiver.WithTraces(createTracesReceiver, component.StabilityLevelAlpha))
}
```

After these changes, you will notice a few imports are missing, so here is what
your `factory.go` file should look like with the proper imports:

> tailtracer/factory.go

```go
package tailtracer

import (
	"context"
	"time"

	"go.opentelemetry.io/collector/component"
	"go.opentelemetry.io/collector/consumer"
	"go.opentelemetry.io/collector/receiver"
)

var (
	typeStr         = component.MustNewType("tailtracer")
)

const (
	defaultInterval = 1 * time.Minute
)

func createDefaultConfig() component.Config {
	return &Config{
		Interval: string(defaultInterval),
	}
}

func createTracesReceiver(_ context.Context, params receiver.Settings, baseCfg component.Config, consumer consumer.Traces) (receiver.Traces, error) {
	return nil, nil
}

// NewFactory creates a factory for tailtracer receiver.
func NewFactory() receiver.Factory {
	return receiver.NewFactory(
		typeStr,
		createDefaultConfig,
		receiver.WithTraces(createTracesReceiver, component.StabilityLevelAlpha))
}
```

> [!NOTE] Check your work
>
> - Imported the `context` package to support the `context.Context` type
>   referenced in the `createTracesReceiver` function.
> - Imported the `go.opentelemetry.io/collector/consumer` package to support the
>   `consumer.Traces` type referenced in the `createTracesReceiver` function.
> - Updated the `NewFactory()` function so it returns the `receiver.Factory`
>   generated by the `receiver.NewFactory()` call with the required parameters.
>   The generated receiver factory will be capable of processing traces via the
>   call to
>   `receiver.WithTraces(createTracesReceiver, component.StabilityLevelAlpha)`

## Implementing the receiver component

All the receiver APIs are currently declared in the
[receiver/receiver.go](<https://github.com/open-telemetry/opentelemetry-collector/blob/v{{% param vers %}}/receiver/receiver.go>)
file in the Collector project. Open the file and take a minute to browse through
all the interfaces.

Notice that `receiver.Traces` (and its siblings `receiver.Metrics` and
`receiver.Logs`) at this point, doesn't describe any specific methods other than
the ones it "inherits" from `component.Component`.

It may feel weird, but remember, the Collector API was meant to be extensible.
The components and their signals may evolve in different ways, so the role of
those interfaces exists to help support that.

To create a `receiver.Traces`, you need to implement the following methods
described by `component.Component` interface:

```go
Start(ctx context.Context, host Host) error
Shutdown(ctx context.Context) error
```

Both methods act as event handlers used by the Collector to communicate with its
components as part of their lifecycle.

The `Start()` method represents a signal of the Collector telling the component
to start its processing. As part of the event, the Collector will pass the
following information:

- `context.Context`: Most of the time, a receiver will be processing a
  long-running operation, so the recommendation is to ignore this context and
  actually create a new one from context.Background().
- `Host`: The host is meant to enable the receiver to communicate with the
  Collector host once it is up and running.

The `Shutdown()` method represents a signal of the Collector telling the
component that the service is getting shutdown and as such, the component should
stop its processing and make all the necessary cleanup work required:

- `context.Context`: the context passed by the Collector as part of the shutdown
  operation.

You will start the implementation by creating a new file called
`trace-receiver.go` in `tailtracer` folder:

```sh
touch tailtracer/trace-receiver.go
```

And then add the declaration to a type called `tailtracerReceiver` as follows:

```go
type tailtracerReceiver struct{

}
```

Now that you have the `tailtracerReceiver` type, you can implement the `Start()`
and `Shutdown()` methods so the receiver type can be compliant with the
`receiver.Traces` interface.

> tailtracer/trace-receiver.go

```go
package tailtracer

import (
	"context"
	"go.opentelemetry.io/collector/component"
)

type tailtracerReceiver struct {
}

func (tailtracerRcvr *tailtracerReceiver) Start(ctx context.Context, host component.Host) error {
	return nil
}

func (tailtracerRcvr *tailtracerReceiver) Shutdown(ctx context.Context) error {
	return nil
}
```

> [!NOTE] Check your work
>
> - Imported the `context` package which is where the `Context` type and
>   functions are declared.
> - Imported the `go.opentelemetry.io/collector/component` package which is
>   where the `Host` type is declared.
> - Added a bootstrap implementation of the
>   `Start(ctx context.Context, host component.Host)` method to comply with the
>   `receiver.Traces` interface.
> - Added a bootstrap implementation of the `Shutdown(ctx context.Context)`
>   method to comply with the `receiver.Traces` interface.

The `Start()` method is passing 2 references (`context.Context` and
`component.Host`) that your receiver may need to keep so they can be used as
part of its processing operations.

The `context.Context` reference should be used for creating a new context to
support the receiver processing operations. You will need to decide the best way
to handle context cancellation so you can finalize it properly as part of the
component's shutdown in the `Shutdown()` method.

The `component.Host` can be useful during the whole lifecycle of the receiver so
keep that reference in the `tailtracerReceiver` type.

Here is what the `tailtracerReceiver` type declaration will look like after you
include the fields for keeping the references suggested above:

```go
type tailtracerReceiver struct {
	host   component.Host
	cancel context.CancelFunc
}
```

Now you need to update the `Start()` method so the receiver can properly
initialize its own processing context, keep the cancellation function in the
`cancel` field, and initialize its `host` field value. You will also update the
`Stop()` method to finalize the context by calling the `cancel` function.

Here is what the `trace-receiver.go` file looks like after making the changes:

> tailtracer/trace-receiver.go

```go
package tailtracer

import (
	"context"
	"go.opentelemetry.io/collector/component"
)

type tailtracerReceiver struct {
	host   component.Host
	cancel context.CancelFunc
}

func (tailtracerRcvr *tailtracerReceiver) Start(ctx context.Context, host component.Host) error {
	tailtracerRcvr.host = host
	ctx = context.Background()
	ctx, tailtracerRcvr.cancel = context.WithCancel(ctx)

	return nil
}

func (tailtracerRcvr *tailtracerReceiver) Shutdown(ctx context.Context) error {
	if tailtracerRcvr.cancel != nil {
		tailtracerRcvr.cancel()
	}
	return nil
}
```

> [!NOTE] Check your work
>
> Updated the `Start()` method by adding the initialization to the `host` field
> with the `component.Host` reference passed by the Collector.
>
> - Set the `cancel` function field with the cancellation based on a new context
>   created with `context.Background()` (according to the Collector API
>   documentation suggestions).
> - Updated the `Shutdown()` method by adding a call to the `cancel()` context
>   cancellation function.

## Keeping information passed by the receiver's factory

Now that you have implemented the `receiver.Traces` interface methods, your
`tailtracer` receiver component is ready to be instantiated and returned by its
factory.

Open the `tailtracer/factory.go` file and navigate to the
`createTracesReceiver()` function. Notice that the factory will pass references
as part of the `createTracesReceiver()` function parameters that your receiver
requires to work properly. These include its configuration settings
(`component.Config`), the next `Consumer` in the pipeline that will consume the
generated traces (`consumer.Traces`), and the Collector logger. This is so that
the `tailtracer` receiver can add meaningful events to it (`receiver.Settings`).

Given that all this information will only be made available to the receiver at
the moment it is instantiated by the factory, the `tailtracerReceiver` type will
need fields to keep that information and use it in other stages of its
lifecycle.

Here is what the `trace-receiver.go` file looks like with the updated
`tailtracerReceiver` type declaration:

> tailtracer/trace-receiver.go

```go
package tailtracer

import (
	"context"
	"time"
	"go.opentelemetry.io/collector/component"
	"go.opentelemetry.io/collector/consumer"
	"go.uber.org/zap"
)

type tailtracerReceiver struct {
	host         component.Host
	cancel       context.CancelFunc
	logger       *zap.Logger
	nextConsumer consumer.Traces
	config       *Config
}

func (tailtracerRcvr *tailtracerReceiver) Start(ctx context.Context, host component.Host) error {
	tailtracerRcvr.host = host
	ctx = context.Background()
	ctx, tailtracerRcvr.cancel = context.WithCancel(ctx)

	interval, _ := time.ParseDuration(tailtracerRcvr.config.Interval)
	go func() {
		ticker := time.NewTicker(interval)
		defer ticker.Stop()

		for {
			select {
				case <-ticker.C:
					tailtracerRcvr.logger.Info("I should start processing traces now!")
				case <-ctx.Done():
					return
			}
		}
	}()

	return nil
}

func (tailtracerRcvr *tailtracerReceiver) Shutdown(ctx context.Context) error {
	if tailtracerRcvr.cancel != nil {
		tailtracerRcvr.cancel()
	}
	return nil
}
```

> [!NOTE] Check your work
>
> - Imported the `go.opentelemetry.io/collector/consumer` which is where the
>   pipeline's consumer types and interfaces are declared.
> - Imported the `go.uber.org/zap` package, which is what the Collector uses for
>   its debugging capabilities.
> - Added a `zap.Logger` field named `logger` so we can have access to the
>   Collector logger reference from within the receiver.
> - Added a `consumer.Traces` field named `nextConsumer` so we can push the
>   traces generated by the `tailtracer` receiver to the next consumer, declared
>   in the Collector pipeline.
> - Added a `Config` field named `config` so we can have access to receiver's
>   configuration settings defined in the Collector config.
> - Added a variable named `interval` that is initialized as a `time.Duration`
>   based on the value of the `interval` settings of the `tailtracer` receiver,
>   defined in the Collector config.
> - Added a `go func()` to implement the `ticker` mechanism so the receiver can
>   generate traces every time the `ticker` reaches the amount of time specified
>   by the `interval` variable.
> - Used the `tailtracerRcvr.logger` field to generate an info message every
>   time the receiver is supposed to generate traces.

The `tailtracerReceiver` type is ready to be instantiated and will keep all
meaningful information passed by its factory.

Open the `tailtracer/factory.go` file and navigate to the
`createTracesReceiver()` function.

The receiver is only instantiated if it is declared as a component in a
pipeline, and the factory is responsible to make sure the next consumer (either
a processor or exporter) in the pipeline is valid. Otherwise, it should generate
an error.

The `createTracesReceiver()` function will need a guard clause to make that
validation.

You will also need variables to properly initialize the `config` and the
`logger` fields of the `tailtracerReceiver` instance.

Here is what the `factory.go` file looks like with the updated
`createTracesReceiver()` function:

> tailtracer/factory.go

