===========================
The internals of Xinference
===========================

.. contents:: Table of contents:
   :local:

Overview
========
Xinference leverages `Xoscar <https://github.com/xorbitsai/xoscar>`_, an actor programming framework we designed,
as its core component to manage machines, devices, and model inference processes. Each actor serves as a basic
unit for model inference and various inference backends can be integrate into the actor, enabling us to support
multiple inference engines and hardware. These actors are hosted and scheduled within actor pools, which are
designed to be asynchronous and non-blocking and function as resource pools.

.. raw:: html

    <img class="align-center" alt="actor" src="../_static/actor.svg" style="background-color: transparent", width="77%">

====

Both supervisor and worker are actor instances. Initially, an actor pool, serving as a resource pool, needs to be created
on each server; and each actor can utilize a CPU core or a GPU device. Each server has its own address (IP address or
hostname), so actors on different computing nodes can communicate with each other through these addresses. See `Actor`_ for more information.

RESTful API
===========
The RESTful API is implemented using `FastAPI <https://github.com/tiangolo/fastapi>`_, as specified in
`api/restful_api.py <https://github.com/xorbitsai/inference/tree/main/xinference/api/restful_api.py>`_.

::

  self._router.add_api_route("/status", self.get_status, methods=["GET"])

This is an example of the API ``/status``, it's corresponding function is ``get_status``. You can add connection
between RESTful API and the backend function you want in `api/restful_api.py <https://github.com/xorbitsai/inference/tree/main/xinference/api/restful_api.py>`_.

Command Line
============
The Command Line is implemented using `Click <https://click.palletsprojects.com/>`_, as specified in
`deploy/cmdline.py <https://github.com/xorbitsai/inference/tree/main/xinference/deploy/cmdline.py>`_,
allowing users to interact with the Xinference deployment features directly from the terminal.

Entry Points
------------
Take the command-lines we implemented as examples:

- ``xinference``: Provides commands for model management, including registering/unregistering models, listing all
  registered/running models, and launching or terminating specific models.
  It also features interactive commands like generate and chat for testing and interacting with deployed models in real-time.

- ``xinference-local``: Starts a local Xinference service.

- ``xinference-supervisor``: Initiates a supervisor process that manages and monitors worker actors within a distributed setup.

- ``xinference-worker``: Starts a worker process that executes tasks assigned by the supervisor, utilizing available
  computational resources effectively.

Each command is equipped with ``options`` and ``flags`` to customize its behavior, such as specifying log levels,
host addresses, port numbers, and other relevant settings.

Python projects define command-line console entry points in ``pyproject.toml``.

::

  [project.scripts]
  xinference = "xinference.deploy.cmdline:cli"
  xinference-local = "xinference.deploy.cmdline:local"
  xinference-supervisor = "xinference.deploy.cmdline:supervisor"
  xinference-worker = "xinference.deploy.cmdline:worker"

The command-line ``xinference`` can be referred to code in ``xinference.deploy.cmdline:cli``.

Click
-----
We use Click to implement a specific command-line:

::

  @click.option(
        "--host",
        "-H",
        default=XINFERENCE_DEFAULT_DISTRIBUTED_HOST,
        type=str,
        help="Specify the host address for the supervisor.",
    )
    @click.option(
        "--port",
        "-p",
        default=XINFERENCE_DEFAULT_ENDPOINT_PORT,
        type=int,
        help="Specify the port number for the Xinference web ui and service.",
    )

For example, the ``xinference-local`` command allows you to define the host address and port.

Actor
=====
Xinference is fundamentally based on `Xoscar <https://github.com/xorbitsai/xoscar>`_, our actor framework,
which can manage computational resources and Python processes to support scalable and concurrent programming.
The following is a pseudocode demonstrating how our Worker Actor works, the actual Worker Actor is more complex than this.

::

  import xoscar as xo

  class WorkerActor(xo.Actor):
      def __init__(self, *args, **kwargs):
          ...
      async def launch_model(self, model_id, n_gpu, ...):
          # launch an inference engine, use specific model class to load model checkpoints
          ...
      async def list_models(self):
          # list models on this actor
          ...
      async def terminate_model(self, model_id):
          # terminate the model
          ...
      async def __post_create__(self):
          # called after the actor instance is created
          ...
      async def __pre_destroy__(self):
          # called before the actor instance is destroyed
          ...

