---
title: "What are Traces"
---


## Spans

A span represents a unit of work or operation (think a `span` of time). It tracks specific operations that a request makes, painting a picture of what happened during the time in which that operation was executed.

A span contains name, time-related data, structured log messages, and other metadata (that is, Attributes) to provide information about the operation it tracks. A span for an LLM execution in JSON format is displayed below

```json
{
   "name": "llm",
   "context": {
       "trace_id": "0x6c80880dbeb609e2ed41e06a6397a0dd",
       "span_id": "0xd9bdedf0df0b7208",
       "trace_state": "[]"
   },
   "kind": "SpanKind.INTERNAL",
   "parent_id": "0x7eb5df0046c77cd2",
   "start_time": "2024-05-08T21:46:11.480777Z",
   "end_time": "2024-05-08T21:46:35.368042Z",
   "status": {
       "status_code": "OK"
   },
   "attributes": {
       "openinference.span.kind": "LLM",
       "llm.input_messages.0.message.role": "system",
       "llm.input_messages.0.message.content": "\n  The following is a friendly conversation between a user and an AI assistant.\n  The assistant is talkative and provides lots of specific details from its context.\n  If the assistant does not know the answer to a question, it truthfully says it\n  does not know.\n\n  Here are the relevant documents for the context:\n\n  page_label: 7\nfile_path: /Users/mikeldking/work/openinference/python/examples/llama-index-new/backend/data/101.pdf\n\nDomestic Mail Manual \u2022 Updated 7-9-23101\n101.6.4Retail Mail: Physical Standards for Letters, Cards, Flats, and Parcels\na. No piece may weigh more than 70 pounds.\nb. The combined length and girth of a piece (the length of its longest side plus \nthe distance around its thickest part) may not exceed 108 inches.\nc. Lower size or weight standards apply to mail addressed to certain APOs and \nFPOs, subject to 703.2.0  and 703.4.0  and for Department of State mail, \nsubject to 703.3.0 .\n\npage_label: 6\nfile_path: /Users/mikeldking/work/openinference/python/examples/llama-index-new/backend/data/101.pdf\n\nDomestic Mail Manual \u2022 Updated 7-9-23101\n101.6.2.10Retail Mail: Physical Standards for Letters, Cards, Flats, and Parcels\na. The reply half of a double card must be used for reply only and may not be \nused to convey a message to the original addressee or to send statements \nof account. The reply half may be formatted for response purposes (e.g., contain blocks for completion by the addressee).\nb. A double card must be folded before mailing and prepared so that the \naddress on the reply half is on the inside when the double card is originally \nmailed. The address side of the reply half may be prepared as Business \nReply Mail, Courtesy Reply Mail, meter reply mail, or as a USPS Returns service label.\nc. Plain stickers, seals, or a single wire stitch (staple) may be used to fasten the \nopen edge at the top or bottom once the card is folded if affixed so that the \ninner surfaces of the cards can be readily examined. Fasteners must be \naffixed according to the applicable preparation requirements for the price claimed. Any sealing on the left and right sides of the cards, no matter the \nsealing process used, is not permitted.\nd. The first half of a double card must be detached when the reply half is \nmailed for return. \n6.2.10   Enclosures\nEnclosures in double postcards are prohibited at card prices. \n6.3 Nonmachinable Pieces\n6.3.1   Nonmachinable Letters\nLetter-size pieces (except card-size pieces) that meet one or more of the \nnonmachinable characteristics in 1.2 are subject to the nonmachinable \nsurcharge (see 133.1.7 ). \n6.3.2   Nonmachinable Flats\nFlat-size pieces that do not meet the standards in 2.0 are considered parcels, \nand the mailer must pay the applicable parcel price.  \n6.4 Parcels \n[7-9-23]  USPS Ground Advantage \u2014 Retail parcels are eligible for USPS \nTracking and Signature Confirmation service. A USPS Ground Advantage \u2014 \nRetail parcel is the following:\na. A mailpiece that exceeds any one of the maximum dimensions for a flat \n(large envelope). See 2.1.\nb. A flat-size mailpiece, regardless of thickness, that is rigid or nonrectangular. \nc. A flat-size mailpiece that is not uniformly thick under 2.4. \nd.[7-9-23]  A mailpiece that does not exceed 130 inches in combined length \nand girth.\n7.0 Additional Physical Standards for Media Mail and Library \nMail\nThese standards apply to Media Mail and Library Mail:\n\npage_label: 4\nfile_path: /Users/mikeldking/work/openinference/python/examples/llama-index-new/backend/data/101.pdf\n\nDomestic Mail Manual \u2022 Updated 7-9-23101\n101.6.1Retail Mail: Physical Standards for Letters, Cards, Flats, and Parcels\n4.0 Additional Physical Standa rds for Priority Mail Express\nEach piece of Priority Mail Express may not weigh more than 70 pounds. The \ncombined length and girth of a piece (the length of its longest side plus the \ndistance around its thickest part) may not exceed 108 inches. Lower size or weight standards apply to Priority Mail Express addressed to certain APO/FPO \nand DPOs. Priority Mail Express items must be large enough to hold the required \nmailing labels and indicia on a single optical plane without bending or folding.\n5.0 Additional Physical St andards for Priority Mail\nThe maximum weight is 70 pounds. The combined length and girth of a piece \n(the length of its longest side plus the distance around its thickest part) may not \nexceed 108 inches. Lower size and weight standards apply for some APO/FPO \nand DPO mail subject to 703.2.0 , and 703.4.0 , and for Department of State mail \nsubject to 703.3.0 . \n[7-9-23] \n6.0 Additional Physical Standa rds for First-Class Mail and \nUSPS Ground Advantage \u2014 Retail\n[7-9-23]\n6.1 Maximum Weight\n6.1.1   First-Class Mail\nFirst-Class Mail (letters and flats) must not exceed 13 ounces. \n6.1.2   USPS Ground Advantage \u2014 Retail\nUSPS Ground Advantage \u2014 Retail mail must not exceed 70 pounds.\n6.2 Cards Claimed at Card Prices\n6.2.1   Card Price\nA card may be a single or double (reply) stamped card or a single or double postcard. Stamped cards are available from USPS with postage imprinted on \nthem. Postcards are commercially available or privately printed mailing cards. To \nbe eligible for card pricing, a card and each half of a double card must meet the physical standards in 6.2 and the applicable eligibility for the price claimed. \nIneligible cards are subject to letter-size pricing. \n6.2.2   Postcard Dimensions\nEach card and part of a double card claimed at card pricing must be the following: \na. Rectangular.b. Not less than 3-1/2 inches high, 5 inches long, and 0.007 inch thick.\nc. Not more than 4-1/4 inches high, or more than 6 inches long, or greater than \n0.016 inch thick.\nd. Not more than 3.5 ounces (Charge flat-size prices for First-Class Mail \ncard-type pieces over 3.5 ounces.)\n\n  Instruction: Based on the above documents, provide a detailed answer for the user question below.\n  Answer \"don't know\" if not present in the document.\n  ",
       "llm.input_messages.1.message.role": "user",
       "llm.input_messages.1.message.content": "Hello",
       "llm.model_name": "gpt-4-turbo-preview",
       "llm.invocation_parameters": "{\"temperature\": 0.1, \"model\": \"gpt-4-turbo-preview\"}",
       "output.value": "How are you?" },
   "events": [],
   "links": [],
   "resource": {
       "attributes": {},
       "schema_url": ""
   }
}
```

