Add StatisticsCollector to Options for custom statistics tracking

src/main/java/io/nats/client/Options.java

@@ -227,6 +227,11 @@ public class Options {
      * {@link Builder#errorListener(ErrorListener) errorListener}.
      */
     public static final String PROP_ERROR_LISTENER = PFX + "callback.error";
+    /**
+     * Property used to configure a builder from a Properties object. {@value}, see
+     * {@link Builder#statisticsCollector(StatisticsCollector) statisticsCollector}.
+     */
+    public static final String PROP_STATISTICS_COLLECTOR = PFX + "statisticscollector";
     /**
      * Property used to configure a builder from a Properties object. {@value}, see {@link Builder#maxPingsOut(int) maxPingsOut}.
      */
@@ -556,6 +561,7 @@ public class Options {
 
     private final ErrorListener errorListener;
     private final ConnectionListener connectionListener;
+    private final StatisticsCollector statisticsCollector;
     private final String dataPortType;
 
     private final boolean trackAdvancedStats;
@@ -661,6 +667,7 @@ public static class Builder {
 
         private ErrorListener errorListener = null;
         private ConnectionListener connectionListener = null;
+        private StatisticsCollector statisticsCollector = null;
         private String dataPortType = DEFAULT_DATA_PORT_TYPE;
         private ExecutorService executor;
         private List<java.util.function.Consumer<HttpRequest>> httpRequestInterceptors;
@@ -762,6 +769,7 @@ public Builder properties(Properties props) {
 
             classnameProperty(props, PROP_ERROR_LISTENER, o -> this.errorListener = (ErrorListener) o);
             classnameProperty(props, PROP_CONNECTION_CB, o -> this.connectionListener = (ConnectionListener) o);
+            classnameProperty(props, PROP_STATISTICS_COLLECTOR, o -> this.statisticsCollector = (StatisticsCollector) o);
 
             stringProperty(props, PROP_DATA_PORT_TYPE, s -> this.dataPortType = s);
             stringProperty(props, PROP_INBOX_PREFIX, this::inboxPrefix);
@@ -1327,6 +1335,19 @@ public Builder connectionListener(ConnectionListener listener) {
             return this;
         }
 
+        /**
+         * Set the {@link StatisticsCollector StatisticsCollector} to collect connection metrics.
+         * <p>
+         * If not set, then a default implementation will be used.
+         *
+         * @param collector the new StatisticsCollector for this connection.
+         * @return the Builder for chaining
+         */
+        public Builder statisticsCollector(StatisticsCollector collector) {
+            this.statisticsCollector = collector;
+            return this;
+        }
+
         /**
          * Set the {@link ExecutorService ExecutorService} used to run threaded tasks. The default is a
          * cached thread pool that names threads after the connection name (or a default). This executor
@@ -1532,6 +1553,7 @@ else if (useDefaultTls) {
                     new SynchronousQueue<>(),
                     new DefaultThreadFactory(threadPrefix));
             }
+
             return new Options(this);
         }
 
@@ -1580,6 +1602,7 @@ public Builder(Options o) {
 
             this.errorListener = o.errorListener;
             this.connectionListener = o.connectionListener;
+            this.statisticsCollector = o.statisticsCollector;
             this.dataPortType = o.dataPortType;
             this.trackAdvancedStats = o.trackAdvancedStats;
             this.executor = o.executor;
@@ -1638,6 +1661,7 @@ private Options(Builder b) {
 
         this.errorListener = b.errorListener == null ? new ErrorListenerLoggerImpl() : b.errorListener;
         this.connectionListener = b.connectionListener;
+        this.statisticsCollector = b.statisticsCollector;
         this.dataPortType = b.dataPortType;
         this.trackAdvancedStats = b.trackAdvancedStats;
         this.executor = b.executor;
@@ -1689,6 +1713,13 @@ public ConnectionListener getConnectionListener() {
         return this.connectionListener;
     }
 