```go
package tailtracer

import (
	"context"
	"time"

	"go.opentelemetry.io/collector/component"
	"go.opentelemetry.io/collector/consumer"
	"go.opentelemetry.io/collector/receiver"
)

var (
	typeStr         = component.MustNewType("tailtracer")
)

const (
	defaultInterval = 1 * time.Minute
)

func createDefaultConfig() component.Config {
	return &Config{
		Interval: string(defaultInterval),
	}
}

func createTracesReceiver(_ context.Context, params receiver.Settings, baseCfg component.Config, consumer consumer.Traces) (receiver.Traces, error) {

	logger := params.Logger
	tailtracerCfg := baseCfg.(*Config)

	traceRcvr := &tailtracerReceiver{
		logger:       logger,
		nextConsumer: consumer,
		config:       tailtracerCfg,
	}

	return traceRcvr, nil
}

// NewFactory creates a factory for tailtracer receiver.
func NewFactory() receiver.Factory {
	return receiver.NewFactory(
		typeStr,
		createDefaultConfig,
		receiver.WithTraces(createTracesReceiver, component.StabilityLevelAlpha))
}
```

> [!NOTE] Check your work
>
> - Added a variable called `logger` and initialized it with the Collector
>   logger that is available as a field named `Logger`, in the
>   `receiver.Settings` reference.
> - Added a variable called `tailtracerCfg` and initialized it by casting the
>   `component.Config` reference to the `tailtracer` receiver `Config`.
> - Added a variable called `traceRcvr` and initialized it with the
>   `tailtracerReceiver` instance using the factory information stored in the
>   variables.
> - Updated the return statement to include the `traceRcvr` instance.

So far, the skeleton of the receiver has been fully implemented.

## Updating the Collector initialization process with the receiver

For the receiver to participate in the Collector pipelines, we need to make some
updates in the generated `otelcol-dev/components.go` file where all the
Collector components are registered and instantiated.

The `tailtracer` receiver factory instance has to be added to the `factories`
map so the Collector can load it properly as part of its initialization process.

Here is what the `components.go` file looks like after making the changes to
support that:

> otelcol-dev/components.go

```go
// Code generated by "go.opentelemetry.io/collector/cmd/builder". DO NOT EDIT.

package main

import (
	"go.opentelemetry.io/collector/exporter"
	"go.opentelemetry.io/collector/extension"
	"go.opentelemetry.io/collector/otelcol"
	"go.opentelemetry.io/collector/processor"
	"go.opentelemetry.io/collector/receiver"
	debugexporter "go.opentelemetry.io/collector/exporter/debugexporter"
	otlpexporter "go.opentelemetry.io/collector/exporter/otlpexporter"
	otlpreceiver "go.opentelemetry.io/collector/receiver/otlpreceiver"
	tailtracer "github.com/open-telemetry/opentelemetry-tutorials/trace-receiver/tailtracer" // newly added line
)

func components() (otelcol.Factories, error) {
	var err error
	factories := otelcol.Factories{}

	factories.Extensions, err = otelcol.MakeFactoryMap[extension.Factory](
	)
	if err != nil {
		return otelcol.Factories{}, err
	}

	factories.Receivers, err = otelcol.MakeFactoryMap[receiver.Factory](
		otlpreceiver.NewFactory(),
		tailtracer.NewFactory(), // newly added line
	)
	if err != nil {
		return otelcol.Factories{}, err
	}

	factories.Exporters, err = otelcol.MakeFactoryMap[exporter.Factory](
		debugexporter.NewFactory(),
		otlpexporter.NewFactory(),
	)
	if err != nil {
		return otelcol.Factories{}, err
	}

	factories.Processors, err = otelcol.MakeFactoryMap[processor.Factory](
	)
	if err != nil {
		return otelcol.Factories{}, err
	}

	return factories, nil
}
```

> [!NOTE] Check your work
>
> - Imported the receiver module
>   `github.com/open-telemetry/opentelemetry-tutorials/trace-receiver/tailtracer`,
>   which is where the receiver types and functions are.
> - Added a call to `tailtracer.NewFactory()` as a parameter of the
>   `otelcol.MakeFactoryMap()` call so your `tailtracer` receiver factory is
>   properly added to the `factories` map.

## Running and debugging the receiver

Ensure that the Collector `config.yaml` has been updated properly with the
`tailtracer` receiver configured as one of the receivers used in the
pipeline(s).

> config.yaml

```yaml
receivers:
  otlp:
    protocols:
      grpc:
        endpoint: 0.0.0.0:4317
  tailtracer: # this line represents the ID of your receiver
    interval: 1m
    number_of_traces: 1

exporters:
  debug:
    verbosity: detailed
  otlp/jaeger:
    endpoint: localhost:14317
    tls:
      insecure: true
    sending_queue:
      batch:

service:
  pipelines:
    traces:
      receivers: [otlp, tailtracer]
      exporters: [otlp/jaeger, debug]
  telemetry:
    logs:
      level: debug
```

Let's use the `go run` command instead of the previously generated
`./otelcol-dev/otelcol-dev` binary file, to start the updated Collector as we
have had code changes in the `otelcol-dev/components.go` file.

```sh
go run ./otelcol-dev --config config.yaml
```

The output should look like this:

```log
2023-11-08T21:38:36.621+0800	info	service@v0.88.0/telemetry.go:84	Setting up own telemetry...
2023-11-08T21:38:36.621+0800	info	service@v0.88.0/telemetry.go:201	Serving Prometheus metrics	{"address": ":8888", "level": "Basic"}
2023-11-08T21:38:36.621+0800	info	exporter@v0.88.0/exporter.go:275	Development component. May change in the future.	{"kind": "exporter", "data_type": "traces", "name": "debug"}
2023-11-08T21:38:36.621+0800	debug	exporter@v0.88.0/exporter.go:273	Stable component.	{"kind": "exporter", "data_type": "traces", "name": "otlp/jaeger"}
2023-11-08T21:38:36.621+0800	debug	receiver@v0.88.0/receiver.go:294	Stable component.	{"kind": "receiver", "name": "otlp", "data_type": "traces"}
2023-11-08T21:38:36.621+0800	debug	receiver@v0.88.0/receiver.go:294	Alpha component. May change in the future.	{"kind": "receiver", "name": "tailtracer", "data_type": "traces"}
2023-11-08T21:38:36.622+0800	info	service@v0.88.0/service.go:143	Starting otelcol-dev...	{"Version": "1.0.0", "NumCPU": 10}
2023-11-08T21:38:36.622+0800	info	extensions/extensions.go:33	Starting extensions...

<OMITTED>

2023-11-08T21:38:36.636+0800	info	zapgrpc/zapgrpc.go:178	[core] [Channel #1] Channel Connectivity change to READY	{"grpc_log": true}
2023-11-08T21:39:36.626+0800	info	tailtracer/trace-receiver.go:33	I should start processing traces now!	{"kind": "receiver", "name": "tailtracer", "data_type": "traces"}
2023-11-08T21:40:36.626+0800	info	tailtracer/trace-receiver.go:33	I should start processing traces now!	{"kind": "receiver", "name": "tailtracer", "data_type": "traces"}
...
```

As you can see from the logs, the `tailtracer` has been initialized
successfully. Every minute, there will be a message that reads,
`I should start processing traces now!`, triggered by the dummy ticker in
`tailtracer/trace-receiver.go`.

> [!TIP]
>
> To stop the process press <kbd>Ctrl + C</kbd> in your Collector terminal.

Additionally, you may use your IDE of choice to debug the receiver, just as you
would normally debug a Go project. Here is a simple `launch.json` file for
[Visual Studio Code](https://code.visualstudio.com/) for your reference:

```json
{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Launch otelcol-dev",
      "type": "go",
      "request": "launch",
      "mode": "auto",
      "program": "${workspaceFolder}/otelcol-dev",
      "args": ["--config", "${workspaceFolder}/config.yaml"]
    }
  ]
}
```

As a big milestone, let's take a look at how the folder structure looks like
now:

```console
.
├── builder-config.yaml
├── config.yaml
├── go.work
├── go.work.sum
├── ocb
├── otelcol-dev
│   ├── components.go
│   ├── components_test.go
│   ├── go.mod
│   ├── go.sum
│   ├── main.go
│   ├── main_others.go
│   ├── main_windows.go
│   └── otelcol-dev
└── tailtracer
    ├── config.go
    ├── factory.go
    ├── go.mod
    └── trace-receiver.go
```

In the next section, you will learn more about the OpenTelemetry Trace data
model so the `tailtracer` receiver can finally generate meaningful traces!

## The Collector Trace Data Model

You may be familiar with OpenTelemetry traces by using the SDKs and
instrumenting an application to observe and evaluate your traces in a
distributed tracing backend like Jaeger.

Here is what a trace looks like in Jaeger:

![Jaeger trace](/img/docs/tutorials/Jaeger.jpeg)

Although this is a Jaeger trace, it was generated by a trace pipeline in the
Collector. This can help you understand a few things about the OTel trace data
model:

- A trace consists of one or more spans structured in a hierarchy to represent
  dependencies.
- The spans can represent operations within a service and/or across services.

Creating a trace in the trace receiver will be slightly different from how you
would do it with the SDKs, so let's begin by reviewing the high level concepts.

### Working with Resources

In the OTel world, all telemetry is generated by a `Resource`. Here is the
definition according to the [OTel spec](/docs/specs/otel/resource/sdk):

> A `Resource` is an immutable representation of the entity producing telemetry
> as Attributes. For example, a process producing telemetry that is running in a
> container on Kubernetes has a Pod name, runs in a namespace and may be part of
> a Deployment with its own name. All three of these attributes can be included
> in the `Resource`.

Traces are most commonly used to represent a service request (the Services
entity described in Jaeger's model), which is normally implemented as processes
running in a compute unit. However, OTel's API approach to describe a `Resource`
through attributes, is flexible enough to represent any entity that you may
need, such as ATMs, IoT sensors, and much more.

So it's safe to say that for a trace to exist, a `Resource` will have to start
it.

In this tutorial, we will simulate a system with telemetry that demonstrates
ATMs located in 2 different states (for example, Illinois and California)
accessing the Account's backend system to execute balance, deposit and
withdrawal operations. To achieve this, we will implement code to create the
`Resource` types representing the ATM and the backend system.

Go ahead and create a file named `model.go` inside the `tailtracer` folder.

```sh
touch tailtracer/model.go
```

Now, in the `model.go` file, add the definition for the `Atm` and the
`BackendSystem` types as follows:

> tailtracer/model.go

```go
package tailtracer

type Atm struct{
	ID           int64
	Version      string
	Name         string
	StateID      string
	SerialNumber string
	ISPNetwork   string
}

type BackendSystem struct{
	Version       string
	ProcessName   string
	OSType        string
	OSVersion     string
	CloudProvider string
	CloudRegion   string
	Endpoint      string
}
```

These types are meant to represent the entities as they appear in the system
being observed. They contain information that would be quite meaningful to add
to the traces as part of the `Resource` definition. You will add some helper
functions to generate the instances of these types.

Here is what the `model.go` file will look like with the added helper functions:

> tailtracer/model.go

```go
package tailtracer

import (
	"math/rand"
)

type Atm struct{
	ID           int64
	Version      string
	Name         string
	StateID      string
	SerialNumber string
	ISPNetwork   string
}

type BackendSystem struct{
	Version       string
	ProcessName   string
	OSType        string
	OSVersion     string
	CloudProvider string
	CloudRegion   string
	Endpoint      string
}

func generateAtm() Atm{
	i := getRandomNumber(1, 2)
	var newAtm Atm

	switch i {
		case 1:
			newAtm = Atm{
				ID: 111,
				Name: "ATM-111-IL",
				SerialNumber: "atmxph-2022-111",
				Version: "v1.0",
				ISPNetwork: "comcast-chicago",
				StateID: "IL",

			}

		case 2:
			newAtm = Atm{
				ID: 222,
				Name: "ATM-222-CA",
				SerialNumber: "atmxph-2022-222",
				Version: "v1.0",
				ISPNetwork: "comcast-sanfrancisco",
				StateID: "CA",
			}
	}

	return newAtm
}

func generateBackendSystem() BackendSystem{
	i := getRandomNumber(1, 3)

	newBackend := BackendSystem{
		ProcessName: "accounts",
		Version: "v2.5",
		OSType: "lnx",
		OSVersion: "4.16.10-300.fc28.x86_64",
		CloudProvider: "amzn",
		CloudRegion: "us-east-2",
	}

	switch i {
		case 1:
		 	newBackend.Endpoint = "api/v2.5/balance"
		case 2:
		  	newBackend.Endpoint = "api/v2.5/deposit"
		case 3:
			newBackend.Endpoint = "api/v2.5/withdrawn"

	}

	return newBackend
}

func getRandomNumber(min int, max int) int {
	i := (rand.Intn(max - min + 1) + min)
	return i
}
```

> [!NOTE] Check your work
>
> - Imported the `math/rand` package to support the implementation of the
>   `generateRandomNumber` function.
> - Added the `generateAtm` function, that instantiates an `Atm` type and
>   randomly assigns either Illinois or California as the value for `StateID`,
>   along with the corresponding value for `ISPNetwork`.
> - Added the `generateBackendSystem` function, which creates an instance of the
>   `BackendSystem`type and randomly assigns service endpoint values to the
>   `Endpoint` field.
> - Added the `generateRandomNumber` function to generate random numbers within
>   a specified range.

Now that you have the functions to generate object instances representing the
entities generating telemetry, you are ready to represent those entities in the
OTel Collector world.

The Collector API provides a package named `ptrace`, which is nested under the
`pdata` package. It includes all the types, interfaces and helper functions
required to work with traces in the Collector pipeline components.

Open the `tailtracer/model.go` file and add
`go.opentelemetry.io/collector/pdata/ptrace` to the `import` clause so you can
have access to the `ptrace` package capabilities.

Before you can define a `Resource`, you need to create a `ptrace.Traces` that
will be responsible for propagating the traces via the Collector pipeline. You
can use the helper function `ptrace.NewTraces()`, to instantiate it. You will
also need to create instances of the `Atm` and `BackendSystem` types so you can
have data to represent the telemetry sources involved in your trace.

Open the `tailtracer/model.go` file and add the following function to it:

```go
func generateTraces(numberOfTraces int) ptrace.Traces{
	traces := ptrace.NewTraces()

	for i := 0; i < numberOfTraces; i++{
		newAtm := generateAtm()
		newBackendSystem := generateBackendSystem()
	}

	return traces
}
```

By now, you have heard and read enough about how traces are made up of spans.
You may have even written some instrumentation code using the SDK's functions
and types available to create them. However, what you may not know is that there
are other types of "spans" involved in the creation of a trace in the Collector
API.

You will start with a type called `ptrace.ResourceSpans` which represents the
resource and all the operations that it originated or received while
participating in a trace. You can find its definition in the
[/pdata/ptrace/generated_resourcespans.go](<https://github.com/open-telemetry/opentelemetry-collector/blob/v{{% param vers %}}/pdata/ptrace/generated_resourcespans.go>)
file.

`ptrace.Traces` has a method named `ResourceSpans()` which returns an instance
of a helper type called `ptrace.ResourceSpansSlice`. The
`ptrace.ResourceSpansSlice` type has methods to help you handle the array of
`ptrace.ResourceSpans`. The array will contain as many items as the number of
`Resource` entities participating in the request represented by the trace.

`ptrace.ResourceSpansSlice` has a method named `AppendEmpty()` that adds a new
`ptrace.ResourceSpan` to the array and returns its reference.

Once you have an instance of a `ptrace.ResourceSpan`, you will use a method
named `Resource()` which will return the instance of the `pcommon.Resource`
associated with the `ResourceSpan`.

Update the `generateTrace()` function with the following changes:

- add a variable named `resourceSpan` to represent the `ResourceSpan`.
- add a variable named `atmResource` to represent the `pcommon.Resource`
  associated with the `ResourceSpan`.
- Use the methods mentioned above to initialize both variables, respectively.

Here is what the function should look like after you implement the changes:

