Add developer documentation for the Federation Sender and add a documentation mechanism using Sphinx. (#15265)
Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>
This commit is contained in:
reivilibre
GitHub
parent
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commit
d5324ee111
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@ -35,9 +35,9 @@ sed -i \
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# compatible (as far the package metadata declares, anyway); pip's package resolver
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# is more lax.
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#
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# Rather than `poetry install --no-dev`, we drop all dev dependencies from the
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# toml file. This means we don't have to ensure compatibility between old deps and
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# dev tools.
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# Rather than `poetry install --no-dev`, we drop all dev dependencies and the dev-docs
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# group from the toml file. This means we don't have to ensure compatibility between
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# old deps and dev tools.
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pip install toml wheel
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@ -47,6 +47,7 @@ with open('pyproject.toml', 'r') as f:
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data = toml.loads(f.read())
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del data['tool']['poetry']['dev-dependencies']
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del data['tool']['poetry']['group']['dev-docs']
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with open('pyproject.toml', 'w') as f:
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toml.dump(data, f)
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@ -13,25 +13,10 @@ on:
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workflow_dispatch:
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jobs:
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pages:
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name: GitHub Pages
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pre:
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name: Calculate variables for GitHub Pages deployment
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runs-on: ubuntu-latest
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steps:
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- uses: actions/checkout@v3
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- name: Setup mdbook
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uses: peaceiris/actions-mdbook@adeb05db28a0c0004681db83893d56c0388ea9ea # v1.2.0
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with:
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mdbook-version: '0.4.17'
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- name: Build the documentation
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# mdbook will only create an index.html if we're including docs/README.md in SUMMARY.md.
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# However, we're using docs/README.md for other purposes and need to pick a new page
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# as the default. Let's opt for the welcome page instead.
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run: |
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mdbook build
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cp book/welcome_and_overview.html book/index.html
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# Figure out the target directory.
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#
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# The target directory depends on the name of the branch
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@ -55,11 +40,65 @@ jobs:
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# finally, set the 'branch-version' var.
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echo "branch-version=$branch" >> "$GITHUB_OUTPUT"
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outputs:
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branch-version: ${{ steps.vars.outputs.branch-version }}
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################################################################################
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pages-docs:
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name: GitHub Pages
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runs-on: ubuntu-latest
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needs:
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- pre
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steps:
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- uses: actions/checkout@v3
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- name: Setup mdbook
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uses: peaceiris/actions-mdbook@adeb05db28a0c0004681db83893d56c0388ea9ea # v1.2.0
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with:
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mdbook-version: '0.4.17'
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- name: Build the documentation
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# mdbook will only create an index.html if we're including docs/README.md in SUMMARY.md.
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# However, we're using docs/README.md for other purposes and need to pick a new page
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# as the default. Let's opt for the welcome page instead.
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run: |
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mdbook build
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cp book/welcome_and_overview.html book/index.html
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# Deploy to the target directory.
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- name: Deploy to gh pages
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uses: peaceiris/actions-gh-pages@bd8c6b06eba6b3d25d72b7a1767993c0aeee42e7 # v3.9.2
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with:
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github_token: ${{ secrets.GITHUB_TOKEN }}
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publish_dir: ./book
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destination_dir: ./${{ steps.vars.outputs.branch-version }}
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destination_dir: ./${{ needs.pre.outputs.branch-version }}
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################################################################################
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pages-devdocs:
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name: GitHub Pages (developer docs)
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runs-on: ubuntu-latest
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needs:
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- pre
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steps:
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- uses: action/checkout@v3
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- name: "Set up Sphinx"
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uses: matrix-org/setup-python-poetry@v1
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with:
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python-version: "3.x"
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poetry-version: "1.3.2"
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groups: "dev-docs"
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extras: ""
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- name: Build the documentation
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run: |
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cd dev-docs
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poetry run make html
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# Deploy to the target directory.
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- name: Deploy to gh pages
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uses: peaceiris/actions-gh-pages@bd8c6b06eba6b3d25d72b7a1767993c0aeee42e7 # v3.9.2
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with:
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github_token: ${{ secrets.GITHUB_TOKEN }}
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publish_dir: ./dev-docs/_build/html
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destination_dir: ./dev-docs/${{ needs.pre.outputs.branch-version }}
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@ -53,6 +53,7 @@ __pycache__/
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/coverage.*
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/dist/
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/docs/build/
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/dev-docs/_build/
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/htmlcov
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/pip-wheel-metadata/
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@ -0,0 +1 @@
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Add developer documentation for the Federation Sender and add a documentation mechanism using Sphinx.
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@ -0,0 +1,20 @@
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# Minimal makefile for Sphinx documentation
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#
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# You can set these variables from the command line, and also
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# from the environment for the first two.
