Use dynamic ports in PrometheusOutputTest instead of PortAuthority.

Allow to lookup dynamic address of Prometheus server. Update test to use
newly introduced capability.

enterprise/metrics/src/main/java/org/neo4j/metrics/output/PrometheusHttpServer.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2002-2018 "Neo4j,"
+ * Neo4j Sweden AB [http://neo4j.com]
+ *
+ * This file is part of Neo4j Enterprise Edition. The included source
+ * code can be redistributed and/or modified under the terms of the
+ * GNU AFFERO GENERAL PUBLIC LICENSE Version 3
+ * (http://www.fsf.org/licensing/licenses/agpl-3.0.html) with the
+ * Commons Clause, as found in the associated LICENSE.txt file.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * Neo4j object code can be licensed independently from the source
+ * under separate terms from the AGPL. Inquiries can be directed to:
+ * licensing@neo4j.com
+ *
+ * More information is also available at:
+ * https://neo4j.com/licensing/
+ */
+package org.neo4j.metrics.output;
+
+import io.prometheus.client.exporter.HTTPServer;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+
+class PrometheusHttpServer extends HTTPServer
+{
+    PrometheusHttpServer( String host, int port ) throws IOException
+    {
+        super( host, port, true );
+    }
+
+    InetSocketAddress getAddress()
+    {
+        return server.getAddress();
+    }
+}

enterprise/metrics/src/main/java/org/neo4j/metrics/output/PrometheusOutput.java

@@ -30,7 +30,6 @@
 import com.codahale.metrics.Timer;
 import io.prometheus.client.CollectorRegistry;
 import io.prometheus.client.dropwizard.DropwizardExports;
-import io.prometheus.client.exporter.HTTPServer;
 
 import java.util.Map;
 import java.util.SortedMap;
@@ -45,15 +44,14 @@
  */
 public class PrometheusOutput implements Lifecycle, EventReporter
 {
+    protected PrometheusHttpServer server;
     private final HostnamePort hostnamePort;
     private final MetricRegistry registry;
     private final Log logger;
-
-    private HTTPServer server;
-    private Map<String,Object> registeredEvents = new ConcurrentHashMap<>();
+    private final Map<String,Object> registeredEvents = new ConcurrentHashMap<>();
     private final MetricRegistry eventRegistry;
 
-    public PrometheusOutput( HostnamePort hostnamePort, MetricRegistry registry, Log logger )
+    PrometheusOutput( HostnamePort hostnamePort, MetricRegistry registry, Log logger )
     {
         this.hostnamePort = hostnamePort;
         this.registry = registry;
@@ -76,7 +74,7 @@ public void start() throws Throwable
     {
         if ( server == null )
         {
-            server = new HTTPServer( hostnamePort.getHost(), hostnamePort.getPort(), true );
+            server = new PrometheusHttpServer( hostnamePort.getHost(), hostnamePort.getPort() );
             logger.info( "Started publishing Prometheus metrics at http://" + hostnamePort + "/metrics" );
         }
     }

enterprise/metrics/src/test/java/org/neo4j/metrics/output/PrometheusOutputTest.java

@@ -25,9 +25,9 @@
 import com.codahale.metrics.Gauge;
 import com.codahale.metrics.MetricRegistry;
 import org.junit.Test;
-import org.mockito.Mockito;
 
 import java.io.IOException;
+import java.net.InetSocketAddress;
 import java.net.URL;
 import java.net.URLConnection;
 import java.util.Scanner;
@@ -36,34 +36,33 @@
 
 import org.neo4j.helpers.HostnamePort;
 import org.neo4j.logging.Log;
-import org.neo4j.ports.allocation.PortAuthority;
 
 import static java.util.Collections.emptySortedMap;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
 
 public class PrometheusOutputTest
 {
     @Test
     public void eventsShouldBeRedirectedToGauges() throws Throwable
     {
-        String serverAddress = "localhost:" + PortAuthority.allocatePort();
         MetricRegistry registry = new MetricRegistry();
-        PrometheusOutput prometheusOutput =
-                new PrometheusOutput( new HostnamePort( serverAddress ), registry, Mockito.mock( Log.class ) );
+        DynamicAddressPrometheusOutput dynamicOutput = new DynamicAddressPrometheusOutput( "localhost", registry, mock( Log.class ) );
 