```go
func generateTraces(numberOfTraces int) ptrace.Traces{
	traces := ptrace.NewTraces()

	for i := 0; i < numberOfTraces; i++{
		newAtm := generateAtm()
		newBackendSystem := generateBackendSystem()

		resourceSpan := traces.ResourceSpans().AppendEmpty()
		atmResource := resourceSpan.Resource()
	}

	return traces
}
```

> [!NOTE] Check your work
>
> - Added the `resourceSpan` variable and initialized it with the `ResourceSpan`
>   reference returned by the `traces.ResourceSpans().AppendEmpty()` call.
> - Added the `atmResource` variable and initialized it with the
>   `pcommon.Resource` reference returned by the `resourceSpan.Resource()` call.

### Describing Resources through attributes

The Collector API provides a package named `pcommon`, which is nested under the
`pdata` package. It contains all the types and helper functions required to
describe a `Resource`.

In the context of the Collector, a `Resource` is described by attributes in a
key/value pair format represented by the `pcommon.Map` type.

You can refer to the definition of the `pcommon.Map` type and its related helper
functions for creating attribute values using the supported formats in the
[/pdata/pcommon/map.go](<https://github.com/open-telemetry/opentelemetry-collector/blob/v{{% param vers %}}/pdata/pcommon/map.go>)
file in the Collector GitHub project.

Key/value pairs provide a lot of flexibility to help model your `Resource` data.
The OTel specification has some guidelines in place to help organize and
minimize the conflicts across all the different types of telemetry generation
entities that it may need to represent.

These guidelines are known as
[Resource Semantic Conventions](/docs/specs/semconv/resource/) and are
documented in the OTel specification.

When creating your own attributes to represent your own telemetry generation
entities, you should follow the guidelines provided by the specification:

> Attributes are grouped logically by the type of concept that they describe.
> Attributes in the same group have a common prefix that ends with a dot. For
> example, all attributes that describe Kubernetes properties start with `k8s.`

Let's start by opening the `tailtracer/model.go` file and adding
`go.opentelemetry.io/collector/pdata/pcommon` to the `import` clause so you can
have access to the `pcommon` package capabilities.

Now, go ahead and add a function to read the field values from an `Atm` instance
and write them as attributes (grouped by the prefix "atm.") into a
`pcommon.Resource` instance. Here is what the function looks like:

```go
func fillResourceWithAtm(resource *pcommon.Resource, atm Atm){
   atmAttrs := resource.Attributes()
   atmAttrs.PutInt("atm.id", atm.ID)
   atmAttrs.PutStr("atm.stateid", atm.StateID)
   atmAttrs.PutStr("atm.ispnetwork", atm.ISPNetwork)
   atmAttrs.PutStr("atm.serialnumber", atm.SerialNumber)
}
```

> [!NOTE] Check your work
>
> - Declared a variable called `atmAttrs` and initialized it with the
>   `pcommon.Map` reference returned by the `resource.Attributes()` call.
> - Used the `PutInt()` and `PutStr()` methods from `pcommon.Map` to add int and
>   string attributes based on the equivalent `Atm` field types. Notice that
>   because these attributes are specific to and only represent the `Atm`
>   entity, they are all grouped within the `atm.` prefix.

The resource semantic conventions also have prescriptive attribute names and
well-known values to represent telemetry generation entities that are common and
applicable across different domains such as
[compute unit](/docs/specs/semconv/resource/#compute-unit),
[environment](/docs/specs/semconv/resource/#compute-unit) and others.

For the `BackendSystem` entity, it has fields representing information relating
to [Operating System](/docs/specs/semconv/resource/os/) and
[Cloud](/docs/specs/semconv/resource/cloud/). We will use the attribute names
and values specified by the resource semantic convention to represent this
information on its `Resource`.

The resource semantic convention keys and well-known values are defined by the
OpenTelemetry semantic conventions package:
[`go.opentelemetry.io/otel/semconv/v1.38.0`](https://pkg.go.dev/go.opentelemetry.io/otel/semconv/v1.38.0).

Let's create a function to read the field values from a `BackendSystem` instance
and write them as attributes into a `pcommon.Resource` instance. Open the
`tailtracer/model.go` file and add the following function:

```go
func fillResourceWithBackendSystem(resource *pcommon.Resource, backend BackendSystem){
	backendAttrs := resource.Attributes()
	var osType, cloudProvider string

	switch {
		case backend.CloudProvider == "amzn":
			cloudProvider = semconv.CloudProviderAWS.Value.AsString()
		case backend.CloudProvider == "mcrsft":
			cloudProvider = semconv.CloudProviderAzure.Value.AsString()
		case backend.CloudProvider == "gogl":
			cloudProvider = semconv.CloudProviderGCP.Value.AsString()
	}

	backendAttrs.PutStr(string(semconv.CloudProviderKey), cloudProvider)
	backendAttrs.PutStr(string(semconv.CloudRegionKey), backend.CloudRegion)

	switch {
		case backend.OSType == "lnx":
			osType = semconv.OSTypeLinux.Value.AsString()
		case backend.OSType == "wndws":
			osType = semconv.OSTypeWindows.Value.AsString()
		case backend.OSType == "slrs":
			osType = semconv.OSTypeSolaris.Value.AsString()
	}

	backendAttrs.PutStr(string(semconv.OSTypeKey), osType)
	backendAttrs.PutStr(string(semconv.OSVersionKey), backend.OSVersion)
 }
```

Notice that we didn't add an attribute named "atm.name" or "backendsystem.name"
to the `pcommon.Resource` representing the `Atm` and `BackendSystem` entity
names. This is because most (not to say all) distributed tracing backend systems
compatible with the OTel trace specification interpret the `pcommon.Resource`
described in a trace as a `Service`. Therefore, they expect the
`pcommon.Resource` to have a required attribute named `service.name` as
prescribed by the resource semantic convention.

We will also use a non-required attribute named `service.version` to represent
the version information for both the `Atm` and `BackendSystem` entities.

Here is what the `tailtracer/model.go` file looks like after adding the code for
properly assigning the "service." group attributes:

> tailtracer/model.go

```go
package tailtracer

import (
	"math/rand"
	"time"

	"go.opentelemetry.io/collector/pdata/pcommon"
	"go.opentelemetry.io/collector/pdata/ptrace"
	"go.opentelemetry.io/otel/semconv/v1.38.0"
)

type Atm struct {
	ID           int64
	Version      string
	Name         string
	StateID      string
	SerialNumber string
	ISPNetwork   string
}

type BackendSystem struct {
	Version       string
	ProcessName   string
	OSType        string
	OSVersion     string
	CloudProvider string
	CloudRegion   string
	Endpoint      string
}

func generateAtm() Atm {
	i := getRandomNumber(1, 2)
	var newAtm Atm

	switch i {
	case 1:
		newAtm = Atm{
			ID:           111,
			Name:         "ATM-111-IL",
			SerialNumber: "atmxph-2022-111",
			Version:      "v1.0",
			ISPNetwork:   "comcast-chicago",
			StateID:      "IL",
		}

	case 2:
		newAtm = Atm{
			ID:           222,
			Name:         "ATM-222-CA",
			SerialNumber: "atmxph-2022-222",
			Version:      "v1.0",
			ISPNetwork:   "comcast-sanfrancisco",
			StateID:      "CA",
		}
	}

	return newAtm
}

func generateBackendSystem() BackendSystem {
	i := getRandomNumber(1, 3)

	newBackend := BackendSystem{
		ProcessName:   "accounts",
		Version:       "v2.5",
		OSType:        "lnx",
		OSVersion:     "4.16.10-300.fc28.x86_64",
		CloudProvider: "amzn",
		CloudRegion:   "us-east-2",
	}

	switch i {
	case 1:
		newBackend.Endpoint = "api/v2.5/balance"
	case 2:
		newBackend.Endpoint = "api/v2.5/deposit"
	case 3:
		newBackend.Endpoint = "api/v2.5/withdrawn"
	}

	return newBackend
}

func getRandomNumber(min int, max int) int {
	i := (rand.Intn(max-min+1) + min)
	return i
}

func generateTraces(numberOfTraces int) ptrace.Traces {
	traces := ptrace.NewTraces()

	for i := 0; i < numberOfTraces; i++ {
		newAtm := generateAtm()
		newBackendSystem := generateBackendSystem()

		resourceSpan := traces.ResourceSpans().AppendEmpty()
		atmResource := resourceSpan.Resource()
		fillResourceWithAtm(&atmResource, newAtm)

		resourceSpan = traces.ResourceSpans().AppendEmpty()
		backendResource := resourceSpan.Resource()
		fillResourceWithBackendSystem(&backendResource, newBackendSystem)
	}

	return traces
}

func fillResourceWithAtm(resource *pcommon.Resource, atm Atm) {
	atmAttrs := resource.Attributes()
	atmAttrs.PutInt("atm.id", atm.ID)
	atmAttrs.PutStr("atm.stateid", atm.StateID)
	atmAttrs.PutStr("atm.ispnetwork", atm.ISPNetwork)
	atmAttrs.PutStr("atm.serialnumber", atm.SerialNumber)
	atmAttrs.PutStr(string(semconv.ServiceNameKey), atm.Name)
	atmAttrs.PutStr(string(semconv.ServiceVersionKey), atm.Version)

