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Releases

CometBFT uses modified semantic versioning with each release following a vX.Y.Z format. CometBFT is currently on major version 0 and uses the minor version to signal breaking changes. The main branch is used for active development and thus it is not advisable to build against it.

The latest changes are always initially merged into main. Releases are specified using tags and are built from long-lived "backport" branches that are cut from main when the release process begins. Each release "line" (e.g. 0.34 or 0.33) has its own long-lived backport branch, and the backport branches have names like v0.34.x or v0.33.x (literally, x; it is not a placeholder in this case). CometBFT only maintains the last two releases at a time (the oldest release is predominantly just security patches).

Backporting

As non-breaking changes land on main, they should also be backported to these backport branches.

We use Mergify's backport feature to automatically backport to the needed branch. There should be a label for any backport branch that you'll be targeting. To notify the bot to backport a pull request, mark the pull request with the label corresponding to the correct backport branch. For example, to backport to v0.38.x, add the label S:backport-to-v0.38.x. Once the original pull request is merged, the bot will try to cherry-pick the pull request to the backport branch. If the bot fails to backport, it will open a pull request. The author of the original pull request is responsible for solving the conflicts and merging the pull request.

Creating a backport branch

If this is the first release candidate for a minor version release, e.g. v0.25.0, you get to have the honor of creating the backport branch!

Note that, after creating the backport branch, you'll also need to update the tags on main so that go mod is able to order the branches correctly. You should tag main with a "dev" tag that is "greater than" the backport branches tags. Otherwise, go mod does not 'know' whether commits on main come before or after the release.

In the following example, we'll assume that we're making a backport branch for the 0.38.x line.

  1. Start on main

  2. Ensure that there is a branch protection rule for the branch you are about to create (you will need admin access to the repository in order to do this).

  3. Create and push the backport branch:

    git checkout -b v0.38.x
git push origin v0.38.x

  4. Create a PR to update the documentation directory for the backport branch.

    We rewrite any URLs pointing to main to point to the backport branch, so that generated documentation will link to the correct versions of files elsewhere in the repository. The following files are to be excluded from this search:

    The following links are to always point to main, regardless of where they occur in the codebase:

    • https://github.com/cometbft/cometbft/blob/main/LICENSE

    Be sure to search for all of the following links and replace main with your corresponding branch label or version (e.g. v0.38.x or v0.38):

    • github.com/cometbft/cometbft/blob/main -> github.com/cometbft/cometbft/blob/v0.38.x
    • github.com/cometbft/cometbft/tree/main -> github.com/cometbft/cometbft/tree/v0.38.x
    • docs.cometbft.com/main -> docs.cometbft.com/v0.38

    Once you have updated all of the relevant documentation:

    # Create and push the PR.
git checkout -b update-docs-v038x
git commit -m "Update docs for v0.38.x backport branch."
git push -u origin update-docs-v038x

    Be sure to merge this PR before making other changes on the newly-created backport branch.

  5. Ensure that the RPC docs' version field in rpc/openapi/openapi.yaml has been updated from main to the backport branch version.

  6. Prepare the CometBFT documentation repository to build the release branch's version by updating the VERSIONS file.

After doing these steps, go back to main and do the following:

  1. Create a new workflow to run e2e nightlies for the new backport branch. (See e2e-nightly-main.yml for an example.)

  2. Add a new section to the Mergify config (.github/mergify.yml) to enable the backport bot to work on this branch, and add a corresponding backport-to-v0.38.x label so the bot can be triggered.

  3. Add a new section to the Dependabot config (.github/dependabot.yml) to enable automatic update of Go dependencies on this branch. Copy and edit one of the existing branch configurations to set the correct target-branch.

Pre-releases

Before creating an official release, especially a minor release, we may want to create an alpha or beta version, or release candidate (RC) for our friends and partners to test out. We use git tags to create pre-releases, and we build them off of backport branches, for example:

  • v0.38.0-alpha.1 - The first alpha release of v0.38.0. Subsequent alpha releases will be numbered v0.38.0-alpha.2, v0.38.0-alpha.3, etc.

    Alpha releases are to be considered the most unstable of pre-releases, and are most likely not yet properly QA'd. These are made available to allow early adopters to start integrating and testing new functionality before we're done with QA.

  • v0.38.0-beta.1 - The first beta release of v0.38.0. Subsequent beta releases will be numbered v0.38.0-beta.2, v0.38.0-beta.3, etc.

    Beta releases can be considered more stable than alpha releases in that we will have QA'd them better than alpha releases, but there still may be minor breaking API changes if users have strong demands for such changes.

  • v0.38.0-rc1 - The first release candidate (RC) of v0.38.0. Subsequent RCs will be numbered v0.38.0-rc2, v0.38.0-rc3, etc.

    RCs are considered more stable than beta releases in that we will have completed our QA on them. APIs will most likely be stable at this point. The difference between an RC and a release is that there may still be small changes (bug fixes, features) that may make their way into the series before cutting a final release.

(Note that branches and tags cannot have the same names, so it's important that these branches have distinct names from the tags/release names.)

