Using current time for latency in performance tool

For interoperability between tools and processes.
Good enough for latency calculation in a performance tool.

Author: acogoluegnes

src/main/java/com/rabbitmq/stream/perf/DefaultPerformanceMetrics.java

@@ -187,12 +187,12 @@ public void start(String description) throws Exception {
     com.codahale.metrics.Timer latency = metricRegistry.getTimers().get(metricLatency);
 
     Function<Number, Number> convertDuration =
-        in -> in instanceof Long ? in.longValue() / 1000 : in.doubleValue() / 1000;
+        in -> in instanceof Long ? in.longValue() / 1_000_000 : in.doubleValue() / 1_000_000;
     Function<com.codahale.metrics.Timer, String> formatLatency =
         timer -> {
           Snapshot snapshot = timer.getSnapshot();
           return String.format(
-              "latency min/median/75th/95th/99th %.0f/%.0f/%.0f/%.0f/%.0f µs",
+              "latency min/median/75th/95th/99th %.0f/%.0f/%.0f/%.0f/%.0f ms",
               convertDuration.apply(snapshot.getMin()),
               convertDuration.apply(snapshot.getMedian()),
               convertDuration.apply(snapshot.get75thPercentile()),
@@ -261,7 +261,7 @@ public void start(String description) throws Exception {
           Function<com.codahale.metrics.Timer, String> formatLatencySummary =
               histogram ->
                   String.format(
-                      "latency 95th %.0f µs",
+                      "latency 95th %.0f ms",
                       convertDuration.apply(latency.getSnapshot().get95thPercentile()));
 
           StringBuilder builder = new StringBuilder("Summary: ");

src/main/java/com/rabbitmq/stream/perf/StreamPerfTest.java

@@ -664,7 +664,11 @@ public Integer call() throws Exception {
                         try {
                           while (true && !Thread.currentThread().isInterrupted()) {
                             rateLimiterCallback.run();
-                            long creationTime = System.nanoTime();
+                            // Using current time for interoperability with other tools
+                            // and also across different processes.
+                            // This is good enough to measure duration/latency this way
+                            // in a performance tool.
+                            long creationTime = System.currentTimeMillis();
                             byte[] payload = new byte[msgSize];
                             Utils.writeLong(payload, creationTime);
                             producer.send(
@@ -716,7 +720,9 @@ public Integer call() throws Exception {
                                 if (messageCount.incrementAndGet() % 100 == 0) {
                                   try {
                                     long time = Utils.readLong(message.getBodyAsBinary());
-                                    metrics.latency(System.nanoTime() - time, TimeUnit.NANOSECONDS);
+                                    // see above why we use current time to measure latency
+                                    metrics.latency(
+                                        System.currentTimeMillis() - time, TimeUnit.MILLISECONDS);
                                   } catch (Exception e) {
                                     // not able to read the body, maybe not a message from the tool
                                   }