Announce that legacy metric names are deprecated, will be turned off by default in Synapse v1.71.0 and removed altogether in Synapse v1.73.0. (#14024)

1 files changed, 25 insertions, 0 deletions

diff --git a/docs/usage/configuration/config_documentation.md b/docs/usage/configuration/config_documentation.md
index f46b4932fd..5e40166ff5 100644
--- a/docs/usage/configuration/config_documentation.md
+++ b/docs/usage/configuration/config_documentation.md
@@ -2436,6 +2436,31 @@ Example configuration:
 enable_metrics: true
 ```
 ---
+### `enable_legacy_metrics`
+
+Set to `true` to publish both legacy and non-legacy Prometheus metric names,
+or to `false` to only publish non-legacy Prometheus metric names.
+Defaults to `true`. Has no effect if `enable_metrics` is `false`.
+**In Synapse v1.71.0, this will default to `false` before being removed in Synapse v1.73.0.**
+
+Legacy metric names include:
+- metrics containing colons in the name, such as `synapse_util_caches_response_cache:hits`, because colons are supposed to be reserved for user-defined recording rules;
+- counters that don't end with the `_total` suffix, such as `synapse_federation_client_sent_edus`, therefore not adhering to the OpenMetrics standard.
+
+These legacy metric names are unconventional and not compliant with OpenMetrics standards.
+They are included for backwards compatibility.
+
+Example configuration:
+```yaml
+enable_legacy_metrics: false
+```
+
+See https://github.com/matrix-org/synapse/issues/11106 for context.
+
+*Since v1.67.0.*
+
+**Will be removed in v1.73.0.**
+---
 ### `sentry`
 
 Use this option to enable sentry integration. Provide the DSN assigned to you by sentry