}

func fillResourceWithBackendSystem(resource *pcommon.Resource, backend BackendSystem) {
	backendAttrs := resource.Attributes()
	var osType, cloudProvider string

	switch {
	case backend.CloudProvider == "amzn":
		cloudProvider = semconv.CloudProviderAWS.Value.AsString()
	case backend.CloudProvider == "mcrsft":
		cloudProvider = semconv.CloudProviderAzure.Value.AsString()
	case backend.CloudProvider == "gogl":
		cloudProvider = semconv.CloudProviderGCP.Value.AsString()
	}

	backendAttrs.PutStr(string(semconv.CloudProviderKey), cloudProvider)
	backendAttrs.PutStr(string(semconv.CloudRegionKey), backend.CloudRegion)

	switch {
	case backend.OSType == "lnx":
		osType = semconv.OSTypeLinux.Value.AsString()
	case backend.OSType == "wndws":
		osType = semconv.OSTypeWindows.Value.AsString()
	case backend.OSType == "slrs":
		osType = semconv.OSTypeSolaris.Value.AsString()
	}

	backendAttrs.PutStr(string(semconv.OSTypeKey), osType)
	backendAttrs.PutStr(string(semconv.OSVersionKey), backend.OSVersion)

	backendAttrs.PutStr(string(semconv.ServiceNameKey), backend.ProcessName)
	backendAttrs.PutStr(string(semconv.ServiceVersionKey), backend.Version)
}
```

> [!NOTE] Check your work
>
> - Updated the `fillResourceWithAtm()` function by adding lines to properly
>   assign the "service.name" and "service.version" attributes to the
>   `pcommon.Resource` that represents the `Atm` entity.
> - Updated the `fillResourceWithBackendSystem()` function by adding lines to
>   properly assign the "service.name" and "service.version" attributes to the
>   `pcommon.Resource` that represents the `BackendSystem` entity.
> - Updated the `generateTraces` function by adding lines to properly
>   instantiate a `pcommon.Resource` and fill in the attribute information for
>   both `Atm` and `BackendSystem` entities using the `fillResourceWithAtm()`
>   and `fillResourceWithBackendSystem()` functions.

### Representing operations with spans

You now have a `ResourceSpan` instance with the respective `Resource` properly
filled with attributes to represent the `Atm` and `BackendSystem` entities. You
are now ready to represent the operations that each `Resource` executes as part
of a trace in the `ResourceSpan`.

In the OTel world, for a system to generate telemetry, it needs to be
instrumented either manually or automatically via an instrumentation library.

The instrumentation libraries are responsible for setting the scope (also known
as the instrumentation scope), within which the operations participating in a
trace occur, and describing these operations as spans in the context of the
trace.

`pdata.ResourceSpans` has a method named `ScopeSpans()` which returns an
instance of a helper type called `ptrace.ScopeSpansSlice`. The
`ptrace.ScopeSpansSlice` type has methods to help you handle the array of
`ptrace.ScopeSpans`. The array will contain as many items as the number of
`ptrace.ScopeSpan` representing the different instrumentation scopes and the
spans it generated within the context of a trace.

`ptrace.ScopeSpansSlice` has a method named `AppendEmpty()` that adds a new
`ptrace.ScopeSpans` to the array and return its reference.

Let's create a function to instantiate a `ptrace.ScopeSpans` representing the
ATM system's instrumentation scope and its spans. Open the `tailtracer/model.go`
file and add the following function:

```go
func appendAtmSystemInstrScopeSpans(resourceSpans *ptrace.ResourceSpans) ptrace.ScopeSpans {
	scopeSpans := resourceSpans.ScopeSpans().AppendEmpty()

	return scopeSpans
}
```

The `ptrace.ScopeSpans` has a method named `Scope()` that returns a reference to
the `pcommon.InstrumentationScope` instance representing the instrumentation
scope that generated the spans.

`pcommon.InstrumentationScope` has the following methods to describe an
instrumentation scope:

- `SetName(v string)` sets the name for the instrumentation library.

- `SetVersion(v string)` sets the version for the instrumentation library.

- `Name() string` returns the name associated with the instrumentation library.

- `Version() string` returns the version associated with the instrumentation
  library.

Let's update the `appendAtmSystemInstrScopeSpans` function so we can set the
name and version of the instrumentation scope for the new `ptrace.ScopeSpans`.
Here is what `appendAtmSystemInstrScopeSpans` looks like after the update:

```go
func appendAtmSystemInstrScopeSpans(resourceSpans *ptrace.ResourceSpans) ptrace.ScopeSpans {
	scopeSpans := resourceSpans.ScopeSpans().AppendEmpty()
	scopeSpans.Scope().SetName("atm-system")
	scopeSpans.Scope().SetVersion("v1.0")
	return scopeSpans
}
```

You can now update the `generateTraces` function and add variables to represent
the instrumentation scope used by both `Atm` and `BackendSystem` entities by
initializing them with the `appendAtmSystemInstrScopeSpans()`. Here is what
`generateTraces()` looks like after the update:

```go
func generateTraces(numberOfTraces int) ptrace.Traces{
	traces := ptrace.NewTraces()

	for i := 0; i < numberOfTraces; i++{
		newAtm := generateAtm()
		newBackendSystem := generateBackendSystem()

		resourceSpan := traces.ResourceSpans().AppendEmpty()
		atmResource := resourceSpan.Resource()
		fillResourceWithAtm(&atmResource, newAtm)

		atmInstScope := appendAtmSystemInstrScopeSpans(&resourceSpan)

		resourceSpan = traces.ResourceSpans().AppendEmpty()
		backendResource := resourceSpan.Resource()
		fillResourceWithBackendSystem(&backendResource, newBackendSystem)

		backendInstScope := appendAtmSystemInstrScopeSpans(&resourceSpan)
	}

	return traces
}
```

At this point, you have everything needed to represent the telemetry generation
entities in your system, as well as the instrumentation scope responsible for
identifying operations and generating the traces for the system. The next step
is to create the spans representing the operations that the given
instrumentation scope generated as part of a trace.

`ptrace.ScopeSpans` has a method named `Spans()` which returns an instance of a
helper type called `ptrace.SpanSlice`. The `ptrace.SpanSlice` type has methods
to help you handle the array of `ptrace.Span`. The array will contain as many
items as the number of operations the instrumentation scope was able to identify
and describe as part of the trace.

`ptrace.SpanSlice` has a method named `AppendEmpty()` that adds a new
`ptrace.Span` to the array and return its reference.

`ptrace.Span` has the following methods to describe an operation:

- `SetTraceID(v pcommon.TraceID)` sets the `pcommon.TraceID` uniquely
  identifying the trace that this span is associated with.

- `SetSpanID(v pcommon.SpanID)` sets the `pcommon.SpanID` uniquely identifying
  this span in the context of the trace it is associated with.

- `SetParentSpanID(v pcommon.SpanID)` sets `pcommon.SpanID` for the parent
  span/operation in case the operation represented by this span is executed as
  part of the parent (nested).

- `SetName(v string)` sets the name of the operation for the span

- `SetKind(v ptrace.SpanKind)` sets `ptrace.SpanKind` defining the kind of
  operation the span represents.

- `SetStartTimestamp(v pcommon.Timestamp)` sets the `pcommon.Timestamp`
  representing the date and time when the operation associated with the span has
  started.

- `SetEndTimestamp(v pcommon.Timestamp)` sets the `pcommon.Timestamp`
  representing the date and time when the operation associated with the span has
  ended.

As you can see from the methods above, a `ptrace.Span` is uniquely identified by
2 required IDs; their own unique ID represented by the `pcommon.SpanID` type and
the ID of the trace they are associated with, represented by a `pcommon.TraceID`
type.

The `pcommon.TraceID` has to carry a globally unique ID represented as a 16-byte
array, and should follow the
[W3C Trace Context specification](https://www.w3.org/TR/trace-context/#trace-id).
The `pcommon.SpanID` is a unique ID in the context of the trace they are
associated with and is represented as an 8-byte array.

The `pcommon` package provides the following types for generating span IDs:

- `type TraceID [16]byte`

- `type SpanID [8]byte`

For this tutorial, you will create the IDs using functions from the
`github.com/google/uuid` package for the `pcommon.TraceID`, and functions from
the `crypto/rand` package to randomly generate the `pcommon.SpanID`. First, open
the `tailtracer/model.go` file and add both packages to the `import` statement.
After that, add the following functions to help generate both IDs:

```go
import (
	crand "crypto/rand"
	"math/rand"
  	...
)

func NewTraceID() pcommon.TraceID {
	return pcommon.TraceID(uuid.New())
}

func NewSpanID() pcommon.SpanID {
	var rngSeed int64
	_ = binary.Read(crand.Reader, binary.LittleEndian, &rngSeed)
	randSource := rand.New(rand.NewSource(rngSeed))

	var sid [8]byte
	randSource.Read(sid[:])
	spanID := pcommon.SpanID(sid)

	return spanID
}
```

> [!NOTE] Check your work
>
> - Imported `crypto/rand` as `crand`, to avoid conflicts with `math/rand`.
> - Added new functions `NewTraceID()` and `NewSpanID()`, to generate trace ID
>   and span ID, respectively.

Now that you have a way to identify the spans properly, you can start creating
them to represent the operations both within and across the entities in your
system.

As part of the `generateBackendSystem()` function, we have randomly assigned the
operations that the `BackEndSystem` entity can provide as services to the
system. Next, we will open the `tailtracer/model.go` file and look at the
function named `appendTraceSpans()`, which will be responsible for creating a
trace and appending spans that represent the `BackendSystem` operations. Here is
what the initial implementation for the `appendTraceSpans()` function looks
like:

```go
func appendTraceSpans(backend *BackendSystem, backendScopeSpans *ptrace.ScopeSpans, atmScopeSpans *ptrace.ScopeSpans) {
	traceId := NewTraceID()
	backendSpanId := NewSpanID()

	backendDuration, _ := time.ParseDuration("1s")
	backendSpanStartTime := time.Now()
	backendSpanFinishTime := backendSpanStartTime.Add(backendDuration)

	backendSpan := backendScopeSpans.Spans().AppendEmpty()
	backendSpan.SetTraceID(traceId)
	backendSpan.SetSpanID(backendSpanId)
	backendSpan.SetName(backend.Endpoint)
	backendSpan.SetKind(ptrace.SpanKindServer)
	backendSpan.SetStartTimestamp(pcommon.NewTimestampFromTime(backendSpanStartTime))
	backendSpan.SetEndTimestamp(pcommon.NewTimestampFromTime(backendSpanFinishTime))
}
```

> [!NOTE] Check your work
>
> - Added `traceId` and `backendSpanId` variables to represent the trace and the
>   span ID, respectively, and initialized them with the helper functions
>   created previously.
> - Added `backendSpanStartTime` and `backendSpanFinishTime` to represent the
>   start and the end time of the operation. For the tutorial, any
>   `BackendSystem` operation will take 1 second.
> - Added a variable named `backendSpan` which will hold the instance of the
>   `ptrace.Span` representing this operation.
> - Set the `Name` of the span with the `Endpoint` field value from the
>   `BackendSystem` instance.
> - Set the `Kind` of the span to `ptrace.SpanKindServer`. Refer to the
>   [SpanKind section](/docs/specs/otel/trace/api/#spankind) in the trace
>   specification to understand how to define SpanKind properly.
> - Used all the methods mentioned above to fill the `ptrace.Span` with the
>   proper values to represent the `BackendSystem` operation.

You may have noticed that there are 2 references to `ptrace.ScopeSpans` as
parameters in the `appendTraceSpans()` function, but we only used one of them.
Don't worry about it for now; we will get back to it later.

Next, you will update the `generateTraces()` function so that it can generate
the trace by calling the `appendTraceSpans()` function. Here is what the updated
`generateTraces()` function looks like:

```go
func generateTraces(numberOfTraces int) ptrace.Traces {
	traces := ptrace.NewTraces()

	for i := 0; i < numberOfTraces; i++ {
		newAtm := generateAtm()
		newBackendSystem := generateBackendSystem()

		resourceSpan := traces.ResourceSpans().AppendEmpty()
		atmResource := resourceSpan.Resource()
		fillResourceWithAtm(&atmResource, newAtm)

		atmInstScope := appendAtmSystemInstrScopeSpans(&resourceSpan)

		resourceSpan = traces.ResourceSpans().AppendEmpty()
		backendResource := resourceSpan.Resource()
		fillResourceWithBackendSystem(&backendResource, newBackendSystem)

		backendInstScope := appendAtmSystemInstrScopeSpans(&resourceSpan)

		appendTraceSpans(&newBackendSystem, &backendInstScope, &atmInstScope)
	}

	return traces
}
```

You now have the `BackendSystem` entity and its operations represented in spans
in a proper trace context! Next, you need to push the generated trace through
the pipeline so that the next consumer, either a processor or an exporter, can
receive and process it.

Here is how the `tailtracer/model.go` file looks:

> tailtracer/model.go

```go
package tailtracer

import (
	crand "crypto/rand"
	"encoding/binary"
	"math/rand"
	"time"

	"github.com/google/uuid"
	"go.opentelemetry.io/collector/pdata/pcommon"
	"go.opentelemetry.io/collector/pdata/ptrace"
	"go.opentelemetry.io/otel/semconv/v1.38.0"
)

type Atm struct {
	ID           int64
	Version      string
	Name         string
	StateID      string
	SerialNumber string
	ISPNetwork   string
}

type BackendSystem struct {
	Version       string
	ProcessName   string
	OSType        string
	OSVersion     string
	CloudProvider string
	CloudRegion   string
	Endpoint      string
}

func generateAtm() Atm {
	i := getRandomNumber(1, 2)
	var newAtm Atm

	switch i {
	case 1:
		newAtm = Atm{
			ID:           111,
			Name:         "ATM-111-IL",
			SerialNumber: "atmxph-2022-111",
			Version:      "v1.0",
			ISPNetwork:   "comcast-chicago",
			StateID:      "IL",
		}

	case 2:
		newAtm = Atm{
			ID:           222,
			Name:         "ATM-222-CA",
			SerialNumber: "atmxph-2022-222",
			Version:      "v1.0",
			ISPNetwork:   "comcast-sanfrancisco",
			StateID:      "CA",
		}
	}

	return newAtm
}

func generateBackendSystem() BackendSystem {
	i := getRandomNumber(1, 3)

	newBackend := BackendSystem{
		ProcessName:   "accounts",
		Version:       "v2.5",
		OSType:        "lnx",
		OSVersion:     "4.16.10-300.fc28.x86_64",
		CloudProvider: "amzn",
		CloudRegion:   "us-east-2",
	}

	switch i {
	case 1:
		newBackend.Endpoint = "api/v2.5/balance"
	case 2:
		newBackend.Endpoint = "api/v2.5/deposit"
	case 3:
		newBackend.Endpoint = "api/v2.5/withdrawn"
	}

	return newBackend
}

func getRandomNumber(min int, max int) int {
	i := (rand.Intn(max-min+1) + min)
	return i
}

func generateTraces(numberOfTraces int) ptrace.Traces {
	traces := ptrace.NewTraces()

	for i := 0; i < numberOfTraces; i++ {
		newAtm := generateAtm()
		newBackendSystem := generateBackendSystem()

		resourceSpan := traces.ResourceSpans().AppendEmpty()
		atmResource := resourceSpan.Resource()
		fillResourceWithAtm(&atmResource, newAtm)

		atmInstScope := appendAtmSystemInstrScopeSpans(&resourceSpan)

		resourceSpan = traces.ResourceSpans().AppendEmpty()
		backendResource := resourceSpan.Resource()
		fillResourceWithBackendSystem(&backendResource, newBackendSystem)

		backendInstScope := appendAtmSystemInstrScopeSpans(&resourceSpan)

		appendTraceSpans(&newBackendSystem, &backendInstScope, &atmInstScope)
	}

	return traces
}

func fillResourceWithAtm(resource *pcommon.Resource, atm Atm) {
	atmAttrs := resource.Attributes()
	atmAttrs.PutInt("atm.id", atm.ID)
	atmAttrs.PutStr("atm.stateid", atm.StateID)
	atmAttrs.PutStr("atm.ispnetwork", atm.ISPNetwork)
	atmAttrs.PutStr("atm.serialnumber", atm.SerialNumber)
	atmAttrs.PutStr(string(semconv.ServiceNameKey), atm.Name)
	atmAttrs.PutStr(string(semconv.ServiceVersionKey), atm.Version)

}

func fillResourceWithBackendSystem(resource *pcommon.Resource, backend BackendSystem) {
	backendAttrs := resource.Attributes()
	var osType, cloudProvider string

	switch {
	case backend.CloudProvider == "amzn":
		cloudProvider = semconv.CloudProviderAWS.Value.AsString()
	case backend.CloudProvider == "mcrsft":
		cloudProvider = semconv.CloudProviderAzure.Value.AsString()
	case backend.CloudProvider == "gogl":
		cloudProvider = semconv.CloudProviderGCP.Value.AsString()
	}

	backendAttrs.PutStr(string(semconv.CloudProviderKey), cloudProvider)
	backendAttrs.PutStr(string(semconv.CloudRegionKey), backend.CloudRegion)

	switch {
	case backend.OSType == "lnx":
		osType = semconv.OSTypeLinux.Value.AsString()
	case backend.OSType == "wndws":
		osType = semconv.OSTypeWindows.Value.AsString()
	case backend.OSType == "slrs":
		osType = semconv.OSTypeSolaris.Value.AsString()
	}

	backendAttrs.PutStr(string(semconv.OSTypeKey), osType)
	backendAttrs.PutStr(string(semconv.OSVersionKey), backend.OSVersion)

	backendAttrs.PutStr(string(semconv.ServiceNameKey), backend.ProcessName)
	backendAttrs.PutStr(string(semconv.ServiceVersionKey), backend.Version)
}

func appendAtmSystemInstrScopeSpans(resourceSpans *ptrace.ResourceSpans) ptrace.ScopeSpans {
	scopeSpans := resourceSpans.ScopeSpans().AppendEmpty()
	scopeSpans.Scope().SetName("atm-system")
	scopeSpans.Scope().SetVersion("v1.0")
	return scopeSpans
}

func NewTraceID() pcommon.TraceID {
	return pcommon.TraceID(uuid.New())
}

func NewSpanID() pcommon.SpanID {
	var rngSeed int64
	_ = binary.Read(crand.Reader, binary.LittleEndian, &rngSeed)
	randSource := rand.New(rand.NewSource(rngSeed))

	var sid [8]byte
	randSource.Read(sid[:])
	spanID := pcommon.SpanID(sid)

	return spanID
}

func appendTraceSpans(backend *BackendSystem, backendScopeSpans *ptrace.ScopeSpans, atmScopeSpans *ptrace.ScopeSpans) {
	traceId := NewTraceID()
	backendSpanId := NewSpanID()

	backendDuration, _ := time.ParseDuration("1s")
	backendSpanStartTime := time.Now()
	backendSpanFinishTime := backendSpanStartTime.Add(backendDuration)

	backendSpan := backendScopeSpans.Spans().AppendEmpty()
	backendSpan.SetTraceID(traceId)
	backendSpan.SetSpanID(backendSpanId)
	backendSpan.SetName(backend.Endpoint)
	backendSpan.SetKind(ptrace.SpanKindServer)
	backendSpan.SetStartTimestamp(pcommon.NewTimestampFromTime(backendSpanStartTime))
	backendSpan.SetEndTimestamp(pcommon.NewTimestampFromTime(backendSpanFinishTime))
}
```

The `consumer.Traces` has a method called `ConsumeTraces()`, which is
responsible for pushing the generated traces to the next consumer in the
pipeline. You need to update the `Start()` method in the `tailtracerReceiver`
type and add the code to use it.

Open the `tailtracer/trace-receiver.go` file and update the `Start()` method as
follows:

