ci: introduce towncrier to generate changelog from fragments by MikeGoldsmith · Pull Request #5187 · open-telemetry/opentelemetry-python

MikeGoldsmith · 2026-05-08T12:05:28Z

Description

Replace manual CHANGELOG.md editing with towncrier fragment-based changelog management. Each PR adds a small text file in .changelog/ instead of editing the changelog directly, eliminating merge conflicts.

This supersedes #4382 (PoC by @emdneto) — builds on that foundation with updates for current main, additional features informed by how pip, pytest, attrs, and Twisted use towncrier.

Fixes #4307
Fixes #4309

What changed

Core towncrier setup:

pyproject.toml: towncrier config with 5 fragment types (added, changed, deprecated, removed, fixed), pinned towncrier==25.8.0 in CI
scripts/changelog_template.j2: custom Jinja2 template matching existing changelog format
CHANGELOG.md:  marker added above existing ## Unreleased section; existing entries preserved as-is and can be migrated to fragments at the next release

CI & workflows:

.github/workflows/changelog.yml: rejects direct CHANGELOG.md edits, validates fragments exist via git diff, previews rendered changelog with towncrier build --draft
.github/workflows/prepare-release-branch.yml: sed replaced with towncrier build
.github/workflows/prepare-patch-release.yml: same + adds backport step to sync changelog to main

Documentation:

CONTRIBUTING.md: changelog section with style guidance (imperative tone, package prefix, <80 chars)
RELEASING.md: updated backporting section

Improvements over #4382

Added deprecated and removed categories (original only had added/changed/fixed)
Style guidance in CONTRIBUTING.md
towncrier added to dev dependency group
Updated bot references to otelbot[bot]
Based on current main (original PR was months stale)

Type of change

New feature (non-breaking change which adds functionality)
This change requires a documentation update

How Has This Been Tested?

towncrier build --draft --version "Unreleased" — verified fragment parsing and categorized output
towncrier build --yes --version "1.42.0/0.63b0" — verified full build inserts into CHANGELOG.md at marker, deletes fragments
Verified CI changelog preview step renders correctly

Does This PR Require a Contrib Repo Change?

Yes. — Link to PR: ci: introduce towncrier to generate changelog from fragments opentelemetry-python-contrib#4573

Checklist:

Followed the style guidelines of this project
Changelogs have been updated
Unit tests have been added
Documentation has been updated

linux-foundation-easycla · 2026-05-08T12:05:36Z

The committers listed above are authorized under a signed CLA.

✅ login: emdneto / name: Emídio Neto (f664c36)
✅ login: MikeGoldsmith / name: Mike Goldsmith (0bd5867, 21c4873, 5ddece8, 988c2e7, 9f096aa, b9306e7, f664c36, fd3eef6)

@emdneto

Replace manual CHANGELOG.md editing with towncrier fragment-based changelog management. Each PR adds a small text file in .changelog/ instead of editing the changelog directly, eliminating merge conflicts. Changes: - Add towncrier configuration in pyproject.toml with 5 fragment types (added, changed, deprecated, removed, fixed) - Replace sed-based changelog generation in release workflows with towncrier build - Add changelog backport step to patch release workflow - Update CI to use towncrier check for fragment validation - Add pre-commit check via scripts/check_changelog_fragment.py - Add tox environments: changelog (preview) and new-changelog (create) - Add contributor documentation in CONTRIBUTING.md - Convert existing unreleased entries to fragment files - Add custom Jinja2 template for changelog output Based on the proof-of-concept in open-telemetry#4382 by @emdneto. Co-authored-by: Emídio Neto <9735060+emdneto@users.noreply.github.com> Assisted-by: Claude Opus 4.6

Existing ## Unreleased entries stay in CHANGELOG.md — the towncrier marker is placed above them. Fragment migration can happen at the next release. Assisted-by: Claude Opus 4.6

- Regenerate misc.yml for new changelog/new-changelog tox envs - Update uv.lock for towncrier dependency - Apply ruff formatting to check_changelog_fragment.py Assisted-by: Claude Opus 4.6

emdneto

Awesome. Thanks for resurrecting this 👍🏻 Left some comments

aabmass · 2026-05-11T14:35:02Z

Awesome thanks Mike! I think we discussed it on slack but I can't remember the pro/cons of town crier vs chloggen.

@emdneto

Per review feedback from @emdneto: - Remove changelog/new-changelog tox envs (they generate CI jobs) - Remove pre-commit hook (not all PRs need changelog, PR number unknown at commit time) - Simplify CONTRIBUTING.md to document direct file creation - Regenerate misc.yml Assisted-by: Claude Opus 4.6

MikeGoldsmith · 2026-05-11T14:53:38Z

Awesome thanks Mike! I think we discussed it on slack but I can't remember the pro/cons of town crier vs chloggen.

Both tools solve the same problem in a similar way - they replace a single CHANGELOG.md that causes merge conflicts with per-PR fragment files that get compiled at release time.

	towncrier	chloggen
Language	Python (pip install)	Go binary
Fragment format	Plain text file	Structured YAML (change_type, component, note, issues, subtext)
File naming	`<PR#>.<type>`	Auto-generated from git branch name
Validation	`towncrier check` (branch-level)	`chloggen validate` (validates against component list)
Used by	pip, pytest, attrs, Twisted	OTel Collector, Collector Contrib
Install in CI	`pip install towncrier`	Requires Go toolchain or pre-built binary

I suggested Towncrier because it's built for use with with python projects, chloggen is a custom OTel tool used by the collector and requires a go binary.

