Finished adding histogram and finished connection pool metrics

Zhen · Zhen · commit 0b33ab4c953c · 2018-02-15T17:28:45.000Z
diff --git a/driver/src/main/java/org/neo4j/driver/internal/DriverFactory.java b/driver/src/main/java/org/neo4j/driver/internal/DriverFactory.java
@@ -38,7 +38,7 @@
 import org.neo4j.driver.internal.cluster.loadbalancing.LoadBalancingStrategy;
 import org.neo4j.driver.internal.cluster.loadbalancing.RoundRobinLoadBalancingStrategy;
 import org.neo4j.driver.internal.logging.NettyLogging;
-import org.neo4j.driver.internal.metrics.DriverMetricsHandler;
+import org.neo4j.driver.internal.metrics.DriverMetricsListener;
 import org.neo4j.driver.internal.metrics.InternalAbstractDriverMetrics;
 import org.neo4j.driver.internal.metrics.InternalDriverMetrics;
 import org.neo4j.driver.internal.retry.ExponentialBackoffRetryLogic;
@@ -94,7 +94,7 @@ public final Driver newInstance( URI uri, AuthToken authToken, RoutingSettings r
         return driver;
     }
 
-    protected ConnectionPool createConnectionPool( AuthToken authToken, SecurityPlan securityPlan, Bootstrap bootstrap, DriverMetricsHandler metrics, Config config )
+    protected ConnectionPool createConnectionPool( AuthToken authToken, SecurityPlan securityPlan, Bootstrap bootstrap, DriverMetricsListener metrics, Config config )
     {
         Clock clock = createClock();
         ConnectionSettings settings = new ConnectionSettings( authToken, config.connectionTimeoutMillis() );
diff --git a/driver/src/main/java/org/neo4j/driver/internal/async/pool/ConnectionPoolImpl.java b/driver/src/main/java/org/neo4j/driver/internal/async/pool/ConnectionPoolImpl.java
@@ -36,9 +36,8 @@
 import org.neo4j.driver.internal.BoltServerAddress;
 import org.neo4j.driver.internal.async.ChannelConnector;
 import org.neo4j.driver.internal.async.NettyConnection;
-import org.neo4j.driver.internal.metrics.DriverMetricsHandler;
+import org.neo4j.driver.internal.metrics.DriverMetricsListener;
 import org.neo4j.driver.internal.metrics.ListenerEvent;
-import org.neo4j.driver.internal.metrics.SimpleTimerListenerEvent;
 import org.neo4j.driver.internal.spi.Connection;
 import org.neo4j.driver.internal.spi.ConnectionPool;
 import org.neo4j.driver.internal.util.Clock;
@@ -56,19 +55,19 @@ public class ConnectionPoolImpl implements ConnectionPool
     private final PoolSettings settings;
     private final Clock clock;
     private final Logger log;
-    private DriverMetricsHandler driverMetrics;
+    private DriverMetricsListener driverMetrics;
 
     private final ConcurrentMap<BoltServerAddress,ChannelPool> pools = new ConcurrentHashMap<>();
     private final AtomicBoolean closed = new AtomicBoolean();
 
     public ConnectionPoolImpl( ChannelConnector connector, Bootstrap bootstrap, PoolSettings settings,
-            DriverMetricsHandler metricsHandler, Logging logging, Clock clock )
+            DriverMetricsListener metricsHandler, Logging logging, Clock clock )
     {
         this( connector, bootstrap, new NettyChannelTracker( metricsHandler, logging ), settings, metricsHandler, logging, clock );
     }
 
     ConnectionPoolImpl( ChannelConnector connector, Bootstrap bootstrap, NettyChannelTracker nettyChannelTracker,
-            PoolSettings settings, DriverMetricsHandler driverMetrics, Logging logging, Clock clock )
+            PoolSettings settings, DriverMetricsListener driverMetrics, Logging logging, Clock clock )
     {
         this.connector = connector;
         this.bootstrap = bootstrap;
@@ -85,11 +84,10 @@ public CompletionStage<Connection> acquire( BoltServerAddress address )
     {
         log.trace( "Acquiring a connection from pool towards %s", address );
 
