ZOOKEEPER-4972: Fix flaky tests in PrometheusMetricsProviderConfigTest

Reviewers: anmolnar
Author: kezhuw
Closes #2311 from kezhuw/ZOOKEEPER-4972-fix-flaky-PrometheusMetricsProviderConfigTest-tests

Author: kezhuw

zookeeper-metrics-providers/zookeeper-prometheus-metrics/pom.xml

@@ -69,6 +69,12 @@
       <artifactId>jetty-servlet</artifactId>
       <scope>provided</scope>
     </dependency>
+    <dependency>
+      <groupId>ch.qos.logback</groupId>
+      <artifactId>logback-classic</artifactId>
+      <scope>runtime</scope>
+      <optional>true</optional>
+    </dependency>
     <dependency>
       <groupId>org.mockito</groupId>
       <artifactId>mockito-core</artifactId>

zookeeper-metrics-providers/zookeeper-prometheus-metrics/src/main/java/org/apache/zookeeper/metrics/prometheus/PrometheusMetricsProvider.java

@@ -23,7 +23,6 @@
 import io.prometheus.client.exporter.MetricsServlet;
 import io.prometheus.client.hotspot.DefaultExports;
 import java.io.IOException;
-import java.net.InetSocketAddress;
 import java.util.Enumeration;
 import java.util.Objects;
 import java.util.Optional;
@@ -170,35 +169,45 @@ public void configure(Properties configuration) throws MetricsProviderLifeCycleE
     public void start() throws MetricsProviderLifeCycleException {
         this.executorOptional = createExecutor();
         try {
-            LOG.info("Starting /metrics {} endpoint at HTTP port: {}, HTTPS port: {}, exportJvmInfo: {}",
-                    httpPort > 0 ? httpPort : "disabled",
-                    httpsPort > 0 ? httpsPort : "disabled",
+            LOG.info("Starting /metrics endpoint at HTTP port: {}, HTTPS port: {}, exportJvmInfo: {}",
+                    httpPort >= 0 ? httpPort : "disabled",
+                    httpsPort >= 0 ? httpsPort : "disabled",
                     exportJvmInfo);
             if (exportJvmInfo) {
                 DefaultExports.initialize();
             }
-            if (httpPort == -1) {
-                server = new Server();
-            } else {
-                server = new Server(new InetSocketAddress(host, httpPort));
+            server = new Server();
+            ServerConnector httpConnector = null;
+            ServerConnector httpsConnector = null;
+            if (httpPort >= 0) {
+                httpConnector = new ServerConnector(server);
+                httpConnector.setHost(host);
+                httpConnector.setPort(httpPort);
+                server.addConnector(httpConnector);
             }
-            if (httpsPort != -1) {
+            if (httpsPort >= 0) {
                 SslContextFactory sslServerContextFactory = new SslContextFactory.Server();
                 configureSslContextFactory(sslServerContextFactory);
                 KeyStoreScanner keystoreScanner = new KeyStoreScanner(sslServerContextFactory);
                 keystoreScanner.setScanInterval(SCAN_INTERVAL);
                 server.addBean(keystoreScanner);
-                ServerConnector connector = new ServerConnector(server, sslServerContextFactory);
-                connector.setPort(httpsPort);
-                connector.setHost(host);
-                server.addConnector(connector);
+                httpsConnector = new ServerConnector(server, sslServerContextFactory);
+                httpsConnector.setHost(host);
+                httpsConnector.setPort(httpsPort);
+                server.addConnector(httpsConnector);
             }
             ServletContextHandler context = new ServletContextHandler();
             context.setContextPath("/");
             constrainTraceMethod(context);
             server.setHandler(context);
             context.addServlet(new ServletHolder(servlet), "/metrics");
             server.start();
+            if (httpPort == 0) {
+                LOG.info("Bound /metrics endpoint to HTTP port: {}", httpConnector.getLocalPort());
+            }
+            if (httpsPort == 0) {
+                LOG.info("Bound /metrics endpoint to HTTPS port: {}", httpsConnector.getLocalPort());
+            }
         } catch (Exception err) {
             LOG.error("Cannot start /metrics server", err);
             if (server != null) {

zookeeper-metrics-providers/zookeeper-prometheus-metrics/src/test/java/org/apache/zookeeper/metrics/prometheus/PrometheusMetricsProviderConfigTest.java

@@ -64,7 +64,7 @@ public void testValidSslConfig() throws MetricsProviderLifeCycleException {
         Properties configuration = new Properties();
         String testDataPath = System.getProperty("test.data.dir", "src/test/resources/data");
         configuration.setProperty("httpHost", "127.0.0.1");
-        configuration.setProperty("httpsPort", "50511");
+        configuration.setProperty("httpsPort", "0");
         configuration.setProperty("ssl.keyStore.location", testDataPath + "/ssl/server_keystore.jks");
         configuration.setProperty("ssl.keyStore.password", "testpass");
         configuration.setProperty("ssl.trustStore.location", testDataPath + "/ssl/server_truststore.jks");
@@ -78,8 +78,8 @@ public void testValidHttpsAndHttpConfig() throws MetricsProviderLifeCycleExcepti
         PrometheusMetricsProvider provider = new PrometheusMetricsProvider();
         Properties configuration = new Properties();
         String testDataPath = System.getProperty("test.data.dir", "src/test/resources/data");
-        configuration.setProperty("httpPort", "50512");
-        configuration.setProperty("httpsPort", "50513");
+        configuration.setProperty("httpPort", "0");
+        configuration.setProperty("httpsPort", "0");
         configuration.setProperty("ssl.keyStore.location", testDataPath + "/ssl/server_keystore.jks");
         configuration.setProperty("ssl.keyStore.password", "testpass");
         configuration.setProperty("ssl.trustStore.location", testDataPath + "/ssl/server_truststore.jks");
@@ -95,7 +95,7 @@ public void testInvalidSslConfig() throws MetricsProviderLifeCycleException {
             PrometheusMetricsProvider provider = new PrometheusMetricsProvider();
             Properties configuration = new Properties();
             String testDataPath = System.getProperty("test.data.dir", "src/test/resources/data");
-            configuration.setProperty("httpsPort", "50514");
+            configuration.setProperty("httpsPort", "0");
             //keystore missing
             configuration.setProperty("ssl.keyStore.password", "testpass");
             configuration.setProperty("ssl.trustStore.location", testDataPath + "/ssl/server_truststore.jks");