Spans can be nested, as is implied by the presence of a parent span ID: child spans represent sub-operations. This allows spans to more accurately capture the work done in an application.

## Traces

A trace records the paths taken by requests (made by an application or end-user) as they propagate through multiple steps.

Without tracing, it is challenging to pinpoint the cause of performance problems in a system.

It improves the visibility of our application or system’s health and lets us debug behavior that is difficult to reproduce locally. Tracing is essential for LLM applications, which commonly have nondeterministic problems or are too complicated to reproduce locally.

Tracing makes debugging and understanding LLM applications less daunting by breaking down what happens within a request as it flows through a system.

A trace is made of one or more spans. The first span represents the root span. Each root span represents a request from start to finish. The spans underneath the parent provide a more in-depth context of what occurs during a request (or what steps make up a request).

## Projects

A `project` is a collection of traces. You can think of a project as a container for all the traces that are related to a single application or service. You can have multiple projects, and each project can have multiple traces. Projects can be useful for various use-cases such as separating out environments, logging traces for evaluation runs, etc. To learn more about how to setup projects, see the how-to guide

## Span Kind

When a span is created, it is created as one of the following: Chain, Retriever, Reranker, LLM, Embedding, Agent, or Tool.

<Frame caption="The SpanKinds supported by OpenInference Tracing">
  <img src="https://storage.googleapis.com/arize-assets/phoenix/assets/images/span_kinds.png" alt="" />
</Frame>

**CHAIN**

A Chain is a starting point or a link between different LLM application steps. For example, a Chain span could be used to represent the beginning of a request to an LLM application or the glue code that passes context from a retriever to and LLM call.

**RETRIEVER**

A Retriever is a span that represents a data retrieval step. For example, a Retriever span could be used to represent a call to a vector store or a database.

**RERANKER**

A Reranker is a span that represents the reranking of a set of input documents. For example, a cross-encoder may be used to compute the input documents' relevance scores with respect to a user query, and the top K documents with the highest scores are then returned by the Reranker.

**LLM**

An LLM is a span that represents a call to an LLM. For example, an LLM span could be used to represent a call to OpenAI or Llama.

**EMBEDDING**

An Embedding is a span that represents a call to an LLM for an embedding. For example, an Embedding span could be used to represent a call OpenAI to get an ada-2 embedding for retrieval.

**TOOL**

A Tool is a span that represents a call to an external tool such as a calculator or a weather API.

**AGENT**

A span that encompasses calls to LLMs and Tools. An agent describes a reasoning block that acts on tools using the guidance of an LLM.

## Span Attributes

Attributes are key-value pairs that contain metadata that you can use to annotate a span to carry information about the operation it is tracking.

For example, if a span invokes an LLM, you can capture the model name, the invocation parameters, the token count, and so on.

Attributes have the following rules:

* Keys must be non-null string values
* Values must be a non-null string, boolean, floating point value, integer, or an array of these values Additionally, there are Semantic Attributes, which are known naming conventions for metadata that is typically present in common operations. It's helpful to use semantic attribute naming wherever possible so that common kinds of metadata are standardized across systems. See [semantic conventions](https://github.com/Arize-ai/openinference/blob/main/spec/semantic_conventions.md) for more information.

## Example OTEL Spans

Below are example OTEL spans for each OpenInference spanKind to be used as reference when doing manual instrumentation