+    /**
+     * @return the statistics collector, or null, see {@link Builder#statisticsCollector(StatisticsCollector) statisticsCollector()} in the builder doc
+     */
+    public StatisticsCollector getStatisticsCollector() {
+        return this.statisticsCollector;
+    }
+
     /**
      * @return the auth handler, or null, see {@link Builder#authHandler(AuthHandler) authHandler()} in the builder doc
      */

src/main/java/io/nats/client/Statistics.java

@@ -20,33 +20,88 @@
  * <p>The Statistics toString() provides a summary of the statistics.
  */
 public interface Statistics {
+
+    /**
+     * @return the total number of pings that have been sent from this connection.
+     */
+    long getPings();
+
+    /**
+     * @return the total number of times this connection has tried to reconnect.
+     */
+    long getReconnects();
+
+    /**
+     * @return the total number of messages dropped by this connection across all slow consumers.
+     */
+    long getDroppedCount();
+
+    /**
+     * @return the total number of op +OKs received by this connection.
+     */
+    long getOKs();
+
+    /**
+     * @return the total number of op -ERRs received by this connection.
+     */
+    long getErrs();
+
+    /**
+     * @return the total number of exceptions seen by this connection.
+     */
+    long getExceptions();
+
+    /**
+     * @return the total number of requests sent by this connection.
+     */
+    long getRequestsSent();
+
+    /**
+     * @return the total number of replies received by this connection.
+     */
+    long getRepliesReceived();
+
+    /**
+     * @return the total number of duplicate replies received by this connection.
+     *
+     * NOTE: This is only counted if advanced stats are enabled.
+     */
+    long getDuplicateRepliesReceived();
+
+    /**
+     * @return the total number of orphan replies received by this connection.
+     *
+     * NOTE: This is only counted if advanced stats are enabled.
+     */
+    long getOrphanRepliesReceived();
+
     /**
      * @return the total number of messages that have come in to this connection.
      */
-    public long getInMsgs();
+    long getInMsgs();
 
     /**
      * @return the total number of messages that have gone out of this connection.
      */
-    public long getOutMsgs();
+    long getOutMsgs();
 
     /**
      * @return the total number of message bytes that have come in to this connection.
      */
-    public long getInBytes();
+    long getInBytes();
 
     /**
-     * @return the total number of message bytes that have gone out of to this connection.
+     * @return the total number of message bytes that have gone out of this connection.
      */
-    public long getOutBytes();
+    long getOutBytes();
 
     /**
-     * @return the total number of times this connection has tried to reconnect.
+     * @return the total number of outgoing message flushes by this connection.
      */
-    public long getReconnects();
+    long getFlushCounter();
 
     /**
-     * @return the total number of messages dropped by this connection across all slow consumers.
+     * @return the count of outstanding of requests from this connection.
      */
-    public long getDroppedCount();
+    long getOutstandingRequests();
 }

src/main/java/io/nats/client/StatisticsCollector.java

@@ -0,0 +1,131 @@
+// Copyright 2023 The NATS Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at:
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package io.nats.client;
+
+/**
+ * A collector for connection metrics.
+ * <p>
+ * Information about key metrics is incremented on this collector by the connection.
+ * <p>
+ * See {@link Statistics} for accessing the collected metrics.
+ */
+public interface StatisticsCollector extends Statistics {
+    /**
+     * Sets whether advanced stats are/should be tracked.
+     */
+    void setAdvancedTracking(boolean trackAdvanced);
+
+    /**
+     * Increments the total number of pings that have been sent from this connection.
+     */
+    void incrementPingCount();
+
+    /**
+     * Increments the total number of times this connection has tried to reconnect.
+     */
+    void incrementReconnects();
+
+    /**
+     * Increments the total number of messages dropped by this connection across all slow consumers.
+     */
+    void incrementDroppedCount();
+
+    /**
+     * Increments the total number of op +OKs received by this connection.
+     */
+    void incrementOkCount();
+
+    /**
+     * Increments the total number of op -ERRs received by this connection.
+     */
+    void incrementErrCount();
+
+    /**
+     * Increments the total number of exceptions seen by this connection.
+     */
+    void incrementExceptionCount();
+
+    /**
+     * Increments the total number of requests sent by this connection.
+     */
+    void incrementRequestsSent();
+
+    /**
+     * Increments the total number of replies received by this connection.
+     */
+    void incrementRepliesReceived();
+
+    /**
+     * Increments the total number of duplicate replies received by this connection.
+     * <p>
+     * NOTE: This is only counted if advanced stats are enabled.
+     */
+    void incrementDuplicateRepliesReceived();
+
+    /**
+     * Increments the total number of orphan replies received by this connection.
+     * <p>
+     * NOTE: This is only counted if advanced stats are enabled.
+     */
+    void incrementOrphanRepliesReceived();
+
+    /**
+     * Increments the total number of messages that have come in to this connection.
+     */
+    void incrementInMsgs();
+
+    /**
+     * Increments the total number of messages that have gone out of this connection.
+     */
+    void incrementOutMsgs();
+
+    /**
+     * Increment the total number of message bytes that have come in to this connection.
+     */
+    void incrementInBytes(long bytes);
+
+    /**
+     * Increment the total number of message bytes that have gone out of this connection.
+     */
+    void incrementOutBytes(long bytes);
+
+    /**
+     * Increment the total number of outgoing message flushes by this connection.
+     */
+    void incrementFlushCounter();
+
+    /**
+     * Increments the count of outstanding of requests from this connection.
+     */
+    void incrementOutstandingRequests();
+
+    /**
+     * Decrements the count of outstanding of requests from this connection.
+     */
+    void decrementOutstandingRequests();
+
+    /**
+     * Registers a Socket read by this connection.
+     * <p>
+     * NOTE: Implementations should only count this if advanced stats are enabled.
+     */
+    void registerRead(long bytes);
+
+    /**
+     * Registers a Socket write by this connection.
+     * <p>
+     * NOTE: Implementations should only count this if advanced stats are enabled.
+     */
+    void registerWrite(long bytes);
+}

