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First of all, you need the ZooKeeper source code. Get the source code on your local drive using gitGo to https://github.com/apache/zookeeper (which is a read only mirror of zookeeper git hosted on Apache) and click the fork button to create your own fork. After forking download your fork to local disk. Most development is done on the "master":

$ git clone https://git-wip-us.apache.org/repos/asfgithub.com/<userid>/zookeeper.git
 my-zookeeper

You may also want to develop against a specific release. You can list the release branches and checkout 3.4 by going into the zookeeper directory and running:

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Before you start, send a message to the ZooKeeper developer mailing list, or file a bug report in Jira. Describe your proposed changes and check that they fit in with what others are doing and have planned for the project. Be patient, it may take folks a while to understand your requirements.

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• All public classes and methods should have informative Javadoc comments.
  • Do not use @author tags.
• Code should be formatted according to Sun's conventions, with these exceptions:
  • Indent four spaces per level, not two or six or eight, etc... four.
  • No tabs for indentation, spaces only
• Contributions should pass existing unit tests.
• New unit tests should be provided to demonstrate bugs and fixes. JUnit is our test framework:
  • You must implement a class that extends junit.framework.TestCase and whose class name ends with Test.
  • Define methods within your class whose names begin with test, and call JUnit's many assert methods to verify conditions; these methods will be executed when you run ant test.
  • By default, do not let tests write any temporary files to /tmp. Instead, the tests should write to the location specified by the test.build.data system property.
  • Place your class in the src/java/test tree.
  • ClientTest.java is an example of a client-server test.
  • You can run all the unit test with the command ant test, or you can run a specific unit test with the command ant -Dtestcase=<class name without package prefix> test (for example ant -Dtestcase=ClientTest test)

Understanding Ant

ZooKeeper is built by Ant, a Java building tool. This section will eventually describe how Ant is used within ZooKeeper. To start, simply read a good Ant tutorial. The following is a good tutorial, though keep in mind that ZooKeeper isn't structured according to the ways outlined in the tutorial. Use the tutorial to get a basic understand of Ant but not to understand how Ant is used for Hadoop:

Good Ant tutorial: http://i-proving.com/2005/10/31/ant-tutorial

Generating a patch

Unit Tests

Contribute Work via Github Pull Request

We accept pull requests via github against the apache/zookeeper repository. Submitting to Apache ZooKeeper via github is no different than submitting any other pull request against a github repository. The developer needs to follow the contribution guidelines to produce changes, just like with patch files, and once it is ready, the developer produces a pull request from his/her own branch. The one constraints we have is that the title of the pull request must match the paring JIRA issue. If the JIRA issue is "ZOOKEEPER-222222: My lovely bug", then the pull request issue must also match "ZOOKEEPER-222222: My lovely bug".

We currently perform QA on pull requests, although the process is still being polished. We also have not completed the JIRA workflow when the developer submits a pull request, which means that the JIRA does not transition to Patch Available when a pull request is submitted. We are currently discussing on the list how to adapt our workflow.

Example workflow

there are many ways to setup your git environment but this one example:

fork the apache github repo

go to https://github.com/apache/zookeeper and click the fork button to create your own fork.

make a local clone of your fork

on your local machine run

$ git clone https://github.com/<userid>/zookeeper.git my-zookeeper

add the apache github repo

$ git remote add apache-github https://github.com/apache/zookeeper.git

make sure you are uptodate

$ git pull apache-github 

create a branch named after the issue you are working on

$ git checkout remotes/apache-github/master
$ git checkout -B ZOOKEEPER-<jiraNumber>

<jiraNumber> is the JIRA you will be working on.

make your changes

sorry can't help you here. it's all up to you to fix the bug 

commit everything

do you will want to do some combination of git add and git commit to get all your changes committed. when you run git commit, you only need a single line in the commit message it should have the form ZOOKEEPER-jiraNumber: jiraTitle.

push your change to git hub

$ git push origin ZOOKEEPER-<jiraNumber>

generate a pull request

go to the github page that lists your branches. you will see a pull request button that you can press. Please make sure your pull request description captures enough information so reviewers can get an idea of what the pull request is targeting without digging into the JIRA or looking into the code. When the pull request is merged, the description will be part of the commit message. Here is an example of a descriptive pull request looks like: https://github.com/apache/zookeeper/pull/211

Check List for Pull Request

This is a check list of things we'd like a contributor to do before opening a pull request.

Unit Tests

Before submitting your pull request, you are encouraged to run the same tools that the automated Jenkins CI system will run on your patch. This enables you to fix problems with your pull request before you submit it. The test Ant target will run your patch through the same checks that Jenkins currently does.

To use this target, you must run it from a clean workspace (ie git status shows no modifications or additions). From your clean workspace, run:

mvn verify spotbugs:check checkstyle:check -Pfull-build -Dsurefire-forkcount=4

At the end, you should get a message on your console that indicates success.

