Patch submission and review

This page is meant to document the various steps to working with git to contribute or review Kafka code. There are probably a lot of bugs in these steps or possible better recipes, so help make this page better. If you want to push your commits without passwd, please see apache git wiki.

Overview

The Kafka project development ecosystem involves git (for version control), JIRA (for issue tracking) and Review Board (for reviewing code changes made by contributors). To make it easier for both the contributors and the reviewers to manage the contributions, the Kafka project also ships a (python based) script which automates the steps that are involved in the context of a patch submission. These steps involve:

• Creating a patch/diff between the local git repo against the project remote repo
• Creating a review task in Review Board and publish the patch/diff that was generated for the changes
• Updating the JIRA, related to these changes, with a comment about a patch being made available and ready for review at Review Board

As you'll notice this requires (automated) integration between JIRA and Review Board. The (python based) script, which is named kafka-patch-review.py (and present in the checked out code of Kafka project), acts as a wrapper around the scripts/tools that are shipped by JIRA and Review Board for such integrations. Since the kafka-patch-review.py is merely a wrapper around those tools, you'll have to install those tools locally to be able to use the kafka-patch-review.py script. This document helps you in setting up those tools as well as helping you understand the usage of the kafka-patch-review.py itself.

Kafka patch review tool

The following sections will help you install and setup the necessary tools which this wrapper script uses for patch submission.

Install/setup jira-python package

Download the jira-python package

sudo easy_install jira-python

(OPTIONAL) Configure JIRA user name and password

During the patch submission process, the kafka-patch-review.py prompts you for your JIRA user name and password that you use for https://issues.apache.org/jira JIRA instance. The tool uses that information  to update the JIRA with the new patch. However, if you do not like being prompted each time you submit the patch, you can configure your JIRA user name and password  be setup in a file named jira.ini under your home directory. The content of such a file would look like:

nnarkhed-mn:~ nnarkhed$ cat ~/jira.ini
user=nehanarkhede
password=***********

Install/setup review board python tools

This is a quick tutorial on using Review Board with Kafka.

Install the post-review tool

If you are on RHEL, Fedora or CentOS, follow these steps

sudo yum install python-setuptools
sudo easy_install -U RBTools

If you are on a Debian based system (like LinuxMint) follow these steps

	sudo apt-get install python-setuptools
	sudo easy_install -U RBTools

If you are on Mac, follow these steps

sudo easy_install -U setuptools
sudo easy_install -U RBTools

For other platforms, follow the instructions here to setup the post-review tool.

Configure review board related stuff

Then you need to configure a few things to make it work:

First set the review board url to use. You can do this from in git:

git config reviewboard.url https://reviews.apache.org

jkreps$ cat ~/.reviewboardrc
REPOSITORY = 'git://git.apache.org/kafka.git'
TARGET_GROUPS = 'kafka'
GUESS_FIELDS = True

Install the argparse module

    On Linux -> sudo yum install python-argparse
    On Mac -> sudo easy_install argparse

Kafka patch review tool usage

nnarkhed-mn:kafka-git-idea nnarkhed$ python kafka-patch-review.py --help
usage: kafka-patch-review.py [-h] -b BRANCH -j JIRA [-s SUMMARY]
                             [-d DESCRIPTION] [-r REVIEWBOARD] [-t TESTING]
                             [-v VERSION] [-db]

Kafka patch review tool

optional arguments:
  -h, --help            show this help message and exit
  -b BRANCH, --branch BRANCH
                        Tracking branch to create diff against
  -j JIRA, --jira JIRA  JIRA corresponding to the reviewboard
  -s SUMMARY, --summary SUMMARY
                        Summary for the reviewboard
  -d DESCRIPTION, --description DESCRIPTION
                        Description for reviewboard
  -r REVIEWBOARD, --rb REVIEWBOARD
                        Review board that needs to be updated
  -t TESTING, --testing-done TESTING
                        Text for the Testing Done section of the reviewboard
  -v VERSION, --version VERSION
                        Version of the patch
  -db, --debug          Enable debug mode

Upload patch

1. Specify the branch against which the patch should be created (-b)
2. Specify the corresponding JIRA (-j)
3. Specify an optional summary (-s) and description (-d) for the reviewboard

Example:

 python kafka-patch-review.py -b origin/trunk -j KAFKA-42

Update patch

1. Specify the branch against which the patch should be created (-b)
2. Specify the corresponding JIRA (--jira)
3. Specify the rb to be updated (-r)
4. Specify an optional summary (-s) and description (-d) for the reviewboard, if you want to update it
5. Specify an optional version of the patch. This will be appended to the jira to create a file named JIRA-<version>.patch. The purpose is to be able to upload multiple patches to the JIRA. This has no bearing on the reviewboard update.

