Before you start, ensure you’ve read the Pre-requisites to start with development.
See also
This is a short guide on how to send your patches to LAVA. The LAVA team uses the gerrit code review system to review changes.
If you do not already have a Linaro account, you will first need to Register with Linaro as a Community contributor.
So the first step will be logging in to gerrit and uploading you SSH public key there.
There are two main components to LAVA, lava-server and lava-dispatcher.
git clone https://git.linaro.org/git/lava/lava-server.git
cd lava-server
git clone https://git.linaro.org/git/lava/lava-dispatcher.git
cd lava-dispatcher
There is also lava-tool which is gaining more support for operations involving the Lava Dispatcher Design:
git clone https://git.linaro.org/git/lava/lava-tool.git
cd lava-tool
If you have not done so already, git review needs to be setup for each clone of each source:
git review -s
We recommend never working off the master branch (unless you are a git expert and really know what you are doing). You should create a topic branch for each logically distinct change you work on.
Note
Unless your change directly depends on changes made in an earlier commit on a branch, this means making a fresh branch for each change with one commit per branch.
Before you start, make sure your master branch is up to date:
git checkout master
git pull
Now create your topic branch off master:
git checkout -b my-change master
Extra dependencies are required to run the tests. On Debian based distributions, you can install lava-dev.
To run the tests, use the ci-run script:
$ ./ci-run
See also Testing the new design.
Unit tests cannot replicate all tests required on LAVA code, some tests will need to be run with real devices under test. On Debian based distributions, see Developer package build. See Writing a LAVA test definition for information on writing LAVA test jobs to test particular device functionality.
Make sure that your changes do not cause any failures in the unit tests:
$ ./ci-run
Wherever possible, always add new unit tests for new code.
From each topic branch, just run:
git review
If you have multiple commits in that topic branch, git review will warn you. It’s OK to send multiple commits from the same branch, but note that:
Therefore the recommentations are:
There is a convention within the LAVA software team that reviews which have no reviewers other than the automatic lavabot are ignored for review. This allows developers to share changes at an early stage when more than one developer is working on a single change or when another developer needs to base their changes on work being done by someone else.
Therefore, until you add reviewers to your new review, it will not receive attention and is not going to be merged.
There is a shortcut available in gerrit to add the complete team as reviewers, simply click Add in the Reviewers section and enter lava-team in the drop-down box and confirm by pressing Add in the drop-down box.
When reviewers make comments on your change, you should amend the original commit to address the comments, and not submit a new change addressing the comments while leaving the original one untouched.
Gerrit handles this by adding a ChangeId to your commit message. Keep this Id unchanged when amending commit messages.
Locally, you can make a separate commit addressing the reviewer comments, it’s not a problem. But before you resubmit your branch for review, you have to rebase your changes against master to end up with a single, enhanced commit. For example:
$ git branch
master
* my-feature
$ git show-branch master my-feature
! [master] Last commit on master
! [my-feature] address revier comments
--
+ [my-feature] address reviewer comments
+ [my-feature^] New feature or bug fix
-- [master] Last commit on master
$ git rebase -i master
git rebase -i will open your $EDITOR and present you with something like this:
pick xxxxxxx New feature or bug fix
pick yyyyyyy address reviewer comments
You want the last commit to be combined with the first and keep the first commit message, so you change pick to fixup ending up with somehting like this:
pick xxxxxxx New feature or bug fix
fixup yyyyyyy address reviewer comments
If you also want to edit the commit message of the first commit to mention something else, change pick to reword and you will have the chance to do that. Just remember to keep the Change-Id unchanged.
NOTE: if you want to abort the rebase, just delete everything, save the file as empty and exit the $EDITOR.
Now save the file and exit your $EDITOR.
In the end, your original commit will be updated with the changes:
$ git show-branch master my-feature
! [master] Last commit on master
! [my-feature] New feature or bug fix
--
+ [my-feature] New feature or bug fix
-- [master] Last commit on master
Note that the “New feature or bug fix” commit is now not the same as before since it was modified, so it will have a new hash (zzzzzzz instead of the original xxxxxxx). But as long as the commit message still contains the same Change-Id, gerrit will know it is a new version of a previously submitted change.
After placing a few reviews, there will be a number of local branches. To keep the list of local branches under control, the local branches can be easily deleted after the merge. Note: git will warn if the branch has not already been merged when used with the lower case -d option. This is a useful check that you are deleting a merged branch and not an unmerged one, so work with git to help your workflow.
$ git checkout bugfix
$ git rebase master
$ git checkout master
$ git branch -d bugfix
If the final command fails, check the status of the review of the branch. If you are completely sure the branch should still be deleted or if the review of this branch was abandoned, use the -D option instead of -d and repeat the command.
If you haven’t got a clone handy on the instance to be used for the review, prepare a clone as usual.
Gerrit provides a number of ways to apply the changes to be reviewed, so set up a test branch as usual - always ensuring that the master branch of the clone is up to date before creating the review branch.
$ git checkout master
$ git pull
$ git checkout -b review-111
To pull in the changes in the review already marked for commit in your local branch, use the pull link in the patch set of the review you want to run.
Alternatively, to pull in the changes as plain patches, use the patch` link and pipe that to patch -p1. In this full example, the second patch set of review 159 is applied to the review-159 branch as a patch set.
$ git checkout master
$ git pull
$ git checkout -b review-159
$ git fetch https://review.linaro.org/lava/lava-server refs/changes/59/159/2 && git format-patch -1 --stdout FETCH_HEAD | patch -p1
$ git status
Handle the local branch as normal. If the reviewed change needs modification and a new patch set is added, revert the local change and apply the new patch set.