If this is the first pre-release for a minor release, you'll have to make a new backport branch (see above). Otherwise:

  1. Start from the backport branch (e.g. v0.38.x).
  2. Run the integration tests and the E2E nightlies (which can be triggered from the GitHub UI; e.g., https://github.com/cometbft/cometbft/actions/workflows/e2e-manual.yml).
  3. Prepare the pre-release documentation:
    • Build the changelog with unclog without doing an unclog release, and commit the built changelog. This ensures that all changelog entries appear under an "Unreleased" heading in the pre-release's changelog. The changes are only considered officially "released" once we cut a regular (final) release.
    • Ensure that UPGRADING.md is up-to-date and includes notes on any breaking changes or other upgrading flows.
  4. Prepare the versioning:
    • Bump TMVersionDefault version in version.go
    • Bump P2P and block protocol versions in version.go, if necessary. Check the changelog for breaking changes in these components.
    • Bump ABCI protocol version in version.go, if necessary
  5. Open a PR with these changes against the backport branch.
  6. Once these changes have landed on the backport branch, be sure to pull them back down locally.
  7. Once you have the changes locally, create the new tag, specifying a name and a tag "message": git tag -a v0.38.0-rc1 -m "Release Candidate v0.38.0-rc1
  8. Push the tag back up to origin: git push origin v0.38.0-rc1 Now the tag should be available on the repo's releases page.
  9. Future pre-releases will continue to be built off of this branch.

Minor release

This minor release process assumes that this release was preceded by release candidates. If there were no release candidates, begin by creating a backport branch, as described above.

Before performing these steps, be sure the Minor Release Checklist has been completed.

  1. Start on the backport branch (e.g. v0.38.x)
  2. Run integration tests (make test_integrations) and the e2e nightlies.
  3. Prepare the release:
    • Do a release with unclog for the desired version, ensuring that you write up a good summary of the major highlights of the release that users would be interested in.
    • Build the changelog using unclog, and commit the built changelog.
    • Ensure that UPGRADING.md is up-to-date and includes notes on any breaking changes or other upgrading flows.
    • Bump TMVersionDefault version in version.go
    • Bump P2P and block protocol versions in version.go, if necessary
    • Bump ABCI protocol version in version.go, if necessary
  4. Open a PR with these changes against the backport branch.
  5. Once these changes are on the backport branch, push a tag with prepared release details. This will trigger the actual release v0.38.0.
    • git tag -a v0.38.0 -m 'Release v0.38.0'
    • git push origin v0.38.0
  6. Make sure that main is updated with the latest CHANGELOG.md, CHANGELOG_PENDING.md, and UPGRADING.md.

Patch release

Patch releases are done differently from minor releases: They are built off of long-lived backport branches, rather than from main. As non-breaking changes land on main, they should also be backported into these backport branches.

Patch releases don't have release candidates by default, although any tricky changes may merit a release candidate.

To create a patch release:

  1. Checkout the long-lived backport branch: git checkout v0.38.x
  2. Run integration tests (make test_integrations) and the nightlies.
  3. Check out a new branch and prepare the release:
    • Do a release with unclog for the desired version, ensuring that you write up a good summary of the major highlights of the release that users would be interested in.
    • Build the changelog using unclog, and commit the built changelog.
    • Bump the TMDefaultVersion in version.go
    • Bump the ABCI version number, if necessary. (Note that ABCI follows semver, and that ABCI versions are the only versions which can change during patch releases, and only field additions are valid patch changes.)
  4. Open a PR with these changes that will land them back on v0.38.x
  5. Once this change has landed on the backport branch, make sure to pull it locally, then push a tag.
    • git tag -a v0.38.1 -m 'Release v0.38.1'
    • git push origin v0.38.1
  6. Create a pull request back to main with the CHANGELOG & version changes from the latest release.
    • Remove all R:patch labels from the pull requests that were included in the release.
    • Do not merge the backport branch into main.

Minor Release Checklist

The following set of steps are performed on all releases that increment the minor version, e.g. v0.25 to v0.26. These steps ensure that CometBFT is well tested, stable, and suitable for adoption by the various diverse projects that rely on CometBFT.

Feature Freeze

Ahead of any minor version release of CometBFT, the software enters 'Feature Freeze' for at least two weeks. A feature freeze means that no new features are added to the code being prepared for release. No code changes should be made to the code being released that do not directly improve pressing issues of code quality. The following must not be merged during a feature freeze:

  • Refactors that are not related to specific bug fixes.
  • Dependency upgrades.
  • New test code that does not test a discovered regression.
  • New features of any kind.
  • Documentation or spec improvements that are not related to the newly developed code.

This period directly follows the creation of the backport branch. The CometBFT team instead directs all attention to ensuring that the existing code is stable and reliable. Broken tests are fixed, flakey-tests are remedied, end-to-end test failures are thoroughly diagnosed and all efforts of the team are aimed at improving the quality of the code. During this period, the upgrade harness tests are run repeatedly and a variety of in-house testnets are run to ensure CometBFT functions at the scale it will be used by application developers and node operators.