<CodeGroup>

```json LLM
{
   "name": "llm",
   "context": {
       "trace_id": "0x6c80880dbeb609e2ed41e06a6397a0dd",
       "span_id": "0xd9bdedf0df0b7208",
       "trace_state": "[]"
   },
   "kind": "SpanKind.INTERNAL",
   "parent_id": "0x7eb5df0046c77cd2",
   "start_time": "2024-05-08T21:46:11.480777Z",
   "end_time": "2024-05-08T21:46:35.368042Z",
   "status": {
       "status_code": "OK"
   },
   "attributes": {
       "openinference.span.kind": "LLM",
       "llm.input_messages.0.message.role": "system",
       "llm.input_messages.0.message.content": "\n  The following is a friendly conversation between a user and an AI assistant.\n  The assistant is talkative and provides lots of specific details from its context.\n  If the assistant does not know the answer to a question, it truthfully says it\n  does not know.\n\n  Here are the relevant documents for the context:\n\n  page_label: 7\nfile_path: /Users/mikeldking/work/openinference/python/examples/llama-index-new/backend/data/101.pdf\n\nDomestic Mail Manual \u2022 Updated 7-9-23101\n101.6.4Retail Mail: Physical Standards for Letters, Cards, Flats, and Parcels\na. No piece may weigh more than 70 pounds.\nb. The combined length and girth of a piece (the length of its longest side plus \nthe distance around its thickest part) may not exceed 108 inches.\nc. Lower size or weight standards apply to mail addressed to certain APOs and \nFPOs, subject to 703.2.0  and 703.4.0  and for Department of State mail, \nsubject to 703.3.0 .\n\npage_label: 6\nfile_path: /Users/mikeldking/work/openinference/python/examples/llama-index-new/backend/data/101.pdf\n\nDomestic Mail Manual \u2022 Updated 7-9-23101\n101.6.2.10Retail Mail: Physical Standards for Letters, Cards, Flats, and Parcels\na. The reply half of a double card must be used for reply only and may not be \nused to convey a message to the original addressee or to send statements \nof account. The reply half may be formatted for response purposes (e.g., contain blocks for completion by the addressee).\nb. A double card must be folded before mailing and prepared so that the \naddress on the reply half is on the inside when the double card is originally \nmailed. The address side of the reply half may be prepared as Business \nReply Mail, Courtesy Reply Mail, meter reply mail, or as a USPS Returns service label.\nc. Plain stickers, seals, or a single wire stitch (staple) may be used to fasten the \nopen edge at the top or bottom once the card is folded if affixed so that the \ninner surfaces of the cards can be readily examined. Fasteners must be \naffixed according to the applicable preparation requirements for the price claimed. Any sealing on the left and right sides of the cards, no matter the \nsealing process used, is not permitted.\nd. The first half of a double card must be detached when the reply half is \nmailed for return. \n6.2.10   Enclosures\nEnclosures in double postcards are prohibited at card prices. \n6.3 Nonmachinable Pieces\n6.3.1   Nonmachinable Letters\nLetter-size pieces (except card-size pieces) that meet one or more of the \nnonmachinable characteristics in 1.2 are subject to the nonmachinable \nsurcharge (see 133.1.7 ). \n6.3.2   Nonmachinable Flats\nFlat-size pieces that do not meet the standards in 2.0 are considered parcels, \nand the mailer must pay the applicable parcel price.  \n6.4 Parcels \n[7-9-23]  USPS Ground Advantage \u2014 Retail parcels are eligible for USPS \nTracking and Signature Confirmation service. A USPS Ground Advantage \u2014 \nRetail parcel is the following:\na. A mailpiece that exceeds any one of the maximum dimensions for a flat \n(large envelope). See 2.1.\nb. A flat-size mailpiece, regardless of thickness, that is rigid or nonrectangular. \nc. A flat-size mailpiece that is not uniformly thick under 2.4. \nd.[7-9-23]  A mailpiece that does not exceed 130 inches in combined length \nand girth.\n7.0 Additional Physical Standards for Media Mail and Library \nMail\nThese standards apply to Media Mail and Library Mail:\n\npage_label: 4\nfile_path: /Users/mikeldking/work/openinference/python/examples/llama-index-new/backend/data/101.pdf\n\nDomestic Mail Manual \u2022 Updated 7-9-23101\n101.6.1Retail Mail: Physical Standards for Letters, Cards, Flats, and Parcels\n4.0 Additional Physical Standa rds for Priority Mail Express\nEach piece of Priority Mail Express may not weigh more than 70 pounds. The \ncombined length and girth of a piece (the length of its longest side plus the \ndistance around its thickest part) may not exceed 108 inches. Lower size or weight standards apply to Priority Mail Express addressed to certain APO/FPO \nand DPOs. Priority Mail Express items must be large enough to hold the required \nmailing labels and indicia on a single optical plane without bending or folding.