Machine-readable config description

.github/workflows/schema.yaml

@@ -0,0 +1,45 @@
+name: Schema
+
+on:
+  pull_request:
+    paths:
+      - schema/**
+      - docs/usage/configuration/config_documentation.md
+
+jobs:
+  validate-schema:
+    name: Ensure Synapse config schema is valid
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.x"
+      - name: Install check-jsonschema
+        run: pip install check-jsonschema
+
+      - name: Validate meta schema
+        run: check-jsonschema --check-metaschema schema/meta.schema.json
+      - name: Validate schema
+        run: check-jsonschema --schemafile=schema/meta.schema.json schema/synapse-config.schema.yaml
+      - name: Validate default config
+        run: echo "{}" | check-jsonschema --fill-defaults --schemafile=schema/synapse-config.schema.yaml -
+
+  check-doc-generation:
+    name: Ensure generated documentation is up-to-date
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.x"
+
+      - name: Regenerate config documentation
+        run: |
+          scripts-dev/gen_config_documentation.py \
+            schema/synapse-config.schema.yaml \
+          > docs/usage/configuration/config_documentation.md
+      - name: Log any differences
+        run: git diff
+      - name: Error in case of any differences
+        run: '! git status --porcelain=1 | grep "^ M"'

changelog.d/17892.doc

@@ -0,0 +1 @@
+Generate config documentation from JSON Schema file.

docs/usage/administration/admin_faq.md

@@ -255,7 +255,7 @@ line to `/etc/default/matrix-synapse`:
 
     LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libjemalloc.so.2
 
-*Note*: You may need to set `PYTHONMALLOC=malloc` to ensure that `jemalloc` can accurately calculate memory usage. By default, Python uses its internal small-object allocator, which may interfere with jemalloc's ability to track memory consumption correctly. This could prevent the [cache_autotuning](../configuration/config_documentation.md#caches-and-associated-values) feature from functioning as expected, as the Python allocator may not reach the memory threshold set by `max_cache_memory_usage`, thus not triggering the cache eviction process.
+*Note*: You may need to set `PYTHONMALLOC=malloc` to ensure that `jemalloc` can accurately calculate memory usage. By default, Python uses its internal small-object allocator, which may interfere with jemalloc's ability to track memory consumption correctly. This could prevent the [cache_autotuning](../configuration/config_documentation.md#caches) feature from functioning as expected, as the Python allocator may not reach the memory threshold set by `max_cache_memory_usage`, thus not triggering the cache eviction process.
 
 This made a significant difference on Python 2.7 - it's unclear how
 much of an improvement it provides on Python 3.x.