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SPHINXOPTS ?=
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SPHINXBUILD ?= sphinx-build
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SOURCEDIR = .
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BUILDDIR = _build
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# Put it first so that "make" without argument is like "make help".
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help:
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@$(SPHINXBUILD) -M help "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
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.PHONY: help Makefile
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# Catch-all target: route all unknown targets to Sphinx using the new
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# "make mode" option. $(O) is meant as a shortcut for $(SPHINXOPTS).
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%: Makefile
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@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
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@ -0,0 +1,50 @@
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# Configuration file for the Sphinx documentation builder.
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#
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# For the full list of built-in configuration values, see the documentation:
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# https://www.sphinx-doc.org/en/master/usage/configuration.html
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# -- Project information -----------------------------------------------------
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# https://www.sphinx-doc.org/en/master/usage/configuration.html#project-information
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project = "Synapse development"
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copyright = "2023, The Matrix.org Foundation C.I.C."
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author = "The Synapse Maintainers and Community"
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# -- General configuration ---------------------------------------------------
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# https://www.sphinx-doc.org/en/master/usage/configuration.html#general-configuration
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extensions = [
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"autodoc2",
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"myst_parser",
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]
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templates_path = ["_templates"]
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exclude_patterns = ["_build", "Thumbs.db", ".DS_Store"]
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# -- Options for Autodoc2 ----------------------------------------------------
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autodoc2_docstring_parser_regexes = [
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# this will render all docstrings as 'MyST' Markdown
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(r".*", "myst"),
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]
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autodoc2_packages = [
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{
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"path": "../synapse",
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# Don't render documentation for everything as a matter of course
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"auto_mode": False,
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},
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]
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# -- Options for MyST (Markdown) ---------------------------------------------
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# myst_heading_anchors = 2
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# -- Options for HTML output -------------------------------------------------
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# https://www.sphinx-doc.org/en/master/usage/configuration.html#options-for-html-output
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html_theme = "furo"
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html_static_path = ["_static"]
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@ -0,0 +1,22 @@
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.. Synapse Developer Documentation documentation master file, created by
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sphinx-quickstart on Mon Mar 13 08:59:51 2023.
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You can adapt this file completely to your liking, but it should at least
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contain the root `toctree` directive.
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Welcome to the Synapse Developer Documentation!
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===========================================================
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.. toctree::
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:maxdepth: 2
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:caption: Contents:
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modules/federation_sender
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Indices and tables
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==================
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* :ref:`genindex`
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* :ref:`modindex`
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* :ref:`search`
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@ -0,0 +1,5 @@
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Federation Sender
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=================
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```{autodoc2-docstring} synapse.federation.sender
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```
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File diff suppressed because it is too large
Load Diff
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@ -350,6 +350,18 @@ towncrier = ">=18.6.0rc1"
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# Used for checking the Poetry lockfile
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tomli = ">=1.2.3"
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# Dependencies for building the development documentation
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[tool.poetry.group.dev-docs]
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optional = true
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[tool.poetry.group.dev-docs.dependencies]
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sphinx = {version = "^6.1", python = "^3.8"}
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sphinx-autodoc2 = {version = "^0.4.2", python = "^3.8"}
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myst-parser = {version = "^1.0.0", python = "^3.8"}
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furo = "^2022.12.7"
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[build-system]
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# The upper bounds here are defensive, intended to prevent situations like
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# #13849 and #14079 where we see buildtime or runtime errors caused by build
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@ -91,6 +91,7 @@ else
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"synapse" "docker" "tests"
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"scripts-dev"
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"contrib" "synmark" "stubs" ".ci"
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"dev-docs"
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)
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fi
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fi
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@ -11,6 +11,119 @@
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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The Federation Sender is responsible for sending Persistent Data Units (PDUs)
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and Ephemeral Data Units (EDUs) to other homeservers using
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the `/send` Federation API.
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## How do PDUs get sent?
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The Federation Sender is made aware of new PDUs due to `FederationSender.notify_new_events`.
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When the sender is notified about a newly-persisted PDU that originates from this homeserver
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and is not an out-of-band event, we pass the PDU to the `_PerDestinationQueue` for each
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remote homeserver that is in the room at that point in the DAG.
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### Per-Destination Queues
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There is one `PerDestinationQueue` per 'destination' homeserver.
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The `PerDestinationQueue` maintains the following information about the destination:
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- whether the destination is currently in [catch-up mode (see below)](#catch-up-mode);
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- a queue of PDUs to be sent to the destination; and
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- a queue of EDUs to be sent to the destination (not considered in this section).