```go
func (tailtracerRcvr *tailtracerReceiver) Start(ctx context.Context, host component.Host) error {
	tailtracerRcvr.host = host
	ctx = context.Background()
	ctx, tailtracerRcvr.cancel = context.WithCancel(ctx)

	interval, _ := time.ParseDuration(tailtracerRcvr.config.Interval)
	go func() {
		ticker := time.NewTicker(interval)
		defer ticker.Stop()
		for {
			select {
				case <-ticker.C:
					tailtracerRcvr.logger.Info("I should start processing traces now!")
					tailtracerRcvr.nextConsumer.ConsumeTraces(ctx, generateTraces(tailtracerRcvr.config.NumberOfTraces)) // new line added
				case <-ctx.Done():
					return
			}
		}
	}()

	return nil
}
```

> [!NOTE] Check your work
>
> - Added a line under the `case <=ticker.C` condition calling the
>   `tailtracerRcvr.nextConsumer.ConsumeTraces()` method, passing the new
>   context created in the `Start()` method (`ctx`), and a call to the
>   `generateTraces()` function so the generated traces can be pushed to the
>   next consumer in the pipeline.

Now let's run the `otelcol-dev` again:

```sh
go run ./otelcol-dev --config config.yaml
```

You should see the output like this after a few minutes:

```log
2023-11-09T11:38:19.890+0800	info	service@v0.88.0/telemetry.go:84	Setting up own telemetry...
2023-11-09T11:38:19.890+0800	info	service@v0.88.0/telemetry.go:201	Serving Prometheus metrics	{"address": ":8888", "level": "Basic"}
2023-11-09T11:38:19.890+0800	debug	exporter@v0.88.0/exporter.go:273	Stable component.	{"kind": "exporter", "data_type": "traces", "name": "otlp/jaeger"}
2023-11-09T11:38:19.890+0800	info	exporter@v0.88.0/exporter.go:275	Development component. May change in the future.	{"kind": "exporter", "data_type": "traces", "name": "debug"}
2023-11-09T11:38:19.891+0800	debug	receiver@v0.88.0/receiver.go:294	Stable component.	{"kind": "receiver", "name": "otlp", "data_type": "traces"}
2023-11-09T11:38:19.891+0800	debug	receiver@v0.88.0/receiver.go:294	Alpha component. May change in the future.	{"kind": "receiver", "name": "tailtracer", "data_type": "traces"}
2023-11-09T11:38:19.891+0800	info	service@v0.88.0/service.go:143	Starting otelcol-dev...	{"Version": "1.0.0", "NumCPU": 10}
2023-11-09T11:38:19.891+0800	info	extensions/extensions.go:33	Starting extensions...

<OMITTED>

2023-11-09T11:38:19.903+0800	info	zapgrpc/zapgrpc.go:178	[core] [Channel #1] Channel Connectivity change to READY	{"grpc_log": true}
2023-11-09T11:39:19.894+0800	info	tailtracer/trace-receiver.go:33	I should start processing traces now!	{"kind": "receiver", "name": "tailtracer", "data_type": "traces"}
2023-11-09T11:39:19.913+0800	info	TracesExporter	{"kind": "exporter", "data_type": "traces", "name": "debug", "resource spans": 4, "spans": 2}
2023-11-09T11:39:19.913+0800	info	ResourceSpans #0
Resource SchemaURL:
Resource attributes:
     -> atm.id: Int(222)
     -> atm.stateid: Str(CA)
     -> atm.ispnetwork: Str(comcast-sanfrancisco)
     -> atm.serialnumber: Str(atmxph-2022-222)
     -> service.name: Str(ATM-222-CA)
     -> service.version: Str(v1.0)
ScopeSpans #0
ScopeSpans SchemaURL:
InstrumentationScope
ResourceSpans #1
Resource SchemaURL:
Resource attributes:
     -> cloud.provider: Str(aws)
     -> cloud.region: Str(us-east-2)
     -> os.type: Str(linux)
     -> os.version: Str(4.16.10-300.fc28.x86_64)
     -> service.name: Str(accounts)
     -> service.version: Str(v2.5)
ScopeSpans #0
ScopeSpans SchemaURL:
InstrumentationScope
Span #0
    Trace ID       : bbcb00aead044a138cf96c0bf4a4ba83
    Parent ID      :
    ID             : 5056fe4e9adf621c
    Name           : api/v2.5/withdrawn
    Kind           : Server
    Start time     : 2023-11-09 03:39:19.894881 +0000 UTC
    End time       : 2023-11-09 03:39:20.894881 +0000 UTC
    Status code    : Unset
    Status message :
ResourceSpans #2
Resource SchemaURL:
Resource attributes:
     -> atm.id: Int(111)
     -> atm.stateid: Str(IL)
     -> atm.ispnetwork: Str(comcast-chicago)
     -> atm.serialnumber: Str(atmxph-2022-111)
     -> service.name: Str(ATM-111-IL)
     -> service.version: Str(v1.0)
ScopeSpans #0
ScopeSpans SchemaURL:
InstrumentationScope
ResourceSpans #3
Resource SchemaURL:
Resource attributes:
     -> cloud.provider: Str(aws)
     -> cloud.region: Str(us-east-2)
     -> os.type: Str(linux)
     -> os.version: Str(4.16.10-300.fc28.x86_64)
     -> service.name: Str(accounts)
     -> service.version: Str(v2.5)
ScopeSpans #0
ScopeSpans SchemaURL:
InstrumentationScope
Span #0
    Trace ID       : ba013b8223ec4d29806ae493ecd1a5e4
    Parent ID      :
    ID             : 4feb47b55c9c4129
    Name           : api/v2.5/withdrawn
    Kind           : Server
    Start time     : 2023-11-09 03:39:19.894953 +0000 UTC
    End time       : 2023-11-09 03:39:20.894953 +0000 UTC
    Status code    : Unset
    Status message :
	{"kind": "exporter", "data_type": "traces", "name": "debug"}
...
```

Here is what the generated trace looks like in Jaeger:
![Jaeger trace](/img/docs/tutorials/Jaeger-BackendSystem-Trace.png)

What you currently see in Jaeger represents a service that is receiving a
request from an external entity that is not instrumented by an OTel SDK. As a
result, it cannot be identified as the origin/start of the trace. For a
`ptrace.Span` to understand that it is representing an operation that was
executed as a result of another operation that originated either within or
outside (nested/child) the `Resource` in the same trace context, you will need
to:

- Set the same trace context as the caller operation by calling the
  `SetTraceID()` method and passing the `pcommon.TraceID` of the parent/caller
  `ptrace.Span` as a parameter.
- Define the caller operation in the context of the trace by calling the
  `SetParentId()` method and passing the `pcommon.SpanID` of the parent/caller
  `ptrace.Span` as a parameter.

You will now create a `ptrace.Span` that represents the `Atm` entity operations
and set it as the parent for the `BackendSystem` span. Open the
`tailtracer/model.go` file and update the `appendTraceSpans()` function as
follows:

```go
func appendTraceSpans(backend *BackendSystem, backendScopeSpans *ptrace.ScopeSpans, atmScopeSpans *ptrace.ScopeSpans) {
	traceId := NewTraceID()

	var atmOperationName string

	switch {
		case strings.Contains(backend.Endpoint, "balance"):
			atmOperationName = "Check Balance"
		case strings.Contains(backend.Endpoint, "deposit"):
			atmOperationName = "Make Deposit"
		case strings.Contains(backend.Endpoint, "withdraw"):
			atmOperationName = "Fast Cash"
		}

	atmSpanId := NewSpanID()
	atmSpanStartTime := time.Now()
	atmDuration, _ := time.ParseDuration("4s")
	atmSpanFinishTime := atmSpanStartTime.Add(atmDuration)

	atmSpan := atmScopeSpans.Spans().AppendEmpty()
	atmSpan.SetTraceID(traceId)
	atmSpan.SetSpanID(atmSpanId)
	atmSpan.SetName(atmOperationName)
	atmSpan.SetKind(ptrace.SpanKindClient)
	atmSpan.Status().SetCode(ptrace.StatusCodeOk)
	atmSpan.SetStartTimestamp(pcommon.NewTimestampFromTime(atmSpanStartTime))
	atmSpan.SetEndTimestamp(pcommon.NewTimestampFromTime(atmSpanFinishTime))

	backendSpanId := NewSpanID()

	backendDuration, _ := time.ParseDuration("2s")
	backendSpanStartTime := atmSpanStartTime.Add(backendDuration)

	backendSpan := backendScopeSpans.Spans().AppendEmpty()
	backendSpan.SetTraceID(atmSpan.TraceID())
	backendSpan.SetSpanID(backendSpanId)
	backendSpan.SetParentSpanID(atmSpan.SpanID())
	backendSpan.SetName(backend.Endpoint)
	backendSpan.SetKind(ptrace.SpanKindServer)
	backendSpan.Status().SetCode(ptrace.StatusCodeOk)
	backendSpan.SetStartTimestamp(pcommon.NewTimestampFromTime(backendSpanStartTime))
	backendSpan.SetEndTimestamp(atmSpan.EndTimestamp())
}
```

Here is what the final `tailtracer/model.go` file looks like:

> tailtracer/model.go