Please make sure that all unit tests succeed before constructing your patch submitting pull request and that no new javac compiler warnings are introduced by your patch.

> cd zookeeper-trunk
> ant -Djavac.args="-Xlint -Xmaxwarns 1000" clean test tar

pull request

After a while, if you see

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Please also check the javadoc.

> ant javadocmvn install -DskipTests -pl zookeeper-docs
> firefox build/docs/api/index.html

Examine all public classes you've changed to see that documentation is complete, informative, and properly formatted. Your patch must not generate any javadoc warnings.

Creating a patch

Check to see what files you have modified with:

git status

Add any new files with:

git add src/.../MyNewClass.java
git add src/.../TestMyNewClass.java

Commit your changes, type:

git commit -a

In the commit message should be one line of the form: JIRA: short description. For example 

ZOOKEEPER-1234: fixed the coolness factor calculation

You can then create a patch with the following command

git show --no-prefix > ZOOKEEPER-1234.patch

This will report all modifications done on ZooKeeper sources on your local disk and save them into the ZOOKEEPER-1234.patch file. Read the patch file.
Make sure it includes ONLY the modifications required to fix a single issue.

Documentation

The source documentation is available in src/docs directory. It can be regenerated using forrest (as documented here) however the contributor is not responsible for submitting this as part of the pull request. To be clear: the pull request should include changes to src/docs but not the toplevel (of the source tree) docs directory.

Please don't do in pull request

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:

• reformat code unrelated to the bug being fixed: formatting changes should be separate patches/commits.
• comment out code that is now obsolete: just remove it.
• insert comments around each change, marking the change: folks can use subversion to figure out what's changed and by whom.
• make things public which are not required by end users.

Please do in pull request:

• try to adhere to the coding style of files you edit;
• comment code whose function or rationale is not obvious;
• update documentation (e.g., package.html files, this wiki, etc.)
• name the patch file after the JIRA – ZOOKEEPER-<JIRA#>.patch

Testing your patch

Before submitting your patch, you are encouraged to run the same tools that the automated Jenkins CI system will run on your patch. This enables you to fix problems with your patch before you submit it. The test Ant target will run your patch through the same checks that Jenkins currently does.

To use this target, you must run it from a clean workspace (ie git status shows no modifications or additions). From your clean workspace, run:

ant test

At the end, you should get a message on your console that indicates success.

Some things to note:

• you may need to explicitly set ANT_HOME. Running ant -diagnostics will tell you the default value on your system.
• you may need to explicitly set JAVA_HOME.

Applying a patch

To apply a patch either you generated or found from JIRA, you can issue

patch -p0 < ZOOKEEPER-<JIRA#>.patch

if you just want to check whether the patch applies you can run patch with --dry-run option

patch --dry-run -p0 < ZOOKEEPER-<JIRA#>.patch

If you are an Eclipse user, you can apply a patch by : # Right click project name in Package Explorer , 2. Team -> Apply Patch

Contributing your work

Use GitHub’s "Co-authored-by" when there are multiple authors

Note: This is in case of manual copies, ToDo for me: I will check the commit script to integrate this functionality

There are occasions when there are multiple author for a patch. For example when there is a patch that is abandoned by its original author for any reason, and it can no longer be merged, or it's unfinished, someone might pick it up and finish it. (After asking the original author if he is still working on it or not).

In these occasions, we should also attribute the original author by adding one or more Co-authored-by trailers to the commit’s message. See the GitHub documentation for "Creating a commit with multiple authors".

As this is a GitHub feature, Co-author will show up on GitHub's statistics.

In short, these are the steps to add Co-authors that will be tracked by GitHub:

1. Collect the name and email address for each co-author.

2. Commit the change, but after your commit description, instead of a closing quotation, add two empty lines. (Do not close the commit message with a quotation mark)

3. On the next line of the commit message, type Co-authored-by: name <name@example.com>. After the co-author information, add a closing quotation mark.

Here is the example from the GitHub page, using 2 Co-authors:

$ git commit -m "Refactor usability tests.
>
>
Co-authored-by: name <name@example.com>
Co-authored-by: another-name <another-name@example.com>"

Final Checks on Pull Request

Please Finally, patches should be attached to an issue report in Jira via the Attach File link on the issue's Jira. Please add a comment that asks for a code review following our code review checklist. Please note that the attachment should be granted license to ASF for inclusion in ASF works (as per the Apache License §5).When you believe that your patch is ready to be committed, select the Submit Patch link on the issue's Jira.

Folks should run ant clean test javadoc before selecting Submit Patcha full check (mvn verify spotbugs:check checkstyle:check -Pfull-build -Dsurefire-forkcount=4) before submitting pull request. Tests should all pass. Javadoc should report no warnings or errors. Jenkin's tests are meant to double-check things, and not be used as a primary patch tester, which would create too much noise on the mailing list and in Jira. Submitting patches that fail Jenkins testing is frowned on, (unless the failure is not actually due to the patch).