Nightly End-To-End Tests

The CometBFT team maintains a set of end-to-end tests that run each night on the latest commit of the project and on the code in the tip of each supported backport branch. These tests start a network of containerized CometBFT processes and run automated checks that the network functions as expected in both stable and unstable conditions. During the feature freeze, these tests are run nightly and must pass consistently for a release of CometBFT to be considered stable.

Upgrade Harness

The CometBFT team is creating an upgrade test harness to exercise the workflow of stopping an instance of CometBFT running one version of the software and starting up the same application running the next version. To support upgrade testing, we will add the ability to terminate the CometBFT process at specific pre-defined points in its execution so that we can verify upgrades work in a representative sample of stop conditions.

Large Scale Testnets

The CometBFT end-to-end tests run a small network (~10s of nodes) to exercise basic consensus interactions. Real world deployments of CometBFT often have over a hundred nodes just in the validator set, with many others acting as full nodes and sentry nodes. To gain more assurance before a release, we will also run larger-scale test networks to shake out emergent behaviors at scale.

Large-scale test networks are run on a set of virtual machines (VMs). Each VM is equipped with 4 Gigabytes of RAM and 2 CPU cores. The network runs a very simple key-value store application. The application adds artificial delays to different ABCI calls to simulate a slow application. Each testnet is briefly run with no load being generated to collect a baseline performance. Once baseline is captured, a consistent load is applied across the network. This load takes the form of 10% of the running nodes all receiving a consistent stream of two hundred transactions per minute each.

During each test net, the following metrics are monitored and collected on each node:

  • Consensus rounds per height
  • Maximum connected peers, Minimum connected peers, Rate of change of peer connections
  • Memory resident set size
  • CPU utilization
  • Blocks produced per minute
  • Seconds for each step of consensus (Propose, Prevote, Precommit, Commit)
  • Latency to receive block proposals

For these tests we intentionally target low-powered host machines (with low core counts and limited memory) to ensure we observe similar kinds of resource contention and limitation that real-world deployments of CometBFT experience in production.

200 Node Testnet

To test the stability and performance of CometBFT in a real world scenario, a 200 node test network is run. The network comprises 5 seed nodes, 175 validators and 20 non-validating full nodes. All nodes begin by dialing a subset of the seed nodes to discover peers. The network is run for several days, with metrics being collected continuously. In cases of changes to performance critical systems, testnets of larger sizes should be considered.

Rotating Node Testnet

Real-world deployments of CometBFT frequently see new nodes arrive and old nodes exit the network. The rotating node testnet ensures that CometBFT is able to handle this reliably. In this test, a network with 10 validators and 3 seed nodes is started. A rolling set of 25 full nodes are started and each connects to the network by dialing one of the seed nodes. Once the node is able to blocksync to the head of the chain and begins producing blocks using consensus it is stopped. Once stopped, a new node is started and takes its place. This network is run for several days.

Vote-extension Testnet

CometBFT v0.38.0 introduced vote-extensions, which are added as the name suggests, to precommit votes sent by validators. The Vote-extension Testnet is used to determine how vote-extensions affect the performance of CometBFT, under various settings. The application used in the experiment is the same used on the (#200-node-testnet), but is configured differently to gauge de effects of varying vote extension sizes. In the (#200-node-testnet) the application extends pre-commit votes with a 64 bit number encoded with variable compression. In the Vote-extension Testnet, pre-commit votes are extended with a non-compressed extension of configurable size. Experiments are run with multiple sizes to determine their impact and, for comparison sake, we include a run with the same settings as in the (#200-node-testnet).

The testnet consists of 175 validators, 20 non-validator full-nodes, and 5 seed nodes. All 195 full-nodes begin by dialing a subset of the seed nodes to discover peers. Once all full-nodes are started, a 5 minute period is waited before starting an experiment. For each experiment, the load generators issue requests at a constant rate during 150 seconds, then wait for 5 minutes to allow the system to quiesce, then repeat the load generation; the load generation step is repeated 5 times for each experiment.

Network Partition Testnet

CometBFT is expected to recover from network partitions. A partition where no subset of the nodes is left with the super-majority of the stake is expected to stop making blocks. Upon alleviation of the partition, the network is expected to once again become fully connected and capable of producing blocks. The network partition testnet ensures that CometBFT is able to handle this reliably at scale. In this test, a network with 100 validators and 95 full nodes is started. All validators have equal stake. Once the network is producing blocks, a set of firewall rules is deployed to create a partitioned network with 50% of the stake on one side and 50% on the other. Once the network stops producing blocks, the firewall rules are removed and the nodes are monitored to ensure they reconnect and that the network again begins producing blocks.

Absent Stake Testnet

CometBFT networks often run with some portion of the voting power offline. The absent stake testnet ensures that large networks are able to handle this reliably. A set of 150 validator nodes and three seed nodes is started. The set of 150 validators is configured to only possess a cumulative stake of 67% of the total stake. The remaining 33% of the stake is configured to belong to a validator that is never actually run in the test network. The network is run for multiple days, ensuring that it is able to produce blocks without issue.