OVN Release Process

This document describes the process ordinarily used for OVN development and release. Exceptions are sometimes necessary, so all of the statements here should be taken as subject to change through rough consensus of OVN contributors, obtained through public discussion on, e.g., ovs-dev or the #openvswitch IRC channel.

Release Strategy

OVN feature development takes place on the “master” branch. Ordinarily, new features are rebased against master and applied directly. For features that take significant development, sometimes it is more appropriate to merge a separate branch into master; please discuss this on ovs-dev in advance.

The process of making a release has the following stages. See Release Scheduling for the timing of each stage:

  1. “Soft freeze” of the master branch.

    During the freeze, we ask committers to refrain from applying patches that add new features unless those patches were already being publicly discussed and reviewed before the freeze began. Bug fixes are welcome at any time. Please propose and discuss exceptions on ovs-dev.

  2. Fork a release branch from master, named for the expected release number, e.g. “branch-2019.10” for the branch that will yield OVN 2019.10.x.

    Release branches are intended for testing and stabilization. At this stage and in later stages, they should receive only bug fixes, not new features. Bug fixes applied to release branches should be backports of corresponding bug fixes to the master branch, except for bugs present only on release branches (which are rare in practice).

    At this stage, sometimes there can be exceptions to the rule that a release branch receives only bug fixes. Like bug fixes, new features on release branches should be backports of the corresponding commits on the master branch. Features to be added to release branches should be limited in scope and risk and discussed on ovs-dev before creating the branch.

  3. When committers come to rough consensus that the release is ready, they release the .0 release on its branch, e.g. 2019.10.0 for branch-2019.10. To make the actual release, a committer pushes a signed tag named, e.g. v2019.10.0, to the OVN repository, makes a release tarball available on openvswitch.org, and posts a release announcement to ovs-announce.

  4. As bug fixes accumulate, or after important bugs or vulnerabilities are fixed, committers may make additional releases from a branch: 2019.10.1, 2019.10.2, and so on. The process is the same for these additional release as for a .0 release.

At most two release branches are formally maintained at any given time: the latest release and the latest release designed as LTS. An LTS release is one that the OVN project has designated as being maintained for a longer period of time. Currently, an LTS release is maintained until the next LTS is chosen. There is not currently a strict guideline on how often a new LTS release is chosen, but so far it has been about every 2 years. That could change based on the current state of OVN development. For example, we do not want to designate a new release as LTS that includes disruptive internal changes, as that may make it harder to support for a longer period of time. Discussion about choosing the next LTS release occurs on the OVS development mailing list.

Release Numbering

The version number on master should normally end in .90. This indicates that the OVN version is “almost” the next version to branch.

Forking master into branch-x.y requires two commits to master. The first is titled “Prepare for x.y.0” and increments the version number to x.y. This is the initial commit on branch-x.y. The second is titled “Prepare for post-x.y.0 (x.y.90)” and increments the version number to x.y.90.

The version number on a release branch is x.y.z, where x is the current year, y is the month of the release, and z is initially 0. Making a release requires two commits. The first is titled Set release dates for x.y.z. and updates NEWS and debian/changelog to specify the release date of the new release. This commit is the one made into a tarball and tagged. The second is titled Prepare for x.y.(z+1). and increments the version number and adds a blank item to NEWS with an unspecified date.

Release Scheduling

OVN makes releases at the following three-month cadence. All dates are approximate:

Time (months) Example Dates Stage
T Dec 1, Mar 1, … Begin x.y release cycle
T + 2 Feb 1, May 1, … “Soft freeze” master for x.y release
T + 2.5 Feb 15, May 15, … Fork branch-x.y from master
T + 3 Mar 1, Jun 1, … Release version x.y.0

Release Calendar

The 2020 timetable is shown below. Note that these dates are not set in stone. If extenuating circumstances arise, a release may be delayed from its target date.

Release Soft Freeze Branch Creation Release
20.12.0 Nov 6 Nov 20 Dec 4

Below is the 2021 timetable

Release Soft Freeze Branch Creation Release
21.03.0 Feb 5 Feb 19 Mar 5
21.06.0 May 7 May 21 Jun 4
21.09.0 Aug 6 Aug 20 Sep 3
21.12.0 Nov 5 Nov 19 Dec 3

Contact

Use dev@openvswitch.org to discuss the OVN development and release process.