-        // TODO no need to init if no driver metrics
-        ListenerEvent acquireEvent = new SimpleTimerListenerEvent();
-
         assertNotClosed();
         ChannelPool pool = getOrCreatePool( address );
+
+        ListenerEvent acquireEvent = driverMetrics.createListenerEvent();
         driverMetrics.beforeAcquiring( address, acquireEvent );
         Future<Channel> connectionFuture = pool.acquire();
 
diff --git a/driver/src/main/java/org/neo4j/driver/internal/async/pool/NettyChannelTracker.java b/driver/src/main/java/org/neo4j/driver/internal/async/pool/NettyChannelTracker.java
@@ -26,7 +26,7 @@
 import java.util.concurrent.atomic.AtomicInteger;
 
 import org.neo4j.driver.internal.BoltServerAddress;
-import org.neo4j.driver.internal.metrics.DriverMetricsHandler;
+import org.neo4j.driver.internal.metrics.DriverMetricsListener;
 import org.neo4j.driver.v1.Logger;
 import org.neo4j.driver.v1.Logging;
 
@@ -37,9 +37,9 @@ public class NettyChannelTracker implements ChannelPoolHandler
     private final Map<BoltServerAddress,AtomicInteger> addressToInUseChannelCount = new ConcurrentHashMap<>();
     private final Map<BoltServerAddress,AtomicInteger> addressToIdleChannelCount = new ConcurrentHashMap<>();
     private final Logger log;
-    private DriverMetricsHandler metricsHandler;
+    private DriverMetricsListener metricsHandler;
 
-    public NettyChannelTracker( DriverMetricsHandler metricsHandler, Logging logging )
+    public NettyChannelTracker( DriverMetricsListener metricsHandler, Logging logging )
     {
         this.metricsHandler = metricsHandler;
         this.log = logging.getLog( getClass().getSimpleName() );
diff --git a/driver/src/main/java/org/neo4j/driver/internal/metrics/DriverMetricsListener.java b/driver/src/main/java/org/neo4j/driver/internal/metrics/DriverMetricsListener.java
@@ -21,7 +21,7 @@
 import org.neo4j.driver.internal.BoltServerAddress;
 import org.neo4j.driver.internal.spi.ConnectionPool;
 
-public interface DriverMetricsHandler
+public interface DriverMetricsListener
 {
     void addPoolMetrics(BoltServerAddress serverAddress, ConnectionPool pool);
 
@@ -36,4 +36,6 @@ public interface DriverMetricsHandler
     void beforeAcquiring( BoltServerAddress serverAddress, ListenerEvent listenerEvent );
 
     void afterAcquired( BoltServerAddress serverAddress, ListenerEvent listenerEvent );
+
+    ListenerEvent createListenerEvent();
 }
diff --git a/driver/src/main/java/org/neo4j/driver/internal/metrics/HistogramSnapshot.java b/driver/src/main/java/org/neo4j/driver/internal/metrics/HistogramSnapshot.java
@@ -20,17 +20,23 @@
 
 import org.neo4j.driver.internal.metrics.spi.Histogram;
 
-public class HistogramSanpshot implements Histogram
+public class HistogramSnapshot implements Histogram
 {
     private Histogram copy;
     private Histogram origin;
 
-    public HistogramSanpshot( Histogram copy, Histogram origin )
+    public HistogramSnapshot( Histogram copy, Histogram origin )
     {
         this.copy = copy;
         this.origin = origin;
     }
 
+    @Override
+    public long min()
+    {
+        return copy.min();
+    }
+
     @Override
     public long max()
     {
diff --git a/driver/src/main/java/org/neo4j/driver/internal/metrics/InternalAbstractDriverMetrics.java b/driver/src/main/java/org/neo4j/driver/internal/metrics/InternalAbstractDriverMetrics.java
@@ -26,7 +26,7 @@
 import org.neo4j.driver.internal.metrics.spi.DriverMetrics;
 import org.neo4j.driver.internal.spi.ConnectionPool;
 
-public abstract class InternalAbstractDriverMetrics implements DriverMetrics, DriverMetricsHandler
+public abstract class InternalAbstractDriverMetrics implements DriverMetrics, DriverMetricsListener
 {
     public static final InternalAbstractDriverMetrics DEV_NULL_METRICS = new InternalAbstractDriverMetrics()
     {
@@ -72,6 +72,12 @@ public void afterAcquired( BoltServerAddress serverAddress, ListenerEvent listen
 