         LongConsumer callback = l ->
         {
             TreeMap<String,Gauge> gauges = new TreeMap<>();
             gauges.put( "my.event", () -> l );
-            prometheusOutput.report( gauges, emptySortedMap(), emptySortedMap(), emptySortedMap(), emptySortedMap() );
+            dynamicOutput.report( gauges, emptySortedMap(), emptySortedMap(), emptySortedMap(), emptySortedMap() );
         };
 
         callback.accept( 10 );
 
-        prometheusOutput.init();
-        prometheusOutput.start();
+        dynamicOutput.init();
+        dynamicOutput.start();
 
+        String serverAddress = dynamicOutput.getServerAddress();
         assertTrue( getResponse( serverAddress ).contains( "my_event 10.0" ) );
         assertTrue( getResponse( serverAddress ).contains( "my_event 10.0" ) );
 
@@ -75,42 +74,55 @@ public void eventsShouldBeRedirectedToGauges() throws Throwable
     @Test
     public void metricsRegisteredAfterStartShouldBeIncluded() throws Throwable
     {
-        String serverAddress = "localhost:" + PortAuthority.allocatePort();
         MetricRegistry registry = new MetricRegistry();
-        PrometheusOutput prometheusOutput =
-                new PrometheusOutput( new HostnamePort( serverAddress ), registry, Mockito.mock( Log.class ) );
+        DynamicAddressPrometheusOutput dynamicOutput = new DynamicAddressPrometheusOutput( "localhost", registry, mock( Log.class ) );
 
         LongConsumer callback = l ->
         {
             TreeMap<String,Gauge> gauges = new TreeMap<>();
             gauges.put( "my.event", () -> l );
-            prometheusOutput.report( gauges, emptySortedMap(), emptySortedMap(), emptySortedMap(), emptySortedMap() );
+            dynamicOutput.report( gauges, emptySortedMap(), emptySortedMap(), emptySortedMap(), emptySortedMap() );
         };
 
         registry.register( "my.metric", (Gauge) () -> 10 );
 
-        prometheusOutput.init();
-        prometheusOutput.start();
+        dynamicOutput.init();
+        dynamicOutput.start();
 
         callback.accept( 20 );
 
+        String serverAddress = dynamicOutput.getServerAddress();
         String response = getResponse( serverAddress );
         assertTrue( response.contains( "my_metric 10.0" ) );
         assertTrue( response.contains( "my_event 20.0" ) );
     }
 
-    private String getResponse( String serverAddress ) throws IOException
+    private static String getResponse( String serverAddress ) throws IOException
     {
         String url = "http://" + serverAddress + "/metrics";
         URLConnection connection = new URL( url ).openConnection();
         connection.setDoOutput( true );
         connection.connect();
-        Scanner s = new Scanner( connection.getInputStream(), "UTF-8" ).useDelimiter( "\\A" );
+        try ( Scanner s = new Scanner( connection.getInputStream(), "UTF-8" ).useDelimiter( "\\A" ) )
+        {
+            assertTrue( s.hasNext() );
+            String ret = s.next();
+            assertFalse( s.hasNext() );
+            return ret;
+        }
+    }
+
+    private static class DynamicAddressPrometheusOutput extends PrometheusOutput
+    {
+        DynamicAddressPrometheusOutput( String host, MetricRegistry registry, Log logger )
+        {
+            super( new HostnamePort( host ), registry, logger );
+        }
 
-        assertTrue( s.hasNext() );
-        String ret = s.next();
-        assertFalse( s.hasNext() );
-        s.close();
-        return ret;
+        String getServerAddress()
+        {
+            InetSocketAddress address = server.getAddress();
+            return address.getHostString() + ":" + address.getPort();
+        }
     }
 }