# How to Create a Release of OpenCensus Java (for Maintainers Only)

## Build Environments

We deploy OpenCensus Java to Maven Central under the following systems:

-   Ubuntu 14.04

Other systems may also work, but we haven't verified them.

## Prerequisites

### Setup OSSRH and Signing

If you haven't deployed artifacts to Maven Central before, you need to setup
your OSSRH (OSS Repository Hosting) account and signing keys.

-   Follow the instructions on [this
    page](http://central.sonatype.org/pages/ossrh-guide.html) to set up an
    account with OSSRH.
    -   You only need to create the account, not set up a new project
    -   Contact a OpenCensus Java maintainer to add your account after you
        have created it.
-   (For release deployment only) [Install
    GnuPG](http://central.sonatype.org/pages/working-with-pgp-signatures.html#installing-gnupg)
    and [generate your key
    pair](http://central.sonatype.org/pages/working-with-pgp-signatures.html#generating-a-key-pair).
    You'll also need to [publish your public
    key](http://central.sonatype.org/pages/working-with-pgp-signatures.html#distributing-your-public-key)
    to make it visible to the Sonatype servers.
-   Put your GnuPG key password and OSSRH account information in
    `<your-home-directory>/.gradle/gradle.properties`:

    ```
    # You need the signing properties only if you are making release deployment
    signing.keyId=<8-character-public-key-id>
    signing.password=<key-password>
    signing.secretKeyRingFile=<your-home-directory>/.gnupg/secring.gpg

    ossrhUsername=<ossrh-username>
    ossrhPassword=<ossrh-password>
    checkstyle.ignoreFailures=false
    ```

## Tagging the Release

The first step in the release process is to create a release branch, bump
versions, and create a tag for the release. Our release branches follow the
naming convention of `v<major>.<minor>.x`, while the tags include the patch
version `v<major>.<minor>.<patch>`. For example, the same branch `v0.4.x` would
be used to create all `v0.4` tags (e.g. `v0.4.0`, `v0.4.1`).

In this section upstream repository refers to the main opencensus-java github
repository.

Before any push to the upstream repository you need to create a [personal access
token](https://help.github.com/articles/creating-a-personal-access-token-for-the-command-line/).

1.  Create the release branch and push it to GitHub:

    ```bash
    $ MAJOR=0 MINOR=4 PATCH=0 # Set appropriately for new release
    $ VERSION_FILES=(
      build.gradle
      examples/build.gradle
      examples/pom.xml
      api/src/main/java/io/opencensus/common/OpenCensusLibraryInformation.java
      exporters/metrics/ocagent/src/main/java/io/opencensus/exporter/metrics/ocagent/OcAgentNodeUtils.java
      exporters/trace/ocagent/src/main/java/io/opencensus/exporter/trace/ocagent/OcAgentNodeUtils.java
      examples/spring/servlet/build.gradle
      examples/spring/servlet/pom.xml
      )
    $ git checkout -b v$MAJOR.$MINOR.x master
    $ git push upstream v$MAJOR.$MINOR.x
    ```
    The branch will be automatically protected by the GitHub branch protection rule for release
    branches.

2.  For `master` branch:

    -   Change root build files to the next minor snapshot (e.g.
        `0.5.0-SNAPSHOT`).

    ```bash
    $ git checkout -b bump-version master
    # Change version to next minor (and keep -SNAPSHOT)
    $ sed -i 's/[0-9]\+\.[0-9]\+\.[0-9]\+\(.*CURRENT_OPENCENSUS_VERSION\)/'$MAJOR.$((MINOR+1)).0'\1/' \
      "${VERSION_FILES[@]}"
    $ ./gradlew build
    $ git commit -a -m "Start $MAJOR.$((MINOR+1)).0 development cycle"
    ```

    -   Go through PR review and push the master branch to GitHub:

    ```bash
    $ git checkout master
    $ git merge --ff-only bump-version
    $ git push upstream master
    ```

3.  For `vMajor.Minor.x` branch:

    -   Change root build files to remove "-SNAPSHOT" for the next release
        version (e.g. `0.4.0`). Commit the result and make a tag:

    ```bash
    $ git checkout -b release v$MAJOR.$MINOR.x
    # Change version to remove -SNAPSHOT
    $ sed -i 's/-SNAPSHOT\(.*CURRENT_OPENCENSUS_VERSION\)/\1/' "${VERSION_FILES[@]}"
    $ ./gradlew build
    $ git commit -a -m "Bump version to $MAJOR.$MINOR.$PATCH"
    $ git tag -a v$MAJOR.$MINOR.$PATCH -m "Version $MAJOR.$MINOR.$PATCH"
    ```

    -   Change root build files to the next snapshot version (e.g.
        `0.4.1-SNAPSHOT`). Commit the result:

    ```bash
    # Change version to next patch and add -SNAPSHOT
    $ sed -i 's/[0-9]\+\.[0-9]\+\.[0-9]\+\(.*CURRENT_OPENCENSUS_VERSION\)/'$MAJOR.$MINOR.$((PATCH+1))-SNAPSHOT'\1/' \
     "${VERSION_FILES[@]}"
    $ ./gradlew build
    $ git commit -a -m "Bump version to $MAJOR.$MINOR.$((PATCH+1))-SNAPSHOT"
    ```

    -   Go through PR review and push the release tag and updated release branch
        to GitHub (note: do not squash the commits when you merge otherwise you
        will lose the release tag):

    ```bash
    $ git checkout v$MAJOR.$MINOR.x
    $ git merge --ff-only release
    $ git push upstream v$MAJOR.$MINOR.$PATCH
    $ git push upstream v$MAJOR.$MINOR.x
    ```

## Deployment

Deployment to Maven Central (or the snapshot repo) is for all of the artifacts
from the project.

