ray/doc/source/ray-client.rst
Devin Petersohn 1412f3c546
[docs] page for using Modin with Ray (#13937)
Co-authored-by: Richard Liaw <rliaw@berkeley.edu>
2021-02-06 00:28:04 -08:00

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.. _ray-client:
**********
Ray Client
**********
.. note::
This feature is still in beta and subject to changes.
===========
Basic usage
===========
The Ray client server is automatically started on port ``10001`` when you use ``ray start --head`` or Ray in an autoscaling cluster. The port can be changed by specifying --ray-client-server-port in the ``ray start`` command.
To start the server manually, you can run:
``python -m ray.util.client.server [--host host_ip] [--port port] [--redis-address address] [--redis-password password]``
This runs ``ray.init()`` with default options and exposes the client gRPC port at ``host_ip:port`` (by default, ``0.0.0.0:10001``). Providing ``redis-address`` and ``redis-password`` will be passed into ``ray.init()`` when the server starts, allowing connection to an existing Ray cluster, as per the `cluster setup <cluster/index.html>`_ instructions.
From here, another Ray script can access that server from a networked machine with ``ray.util.connect()``
.. code-block:: python
import ray
import ray.util
ray.util.connect("<head_node_host>:10001") # replace with the appropriate host and port
# Normal Ray code follows
@ray.remote
def f(x):
return x ** x
do_work.remote(2)
#....
When the client disconnects, any object or actor references held by the server on behalf of the client are dropped, as if directly disconnecting from the cluster.
============
Known issues
============
Because Ray client mode affects the behavior of the Ray API, larger scripts or libraries imported before ``ray.util.connect()`` may not realize they're in client mode. This feature is being tracked with `issue #13272 <https://github.com/ray-project/ray/issues/13272>`_ but the workaround here is provided for beta users.
One option is to defer the imports from a ``main`` script that calls ``ray.util.connect()`` first. However, some older scripts or libraries might not support that.
Therefore, an environment variable is also available to force a Ray program into client mode: ``RAY_CLIENT_MODE`` An example usage:
.. code-block:: bash
RAY_CLIENT_MODE=1 python my_ray_program.py