Add calculation of metrics changes since previous snapshot

- Move metric diff calculation to TransportMetrics.Snapshot.
- Remove TransportMetrics.reset() and use changesSince() instead in EchoTest.
- Remove unnecessary volatile modifier on JrtMetrics.previousSnapshot.
- Initialize JrtMetrics.previousSnapshot in constructor.
- Use separate field declarations for fields in TransportMetrics.Snapshot.

1 files changed, 9 insertions, 18 deletions

diff --git a/container-disc/src/main/java/com/yahoo/container/jdisc/metric/JrtMetrics.java b/container-disc/src/main/java/com/yahoo/container/jdisc/metric/JrtMetrics.java
index 6bebaedc28b..1fff1b2ab33 100644
--- a/container-disc/src/main/java/com/yahoo/container/jdisc/metric/JrtMetrics.java
+++ b/container-disc/src/main/java/com/yahoo/container/jdisc/metric/JrtMetrics.java
@@ -4,9 +4,7 @@ package com.yahoo.container.jdisc.metric;
 import com.yahoo.jdisc.Metric;
 import com.yahoo.jrt.TransportMetrics;
 
-import java.util.function.ToLongFunction;
-
-import static com.yahoo.jrt.TransportMetrics.*;
+import static com.yahoo.jrt.TransportMetrics.Snapshot;
 
 /**
  * Emits jrt metrics
@@ -17,7 +15,7 @@ class JrtMetrics {
 
     private final TransportMetrics transportMetrics = TransportMetrics.getInstance();
     private final Metric metric;
-    private volatile Snapshot previousSnapshot;
+    private Snapshot previousSnapshot = transportMetrics.snapshot();
 
     JrtMetrics(Metric metric) {
         this.metric = metric;
@@ -25,20 +23,13 @@ class JrtMetrics {
 
     void emitMetrics() {
         Snapshot snapshot = transportMetrics.snapshot();
-        increment("jrt.transport.tls-certificate-verification-failures", Snapshot::tlsCertificateVerificationFailures, snapshot);
-        increment("jrt.transport.peer-authorization-failures", Snapshot::peerAuthorizationFailures, snapshot);
-        increment("jrt.transport.server.tls-connections-established", Snapshot::serverTlsConnectionsEstablished, snapshot);
-        increment("jrt.transport.client.tls-connections-established", Snapshot::clientTlsConnectionsEstablished, snapshot);
-        increment("jrt.transport.server.unencrypted-connections-established", Snapshot::serverUnencryptedConnectionsEstablished, snapshot);
-        increment("jrt.transport.client.unencrypted-connections-established", Snapshot::clientUnencryptedConnectionsEstablished, snapshot);
+        Snapshot changesSincePrevious = snapshot.changesSince(previousSnapshot);
+        metric.add("jrt.transport.tls-certificate-verification-failures", changesSincePrevious.tlsCertificateVerificationFailures(), null);
+        metric.add("jrt.transport.peer-authorization-failures", changesSincePrevious.peerAuthorizationFailures(), null);
+        metric.add("jrt.transport.server.tls-connections-established", changesSincePrevious.serverTlsConnectionsEstablished(), null);
+        metric.add("jrt.transport.client.tls-connections-established", changesSincePrevious.clientTlsConnectionsEstablished(), null);
+        metric.add("jrt.transport.server.unencrypted-connections-established", changesSincePrevious.serverUnencryptedConnectionsEstablished(), null);
+        metric.add("jrt.transport.client.unencrypted-connections-established", changesSincePrevious.clientUnencryptedConnectionsEstablished(), null);
         previousSnapshot = snapshot;
     }
-
-    private void increment(String metricName, ToLongFunction<Snapshot> metricGetter, Snapshot snapshot) {
-        long currentValue = metricGetter.applyAsLong(snapshot);
-        long increment = previousSnapshot != null
-                ? currentValue - metricGetter.applyAsLong(previousSnapshot)
-                : currentValue;
-        metric.add(metricName, increment, null);
-    }
 }