Creating a Flink Release

Introduction

The Apache Flink project periodically declares and publishes releases. A release is one or more packages of the project artifact(s) that are approved for general public distribution and use. They may come with various degrees of caveat regarding their perceived quality and potential for change, such as “alpha”, “beta”, “incubating”, “stable”, etc.

The Flink community treats releases with great importance. They are a public face of the project and most users interact with the project only through the releases. Releases are signed off by the entire Flink community in a public vote.

Each release is executed by a Release Manager, who is selected among the Flink PMC members. This document describes the process that the Release Manager follows to perform a release. Any changes to this process should be discussed and adopted on the dev@ mailing list.

Please remember that publishing software has legal consequences. This guide complements the foundation-wide Product Release Policy and Release Distribution Policy.

Overview

The release process consists of several steps:

1. Decide to release
2. Prepare for the release
3. Build a release candidate
4. Vote on the release candidate
5. If necessary, fix any issues and go back to step 3.
6. Finalize the release
7. Promote the release

Decide to release

Deciding to release and selecting a Release Manager is the first step of the release process. This is a consensus-based decision of the entire community.

Anybody can propose a release on the dev@ mailing list, giving a solid argument and nominating a committer as the Release Manager (including themselves). There’s no formal process, no vote requirements, and no timing requirements. Any objections should be resolved by consensus before starting the release.

In general, the community prefers to have a rotating set of 3-5 Release Managers. Keeping a small core set of managers allows enough people to build expertise in this area and improve processes over time, without Release Managers needing to re-learn the processes for each release. That said, if you are a committer interested in serving the community in this way, please reach out to the community on the dev@ mailing list.

Checklist to proceed to the next step

1. Community agrees to release
2. Community selects a Release Manager

Prepare for the release

Before your first release, you should perform one-time configuration steps. This will set up your security keys for signing the release and access to various release repositories.

To prepare for each release, you should audit the project status in the JIRA issue tracker, and do necessary bookkeeping. Finally, you should create a release branch from which individual release candidates will be built.

One-time setup instructions

GPG Key

You need to have a GPG key to sign the release artifacts. Please be aware of the ASF-wide release signing guidelines. If you don’t have a GPG key associated with your Apache account, please create one according to the guidelines.

Determine your Apache GPG Key and Key ID, as follows:

gpg --list-keys

This will list your GPG keys. One of these should reflect your Apache account, for example:

--------------------------------------------------
pub   2048R/845E6689 2016-02-23
uid                  Nomen Nescio <anonymous@apache.org>
sub   2048R/BA4D50BE 2016-02-23

Here, the key ID is the 8-digit hex string in the pub line: 845E6689.

Now, add your Apache GPG key to the Flink’s KEYS file both in dev and release repositories at dist.apache.org. Follow the instructions listed at the top of these files. (Note: Only PMC members have write access to the release repository. If you end up getting 403 errors ask on the mailing list for assistance.)

Configure git to use this key when signing code by giving it your key ID, as follows:

git config --global user.signingkey 845E6689

You may drop the --global option if you’d prefer to use this key for the current repository only.

You may wish to start gpg-agent to unlock your GPG key only once using your passphrase. Otherwise, you may need to enter this passphrase hundreds of times. The setup for gpg-agent varies based on operating system, but may be something like this:

eval $(gpg-agent --daemon --no-grab --write-env-file $HOME/.gpg-agent-info)
export GPG_TTY=$(tty)
export GPG_AGENT_INFO

Access to Apache Nexus repository

Configure access to the Apache Nexus repository, which enables final deployment of releases to the Maven Central Repository.

1. You log in with your Apache account.
2. Confirm you have appropriate access by finding org.apache.flink under Staging Profiles.
3. Navigate to your Profile (top right dropdown menu of the page).
4. Choose User Token from the dropdown, then click Access User Token. Copy a snippet of the Maven XML configuration block.

5. Insert this snippet twice into your global Maven settings.xml file, typically ${HOME}/.m2/settings.xml. The end result should look like this, where TOKEN_NAME and TOKEN_PASSWORDare your secret tokens:

   settings.xml

   <settings>
      <servers>
        <server>
          <id>apache.releases.https</id>
          <username>TOKEN_NAME</username>
          <password>TOKEN_PASSWORD</password>
        </server>
        <server>
          <id>apache.snapshots.https</id>
          <username>TOKEN_NAME</username>
          <password>TOKEN_PASSWORD</password>
        </server>
      </servers>
    </settings>

Website development setup

Get ready for updating the Flink website by following the website development instructions.

