fix: improve error handling and update temporality logic

Enhanced error messages with specific names and differentiated warnings. Updated temporality method for Prometheus to always return cumulative temporality, aligning with Prometheus behavior.

Author: kudlatyamroth

opentelemetry-prometheus/src/lib.rs

@@ -97,7 +97,7 @@
 #![cfg_attr(test, deny(warnings))]
 
 use once_cell::sync::{Lazy, OnceCell};
-use opentelemetry::{otel_error, InstrumentationScope, Key, Value};
+use opentelemetry::{otel_error, otel_warn, InstrumentationScope, Key, Value};
 use opentelemetry_sdk::{
     metrics::{
         data::{self, ResourceMetrics},
@@ -165,8 +165,10 @@ impl MetricReader for PrometheusExporter {
         self.reader.shutdown()
     }
 
-    fn temporality(&self, kind: InstrumentKind) -> Temporality {
-        self.reader.temporality(kind)
+    /// Note: Prometheus only supports cumulative temporality, so this will always be
+    /// [Temporality::Cumulative].
+    fn temporality(&self, _kind: InstrumentKind) -> Temporality {
+        Temporality::Cumulative
     }
 }
 
@@ -274,7 +276,7 @@ impl prometheus::core::Collector for Collector {
             Ok(guard) => guard,
             Err(err) => {
                 otel_error!(
-                    name: "OpenTelemetry error occurred.",
+                    name: "OpenTelemetryPrometheus.AcquireLockError",
                     message = err.to_string(),
                 );
                 return Vec::new();
@@ -287,7 +289,7 @@ impl prometheus::core::Collector for Collector {
         };
         if let Err(err) = self.reader.collect(&mut metrics) {
             otel_error!(
-                name: "OpenTelemetry metrics error occurred.",
+                name: "OpenTelemetryPrometheus.ReaderError",
                 message = err.to_string(),
             );
             return vec![];
@@ -419,16 +421,18 @@ fn validate_metrics(
 ) -> (bool, Option<String>) {
     if let Some(existing) = mfs.get(name) {
         if existing.get_field_type() != metric_type {
-            otel_error!(
-                name: "OpenTelemetry metrics error occurred.",
-                message = format!("Instrument type conflict, using existing type definition. Instrument {name}, Existing: {:?}, dropped: {:?}", existing.get_field_type(), metric_type).as_str(),
+            otel_warn!(
+                name: "OpenTelemetryPrometheus.MetricValidation",
+                message = "Instrument type conflict, using existing type definition",
+                metric_type = format!("Instrument {name}, Existing: {:?}, dropped: {:?}", existing.get_field_type(), metric_type).as_str(),
             );
             return (true, None);
         }
         if existing.get_help() != description {
-            otel_error!(
-                name: "OpenTelemetry metrics error occurred.",
-                message = format!("Instrument description conflict, using existing. Instrument {name}, Existing: {:?}, dropped: {:?}", existing.get_help().to_string(), description.to_string()).as_str(),
+            otel_warn!(
+                name: "OpenTelemetryPrometheus.MetricValidation",
+                message = "Instrument description conflict, using existing",
+                metric_description = format!("Instrument {name}, Existing: {:?}, dropped: {:?}", existing.get_help().to_string(), description.to_string()).as_str(),
             );
             return (false, Some(existing.get_help().to_string()));
         }