If your patch PR involves performance optimizations, they should be validated by benchmarks that demonstrate an improvement.

If your patch PR creates an incompatibility with the latest major release, then you must set the Incompatible change flag on the issue's Jira 'and' fill in the Release Note field with an explanation of the impact of the incompatibility and the necessary steps users must take.

If your patch PR implements a major feature or improvement, then you must fill in the Release Note field on the issue's Jira with an explanation of the feature that will be comprehensible by the end user.

Jenkins Pre-commit Check

Once a PR is created, a Jenkins job will be triggered to run a set of pre-commit checks on the pull request, including all Java and C unit tests, find bug test, release audit check, etc. If all checks pass, you should see something like this in your pull request page:

Image Added

After code review and committers sign off, the pull request will be merged. 

If any of the checks fail, you will see this:

Image Added

In this case, please check the Jenkins output by following the "Details" link, and fix the issue, and try trigger a Jenkins build again. There are these ways to trigger a Jenkins build:

• Close and reopen the pull request. This is the recommended approach, and only the contributor who owns the pull request can do this.
• Update the PR by pushing a new commit or amend the previous commit (git commit --amend). This is also recommended approach and only contributor who owns the pull request can do this.
• Any committer or PMC member (actually anyone who is part of 'apache' github organization) can trigger the job just by adding a comment with the magic phrases:
  • 'retest ant build' in order to re run ANT based build
  • 'retest maven build' in order to re run MAVEN based build (update on Sep, 2020 - currently this trigger phrase is broken. Workaround is for committers to manually trigger the job in CI admin UI, or for contributors to do a commit with a new SHA - e.g. commit --amend then push to remote to trigger the job).
• Note for administrators: configuration of these phrases are in the precommit Jenkins jobs, it is using the GitHub Pull Request builder plugin)
  Image Added

For contributors who owns the pull request: please make sure to get a green build to prepare the patch in a landing state.

For committers: please make sure to get a green build before committing a pull request.

Code Review and Accept Pull Request

Once a "+1" comment is received from the automated patch testing system and a code reviewer has set the Reviewed flag on the issue's Jira, a committer should then evaluate it within a few days and either: commit it; or reject it with an explanation.

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Should your patch receive a "-1" from the Jenkins testing, select the Resume Progress on the issue's Jira, upload a new patch update pull request with necessary fixes, and then select the Submit Patch link again.

In some cases a patch may need to be updated based on review comments. In this case the updated patch should be re-attached to the Jira with the same name. Jira will archive the older version of the patch and make the new patch the active patch. This will enable a history of patches on the Jira. As stated above patch naming is generally ZOOKEEPER-#.patch where ZOOKEEPER-# is the id of the Jira.

Committers: for non-trivial changes, it is best to get another committer to review your patches pull request before commit. Use Submit Patch link like other contributors, and then wait for a "+1" from another committer before committing. Please also try to frequently review things in the patch queue.

Pull requests via github (work in progress)

We currently accept pull requests via github against the apache/zookeeper repository. Submitting to Apache ZooKeeper via github is no different than submitting any other pull request against a github repository. The developer needs to follow the contribution guidelines to produce changes, just like with patch files, and once it is ready, the developer produces a pull request from his/her own branch. The one constraints we have is that the title of the pull request must match the paring JIRA issue. If the JIRA issue is "ZOOKEEPER-222222: My lovely bug", then the pull request issue must also match "ZOOKEEPER-222222: My lovely bug".

We currently perform QA on pull requests, although the process is still being polished. We also have not completed the JIRA workflow when the developer submits a pull request, which means that the JIRA does not transition to Patch Available when a pull request is submitted. We are currently discussing on the list how to adapt our workflow.

Example workflow

there are many ways to setup your git environment but this one example:

fork the apache github repo

go to https://github.com/apache/zookeeper and click the fork button to create your own fork.

make a local clone of your fork

on your local machine run

$ git clone https://github.com/<userid>/zookeeper.git my-zookeeper

add the apache github repo

$ git remote add apache-github https://github.com/apache/zookeeper.git

make sure you are uptodate

$ git pull apache-github 

create a branch named after the issue you are working on

$ git checkout remotes/apache-github/master
$ git checkout -B ZOOKEEPER-<jiraNumber>

<jiraNumber> is the JIRA you will be working on.

make your changes

sorry can't help you here. it's all up to you to fix the bug 

commit everything

do you will want to do some combination of git add and git commit to get all your changes committed. when you run git commit, you only need a single line in the commit message it should have the form ZOOKEEPER-jiraNumber: jiraTitle.

push your change to git hub

$ git push origin ZOOKEEPER-<jiraNumber>

generate a pull request

go to the github page that lists your branches. you will see a pull request button that you can press.

Committing Guidelines for committers

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Jira Guidelines

Please comment on issues in Jira, making their concerns known. Please also vote for issues that are a high priority for you.

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