simplify metrics to the reliable ones

Author: SylvainJuge

instrumentation/jmx-metrics/library/jetty.md

@@ -19,10 +19,8 @@ Those metrics require the following Jetty modules to be enabled : `jmx`, `http`,
 | jetty.thread.queue.size | UpDownCounter |               | The current job queue size                |
 | jetty.io.select.count   | Counter       |               | The number of select calls                |
 | jetty.session.count     | UpDownCounter | jetty.context | Current number of active sessions         |
-| jetty.session.count.max | Gauge         | jetty.context | Maximum number of active sessions (*)     |
 
 - `jetty.context` corresponds to the deployed application subfolder in `webapps` folder.
-- `jetty.session.count.max` metric produces unpredictable values when more than one `org.eclipse.jetty.session:context=*,type=defaultsessioncache,id=*` MBean is present, the default Jetty deployment includes a single one.
 
 ## Jetty 9 to 11
 
@@ -37,9 +35,6 @@ Those metrics require the following Jetty modules to be enabled : `jmx`, `http`
 | jetty.thread.queue.size     | UpDownCounter |               | The current job queue size                |
 | jetty.io.select.count       | Counter       |               | The number of select calls                |
 | jetty.session.created.count | Counter       | jetty.context | The total number of created sessions      |
-| jetty.session.duration.sum  | Gauge         | jetty.context | The cumulated session duration            |
-| jetty.session.duration.max  | Gauge         | jetty.context | The maximum session duration              |
-| jetty.session.duration.mean | Gauge         | jetty.context | The mean session duration                 |
+| jetty.session.duration.sum  | Counter       | jetty.context | The cumulated session duration            |
 
 - `jetty.context` corresponds to the deployed application subfolder in `webapps` folder.
-- `jetty.session.duration.sum`, `jetty.session.duration.max`, `jetty.session.duration.mean` metrics will produce unpredictable results when more than one `org.eclipse.jetty.server.session:context=*,type=sessionhandler,id=*` MBean is present, the default Jetty deployment includes a single one.

instrumentation/jmx-metrics/library/src/main/resources/jmx/rules/jetty.yaml

@@ -44,8 +44,9 @@ rules:
 
   # Session metrics for Jetty 12
   - bean: org.eclipse.jetty.session:context=*,type=defaultsessioncache,id=*
-    # usually a single mbean instance exists per context, thus the metric is aggregated: sum for counter,
-    # gauge metrics will return invalid (last-value) if more than one mbean instance exists.
+    # Usually a single mbean instance exists per context, thus the metric is aggregated: sum for counter,
+    # gauge metrics will return invalid (last-value) with more than 1 mbean instance, thus none
+    # is included in this provided configuration.
     prefix: jetty.session.
     unit: "{session}"
     metricAttribute:
@@ -57,17 +58,12 @@ rules:
         metric: count
         type: updowncounter
         desc: Current number of active sessions
-      # jetty.session.count.max
-      sessionsMax:
-        metric: count.max
-        # gauge because it can't be aggregated
-        type: gauge
-        desc: Maximum number of active sessions
 
   # Session metrics for Jetty 9 to 11
   - bean: org.eclipse.jetty.server.session:context=*,type=sessionhandler,id=*
-    # usually a single mbean instance exists per context, thus the metric is aggregated: sum for counter,
-    # gauge metrics will return invalid (last-value) if more than one mbean instance exists.
+    # Usually a single mbean instance exists per context, thus the metric is aggregated: sum for counter,
+    # gauge metrics will return invalid (last-value) with more than 1 mbean instance, thus none
+    # is included in this provided configuration.
     prefix: jetty.session.
     metricAttribute:
       # 'context' corresponds to the webapp context path
@@ -85,17 +81,3 @@ rules:
         unit: s
         type: counter
         desc: The cumulated session duration
-      # jetty.session.duration.max
-      sessionTimeMax:
-        metric: duration.max
-        unit: s
-        # gauge because it can't be aggregated
-        type: gauge
-        desc: The maximum session duration
-      # jetty.session.duration.mean
-      sessionTimeMean:
-        metric: duration.mean
-        unit: s
-        # gauge because it can't be aggregated
-        type: gauge
-        desc: The mean session duration

instrumentation/jmx-metrics/library/src/test/java/io/opentelemetry/instrumentation/jmx/rules/JettyIntegrationTest.java

@@ -128,23 +128,14 @@ private static MetricsVerifier createMetricsVerifier(int jettyMajorVersion) {
 
     AttributeMatcher contextAttribute = attributeWithAnyValue("jetty.context");
     if (jettyMajorVersion >= 12) {
-      verifier
-          .add(
-              "jetty.session.count",
-              metric ->
-                  metric
-                      .isUpDownCounter()
-                      .hasDescription("Current number of active sessions")
-                      .hasUnit("{session}")
-                      .hasDataPointsWithOneAttribute(contextAttribute))
-          .add(
-              "jetty.session.count.max",
-              metric ->
-                  metric
-                      .isGauge()
-                      .hasDescription("Maximum number of active sessions")
-                      .hasUnit("{session}")
-                      .hasDataPointsWithOneAttribute(contextAttribute));
+      verifier.add(
+          "jetty.session.count",
+          metric ->
+              metric
+                  .isUpDownCounter()
+                  .hasDescription("Current number of active sessions")
+                  .hasUnit("{session}")
+                  .hasDataPointsWithOneAttribute(contextAttribute));
     } else {
       verifier
           .add(
@@ -162,22 +153,6 @@ private static MetricsVerifier createMetricsVerifier(int jettyMajorVersion) {
                       .isCounter()
                       .hasDescription("The cumulated session duration")
                       .hasUnit("s")
-                      .hasDataPointsWithOneAttribute(contextAttribute))
-          .add(
-              "jetty.session.duration.max",
-              metric ->
-                  metric
-                      .isGauge()
-                      .hasDescription("The maximum session duration")
-                      .hasUnit("s")
-                      .hasDataPointsWithOneAttribute(contextAttribute))
-          .add(
-              "jetty.session.duration.mean",
-              metric ->
-                  metric
-                      .isGauge()
-                      .hasDescription("The mean session duration")
-                      .hasUnit("s")
                       .hasDataPointsWithOneAttribute(contextAttribute));
     }
     return verifier;