Disable legacy Prometheus metric names by default. They can still be re-enabled for now, but they will be removed altogether in Synapse 1.73.0. (#14353)

CHANGES.md

@@ -1,3 +1,12 @@
+Synapse (Next) (2022-11-01)
+=========================
+
+Please note that, as announced in the release notes for Synapse 1.69.0, legacy Prometheus metric names are now disabled by default.
+They will be removed altogether in Synapse 1.73.0.
+If not already done, server administrators should update their dashboards and alerting rules to avoid using the deprecated metric names.
+See the [upgrade notes](https://matrix-org.github.io/synapse/v1.71/upgrade.html#upgrading-to-v1710) for more details.
+
+
 Synapse 1.71.0rc1 (2022-11-01)
 ==============================
 

changelog.d/14353.removal

@@ -0,0 +1 @@
+Disable legacy Prometheus metric names by default. They can still be re-enabled for now, but they will be removed altogether in Synapse 1.73.0.

docs/upgrade.md

@@ -116,6 +116,22 @@ local users and some remote users is why the spec was changed/clarified and this
 caveat is no longer supported.
 
 
+## Legacy Prometheus metric names are now disabled by default
+
+Synapse v1.71.0 disables legacy Prometheus metric names by default.
+For administrators that still rely on them and have not yet had chance to update their
+uses of the metrics, it's still possible to specify `enable_legacy_metrics: true` in
+the configuration to re-enable them temporarily.
+
+Synapse v1.73.0 will **remove legacy metric names altogether** and at that point,
+it will no longer be possible to re-enable them.
+
+If you do not use metrics or you have already updated your Grafana dashboard(s),
+Prometheus console(s) and alerting rule(s), there is no action needed.
+
+See [v1.69.0: Deprecation of legacy Prometheus metric names](#deprecation-of-legacy-prometheus-metric-names).
+
+
 # Upgrading to v1.69.0
 
 ## Changes to the receipts replication streams

docs/usage/configuration/config_documentation.md

@@ -2441,8 +2441,8 @@ enable_metrics: true
 
 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.**
+Defaults to `false`. Has no effect if `enable_metrics` is `false`.
+**In Synapse v1.67.0 up to and including Synapse v1.70.1, this defaulted to `true`.**
 
 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;

synapse/config/metrics.py

@@ -43,7 +43,7 @@ class MetricsConfig(Config):
     def read_config(self, config: JsonDict, **kwargs: Any) -> None:
         self.enable_metrics = config.get("enable_metrics", False)
 
-        self.enable_legacy_metrics = config.get("enable_legacy_metrics", True)
+        self.enable_legacy_metrics = config.get("enable_legacy_metrics", False)
 
         self.report_stats = config.get("report_stats", None)
         self.report_stats_endpoint = config.get(