Example:

python kafka-patch-review.py -b origin/trunk -j KAFKA-42 -r 14081

FAQ

When I run the script, it throws the following error and exits

nnarkhed$python kafka-patch-review.py -b trunk -j KAFKA-42
There don't seem to be any diffs

There are 2 reasons that can cause this -

• The code is not checked into your local branch
• The -b branch is not pointing to the remote branch. In the example above, "trunk" is specified as the branch, which is the local branch. The correct value for the -b (--branch) option is the remote branch. "git branch -r" gives the list of the remote branch names.

When I run the script, it throws the following error and exits

Error uploading diff

Your review request still exists, but the diff is not attached.

One of the most common root causes of this error are that the git remote branches are not up-to-date. Since the script already does that, it is probably due to some other problem. You can run the script with the --debug option that will make post-review run in the debug mode and list the root cause of the issue.

Simple contributor workflow

This is the simple workflow and will work well for small features development for people who don't have direct access to check in to the Apache repository. Let's assume you are working on a feature or bug called, xyz:

1. Checkout a new repository:

  git clone https://git-wip-us.apache.org/repos/asf/kafka.git kafka

Or if you already have a copy of the repository, just check for updates

  git fetch

2. Create and checkout a feature branch to work in:

  git checkout -b xyz remotes/origin/trunk

3. Do some work on this branch and periodically checkin locally:

  git commit -a

4. When done (or periodically) rebase your branch to take any changes from trunk:

  git pull --rebase origin trunk

5. Make a patch containing your work and upload it to JIRA:

  git format-patch trunk --stdout > xyz-v1.patch

6. You may need to iterate/rebase your patch a few times as people comment on the code until a commit checks it in to the main repository.

You will also want to ensure you have your username and email setup correctly so that we correctly record the source of the contribution:

git config --global user.name "Palmer Eldritch"
git config --global user.email "peldritch@layoutsinc.com"

Reviewer workflow:

This assumes you already have a copy of the repository.

1. Make sure your code is up-to-date:

  git fetch

2. Checkout the destination branch:

  git checkout trunk

3. See what the patch will do:

  git apply --stat xyz-v1.patch

4. See that the patch will apply cleanly (otherwise prod the contributor to rebase):

  git apply --check xyz-v1.patch

6. Apply the patch to trunk

  git am --signoff < xyz-v1.patch

If you get an error that says "Patch does not have a valid e-mail address." then the patch might have been created by doing git diff in which case you can apply the patch using

patch -p1 < xyz-v1.patch

if the am operation failed you will also need to remove the .git/rebase-apply/ that gets created

7. If things go wrong (tests fail, you find some problem, etc), you can back out:

  git reset --hard HEAD
  git clean -f

8. Push the change back to Apache:

  git push origin trunk

Simple Commiter Workflow

If you have commit access on the apache repository then you will not be applying patches in the manner described in the reviewer workflow. Instead, once your patch has been reviewed you will check it in yourself as follows:

1. Create a branch to work on:

       git fetch
       git checkout -b xyz remotes/origin/trunk
     

2. Implement the feature.

3. Rebase:

       git rebase remotes/origin/trunk
     

4. Post the change to JIRA and get it reviewed.
5. Push the change back to Apache. Pick one of the following:

   • You should almost always collapse your work into a single check-in in order to avoid cluttering the upstream change-log:

          # assuming trunk is up-to-date with origin
          git checkout trunk
          git merge --squash xyz
          git commit -am "KAFKA-XXX xyz feature; reviewed by <reviewers>"
          git push origin trunk
        

   • If you are absolutely sure you want to preserve your local intermediate check-in history then push directly from your feature branch instead of the above merge (or use merge without the squash option):

        # from feature branch xyz
        git push origin trunk
        

Github Workflow

Apache doesn't seem to provide a place to stash your work-in-progress branches or provide some of the nice social features github has. This can be a problem for larger features. Here are instructions for using github as a place to stash your work in progress changes.

Setting Up

1. As in the other workflows begin by checking out kafka (if you haven't already):

  git clone https://git-wip-us.apache.org/repos/asf/kafka.git kafka

This sets up the remote alias "origin" automatically which refers back to the Apache repo.
2. Create a new github repository on your github account to use for stashing changes. There are various ways to do this, I just forked the apache/kafka repo (https://github.com/apache/kafka) which creates a repo https://github.com/jkreps/kafka (where jkreps would be your user name).
3. Add an alias on your local repository to github to avoid typing:

  git remotes add github https://github.com/<your_user>/kafka.git

Now you can push either to origin or to github.

Doing Work

1. You can create a branch named xyz in your local repository and check it out

  git checkout -b xyz remotes/origin/trunk

2. To set up a second machine to work on you can clone the github url.
3. To save your branch to your github repo do

  git push github xyz

4. To pull these changes onto the other machine where you have a copy of the repository you can do:

  git fetch github
  git checkout xyz
  git merge remotes/github/xyz

Review and pushing changes back to Apache works just as before.