         }
 
+        @Override
+        public ListenerEvent createListenerEvent()
+        {
+            return null;
+        }
+
         @Override
         public Map<String,ConnectionPoolMetrics> connectionPoolMetrics()
         {
diff --git a/driver/src/main/java/org/neo4j/driver/internal/metrics/InternalConnectionPoolMetrics.java b/driver/src/main/java/org/neo4j/driver/internal/metrics/InternalConnectionPoolMetrics.java
@@ -152,7 +152,7 @@ public Histogram acquisitionTimeHistogram()
     @Override
     public String toString()
     {
-        return format( "[created=%s, closed=%s, toCreate=%s, failedToCreate=%s inUse=%s, idle=%s, poolStatus=%s, acquisitionTimeHistogram=%n%s]",
+        return format( "[created=%s, closed=%s, toCreate=%s, failedToCreate=%s inUse=%s, idle=%s, poolStatus=%s, acquisitionTimeHistogram=%s]",
                 created(), closed(), toCreate(), failedToCreate(), inUse(), idle(), poolStatus(), acquisitionTimeHistogram() );
     }
 }
diff --git a/driver/src/main/java/org/neo4j/driver/internal/metrics/InternalDriverMetrics.java b/driver/src/main/java/org/neo4j/driver/internal/metrics/InternalDriverMetrics.java
@@ -92,6 +92,12 @@ public void afterAcquired( BoltServerAddress serverAddress, ListenerEvent listen
         poolMetrics.afterAcquire( listenerEvent );
     }
 
+    @Override
+    public ListenerEvent createListenerEvent()
+    {
+        return new NanoTimeBasedListenerEvent();
+    }
+
     @Override
     public Map<String,ConnectionPoolMetrics> connectionPoolMetrics()
     {
diff --git a/driver/src/main/java/org/neo4j/driver/internal/metrics/InternalHistogram.java b/driver/src/main/java/org/neo4j/driver/internal/metrics/InternalHistogram.java
@@ -27,9 +27,11 @@
 
 import org.neo4j.driver.internal.metrics.spi.Histogram;
 
+import static java.lang.String.format;
+
 public class InternalHistogram implements Histogram
 {
-    private static final long DEFAULT_HIGHEST_TRACKABLE_MS = Duration.ofMinutes( 10 ).toMillis();
+    private static final long DEFAULT_HIGHEST_TRACKABLE_MS = Duration.ofMinutes( 10 ).toNanos();
 
     private final AbstractHistogram delegate;
 
@@ -54,6 +56,12 @@ public void recordValue( long value )
         this.delegate.recordValue( newValue );
     }
 
+    @Override
+    public long min()
+    {
+        return delegate.getMinValue();
+    }
+
     @Override
     public long max()
     {
@@ -109,11 +117,17 @@ private static long truncateValue( long value, AbstractHistogram histogram )
 
     public Histogram snapshot()
     {
-        return new HistogramSanpshot( new InternalHistogram( this.delegate.copy() ), this );
+        return new HistogramSnapshot( new InternalHistogram( this.delegate.copy() ), this );
     }
 
     @Override
     public String toString()
+    {
+        return format("[min=%sns, max=%sns, mean=%sns, stdDeviation=%s, totalCount=%s]",
+                min(), max(), mean(), stdDeviation(), totalCount());
+    }
+
+    public String printDistribution()
     {
         ByteArrayOutputStream stream = new ByteArrayOutputStream();
         PrintStream writer = new PrintStream( stream );
diff --git a/driver/src/main/java/org/neo4j/driver/internal/metrics/NanoTimeBasedListenerEvent.java b/driver/src/main/java/org/neo4j/driver/internal/metrics/NanoTimeBasedListenerEvent.java
@@ -19,19 +19,19 @@
 
 package org.neo4j.driver.internal.metrics;
 
-public class SimpleTimerListenerEvent implements ListenerEvent
+public class NanoTimeBasedListenerEvent implements ListenerEvent
 {
-    private long startTimestamp;
+    private long startNanoTime;
 
     @Override
     public void start()
     {
-        startTimestamp = System.currentTimeMillis();
+        startNanoTime = System.nanoTime();
     }
 