### Branch

Before building/deploying, be sure to switch to the appropriate tag. The tag
must reference a commit that has been pushed to the main repository, i.e., has
gone through code review. For the current release use:

```bash
$ git checkout -b v$MAJOR.$MINOR.$PATCH tags/v$MAJOR.$MINOR.$PATCH
```

### Building and Deploying

The following command will build the whole project and upload it to Maven
Central. Parallel building [is not safe during
uploadArchives](https://issues.gradle.org/browse/GRADLE-3420).

```bash
$ ./gradlew clean build && ./gradlew -Dorg.gradle.parallel=false uploadArchives
```

If the version has the `-SNAPSHOT` suffix, the artifacts will automatically go
to the snapshot repository. Otherwise it's a release deployment and the
artifacts will go to a staging repository.

When deploying a Release, the deployment will create [a new staging
repository](https://oss.sonatype.org/#stagingRepositories). You'll need to look
up the ID in the OSSRH UI (usually in the form of `opencensus-*`).

## Releasing on Maven Central

Once all of the artifacts have been pushed to the staging repository, the
repository must first be `closed`, which will trigger several sanity checks on
the repository. If this completes successfully, the repository can then be
`released`, which will begin the process of pushing the new artifacts to Maven
Central (the staging repository will be destroyed in the process). You can see
the complete process for releasing to Maven Central on the [OSSRH
site](http://central.sonatype.org/pages/releasing-the-deployment.html).

## Announcement

Once deployment is done, go to Github [release
page](https://github.com/census-instrumentation/opencensus-java/releases), press
`Draft a new release` to write release notes about the new release.

You can use `git log upstream/v$MAJOR.$((MINOR-1)).x..upstream/v$MAJOR.$MINOR.x --graph --first-parent`
or the Github [compare tool](https://github.com/census-instrumentation/opencensus-java/compare/)
to view a summary of all commits since last release as a reference. In addition, you can refer to 
[CHANGELOG.md](https://github.com/census-instrumentation/opencensus-java/blob/master/CHANGELOG.md)
for a list of major changes since last release.

Please pick major or important user-visible changes only.

## Update release versions in documentations and build files

After releasing is done, you need to update all readmes and examples to point to the
latest version.

1. Update README.md and gradle/maven build files on `master` branch:

```bash
$ git checkout -b bump-document-version master
$ BUILD_FILES=(
  examples/build.gradle
  examples/pom.xml
  )
$ README_FILES=(
  README.md
  contrib/appengine_standard_util/README.md
  contrib/dropwizard/README.md
  contrib/dropwizard5/README.md
  contrib/exemplar_util/README.md
  contrib/grpc_util/README.md
  contrib/http_jaxrs/README.md
  contrib/http_jetty_client/README.md
  contrib/http_servlet/README.md
  contrib/http_util/README.md
  contrib/log_correlation/log4j2/README.md
  contrib/log_correlation/stackdriver/README.md
  contrib/spring/README.md
  contrib/spring_sleuth_v1x/README.md
  contrib/zpages/README.md
  exporters/stats/prometheus/README.md
  exporters/stats/signalfx/README.md
  exporters/stats/stackdriver/README.md
  exporters/trace/datadog/README.md
  exporters/trace/elasticsearch/README.md
  exporters/trace/instana/README.md
  exporters/trace/logging/README.md
  exporters/trace/jaeger/README.md
  exporters/trace/ocagent/README.md
  exporters/trace/stackdriver/README.md
  exporters/trace/zipkin/README.md
  )
# Substitute versions in build files
$ sed -i 's/[0-9]\+\.[0-9]\+\.[0-9]\+\(.*LATEST_OPENCENSUS_RELEASE_VERSION\)/'$MAJOR.$MINOR.$PATCH'\1/' \
 "${BUILD_FILES[@]}"
# Substitute versions in build.gradle examples in README.md
$ sed -i 's/\(\(compile\|runtime\).\+io\.opencensus:.\+:\)[0-9]\+\.[0-9]\+\.[0-9]\+/\1'$MAJOR.$MINOR.$PATCH'/' \
 "${README_FILES[@]}"
# Substitute versions in maven pom examples in README.md
$ sed -i 's/\(<version>\)[0-9]\+\.[0-9]\+\.[0-9]\+/\1'$MAJOR.$MINOR.$PATCH'/' \
 "${README_FILES[@]}"
$ git commit -a -m "Update release versions for all readme and build files." 
```

2. Go through PR review and merge it to GitHub master branch.

3. In addition, create a PR to mark the new release in 
[CHANGELOG.md](https://github.com/census-instrumentation/opencensus-java/blob/master/CHANGELOG.md)
on master branch. Once that PR is merged, cherry-pick the commit and create another PR to the 
release branch (branch v$MAJOR.$MINOR.x).

## Patch Release
All patch releases should include only bug-fixes, and must avoid adding/modifying the public APIs.
To cherry-pick one commit use the following command:
```bash
$ COMMIT=1224f0a # Set the right commit hash.
$ git cherry-pick -x $COMMIT
```

## Known Issues

### Deployment for tag v0.5.0
To rebuild the releases on the tag v0.5.0 use:
```bash
$ ./gradlew clean build && ./gradlew uploadArchives
```

If option `-Dorg.gradle.parallel=false` is used, you will hit [this bug](https://issues.sonatype.org/browse/OSSRH-19485)
caused by [this bug](https://github.com/gradle/gradle/issues/1827) in gradle 3.5.