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Upon a new PDU being enqueued, `attempt_new_transaction` is called to start a new
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transaction if there is not already one in progress.
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### Transactions and the Transaction Transmission Loop
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Each federation HTTP request to the `/send` endpoint is referred to as a 'transaction'.
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The body of the HTTP request contains a list of PDUs and EDUs to send to the destination.
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The *Transaction Transmission Loop* (`_transaction_transmission_loop`) is responsible
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for emptying the queued PDUs (and EDUs) from a `PerDestinationQueue` by sending
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them to the destination.
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There can only be one transaction in flight for a given destination at any time.
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(Other than preventing us from overloading the destination, this also makes it easier to
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reason about because we process events sequentially for each destination.
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This is useful for *Catch-Up Mode*, described later.)
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The loop continues so long as there is anything to send. At each iteration of the loop, we:
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- dequeue up to 50 PDUs (and up to 100 EDUs).
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- make the `/send` request to the destination homeserver with the dequeued PDUs and EDUs.
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- if successful, make note of the fact that we succeeded in transmitting PDUs up to
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the given `stream_ordering` of the latest PDU by
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- if unsuccessful, back off from the remote homeserver for some time.
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If we have been unsuccessful for too long (when the backoff interval grows to exceed 1 hour),
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the in-memory queues are emptied and we enter [*Catch-Up Mode*, described below](#catch-up-mode).
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### Catch-Up Mode
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When the `PerDestinationQueue` has the catch-up flag set, the *Catch-Up Transmission Loop*
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(`_catch_up_transmission_loop`) is used in lieu of the regular `_transaction_transmission_loop`.
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(Only once the catch-up mode has been exited can the regular tranaction transmission behaviour
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be resumed.)
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*Catch-Up Mode*, entered upon Synapse startup or once a homeserver has fallen behind due to
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connection problems, is responsible for sending PDUs that have been missed by the destination
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homeserver. (PDUs can be missed because the `PerDestinationQueue` is volatile — i.e. resets
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on startup — and it does not hold PDUs forever if `/send` requests to the destination fail.)
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The catch-up mechanism makes use of the `last_successful_stream_ordering` column in the
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`destinations` table (which gives the `stream_ordering` of the most recent successfully
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sent PDU) and the `stream_ordering` column in the `destination_rooms` table (which gives,
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for each room, the `stream_ordering` of the most recent PDU that needs to be sent to this
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destination).
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Each iteration of the loop pulls out 50 `destination_rooms` entries with the oldest
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`stream_ordering`s that are greater than the `last_successful_stream_ordering`.
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In other words, from the set of latest PDUs in each room to be sent to the destination,
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the 50 oldest such PDUs are pulled out.
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These PDUs could, in principle, now be directly sent to the destination. However, as an
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optimisation intended to prevent overloading destination homeservers, we instead attempt
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to send the latest forward extremities so long as the destination homeserver is still
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eligible to receive those.
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This reduces load on the destination **in aggregate** because all Synapse homeservers
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will behave according to this principle and therefore avoid sending lots of different PDUs
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at different points in the DAG to a recovering homeserver.
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*This optimisation is not currently valid in rooms which are partial-state on this homeserver,
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since we are unable to determine whether the destination homeserver is eligible to receive
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the latest forward extremities unless this homeserver sent those PDUs — in this case, we
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just send the latest PDUs originating from this server and skip this optimisation.*
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Whilst PDUs are sent through this mechanism, the position of `last_successful_stream_ordering`
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is advanced as normal.
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Once there are no longer any rooms containing outstanding PDUs to be sent to the destination
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*that are not already in the `PerDestinationQueue` because they arrived since Catch-Up Mode
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was enabled*, Catch-Up Mode is exited and we return to `_transaction_transmission_loop`.
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#### A note on failures and back-offs
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If a remote server is unreachable over federation, we back off from that server,
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with an exponentially-increasing retry interval.
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Whilst we don't automatically retry after the interval, we prevent making new attempts
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until such time as the back-off has cleared.
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Once the back-off is cleared and a new PDU or EDU arrives for transmission, the transmission
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loop resumes and empties the queue by making federation requests.
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If the backoff grows too large (> 1 hour), the in-memory queue is emptied (to prevent
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unbounded growth) and Catch-Up Mode is entered.
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It is worth noting that the back-off for a remote server is cleared once an inbound
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request from that remote server is received (see `notify_remote_server_up`).
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At this point, the transaction transmission loop is also started up, to proactively
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send missed PDUs and EDUs to the destination (i.e. you don't need to wait for a new PDU
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or EDU, destined for that destination, to be created in order to send out missed PDUs and
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EDUs).
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"""
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import abc
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import logging
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Loading…
Reference in New Issue