     @Override
     public long elapsed()
     {
-        return System.currentTimeMillis() - startTimestamp;
+        return System.nanoTime() - startNanoTime;
     }
 }
diff --git a/driver/src/main/java/org/neo4j/driver/internal/metrics/spi/Histogram.java b/driver/src/main/java/org/neo4j/driver/internal/metrics/spi/Histogram.java
@@ -20,6 +20,7 @@
 
 public interface Histogram
 {
+    long min();
     long max();
     double mean();
     double stdDeviation();
diff --git a/driver/src/test/java/org/neo4j/driver/internal/DriverFactoryTest.java b/driver/src/test/java/org/neo4j/driver/internal/DriverFactoryTest.java
@@ -33,7 +33,7 @@
 import org.neo4j.driver.internal.async.BootstrapFactory;
 import org.neo4j.driver.internal.cluster.RoutingSettings;
 import org.neo4j.driver.internal.cluster.loadbalancing.LoadBalancer;
-import org.neo4j.driver.internal.metrics.DriverMetricsHandler;
+import org.neo4j.driver.internal.metrics.DriverMetricsListener;
 import org.neo4j.driver.internal.metrics.InternalDriverMetrics;
 import org.neo4j.driver.internal.retry.RetryLogic;
 import org.neo4j.driver.internal.retry.RetrySettings;
@@ -185,7 +185,7 @@ public void shouldNotCreateDriverMetrics() throws Throwable
         // Given
         Config config = mock( Config.class );
         // When
-        DriverMetricsHandler handler = DriverFactory.createDriverMetrics( config );
+        DriverMetricsListener handler = DriverFactory.createDriverMetrics( config );
         // Then
         assertThat( handler, is( DEV_NULL_METRICS ) );
     }
@@ -197,7 +197,7 @@ public void shouldCreateDriverMetricsIfMonitoringEnabled() throws Throwable
         System.setProperty( "driver.metrics.enabled", "True" );
         Config config = mock( Config.class );
         // When
-        DriverMetricsHandler handler = DriverFactory.createDriverMetrics( config );
+        DriverMetricsListener handler = DriverFactory.createDriverMetrics( config );
         // Then
         assertThat( handler instanceof InternalDriverMetrics, is( true ) );
     }
@@ -247,7 +247,7 @@ protected InternalDriver createRoutingDriver( BoltServerAddress address, Connect
         }
 
         @Override
-        protected ConnectionPool createConnectionPool( AuthToken authToken, SecurityPlan securityPlan, Bootstrap bootstrap, DriverMetricsHandler metrics, Config config )
+        protected ConnectionPool createConnectionPool( AuthToken authToken, SecurityPlan securityPlan, Bootstrap bootstrap, DriverMetricsListener metrics, Config config )
         {
             return connectionPool;
         }
@@ -282,7 +282,7 @@ protected SessionFactory createSessionFactory( ConnectionProvider connectionProv
         }
 
         @Override
-        protected ConnectionPool createConnectionPool( AuthToken authToken, SecurityPlan securityPlan, Bootstrap bootstrap, DriverMetricsHandler metrics, Config config )
+        protected ConnectionPool createConnectionPool( AuthToken authToken, SecurityPlan securityPlan, Bootstrap bootstrap, DriverMetricsListener metrics, Config config )
         {
             return connectionPoolMock();
         }
@@ -304,7 +304,7 @@ protected Bootstrap createBootstrap()
         }
 
