.. _rayserve:

============================================
Ray Serve: Scalable and Programmable Serving
============================================

.. image:: logo.svg
    :align: center
    :height: 250px
    :width: 400px

.. _rayserve-overview:

Ray Serve is a scalable model-serving library built on Ray.

For users, Ray Serve is:

- **Framework Agnostic**:Use the same toolkit to serve everything from deep learning models 
  built with frameworks like :ref:`PyTorch <serve-pytorch-tutorial>` or 
  :ref:`Tensorflow & Keras <serve-tensorflow-tutorial>` to :ref:`Scikit-Learn <serve-sklearn-tutorial>` models or arbitrary business logic.
- **Python First**: Configure your model serving with pure Python code - no more YAMLs or 
  JSON configs.

As a library, Ray Serve enables: 

- :ref:`serve-split-traffic` with zero downtime by decoupling routing logic from response handling logic.
- :ref:`serve-batching` built-in to help you meet your performance objectives or use your model for batch and online processing.

Since Ray is built on Ray, Ray Serve also allows you to **scale to many machines**
and allows you to leverage all of the other Ray frameworks so you can deploy and scale on any cloud.

.. note:: 
  If you want to try out Serve, join our `community slack <https://forms.gle/9TSdDYUgxYs8SA9e8>`_ 
  and discuss in the #serve channel.


Installation
============

Ray Serve supports Python versions 3.5 and higher. To install Ray Serve:

.. code-block:: bash

  pip install "ray[serve]"

Ray Serve in 90 Seconds
=======================

Serve a function by defining a function, an endpoint, and a backend (in this case a stateless function) then 
connecting the two by setting traffic from the endpoint to the backend.

.. literalinclude:: ../../../python/ray/serve/examples/doc/quickstart_function.py

Serve a stateful class by defining a class (``Counter``), creating an endpoint and a backend, then connecting
the two by setting traffic from the endpoint to the backend.

.. literalinclude:: ../../../python/ray/serve/examples/doc/quickstart_class.py

See :doc:`key-concepts` for more exhaustive coverage about Ray Serve and its core concepts.

Why Ray Serve?
==============

There are generally two ways of serving machine learning applications, both with serious limitations:
you can build using a **traditional webserver** - your own Flask app or you can use a cloud hosted solution.

The first approach is easy to get started with, but it's hard to scale each component. The second approach
requires vendor lock-in (SageMaker), framework specific tooling (TFServing), and a general
lack of flexibility.

Ray Serve solves these problems by giving a user the ability to leverage the simplicity
of deployment of a simple webserver but handles the complex routing, scaling, and testing logic
necessary for production deployments.

For more on the motivation behind Ray Serve, check out these `meetup slides <https://tinyurl.com/serve-meetup>`_.

When should I use Ray Serve?
----------------------------

Ray Serve is a simple (but flexible) tool for deploying, operating, and monitoring Python based machine learning models.
Ray Serve excels when scaling out to serve models in production is a necessity. This might be because of large scale batch processing
requirements or because you're going to serve a number of models behind different endpoints and may need to run A/B tests or control 
traffic between different models.

If you plan on running on multiple machines, Ray Serve will serve you well.

What's next?
============

Check out the :doc:`key-concepts`, learn more about :doc:`advanced`, look at the :ref:`serve-faq`,
or head over to the :doc:`tutorials/index` to get started building your Ray Serve Applications.