Create a new version in JIRA

When contributors resolve an issue in JIRA, they are tagging it with a release that will contain their changes. With the release currently underway, new issues should be resolved against a subsequent future release. Therefore, you should create a release item for this subsequent release, as follows:

1. In JIRA, navigate to the Flink > Administration > Versions.
2. Add a new release: choose the next minor version number compared to the one currently underway, select today’s date as the Start Date, and choose Add.

Triage release-blocking issues in JIRA

There could be outstanding release-blocking issues, which should be triaged before proceeding to build a release candidate. We track them by assigning a specific Fix version field even before the issue resolved.

The list of release-blocking issues is available at the version status page. Triage each unresolved issue with one of the following resolutions:

• If the issue has been resolved and JIRA was not updated, resolve it accordingly.
• If the issue has not been resolved and it is acceptable to defer this until the next release, update the Fix Version field to the new version you just created. Please consider discussing this with stakeholders and the dev@ mailing list, as appropriate.
• If the issue has not been resolved and it is not acceptable to release until it is fixed, the release cannot proceed. Instead, work with the Flink community to resolve the issue.

Review and update documentation

There are a few pages in the documentation that need to be reviewed and updated for each release.

• Upgrading Applications and Flink Versions: https://ci.apache.org/projects/flink/flink-docs-master/ops/upgrading.html
• please extend this list.

Unless the pages have not been updated before, please create a JIRA ticket and mark it as release blocker.

Review Release Notes in JIRA

JIRA automatically generates Release Notes based on the Fix Version field applied to issues. Release Notes are intended for Flink users (not Flink committers/contributors). You should ensure that Release Notes are informative and useful.

Open the release notes from the version status page by choosing the release underway and clicking Release Notes.

You should verify that the issues listed automatically by JIRA are appropriate to appear in the Release Notes. Specifically, issues should:

• Be appropriately classified as Bug, New Feature, Improvement, etc.
• Represent noteworthy user-facing changes, such as new functionality, backward-incompatible API changes, or performance improvements.
• Have occurred since the previous release; an issue that was introduced and fixed between releases should not appear in the Release Notes.
• Have an issue title that makes sense when read on its own.

Adjust any of the above properties to the improve clarity and presentation of the Release Notes.

Verify that a Release Build Works

Run mvn -Prelease clean install to ensure that the build processes that are specific to that profile are in good shape.

Create a release branch

Release candidates are built from a release branch. As a final step in preparation for the release, you should create the release branch, push it to the code repository (you should probably do this once the whole process is done), and update version information on the original branch.

Check out the version of the codebase from which you start the release. For a new minor or major release, this may be HEAD of the master branch. To build a hotfix/incremental release, instead of the master branch, use the release branch of the release being patched. (Please make sure your cloned repository is up-to-date before starting.)

$ git checkout <master branch OR release tag>

Set up a few environment variables to simplify Maven commands that follow. (We use bash Unix syntax in this guide.)

RELEASE_VERSION="1.4.0"
SHORT_RELEASE_VERSION="1.4"
CURRENT_SNAPSHOT_VERSION="$SHORT_RELEASE_VERSION-SNAPSHOT"
NEXT_SNAPSHOT_VERSION="1.5-SNAPSHOT"

Most of the following commands have to be executed in the tools directory, we will prefix the command prompt to make this explicit.

If you are doing a new major release, first create a branch for the new version that we want to release before updating the master branch to the next development version:

$ git checkout -b release-$SHORT_RELEASE_VERSION 
$ git checkout master
$ cd tools
tools $ OLD_VERSION=$CURRENT_SNAPSHOT_VERSION NEW_VERSION=$NEXT_SNAPSHOT_VERSION releasing/update_branch_version.sh
$ cd ..
$ git checkout -b release-$SHORT_RELEASE_VERSION  

If you're creating a new minor release, you will skip the above step and simply check out the the already existing branch for that version:

$ git checkout -b release-$SHORT_RELEASE_VERSION  

The rest of this guide assumes that commands are run in the root (or tools directory) of a repository on the branch of the release version with the above environment variables set.

Checklist to proceed to the next step

1. Release Manager’s GPG key is published to dist.apache.org
2. Release Manager’s GPG key is configured in git configuration
3. Release Manager has org.apache.flink listed under Staging Profiles in Nexus
4. Release Manager’s Nexus User Token is configured in settings.xml
5. JIRA release item for the subsequent release has been created
6. There are no release blocking JIRA issues
7. Release Notes in JIRA have been audited and adjusted
8. Release branch has been created
9. Originating branch has the version information updated to the new version

Build a release candidate

The core of the release process is the build-vote-fix cycle. Each cycle produces one release candidate. The Release Manager repeats this cycle until the community approves one release candidate, which is then finalized.

