use Cow<'static, str>

core/src/layers/prometheus_client.rs

@@ -15,6 +15,7 @@
 // specific language governing permissions and limitations
 // under the License.
 
+use std::borrow::Cow;
 use std::fmt::Debug;
 use std::fmt::Formatter;
 use std::sync::Arc;
@@ -23,8 +24,6 @@ use std::time::Instant;
 
 use bytes::Buf;
 use futures::TryFutureExt;
-use prometheus_client::encoding::EncodeLabel;
-use prometheus_client::encoding::EncodeLabelSet;
 use prometheus_client::metrics::counter::Counter;
 use prometheus_client::metrics::family::Family;
 use prometheus_client::metrics::histogram;
@@ -115,31 +114,8 @@ impl<A: Access> Layer<A> for PrometheusClientLayer {
     }
 }
 
-type OperationLabels = [(&'static str, String); 4];
-// type ErrorLabels = [(&'static str, String); 5];
-
-#[derive(Debug, Clone, Hash, Eq, PartialEq)]
-pub struct ErrorLabels {
-    scheme: &'static str,
-    op: &'static str,
-    namespace: String,
-    root: String,
-    err: &'static str,
-}
-
-impl<'a> EncodeLabelSet for ErrorLabels {
-    fn encode(
-        &self,
-        mut encoder: prometheus_client::encoding::LabelSetEncoder,
-    ) -> std::result::Result<(), std::fmt::Error> {
-        ("scheme", self.scheme).encode(encoder.encode_label())?;
-        ("op", self.op).encode(encoder.encode_label())?;
-        ("namespace", self.namespace.as_str()).encode(encoder.encode_label())?;
-        ("root", self.root.as_str()).encode(encoder.encode_label())?;
-        ("err", self.err).encode(encoder.encode_label())?;
-        Ok(())
-    }
-}
+type OperationLabels = [(&'static str, Cow<'static, str>); 4];
+type ErrorLabels = [(&'static str, Cow<'static, str>); 5];
 
 /// [`PrometheusClientMetricDefinitions`] provide the definition about RED(Rate/Error/Duration) metrics with the `prometheus-client` crate.
 #[derive(Debug, Clone)]
@@ -213,32 +189,32 @@ impl PrometheusClientMetrics {
     }
 
     fn increment_errors_total(&self, op: &'static str, err: ErrorKind) {
-        let labels = ErrorLabels {
-            op: op,
-            err: err.into_static(),
-            scheme: self.scheme.into_static(),
-            root: self.root.clone(),
-            namespace: self.name.clone(),
-        };
+        let labels = [
+            ("scheme", self.scheme.into_static().into()),
+            ("op", op.into()),
+            ("error", err.into_static().into()),
+            ("namespace", self.name.clone().into()),
+            ("root", self.root.clone().into()),
+        ];
         self.metrics.errors_total.get_or_create(&labels).inc();
     }
 
     fn increment_request_total(&self, scheme: Scheme, op: &'static str) {
         let labels = [
-            ("scheme", scheme.to_string()),
-            ("op", op.to_string()),
-            ("namespace", self.name.to_string()),
-            ("root", self.root.to_string()),
+            ("scheme", scheme.into_static().into()),
+            ("op", op.into()),
+            ("namespace", self.name.clone().into()),
+            ("root", self.root.clone().into()),
         ];
         self.metrics.requests_total.get_or_create(&labels).inc();
     }
 
     fn observe_bytes_total(&self, scheme: Scheme, op: &'static str, bytes: usize) {
         let labels = [
-            ("scheme", scheme.to_string()),
-            ("op", op.to_string()),
-            ("namespace", self.name.to_string()),
-            ("root", self.root.to_string()),
+            ("scheme", scheme.into_static().into()),
+            ("op", op.into()),
+            ("namespace", self.name.clone().into()),
+            ("root", self.root.clone().into()),
         ];
         self.metrics
             .bytes_histogram
@@ -252,10 +228,10 @@ impl PrometheusClientMetrics {
 
     fn observe_request_duration(&self, scheme: Scheme, op: &'static str, duration: Duration) {
         let labels = [
-            ("scheme", scheme.to_string()),
-            ("op", op.to_string()),
-            ("namespace", self.name.to_string()),
-            ("root", self.root.to_string()),
+            ("scheme", scheme.into_static().into()),
+            ("op", op.into()),
+            ("namespace", self.name.clone().into()),
+            ("root", self.root.clone().into()),
         ];
         self.metrics
             .request_duration_seconds