         @Override
-        protected ConnectionPool createConnectionPool( AuthToken authToken, SecurityPlan securityPlan, Bootstrap bootstrap, DriverMetricsHandler metrics, Config config )
+        protected ConnectionPool createConnectionPool( AuthToken authToken, SecurityPlan securityPlan, Bootstrap bootstrap, DriverMetricsListener metrics, Config config )
         {
             return connectionPoolMock();
         }
diff --git a/driver/src/test/java/org/neo4j/driver/internal/metrics/InternalHistogramTest.java b/driver/src/test/java/org/neo4j/driver/internal/metrics/InternalHistogramTest.java
@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2002-2018 "Neo Technology,"
+ * Network Engine for Objects in Lund AB [http://neotechnology.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * 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 org.neo4j.driver.internal.metrics;
+
+import org.junit.Test;
+
+import org.neo4j.driver.internal.metrics.spi.Histogram;
+
+import static java.lang.Math.abs;
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.lessThan;
+import static org.junit.Assert.assertThat;
+
+public class InternalHistogramTest
+{
+    @Test
+    public void shouldRecordSmallValuesPrecisely() throws Throwable
+    {
+        // Given
+        InternalHistogram histogram = new InternalHistogram();
+        histogram.recordValue( 0 );
+        histogram.recordValue( 1 );
+        histogram.recordValue( 2 );
+        histogram.recordValue( 3 );
+        histogram.recordValue( 4 );
+
+        // When
+        assertThat( histogram.min(), equalTo( 0L ) );
+        assertThat( histogram.max(), equalTo( 4L ) );
+        assertThat( histogram.mean(), equalTo( 2.0 ) );
+        assertThat( histogram.totalCount(), equalTo( 5L ) );
+    }
+
+    @Test
+    public void shouldRecordBigValuesPrecisely() throws Throwable
+    {
+        // Given
+        InternalHistogram histogram = new InternalHistogram();
+        histogram.recordValue( 0 );
+        histogram.recordValue( 100000 );
+        histogram.recordValue( 200000 );
+        histogram.recordValue( 300000 );
+        histogram.recordValue( 400000 );
+
+        // When
+        assertThat( histogram.min(), equalTo( 0L ) );
+        assertThat( abs( histogram.max() - 400000L ), lessThan( 500L ) );
+        assertThat( abs( histogram.mean() - 200000.0 ), lessThan( 500.0 ) );
+        assertThat( histogram.totalCount(), equalTo( 5L ) );
+    }
+
+    @Test
+    public void shouldResetOnOriginalHistogram() throws Throwable
+    {
+        // Given
+        InternalHistogram histogram = new InternalHistogram();
+        histogram.recordValue( 0 );
+        histogram.recordValue( 1 );
+        histogram.recordValue( 2 );
+        histogram.recordValue( 3 );
+        histogram.recordValue( 4 );
+
+        // When
+        assertThat( histogram.totalCount(), equalTo( 5L ) );
+        Histogram snapshot = histogram.snapshot();
+        snapshot.reset();
+
+        // Then
+        assertThat( histogram.totalCount(), equalTo( 0L ) );
+    }
+
+}
diff --git a/driver/src/test/java/org/neo4j/driver/internal/util/ChannelTrackingDriverFactory.java b/driver/src/test/java/org/neo4j/driver/internal/util/ChannelTrackingDriverFactory.java
diff --git a/driver/src/test/java/org/neo4j/driver/internal/util/FailingConnectionDriverFactory.java b/driver/src/test/java/org/neo4j/driver/internal/util/FailingConnectionDriverFactory.java
diff --git a/driver/src/test/java/org/neo4j/driver/v1/integration/ConnectionHandlingIT.java b/driver/src/test/java/org/neo4j/driver/v1/integration/ConnectionHandlingIT.java

