ray/doc/source/using-ray-on-a-cluster.rst
Richard Liaw fc9352c588
[docs] Make walkthrough and starting Ray materials clear (#7099)
* make starting ray a separate page

* concept

* Apply suggestions from code review

Co-Authored-By: Edward Oakes <ed.nmi.oakes@gmail.com>

* more fics

* Apply suggestions from code review

Co-Authored-By: Edward Oakes <ed.nmi.oakes@gmail.com>

Co-authored-by: Edward Oakes <ed.nmi.oakes@gmail.com>
2020-02-11 23:17:30 -08:00

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.. _ref-cluster-setup:
Manual Cluster Setup
====================
.. note::
If you're using AWS or GCP you should use the automated `setup commands <autoscaling.html>`_.
The instructions in this document work well for small clusters. For larger
clusters, consider using the pssh package: ``sudo apt-get install pssh`` or
the `setup commands for private clusters <autoscaling.html#quick-start-private-cluster>`_.
Deploying Ray on a Cluster
--------------------------
This section assumes that you have a cluster running and that the nodes in the
cluster can communicate with each other. It also assumes that Ray is installed
on each machine. To install Ray, follow the `installation instructions`_.
.. _`installation instructions`: http://ray.readthedocs.io/en/latest/installation.html
Starting Ray on each machine
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
On the head node (just choose some node to be the head node), run the following.
If the ``--redis-port`` argument is omitted, Ray will choose a port at random.
.. code-block:: bash
ray start --head --redis-port=6379
The command will print out the address of the Redis server that was started
(and some other address information).
**Then on all of the other nodes**, run the following. Make sure to replace
``<address>`` with the value printed by the command on the head node (it
should look something like ``123.45.67.89:6379``).
.. code-block:: bash
ray start --address=<address>
If you wish to specify that a machine has 10 CPUs and 1 GPU, you can do this
with the flags ``--num-cpus=10`` and ``--num-gpus=1``. See the `Configuration <configure.html>`__ page for more information.
Now we've started all of the Ray processes on each node Ray. This includes
- Some worker processes on each machine.
- An object store on each machine.
- A raylet on each machine.
- Multiple Redis servers (on the head node).
To run some commands, start up Python on one of the nodes in the cluster, and do
the following.
.. code-block:: python
import ray
ray.init(address="<address>")
Now you can define remote functions and execute tasks. For example, to verify
that the correct number of nodes have joined the cluster, you can run the
following.
.. code-block:: python
import time
@ray.remote
def f():
time.sleep(0.01)
return ray.services.get_node_ip_address()
# Get a list of the IP addresses of the nodes that have joined the cluster.
set(ray.get([f.remote() for _ in range(1000)]))
Stopping Ray
~~~~~~~~~~~~
When you want to stop the Ray processes, run ``ray stop`` on each node.