fix(telemetry): metrics overflow is logged as a warning rather than e…

…rror (#5287)

Signed-off-by: Benjamin Coenen <5719034+bnjjj@users.noreply.github.com>

.changesets/fix_bnjjj_fix_5173.md

@@ -0,0 +1,7 @@
+### Metrics overflow is logged as a warning rather than error ([Issue #5173](https://github.com/apollographql/router/issues/5173))
+
+If a metric has too high a cardinality the following warning will be displayed as a warning instead of an errorl:
+
+`OpenTelemetry metric error occurred: Metrics error: Warning: Maximum data points for metric stream exceeded/ Entry added to overflow`
+
+By [@bnjjj](https://github.com/bnjjj) in https://github.com/apollographql/router/pull/5287

apollo-router/src/plugins/telemetry/mod.rs

@@ -22,6 +22,7 @@ use http::StatusCode;
 use multimap::MultiMap;
 use once_cell::sync::OnceCell;
 use opentelemetry::global::GlobalTracerProvider;
+use opentelemetry::metrics::MetricsError;
 use opentelemetry::propagation::text_map_propagator::FieldIter;
 use opentelemetry::propagation::Extractor;
 use opentelemetry::propagation::Injector;
@@ -1799,7 +1800,13 @@ fn handle_error_internal<T: Into<opentelemetry::global::Error>>(
                 ::tracing::error!("OpenTelemetry trace error occurred: {}", err)
             }
             opentelemetry::global::Error::Metric(err) => {
-                ::tracing::error!("OpenTelemetry metric error occurred: {}", err)
+                if let MetricsError::Other(msg) = &err {
+                    if msg.contains("Warning") {
+                        ::tracing::warn!("OpenTelemetry metric warning occurred: {}", msg);
+                        return;
+                    }
+                }
+                ::tracing::error!("OpenTelemetry metric error occurred: {}", err);
             }
             opentelemetry::global::Error::Other(err) => {
                 ::tracing::error!("OpenTelemetry error occurred: {}", err)