```go
package tailtracer

import (
	crand "crypto/rand"
	"encoding/binary"
	"math/rand"
	"strings"
	"time"

	"github.com/google/uuid"
	"go.opentelemetry.io/collector/pdata/pcommon"
	"go.opentelemetry.io/collector/pdata/ptrace"
	 "go.opentelemetry.io/otel/semconv/v1.38.0"
)

type Atm struct {
	ID           int64
	Version      string
	Name         string
	StateID      string
	SerialNumber string
	ISPNetwork   string
}

type BackendSystem struct {
	Version       string
	ProcessName   string
	OSType        string
	OSVersion     string
	CloudProvider string
	CloudRegion   string
	Endpoint      string
}

func generateAtm() Atm {
	i := getRandomNumber(1, 2)
	var newAtm Atm

	switch i {
	case 1:
		newAtm = Atm{
			ID:           111,
			Name:         "ATM-111-IL",
			SerialNumber: "atmxph-2022-111",
			Version:      "v1.0",
			ISPNetwork:   "comcast-chicago",
			StateID:      "IL",
		}

	case 2:
		newAtm = Atm{
			ID:           222,
			Name:         "ATM-222-CA",
			SerialNumber: "atmxph-2022-222",
			Version:      "v1.0",
			ISPNetwork:   "comcast-sanfrancisco",
			StateID:      "CA",
		}
	}

	return newAtm
}

func generateBackendSystem() BackendSystem {
	i := getRandomNumber(1, 3)

	newBackend := BackendSystem{
		ProcessName:   "accounts",
		Version:       "v2.5",
		OSType:        "lnx",
		OSVersion:     "4.16.10-300.fc28.x86_64",
		CloudProvider: "amzn",
		CloudRegion:   "us-east-2",
	}

	switch i {
	case 1:
		newBackend.Endpoint = "api/v2.5/balance"
	case 2:
		newBackend.Endpoint = "api/v2.5/deposit"
	case 3:
		newBackend.Endpoint = "api/v2.5/withdrawn"
	}

	return newBackend
}

func getRandomNumber(min int, max int) int {
	i := (rand.Intn(max-min+1) + min)
	return i
}

func generateTraces(numberOfTraces int) ptrace.Traces {
	traces := ptrace.NewTraces()

	for i := 0; i < numberOfTraces; i++ {
		newAtm := generateAtm()
		newBackendSystem := generateBackendSystem()

		resourceSpan := traces.ResourceSpans().AppendEmpty()
		atmResource := resourceSpan.Resource()
		fillResourceWithAtm(&atmResource, newAtm)

		atmInstScope := appendAtmSystemInstrScopeSpans(&resourceSpan)

		resourceSpan = traces.ResourceSpans().AppendEmpty()
		backendResource := resourceSpan.Resource()
		fillResourceWithBackendSystem(&backendResource, newBackendSystem)

		backendInstScope := appendAtmSystemInstrScopeSpans(&resourceSpan)

		appendTraceSpans(&newBackendSystem, &backendInstScope, &atmInstScope)
	}

	return traces
}

func fillResourceWithAtm(resource *pcommon.Resource, atm Atm) {
	atmAttrs := resource.Attributes()
	atmAttrs.PutInt("atm.id", atm.ID)
	atmAttrs.PutStr("atm.stateid", atm.StateID)
	atmAttrs.PutStr("atm.ispnetwork", atm.ISPNetwork)
	atmAttrs.PutStr("atm.serialnumber", atm.SerialNumber)
	atmAttrs.PutStr(string(semconv.ServiceNameKey), atm.Name)
	atmAttrs.PutStr(string(semconv.ServiceVersionKey), atm.Version)

}

func fillResourceWithBackendSystem(resource *pcommon.Resource, backend BackendSystem) {
	backendAttrs := resource.Attributes()
	var osType, cloudProvider string

	switch {
	case backend.CloudProvider == "amzn":
		cloudProvider = semconv.CloudProviderAWS.Value.AsString()
	case backend.CloudProvider == "mcrsft":
		cloudProvider = semconv.CloudProviderAzure.Value.AsString()
	case backend.CloudProvider == "gogl":
		cloudProvider = semconv.CloudProviderGCP.Value.AsString()
	}

	backendAttrs.PutStr(string(semconv.CloudProviderKey), cloudProvider)
	backendAttrs.PutStr(string(semconv.CloudRegionKey), backend.CloudRegion)

	switch {
	case backend.OSType == "lnx":
		osType = semconv.OSTypeLinux.Value.AsString()
	case backend.OSType == "wndws":
		osType = semconv.OSTypeWindows.Value.AsString()
	case backend.OSType == "slrs":
		osType = semconv.OSTypeSolaris.Value.AsString()
	}

	backendAttrs.PutStr(string(semconv.OSTypeKey), osType)
	backendAttrs.PutStr(string(semconv.OSVersionKey), backend.OSVersion)

	backendAttrs.PutStr(string(semconv.ServiceNameKey), backend.ProcessName)
	backendAttrs.PutStr(string(semconv.ServiceVersionKey), backend.Version)
}

func appendAtmSystemInstrScopeSpans(resourceSpans *ptrace.ResourceSpans) ptrace.ScopeSpans {
	scopeSpans := resourceSpans.ScopeSpans().AppendEmpty()
	scopeSpans.Scope().SetName("atm-system")
	scopeSpans.Scope().SetVersion("v1.0")
	return scopeSpans
}

func NewTraceID() pcommon.TraceID {
	return pcommon.TraceID(uuid.New())
}

func NewSpanID() pcommon.SpanID {
	var rngSeed int64
	_ = binary.Read(crand.Reader, binary.LittleEndian, &rngSeed)
	randSource := rand.New(rand.NewSource(rngSeed))

	var sid [8]byte
	randSource.Read(sid[:])
	spanID := pcommon.SpanID(sid)

	return spanID
}

func appendTraceSpans(backend *BackendSystem, backendScopeSpans *ptrace.ScopeSpans, atmScopeSpans *ptrace.ScopeSpans) {
	traceId := NewTraceID()

	var atmOperationName string

	switch {
	case strings.Contains(backend.Endpoint, "balance"):
		atmOperationName = "Check Balance"
	case strings.Contains(backend.Endpoint, "deposit"):
		atmOperationName = "Make Deposit"
	case strings.Contains(backend.Endpoint, "withdraw"):
		atmOperationName = "Fast Cash"
	}

	atmSpanId := NewSpanID()
	atmSpanStartTime := time.Now()
	atmDuration, _ := time.ParseDuration("4s")
	atmSpanFinishTime := atmSpanStartTime.Add(atmDuration)

	atmSpan := atmScopeSpans.Spans().AppendEmpty()
	atmSpan.SetTraceID(traceId)
	atmSpan.SetSpanID(atmSpanId)
	atmSpan.SetName(atmOperationName)
	atmSpan.SetKind(ptrace.SpanKindClient)
	atmSpan.Status().SetCode(ptrace.StatusCodeOk)
	atmSpan.SetStartTimestamp(pcommon.NewTimestampFromTime(atmSpanStartTime))
	atmSpan.SetEndTimestamp(pcommon.NewTimestampFromTime(atmSpanFinishTime))

	backendSpanId := NewSpanID()

	backendDuration, _ := time.ParseDuration("2s")
	backendSpanStartTime := atmSpanStartTime.Add(backendDuration)

	backendSpan := backendScopeSpans.Spans().AppendEmpty()
	backendSpan.SetTraceID(atmSpan.TraceID())
	backendSpan.SetSpanID(backendSpanId)
	backendSpan.SetParentSpanID(atmSpan.SpanID())
	backendSpan.SetName(backend.Endpoint)
	backendSpan.SetKind(ptrace.SpanKindServer)
	backendSpan.Status().SetCode(ptrace.StatusCodeOk)
	backendSpan.SetStartTimestamp(pcommon.NewTimestampFromTime(backendSpanStartTime))
	backendSpan.SetEndTimestamp(atmSpan.EndTimestamp())
}
```

Run the `otelcol-dev` again:

```sh
go run ./otelcol-dev --config config.yaml
```

After about 2 minutes, you should start seeing traces in Jaeger that look like
the following:
![Jaeger trace](/img/docs/tutorials/Jaeger-FullSystem-Traces-List.png)

We now have services representing both the `Atm` and the `BackendSystem`
telemetry generation entities in our system. We fully understand how both
entities are being used and how they contribute to the performance of an
operation executed by a user.

Here is the detailed view of one of those traces in Jaeger:
![Jaeger trace](/img/docs/tutorials/Jaeger-FullSystem-Trace-Details.png)

That's it! You have now reached the end of this tutorial and successfully
implemented a trace receiver, congratulations!