We use the ``WorkerActor`` as an example to illustrate how we build the Xinference. Each actor class
is a standard Python class that inherits from ``xoscar.Actor``. An instance of this class is a specific actor
within the actor pool.

- **Define Actor Actions**: Each actor needs to define certain actions or behaviors to accomplish specific tasks.
  For instance, the model inference ``WorkerActor`` needs to launch the model (``launch_model``), list the models
  in this actor (``list_models``), terminate a model (``terminate_model``). There are two special methods worth
  noting. The ``__post_create__`` is invoked before the actor is created, allowing for necessary initializations.
  The ``__pre_destroy__`` is called after the actor is destroyed, allowing for cleanup or finalization tasks.

- **Reference Actor and Invoke Methods**: When an actor is created, it yields a reference variable so that other
  actors can reference it. The actor reference can also be referenced with the address. Suppose the ``WorkerActor``
  is created and the reference variable is ``worker_ref``,  the ``launch_model`` method of this actor class can
  be invoked by calling ``worker_ref.launch_model()``.
  Even if the actor's method is originally a synchronized method, when called with an actor reference, it will
  become as an asynchronous method.

- **Inference Engine**: The actor can manage the process, and the inference engine is also a process. In the launch
  model part of the ``WorkerActor``, we can initialize different inference engines according to the user's need.
  Therefore, Xinference can support multiple inference engines and can easily adapt to new inference engines in the
  future.

See `Xoscar document <https://xoscar.dev/en/latest/getting_started/llm-inference.html>`_ for more actor use cases.

Asynchronous Programming
========================

Both Xinference and Xoscar highly utilize asynchronous programming of ``asyncio``.
Asynchronous programming is a programming paradigm that does not block.
Instead, requests and function calls are issued and executed in the background
and results are returned in the future. This enables us to perform
activities concurrently.

If you're not familiar with Pythons's ``asyncio``, you can see more tutorials for help:

  - `Python Asyncio Tutorial <https://bbc.github.io/cloudfit-public-docs/asyncio/asyncio-part-1.html>`__

  - `Real Python's asyncio Tutorial <https://realpython.com/async-io-python/>`__

  - `Python Official Documentation <https://docs.python.org/3/library/asyncio.html>`__


Model
=====

Xinference supports different types of models including large language models (LLMs), image models, audio models, embedding models, etc.
All models are implemented in `model/ <https://github.com/xorbitsai/inference/tree/main/xinference/model>`_.

LLM
---

Take `model/llm/ <https://github.com/xorbitsai/inference/tree/main/xinference/model/llm>`_ for example, it focuses on
the management and instantiation of LLMs. It includes detailed implementations for loading, configuring,
and deploying LLMs.

We support many backends such as GGML, PyTorch, and vLLM. Our generated content is compatible with the format of OpenAI, supporting features such as streaming output and returning chat completion format (for chat models only).
Therefore, there is a lot of adaptation work to be done after the model generate content. These tasks are not difficult, but they do require some time. When writing this part of the code, please refer to the `OpenAI API documentation <https://platform.openai.com/docs/introduction>`_ and the documentation of various inference backends, and make the necessary adaptations.

JSON
----

In `model/llm/llm_family.json <https://github.com/xorbitsai/inference/blob/main/xinference/model/llm/llm_family.json>`_,
we utilize JSON files to manage the metadata of emerging open-source models. Adding a new model does not necessitate writing new code,
it merely requires appending new metadata to the existing JSON file.

::

  {
      "model_name": "llama-2-chat",
      "model_ability": ["chat"],
      "model_specs": [
          {
              "model_format": "ggmlv3",
              "model_size_in_billions": 70,
              "quantization": ["q8_0", ...],
              "model_id": "TheBloke/Llama-2-70B-Chat-GGML",
          },
          ...
      ],
      "prompt_style": {
          "style_name": "LLAMA2",
          "system_prompt": "<s>[INST] <<SYS>>\nYou are a helpful AI assistant.\n<</SYS>>\n\n",
          "roles": ["[INST]", "[/INST]"],
          "stop_token_ids": [2],
          "stop": ["</s>"]
      }
  }

This is an example of how to define the Llama-2 chat model. The ``model_specs`` define the information of the model, as one model family
usually comes with various sizes, quantization methods, and file formats.
For instance, the ``model_format`` could be ``pytorch`` (using Hugging Face Transformers or vLLM as backend),
``ggmlv3`` (a tensor library associated with llama.cpp), or ``gptq`` (a post-training quantization framework).
The ``model_id`` defines the repository of the model hub from which Xinference downloads the checkpoint files.
Furthermore, due to distinct instruction-tuning processes, different model families have varying prompt styles.
The ``prompt_style`` in the JSON file specifies how to format prompts for this particular model.
For example, ``system_prompt`` and ``roles`` are used to specify the instructions and personality of the model.