\n5.0 Additional Physical St andards for Priority Mail\nThe maximum weight is 70 pounds. The combined length and girth of a piece \n(the length of its longest side plus the distance around its thickest part) may not \nexceed 108 inches. Lower size and weight standards apply for some APO/FPO \nand DPO mail subject to 703.2.0 , and 703.4.0 , and for Department of State mail \nsubject to 703.3.0 . \n[7-9-23] \n6.0 Additional Physical Standa rds for First-Class Mail and \nUSPS Ground Advantage \u2014 Retail\n[7-9-23]\n6.1 Maximum Weight\n6.1.1   First-Class Mail\nFirst-Class Mail (letters and flats) must not exceed 13 ounces. \n6.1.2   USPS Ground Advantage \u2014 Retail\nUSPS Ground Advantage \u2014 Retail mail must not exceed 70 pounds.\n6.2 Cards Claimed at Card Prices\n6.2.1   Card Price\nA card may be a single or double (reply) stamped card or a single or double postcard. Stamped cards are available from USPS with postage imprinted on \nthem. Postcards are commercially available or privately printed mailing cards. To \nbe eligible for card pricing, a card and each half of a double card must meet the physical standards in 6.2 and the applicable eligibility for the price claimed. \nIneligible cards are subject to letter-size pricing. \n6.2.2   Postcard Dimensions\nEach card and part of a double card claimed at card pricing must be the following: \na. Rectangular.b. Not less than 3-1/2 inches high, 5 inches long, and 0.007 inch thick.\nc. Not more than 4-1/4 inches high, or more than 6 inches long, or greater than \n0.016 inch thick.\nd. Not more than 3.5 ounces (Charge flat-size prices for First-Class Mail \ncard-type pieces over 3.5 ounces.)\n\n  Instruction: Based on the above documents, provide a detailed answer for the user question below.\n  Answer \"don't know\" if not present in the document.\n  ",
       "llm.input_messages.1.message.role": "user",
       "llm.input_messages.1.message.content": "Hello",
       "llm.model_name": "gpt-4-turbo-preview",
       "llm.invocation_parameters": "{\"temperature\": 0.1, \"model\": \"gpt-4-turbo-preview\"}",
       "output.value": "How are you?" },
   "events": [],
   "links": [],
   "resource": {
       "attributes": {},
       "schema_url": ""
   }
}
```

```json Retriever
{
     "name": "retrieve",
     "context": {
         "trace_id": "0x6c80880dbeb609e2ed41e06a6397a0dd",
         "span_id": "0x03f3466720f4bfc7",
         "trace_state": "[]"
     },
     "kind": "SpanKind.INTERNAL",
     "parent_id": "0x7eb5df0046c77cd2",
     "start_time": "2024-05-08T21:46:11.044464Z",
     "end_time": "2024-05-08T21:46:11.465803Z",
     "status": {
         "status_code": "OK"
     },
     "attributes": {
         "openinference.span.kind": "RETRIEVER",
         "input.value": "tell me about postal service",
         "retrieval.documents.0.document.id": "6d4e27be-1d6d-4084-a619-351a44834f38",
         "retrieval.documents.0.document.score": 0.7711453293100421,
         "retrieval.documents.0.document.content": "<document-chunk-1>",
         "retrieval.documents.0.document.metadata": "{\"page_label\": \"7\", \"file_name\": \"/data/101.pdf\", \"file_path\": \"/data/101.pdf\", \"file_type\": \"application/pdf\", \"file_size\": 47931, \"creation_date\": \"2024-04-12\", \"last_modified_date\": \"2024-04-12\"}",
         "retrieval.documents.1.document.id": "869d9f6d-db9a-43c4-842f-74bd8d505147",
         "retrieval.documents.1.document.score": 0.7672439175862021,
         "retrieval.documents.1.document.content": "<document-chunk-2>",
         "retrieval.documents.1.document.metadata": "{\"page_label\": \"6\", \"file_name\": \"/data/101.pdf\", \"file_path\": \"/data/101.pdf\", \"file_type\": \"application/pdf\", \"file_size\": 47931, \"creation_date\": \"2024-04-12\", \"last_modified_date\": \"2024-04-12\"}",
         "retrieval.documents.2.document.id": "72b5cb6b-464f-4460-b497-cc7c09d1dbef",
         "retrieval.documents.2.document.score": 0.7647611816897794,
         "retrieval.documents.2.document.content": "<document-chunk-3>",
         "retrieval.documents.2.document.metadata": "{\"page_label\": \"4\", \"file_name\": \"/data/101.pdf\", \"file_path\": \"/data/101.pdf\", \"file_type\": \"application/pdf\", \"file_size\": 47931, \"creation_date\": \"2024-04-12\", \"last_modified_date\": \"2024-04-12\"}"
     },
     "events": [],
     "links": [],
     "resource": {
         "attributes": {},
         "schema_url": ""
     }
 }
```
</CodeGroup>