src/main/java/io/nats/client/impl/NatsConnection.java

@@ -50,7 +50,7 @@ class NatsConnection implements Connection {
 
     private final Options options;
 
-    private final NatsStatistics statistics;
+    private final StatisticsCollector statistics;
 
     private boolean connecting; // you can only connect in one thread
     private boolean disconnecting; // you can only disconnect in one thread
@@ -111,7 +111,8 @@ class NatsConnection implements Connection {
         this.options = options;
 
         advancedTracking = options.isTrackAdvancedStats();
-        this.statistics = new NatsStatistics(advancedTracking);
+        this.statistics = options.getStatisticsCollector() == null ? new NatsStatistics() : options.getStatisticsCollector();
+        this.statistics.setAdvancedTracking(advancedTracking);
 
         this.statusLock = new ReentrantLock();
         this.statusChanged = this.statusLock.newCondition();
@@ -1231,11 +1232,12 @@ void deliverReply(Message msg) {
             statistics.incrementRepliesReceived();
         }
         else if (!oldStyle && !subject.startsWith(mainInbox)) {
-            if (advancedTracking && responsesRespondedTo.get(key) != null) {
-                statistics.incrementDuplicateRepliesReceived();
-            }
-            else {
-                statistics.incrementOrphanRepliesReceived();
+            if (advancedTracking) {
+                if (responsesRespondedTo.get(key) != null) {
+                    statistics.incrementDuplicateRepliesReceived();
+                } else {
+                    statistics.incrementOrphanRepliesReceived();
+                }
             }
         }
     }
@@ -1719,7 +1721,7 @@ public Statistics getStatistics() {
         return this.statistics;
     }
 
-    NatsStatistics getNatsStatistics() {
+    StatisticsCollector getNatsStatistics() {
         return this.statistics;
     }
 

src/main/java/io/nats/client/impl/NatsConnectionWriter.java

@@ -14,6 +14,7 @@
 package io.nats.client.impl;
 
 import io.nats.client.Options;
+import io.nats.client.StatisticsCollector;
 
 import java.io.IOException;
 import java.nio.BufferOverflowException;
@@ -108,7 +109,7 @@ Future<Boolean> stop() {
         return this.stopped;
     }
 
-    synchronized void sendMessageBatch(NatsMessage msg, DataPort dataPort, NatsStatistics stats)
+    synchronized void sendMessageBatch(NatsMessage msg, DataPort dataPort, StatisticsCollector stats)
         throws IOException {
 
         int sendPosition = 0;
@@ -167,7 +168,7 @@ public void run() {
 
         try {
             dataPort = this.dataPortFuture.get(); // Will wait for the future to complete
-            NatsStatistics stats = this.connection.getNatsStatistics();
+            StatisticsCollector stats = this.connection.getNatsStatistics();
             int maxAccumulate = Options.MAX_MESSAGES_IN_NETWORK_BUFFER;
 
             while (this.running.get()) {