ray/doc/source/development.rst

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Development Tips
================
If you are doing development on the Ray codebase, the following tips may be
helpful.
1. **Speeding up compilation:** Be sure to install Ray with
.. code-block:: shell
cd ray/python
pip install -e . --verbose
The ``-e`` means "editable", so changes you make to files in the Ray
directory will take effect without reinstalling the package. In contrast, if
you do ``python setup.py install``, files will be copied from the Ray
directory to a directory of Python packages (often something like
``/home/ubuntu/anaconda3/lib/python3.6/site-packages/ray``). This means that
changes you make to files in the Ray directory will not have any effect.
If you run into **Permission Denied** errors when running ``pip install``,
you can try adding ``--user``. You may also need to run something like ``sudo
chown -R $USER /home/ubuntu/anaconda3`` (substituting in the appropriate
path).
If you make changes to the C++ files, you will need to recompile them.
However, you do not need to rerun ``pip install -e .``. Instead, you can
recompile much more quickly by doing
.. code-block:: shell
cd ray/python/ray/core
make -j8
2. **Starting processes in a debugger:** When processes are crashing, it is
often useful to start them in a debugger (``gdb`` on Linux or ``lldb`` on
MacOS). See the latest discussion about how to do this `here`_.
3. **Running tests locally:** Suppose that one of the tests (e.g.,
``runtest.py``) is failing. You can run that test locally by running
``python test/runtest.py``. However, doing so will run all of the tests which
can take a while. To run a specific test that is failing, you can do
.. code-block:: shell
cd ray
python test/runtest.py APITest.testKeywordArgs
When running tests, usually only the first test failure matters. A single
test failure often triggers the failure of subsequent tests in the same
script.
4. **Running linter locally:** To run the Python linter on a specific file, run
something like ``flake8 ray/python/ray/worker.py``. You may need to first run
``pip install flake8``.
5. **Inspecting Redis shards by hand:** To inspect the primary Redis shard by
hand, you can query it with commands like the following.
.. code-block:: python
r_primary = ray.worker.global_worker.redis_client
r_primary.keys("*")
To inspect other Redis shards, you will need to create a new Redis client.
For example (assuming the relevant IP address is ``127.0.0.1`` and the
relevant port is ``1234``), you can do this as follows.
.. code-block:: python
import redis
r = redis.StrictRedis(host='127.0.0.1', port=1234)
You can find a list of the relevant IP addresses and ports by running
.. code-block:: python
r_primary.lrange('RedisShards', 0, -1)
.. _`here`: https://github.com/ray-project/ray/issues/108