Code Walkthrough
================

The main code is located in the `xinference/ <https://github.com/xorbitsai/inference/tree/main/xinference>`_:

- `api/ <https://github.com/xorbitsai/inference/tree/main/xinference/api>`_: `restful_api.py <https://github.com/xorbitsai/inference/tree/main/xinference/api/restful_api.py>`_
  is the core part that sets up and runs the RESTful APIs.
  It integrates an authentication service (the specific code is located in `oauth2/ <https://github.com/xorbitsai/inference/tree/main/xinference/api/oauth2>`_),
  as some or all endpointsrequire user authentication.

- `client/ <https://github.com/xorbitsai/inference/tree/main/xinference/client>`_: This is the client of Xinference.

  - `oscar/ <https://github.com/xorbitsai/inference/tree/main/xinference/client/oscar>`_ defines the Actor Client which acts as
    a client interface for interacting with models deployed in a Xinference cluster.

  - `restful/ <https://github.com/xorbitsai/inference/tree/main/xinference/client/restful>`_ implements a RESTful client for
    interacting with a Xinference service.

- `core/ <https://github.com/xorbitsai/inference/tree/main/xinference/core>`_: This is the core part of Xinference.

  - `metrics.py <https://github.com/xorbitsai/inference/tree/main/xinference/core/metrics.py>`_ and
    `resource.py <https://github.com/xorbitsai/inference/tree/main/xinference/core/resource.py>`_
    defines a set of tools for collecting and reporting metrics and the status of node resources, including model throughput,
    latency, the usage of CPU and GPU, memory usage, and more.

  - `worker.py <https://github.com/xorbitsai/inference/tree/main/xinference/core/worker.py>`_ and
    `supervisor.py <https://github.com/xorbitsai/inference/tree/main/xinference/core/supervisor.py>`_
    respectively define the logic for worker actors and supervisor actor. Worker actors are responsible for carrying out specific
    model computation tasks, while supervisor actors manage the lifecycle of worker nodes, schedule tasks, and monitor system states.

  - `status_guard.py <https://github.com/xorbitsai/inference/tree/main/xinference/core/status_guard.py>`_ implements a status monitor
    to track the status of models (like creating, updating, terminating, etc.). It allows querying status information of model instances
    and managing these statuses based on the model's UID.

  - `cache_tracker.py <https://github.com/xorbitsai/inference/tree/main/xinference/core/cache_tracker.py>`_ defines a cache tracker for
    recording and managing cache status and information of model versions. It supports recording cache locations and statuses of model
    versions and querying model version information based on model names.

  - `event.py <https://github.com/xorbitsai/inference/tree/main/xinference/core/event.py>`_ defines an event collector for gathering and
    reporting various runtime events of models, such as information, warnings, and errors.
    `model.py <https://github.com/xorbitsai/inference/tree/main/xinference/core/model.py>`_ defines a Model Actor, the core component for
    direct model interactions. The Model Actor is responsible for executing model inference requests, handling input and output data streams,
    and supports various types of model operations.

- `deploy/ <https://github.com/xorbitsai/inference/tree/main/xinference/deploy>`_: It provides a command-line interface (CLI) for interacting
  with the Xinference framework, allowing users to perform operations by command line. See `Command Line`_ for more information.

- `locale/ <https://github.com/xorbitsai/inference/tree/main/xinference/locale>`_: It supports multi-language localization. By simply adding
  and updating JSON translation files, it becomes possible to support more languages, improving user experience.

- `model/ <https://github.com/xorbitsai/inference/tree/main/xinference/model>`_: It provides a structure for model descriptions, creation,
  and caching. See `Model`_ for more information.

- `frontend/ <https://github.com/xorbitsai/inference/tree/main/frontend>`_: The Next.js code of the frontend (Web UI).