Native to the Python ecosystem — pip install in CI, no Go toolchain needed
Simpler contributor experience — create a text file with one line, vs filling out a YAML template with multiple fields
Already widely adopted by major Python projects, so many contributors will already be familiar with the workflow
chloggen's component validation is valuable for collector-contrib (200+ components) but less useful for core Python where all packages release together

I'm not against chloggen, they are very similar. chloggen would tie back into more OTel and has a stricter fragment strucure which would be nice.

emdneto

I'm really happy to see that we now have an agreement on this!

My suggestion is we wait for the next release and prioritize merging this ASAP so we can start with a very fresh changelog, and you won't need to map every already merged PR to an entry here. Also, I believe we need at least the same setup for -contrib so the contributor experience is the same in both repos.

@aabmass

Per review feedback from @aabmass. Assisted-by: Claude Opus 4.6

…/towncrier-review

Assisted-by: Claude Opus 4.6

@aabmass

- Pin towncrier==25.8.0 for repeatability (per @aabmass) - Add preview step to print rendered changelog in CI (per @emdneto) - Fix error messages to reference CONTRIBUTING.md Assisted-by: Claude Opus 4.6

Remove references to manual ## Unreleased header requirements. Note that towncrier eliminates changelog merge conflicts during backports. Assisted-by: Claude Opus 4.6

@xrmx

Per feedback from @xrmx — no need to explain the old problem since it's already solved. Assisted-by: Claude Opus 4.6

MikeGoldsmith requested a review from a team as a code owner May 8, 2026 12:05

MikeGoldsmith added the Skip Changelog PRs that do not require a CHANGELOG.md entry label May 8, 2026

otelbot-python Bot added this to Python PR digest May 8, 2026

MikeGoldsmith force-pushed the mike/towncrier-review branch from 6d7185f to f664c36 Compare May 8, 2026 12:09

MikeGoldsmith added 2 commits May 8, 2026 13:19

keep existing unreleased entries, add marker above them

fd3eef6

Existing ## Unreleased entries stay in CHANGELOG.md — the towncrier marker is placed above them. Fragment migration can happen at the next release. Assisted-by: Claude Opus 4.6

fix CI: regenerate workflows, update uv.lock, format script

9f096aa

- Regenerate misc.yml for new changelog/new-changelog tox envs - Update uv.lock for towncrier dependency - Apply ruff formatting to check_changelog_fragment.py Assisted-by: Claude Opus 4.6

emdneto reviewed May 8, 2026

View reviewed changes

Comment thread tox.ini Outdated

Comment thread .pre-commit-config.yaml Outdated

Merge branch 'main' into mike/towncrier-review

21c4873

aabmass approved these changes May 11, 2026

View reviewed changes

Comment thread .github/workflows/changelog.yml Outdated

Comment thread CHANGELOG.md

Comment thread .github/workflows/prepare-release-branch.yml

Comment thread .github/workflows/prepare-patch-release.yml

emdneto approved these changes May 11, 2026

View reviewed changes

Comment thread .github/workflows/changelog.yml

MikeGoldsmith added 5 commits May 11, 2026 19:14

add do-not-edit comment to CHANGELOG.md

0bd5867

Per review feedback from @aabmass. Assisted-by: Claude Opus 4.6

Merge remote-tracking branch 'origin/mike/towncrier-review' into mike…

5ddece8

…/towncrier-review

update CHANGELOG.md do-not-edit comment to match attrs style

b9306e7

Assisted-by: Claude Opus 4.6

address review: pin towncrier version, add draft preview step

d5c2c7e

- Pin towncrier==25.8.0 for repeatability (per @aabmass) - Add preview step to print rendered changelog in CI (per @emdneto) - Fix error messages to reference CONTRIBUTING.md Assisted-by: Claude Opus 4.6

Merge remote-tracking branch 'upstream/main' into mike/towncrier-review

e1cc839

MikeGoldsmith mentioned this pull request May 12, 2026

ci: introduce towncrier to generate changelog from fragments open-telemetry/opentelemetry-python-contrib#4573

Merged

7 tasks

update RELEASING.md to reflect towncrier workflow

13fc770

Remove references to manual ## Unreleased header requirements. Note that towncrier eliminates changelog merge conflicts during backports. Assisted-by: Claude Opus 4.6

xrmx approved these changes May 12, 2026

View reviewed changes

Comment thread RELEASING.md Outdated

address review: drop towncrier explanation from RELEASING.md

c40c3b7

Per feedback from @xrmx — no need to explain the old problem since it's already solved. Assisted-by: Claude Opus 4.6

MikeGoldsmith moved this to Ready for merge in Python PR digest May 12, 2026

lzchen merged commit 5ccb54f into open-telemetry:main May 12, 2026
479 of 480 checks passed

github-project-automation Bot moved this from Ready for merge to Done in Python PR digest May 12, 2026

MikeGoldsmith deleted the mike/towncrier-review branch May 13, 2026 11:42

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ci: introduce towncrier to generate changelog from fragments#5187

ci: introduce towncrier to generate changelog from fragments#5187
lzchen merged 12 commits into
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Description

What changed

Improvements over #4382

Type of change

How Has This Been Tested?

Does This PR Require a Contrib Repo Change?

Checklist:

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