Original file line number	Diff line number	Diff line change
`@@ -21,7 +21,7 @@`
`21`	`21`	`import org.neo4j.driver.internal.BoltServerAddress;`
`22`	`22`	`import org.neo4j.driver.internal.spi.ConnectionPool;`
`23`	`23`
`24`		`-public interface DriverMetricsHandler`
	`24`	`+public interface DriverMetricsListener`
`25`	`25`	`{`
`26`	`26`	`void addPoolMetrics(BoltServerAddress serverAddress, ConnectionPool pool);`
`27`	`27`
`@@ -36,4 +36,6 @@ public interface DriverMetricsHandler`
`36`	`36`	`void beforeAcquiring( BoltServerAddress serverAddress, ListenerEvent listenerEvent );`
`37`	`37`
`38`	`38`	`void afterAcquired( BoltServerAddress serverAddress, ListenerEvent listenerEvent );`
	`39`	`+`
	`40`	`+ ListenerEvent createListenerEvent();`
`39`	`41`	`}`
Original file line number	Diff line number	Diff line change
`@@ -20,17 +20,23 @@`
`20`	`20`
`21`	`21`	`import org.neo4j.driver.internal.metrics.spi.Histogram;`
`22`	`22`
`23`		`-public class HistogramSanpshot implements Histogram`
	`23`	`+public class HistogramSnapshot implements Histogram`
`24`	`24`	`{`
`25`	`25`	`private Histogram copy;`
`26`	`26`	`private Histogram origin;`
`27`	`27`
`28`		`- public HistogramSanpshot( Histogram copy, Histogram origin )`
	`28`	`+ public HistogramSnapshot( Histogram copy, Histogram origin )`
`29`	`29`	`{`
`30`	`30`	`this.copy = copy;`
`31`	`31`	`this.origin = origin;`
`32`	`32`	`}`
`33`	`33`
	`34`	`+ @Override`
	`35`	`+ public long min()`
	`36`	`+ {`
	`37`	`+ return copy.min();`
	`38`	`+ }`
	`39`	`+`
`34`	`40`	`@Override`
`35`	`41`	`public long max()`
`36`	`42`	`{`
Original file line number	Diff line number	Diff line change
`@@ -26,7 +26,7 @@`
`26`	`26`	`import org.neo4j.driver.internal.metrics.spi.DriverMetrics;`
`27`	`27`	`import org.neo4j.driver.internal.spi.ConnectionPool;`
`28`	`28`
`29`		`-public abstract class InternalAbstractDriverMetrics implements DriverMetrics, DriverMetricsHandler`
	`29`	`+public abstract class InternalAbstractDriverMetrics implements DriverMetrics, DriverMetricsListener`
`30`	`30`	`{`
`31`	`31`	`public static final InternalAbstractDriverMetrics DEV_NULL_METRICS = new InternalAbstractDriverMetrics()`
`32`	`32`	`{`
`@@ -72,6 +72,12 @@ public void afterAcquired( BoltServerAddress serverAddress, ListenerEvent listen`
`72`	`72`
`73`	`73`	`}`
`74`	`74`
	`75`	`+ @Override`
	`76`	`+ public ListenerEvent createListenerEvent()`
	`77`	`+ {`
	`78`	`+ return null;`
	`79`	`+ }`
	`80`	`+`
`75`	`81`	`@Override`
`76`	`82`	`public Map<String,ConnectionPoolMetrics> connectionPoolMetrics()`
`77`	`83`	`{`
Original file line number	Diff line number	Diff line change
`@@ -152,7 +152,7 @@ public Histogram acquisitionTimeHistogram()`
`152`	`152`	`@Override`
`153`	`153`	`public String toString()`
`154`	`154`	`{`
`155`		`- return format( "[created=%s, closed=%s, toCreate=%s, failedToCreate=%s inUse=%s, idle=%s, poolStatus=%s, acquisitionTimeHistogram=%n%s]",`
	`155`	`+ return format( "[created=%s, closed=%s, toCreate=%s, failedToCreate=%s inUse=%s, idle=%s, poolStatus=%s, acquisitionTimeHistogram=%s]",`
`156`	`156`	`created(), closed(), toCreate(), failedToCreate(), inUse(), idle(), poolStatus(), acquisitionTimeHistogram() );`
`157`	`157`	`}`
`158`	`158`	`}`
Original file line number	Diff line number	Diff line change
`@@ -92,6 +92,12 @@ public void afterAcquired( BoltServerAddress serverAddress, ListenerEvent listen`
`92`	`92`	`poolMetrics.afterAcquire( listenerEvent );`
`93`	`93`	`}`
`94`	`94`
	`95`	`+ @Override`
	`96`	`+ public ListenerEvent createListenerEvent()`
	`97`	`+ {`
	`98`	`+ return new NanoTimeBasedListenerEvent();`
	`99`	`+ }`
	`100`	`+`
`95`	`101`	`@Override`
`96`	`102`	`public Map<String,ConnectionPoolMetrics> connectionPoolMetrics()`
`97`	`103`	`{`
Original file line number	Diff line number	Diff line change
`@@ -19,19 +19,19 @@`
`19`	`19`
`20`	`20`	`package org.neo4j.driver.internal.metrics;`
`21`	`21`
`22`		`-public class SimpleTimerListenerEvent implements ListenerEvent`
	`22`	`+public class NanoTimeBasedListenerEvent implements ListenerEvent`
`23`	`23`	`{`
`24`		`- private long startTimestamp;`
	`24`	`+ private long startNanoTime;`
`25`	`25`
`26`	`26`	`@Override`
`27`	`27`	`public void start()`
`28`	`28`	`{`
`29`		`- startTimestamp = System.currentTimeMillis();`
	`29`	`+ startNanoTime = System.nanoTime();`
`30`	`30`	`}`
`31`	`31`
`32`	`32`	`@Override`
`33`	`33`	`public long elapsed()`
`34`	`34`	`{`
`35`		`- return System.currentTimeMillis() - startTimestamp;`
	`35`	`+ return System.nanoTime() - startNanoTime;`
`36`	`36`	`}`
`37`	`37`	`}`