Build and stage Java artifacts with Maven

Set up a few environment variables to simplify Maven commands that follow. This identifies the release candidate being built. Start with RC_NUM equal to 1 and increment it for each candidate.

RC_NUM="1"
TAG="release-${VERSION}-rc${RC_NUM}"

Now, create a release branch:

$ cd tools
tools $ OLD_VERSION=$CURRENT_SNAPSHOT_VERSION NEW_VERSION=$RELEASE_VERSION RELEASE_CANDIDATE=$RC_NUM releasing/create_release_branch.sh

We now need to do several things:

• Create the source release archive
• Deploy jar artefacts to the Apache Nexus Repository, which is the staging area for deploying the jars to Maven Central
• Create binary convenience releases for different Hadoop versions

You might want to create a directory on your local machine for collecting the various source and binary releases before uploading them. Creating the binary releases is a lengthy process but you can do this on a another machine (for example, in the "cloud"). When doing this, you can skip signing the release files on the remote machine, download them to your local machine and sign them there.

First, we build the source release:

tools $ RELEASE_VERSION=$RELEASE_VERSION releasing/create_source_release.sh
 

Next, we stage the maven artefacts:

tools $ releasing/deploy_staging_jars.sh

Review all staged artifacts (https://repository.apache.org/). They should contain all relevant parts for each module, including pom.xml, jar, test jar, source, test source, javadoc, etc. Carefully review any new artifacts.

Close the staging repository on Apache Nexus. When prompted for a description, enter “Apache Flink, version X, release candidate Y”.

Finally, we create the binary convenience release files:

tools $ RELEASE_VERSION=$RELEASE_VERSION releasing/create_binary_release.sh

If you want to run this step in parallel on a remote machine you have to make the release commit available there (for example by pushing to a repository). This is important: the commit inside the binary builds has to match the commit of the source builds and the tagged release commit. When building remotely, you can skip gpg signing by setting  GPG_SKIP=true. You would then sign the files manually after downloading them to your machine:

$ for f in flink-*-bin*.tgz; gpg --armor --detach-sig $f; end

Stage source and binary releases on dist.apache.org

Copy the source release to the dev repository of dist.apache.org.

1. If you have not already, check out the Flink section of the dev repository on dist.apache.org via Subversion. In a fresh directory:

    svn co https://dist.apache.org/repos/dist/dev/flink

2. Make a directory for the new release:

    mkdir flink/${VERSION}
    cd flink/${VERSION}

   Copy Flink source/binary distributions, hashes, and GPG signature:

3. Add and commit all the files.

    svn add flink/${VERSION}
    svn commit

4. Verify that files are present.

Propose a pull request for website updates

The final step of building the candidate is to propose a website pull request.

Start by updating the variables for the latest released version in the top-level _config.yml, and list the new release in downloads.md, linking to the source code download and the Release Notes in JIRA. Also add a new blog entry announcing the release in _posts.

Finally, propose a pull request with these changes. (Don’t merge before finalizing the release.)

Checklist to proceed to the next step

1. Maven artifacts deployed to the staging repository of repository.apache.org
2. Source distribution deployed to the dev repository of dist.apache.org
3. Website pull request proposed to list the release

You can (optionally) also do additional verification by:

1. Check hashes (e.g. md5sum -c *.md5 and sha512sum -c *.sha1)
2. Check signatures (e.g. gpg --verify flink-1.2.3-source-release.tar.gz.asc flink-1.2.3-source-release.tar.gz)
3. grep for legal headers in each file.

Vote on the release candidate

Once you have built and individually reviewed the release candidate, please share it for the community-wide review. Please review foundation-wide voting guidelines for more information.

Start the review-and-vote thread on the dev@ mailing list. Here’s an email template; please adjust as you see fit.

From: Release Manager
To: dev@flink.apache.org
Subject: [VOTE] Release 1.2.3, release candidate #3

Hi everyone,
Please review and vote on the release candidate #3 for the version 1.2.3, as follows:
[ ] +1, Approve the release
[ ] -1, Do not approve the release (please provide specific comments)


The complete staging area is available for your review, which includes:
* JIRA release notes [1],
* the official Apache source release and binary convenience releases to be deployed to dist.apache.org [2], which are signed with the key with fingerprint FFFFFFFF [3],
* all artifacts to be deployed to the Maven Central Repository [4],
* source code tag "release-1.2.3-rc3" [5],
* website pull request listing the new release and adding announcement blog post [6]. 

The vote will be open for at least 72 hours. It is adopted by majority approval, with at least 3 PMC affirmative votes.

