# Releases

Tendermint uses modified [semantic versioning](https://semver.org/) with each
release following a `vX.Y.Z` format. Tendermint 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). Tendermint 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](https://mergify.io/features/backports) 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 v0.35.x, add the label
`S:backport-to-v0.35.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. See [#6072](https://github.com/tendermint/tendermint/pull/6072)
for more context.

In the following example, we'll assume that we're making a backport branch for
the 0.35.x line.

1. Start on `main`

2. Create and push the backport branch:
   ```sh
   git checkout -b v0.35.x
   git push origin v0.35.x
   ```

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

   We only maintain RFC and ADR documents on main, to avoid confusion. In
   addition, we rewrite Markdown 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. For context on the latter, see
   https://github.com/tendermint/tendermint/issues/7675.

   To prepare the PR:
   ```sh
   # Remove the RFC and ADR documents from the backport.
   # We only maintain these on main to avoid confusion.
   git rm -r docs/rfc docs/architecture

   # Update absolute links to point to the backport.
   go run ./scripts/linkpatch -recur -target v0.35.x -skip-path docs/DOCS_README.md,docs/README.md docs

   # Create and push the PR.
   git checkout -b update-docs-v035x
   git commit -m "Update docs for v0.35.x backport branch." docs
   git push -u origin update-docs-v035x
   ```

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

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

1. Tag `main` as the dev branch for the _next_ minor version release and push
   it up to GitHub.
   For example:
   ```sh
   git tag -a v0.36.0-dev -m "Development base for Tendermint v0.36."
   git push origin v0.36.0-dev
   ```

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

3. 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 `S:backport-to-v0.35.x`
   [label](https://github.com/tendermint/tendermint/labels) so the bot can be triggered.

4. 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`.

[e2e]: https://github.com/tendermint/tendermint/blob/main/.github/workflows/e2e-nightly-main.yml

## Release candidates

Before creating an official release, especially a minor release, we may want to
create a release candidate (RC) for our friends and partners to test out. We use
git tags to create RCs, and we build them off of backport branches.

Tags for RCs should follow the "standard" release naming conventions, with
`-rcX` at the end (for example, `v0.35.0-rc0`).

(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 RC for a minor release, you'll have to make a new backport
branch (see above). Otherwise:

1. Start from the backport branch (e.g. `v0.35.x`).
2. Run the integration tests and the e2e nightlies
   (which can be triggered from the Github UI;
   e.g., https://github.com/tendermint/tendermint/actions/workflows/e2e-nightly-34x.yml).
3. Prepare the changelog:
   - Move the changes included in `CHANGELOG_PENDING.md` into `CHANGELOG.md`. Each RC should have
     it's own changelog section. These will be squashed when the final candidate is released.
   - Run `python ./scripts/linkify_changelog.py CHANGELOG.md` to add links for
     all PRs
   - 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.
     Check the changelog for breaking changes in these components.
   - Bump ABCI protocol version in `version.go`, if necessary
4. Open a PR with these changes against the backport branch.
5. Once these changes have landed on the backport branch, be sure to pull them back down locally.
6. Once you have the changes locally, create the new tag, specifying a name and a tag "message":
   `git tag -a v0.35.0-rc0 -m "Release Candidate v0.35.0-rc0`
7. Push the tag back up to origin:
   `git push origin v0.35.0-rc0`
   Now the tag should be available on the repo's releases page.
8. Future RCs will continue to be built off of this branch.

Note that this process should only be used for "true" RCs -- release candidates
that, if successful, will be the next release. For more experimental "RCs,"
create a new, short-lived branch and tag that instead.

## 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](#minor-release-checklist) has been completed.

1. Start on the backport branch (e.g. `v0.35.x`)
2. Run integration tests (`make test_integrations`) and the e2e nightlies.
3. Prepare the release:
   - "Squash" changes from the changelog entries for the RCs into a single entry,
      and add all changes included in `CHANGELOG_PENDING.md`.
      (Squashing includes both combining all entries, as well as removing or simplifying
      any intra-RC changes. It may also help to alphabetize the entries by package name.)
   - Run `python ./scripts/linkify_changelog.py CHANGELOG.md` to add links for
     all PRs
   - 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 `v0.35.0`.
   - `git tag -a v0.35.0 -m 'Release v0.35.0'`
   - `git push origin v0.35.0`
6. Make sure that `main` is updated with the latest `CHANGELOG.md`, `CHANGELOG_PENDING.md`, and `UPGRADING.md`.
7. Add the release to the documentation site generator config (see
   [DOCS_README.md](./docs/DOCS_README.md) for more details). In summary:
   - Start on branch `main`.
   - Add a new line at the bottom of [`docs/versions`](./docs/versions) to
     ensure the newest release is the default for the landing page.
   - Add a new entry to `themeConfig.versions` in
     [`docs/.vuepress/config.js`](./docs/.vuepress/config.js) to include the
	 release in the dropdown versions menu.
   - Commit these changes to `main` and backport them into the backport
     branch for this release.

## 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 v0.35.x`
2. Run integration tests (`make test_integrations`) and the nightlies.
3. Check out a new branch and prepare the release:
   - Copy `CHANGELOG_PENDING.md` to top of `CHANGELOG.md`
   - Run `python ./scripts/linkify_changelog.py CHANGELOG.md` to add links for all issues
   - Run `bash ./scripts/authors.sh` to get a list of authors since the latest release, and add the GitHub aliases of external contributors to the top of the CHANGELOG. To lookup an alias from an email, try `bash ./scripts/authors.sh <email>`
   - Reset the `CHANGELOG_PENDING.md`
   - 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 `v0.35.x`
5. Once this change has landed on the backport branch, make sure to pull it locally, then push a tag.
   - `git tag -a v0.35.1 -m 'Release v0.35.1'`
   - `git push origin v0.35.1`
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 Tendermint is well
tested, stable, and suitable for adoption by the various diverse projects that
rely on Tendermint.

### Feature Freeze

Ahead of any minor version release of Tendermint, 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](#creating-a-backport-branch). The Tendermint 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 Tendermint
functions at the scale it will be used by application developers and node
operators.

### Nightly End-To-End Tests

The Tendermint team maintains [a set of end-to-end
tests](https://github.com/tendermint/tendermint/blob/main/test/e2e/README.md#L1)
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 Tendermint 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
Tendermint to be considered stable.

### Upgrade Harness

> TODO(williambanfield): Change to past tense and clarify this section once
> upgrade harness is complete.

The Tendermint team is creating an upgrade test harness to exercise the workflow
of stopping an instance of Tendermint 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 Tendermint 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 Tendermint end-to-end tests run a small network (~10s of nodes) to exercise
basic consensus interactions. Real world deployments of Tendermint 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 Tendermint experience in production.

#### 200 Node Testnet

To test the stability and performance of Tendermint in a real world scenario,
a 200 node test network is run. The network comprises 5 seed nodes, 100
validators and 95 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 Tendermint frequently see new nodes arrive and old
nodes exit the network. The rotating node testnet ensures that Tendermint 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
Tendermint consensus it is stopped. Once stopped, a new node is started and
takes its place. This network is run for several days.

#### Network Partition Testnet

Tendermint 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 Tendermint 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

Tendermint 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.