All developers are encouraged to write code with futuristic changes in mind, so that it is easy to do a technology upgrade, which includes watching for errors and warnings generated by dependency packages as well as upgrading and migrating to newer APIs as a normal part of development.
This is particularly true for Django where the lava-server package needs to retain support for multiple django versions as well as monitoring for deprecation warnings in the newest django version. Where necessary, write code for different versions and separate with:
import django
if django.VERSION > (1, 8):
pass # newer code
else:
pass # older compatibility code
LAVA recommends Debian Jessie but also supports testing and unstable which have a newer version of python-django.
Database migrations on Debian Jessie and later are managed within django. Support for python-django-south has been dropped. Only django migration types should be included in any reviews which involve a database migration.
Once modified, the updated models.py file needs to be copied into the system location for the relevant extension, e.g. lava_scheduler_app. This is a step which needs to be done by the developer - developer packages cannot be installed cleanly and unit tests will likely fail until the migration has been created and applied.
On Debian Jessie and later:
$ sudo lava-server manage makemigrations lava_scheduler_app
The migration file will be created in /usr/lib/python2.7/dist-packages/lava_scheduler_app/migrations/ (which is why sudo is required) and will need to be copied into your git working copy and added to the review.
The migration is applied using:
$ sudo lava-server manage migrate lava_scheduler_app
See django docs for more information.
LAVA dispatcher now supports python3 testing but only for the pipeline unit tests. Code changes to the V2 dispatcher code (i.e. in the lava_dispatcher/pipeline tree) must be sufficiently aware of Python3 to not break the unit tests when run using python3.
LAVA is not yet ready to use python 3.x support at runtime, particularly in lava-server, due to the lack of python 3.x migrations in dependencies. However it is good to take python 3.x support into account in lava-server, when writing new code for LAVA v2, so that it makes it easy during the move anytime in the future.
All reviews run the lava-dispatcher.pipelnie V2 unit tests against python 3.x and changes must pass without breaking compatibility with python 2.x
The ./ci-run script for lava-dispatcher shows how to run the python3 unit tests:
# to run python3 unit tests, you can use
# python3 -m unittest discover -v lava_dispatcher.pipeline
# but the python3 dependencies are not automatically installed.
The list of python3 dependencies needed for the pipeline unit tests is maintained as part of the functional tests:
From time to time, reviews may add more python dependencies - check on the Mailing lists if your tests start to fail after rebasing on current master or if you want to help with more python3 support in LAVA V2.
Avoid making changes to LAVA V1 code for python3 - only LAVA V2 is going to support python3.
Pylint is a tool that checks for errors in Python code, tries to enforce a coding standard and looks for bad code smells. We encourage developers to run LAVA code through pylint and fix warnings or errors shown by pylint to maintain a good score. For more information about code smells, refer to Martin Fowler’s refactoring book. LAVA developers stick on to PEP 008 (aka Guido’s style guide) across all the LAVA component code.
pylint does need to be used with some caution, the messages produced should not be followed blindly. It can be very useful for spotting unused imports, unused variables and other issues. One notable problem is with logging-not-lazy as there can be times when lazy logging can result in out of date or invalid information being logged. This is a particular problem when passing variables like dictionaries and lists to the logger in the dispatcher as these later need to be turned into YAML.
To simplify the pylint output, some warnings are recommended to be disabled:
$ pylint -d line-too-long -d missing-docstring
Note
Docstrings should still be added wherever a docstring would be useful.
pylint also supports local disabling of warnings and there are many examples of:
variable = func_call() # pylint: disable=
There is a pylint-django plugin available in unstable and testing and whilst it improves the pylint output for the lava-server codebase, it still has a high level of false indications.
In order to check for PEP 008 compliance the following command is recommended:
$ pep8 --ignore E501
pep8 can be installed in debian based systems as follows:
$ apt install pep8
LAVA has set of unit tests which the developers can run on a regular basis for each change they make in order to check for regressions if any. Most of the LAVA components such as lava-server, lava-dispatcher, lava-tool have unit tests.
Extra dependencies are required to run the tests. On Debian based distributions, you can install lava-dev.
To run the tests, use the ci-run / ci-build scripts:
$ ./ci-run
See also
Testing the new design for examples of how to run individual unit tests or all unit tests within a class or module.
LAVA database models can be visualized with the help of django_extensions along with tools such as pydot. In debian based systems install the following packages to get the visualization of LAVA database models:
$ apt install python-django-extensions python-pydot
Once the above packages are installed successfully, use the following command to get the visualization of lava-server models in PNG format:
$ sudo lava-server manage graph_models --pydot -a -g -o lava-server-model.png
More documentation about graph models is available in https://django-extensions.readthedocs.org/en/latest/graph_models.html
Other useful features from django_extensions are as follows:
models
validate_templates - check templates for rendering errors
$ sudo lava-server manage validate_templates
runscript - run arbitrary scripts inside lava-server environment
$ sudo lava-server manage runscript fix_user_names –script-args=all
Default configurations use a side-effect of the logging behaviour to restrict access to the lava-server manage operations which typical Django apps expose through the manage.py interface. This is because lava-server manage shell provides read-write access to the database, so the command requires sudo.
On developer machines, this can be unnecessary. Set the location of the django log to a new location to allow easier access to the management commands to simplify debugging and to be able to run a Django Python Console inside a development environment. In /etc/lava-server/settings.conf add:
"DJANGO_LOGFILE": "/tmp/django.log"
Note
settings.conf is JSON syntax, so ensure that the previous line ends with a comma and that the resulting file validates as JSON. Use JSONLINT
The new location needs to be writable by the lavaserver user (for use by localhost) and by the developer user (but would typically be writeable by anyone).