Thanks,
Release Manager

[1] link
[2] link
[3] https://dist.apache.org/repos/dist/release/flink/KEYS
[4] link
[5] link
[6] link

If there are any issues found in the release candidate, reply on the vote thread to cancel the vote. There’s no need to wait 72 hours. Proceed to the Fix Issues step below and address the problem. However, some issues don’t require cancellation. For example, if an issue is found in the website pull request, just correct it on the spot and the vote can continue as-is.

If there are no issues, reply on the vote thread to close the voting. Then, tally the votes in a separate email. Here’s an email template; please adjust as you see fit.

From: Release Manager
To: dev@flink.apache.org
Subject: [RESULT] [VOTE] Release 1.2.3, release candidate #3

I'm happy to announce that we have unanimously approved this release.

There are XXX approving votes, XXX of which are binding:
* approver 1
* approver 2
* approver 3
* approver 4

There are no disapproving votes.

Thanks everyone!

Checklist to proceed to the finalization step

1. Community votes to release the proposed candidate, with at least three approving PMC votes

Fix any issues

Any issues identified during the community review and vote should be fixed in this step.

Code changes should be proposed as standard pull requests to the master branch and reviewed using the normal contributing process. Then, relevant changes should be cherry-picked into the release branch. The cherry-pick commits should then be proposed as the pull requests against the release branch, again reviewed and merged using the normal contributing process.

Once all issues have been resolved, you should go back and build a new release candidate with these changes.

Checklist to proceed to the next step

1. Issues identified during vote have been resolved, with fixes committed to the release branch.

Finalize the release

Once the release candidate has been reviewed and approved by the community, the release should be finalized. This involves the final deployment of the release candidate to the release repositories, merging of the website changes, etc.

Deploy artifacts to Maven Central Repository

Use the Apache Nexus repository to release the staged binary artifacts to the Maven Central repository. In the Staging Repositories section, find the relevant release candidate orgapacheflink-XXX entry and click Release. Drop all other release candidates that are not being released.

Deploy source and binary releases to dist.apache.org

Copy the source and binary releases from the dev repository to the release repository at dist.apache.org using Subversion.

Git tag

Create a new Git tag for the released version by copying the tag for the final release candidate, as follows:

git tag -s “release-${VERSION}” ${TAG}

Merge website pull request

Merge the website pull request to list the release.

Mark the version as released in JIRA

In JIRA, inside version management, hover over the current release and a settings menu will appear. Click Release, and select today’s date.

Checklist to proceed to the next step

• Maven artifacts released and indexed in the Maven Central Repository
• Source distribution available in the release repository of dist.apache.org
• Source distribution removed from the dev repository of dist.apache.org
• Website pull request to list the release merged
• Release tagged in the source code repository
• Release version finalized in JIRA. (Note: Not all committers have administrator access to JIRA. If you end up getting permissions errors ask on the mailing list for assistance.)

Promote the release

Once the release has been finalized, the last step of the process is to promote the release within the project and beyond.

Apache mailing lists

Announce on the dev@ mailing list that the release has been finished.

Announce on the release on the user@ mailing list, listing major improvements and contributions.

Announce the release on the announce@apache.org mailing list.

Recordkeeping

Use reporter.apache.org to seed the information about the release into future project reports.

Flink blog

Major or otherwise important releases should have a blog post. Write one if needed for this particular release. Minor releases that don’t introduce new major functionality don’t necessarily need to be blogged.

Social media

Tweet, post on Facebook, LinkedIn, and other platforms. Ask other contributors to do the same.

Checklist to declare the process completed

1. Release announced on the user@ mailing list.
2. Blog post published, if applicable.
3. Release recorded in reporter.apache.org.
4. Release announced on social media.
5. Completion declared on the dev@ mailing list.
6. Update list of contributors wiki page with new contributors in the release
7. Update Homebrew: https://gist.github.com/EronWright/b62bd3b192a15be4c200a2542f7c9376
8. Update the reference Flink version in the japicmp maven plugin for the API stability checks to the just released major version.
9. Set show_outdated_warning: true in docs/_config.yml in the branch of the previous Flink version
10. Update stable and master alias in flink.conf found in https://svn.apache.org/repos/infra/infrastructure/buildbot/aegis/buildmaster/master1/projects
11. Update doc to "stable" in docs/_config.yml

Improve the process

It is important that we improve the release processes over time. Once you’ve finished the release, please take a step back and look what areas of this process and be improved. Perhaps some part of the process can be simplified. Perhaps parts of this guide can be clarified.

If we have specific ideas, please start a discussion on the dev@ mailing list and/or propose a pull request to update this guide. Thanks!