HDFS-9444. Add utility to find set of available ephemeral ports to ServerSocketUtil. Contributed by Masatake Iwasaki

(cherry picked from commit e9a34ae29c7390f3ffcbeee02dc5faa26fca482a)
(cherry picked from commit 5f754e8638d5a35ab12765edec6561228312f71c)

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/net/ServerSocketUtil.java

@@ -60,4 +60,26 @@ public class ServerSocketUtil {
     }
   }
 
+  /**
+   * Find the specified number of unique ports available.
+   * The ports are all closed afterwards,
+   * so other network services started may grab those same ports.
+   *
+   * @param numPorts number of required port nubmers
+   * @return array of available port numbers
+   * @throws IOException
+   */
+  public static int[] getPorts(int numPorts) throws IOException {
+    ServerSocket[] sockets = new ServerSocket[numPorts];
+    int[] ports = new int[numPorts];
+    for (int i = 0; i < numPorts; i++) {
+      ServerSocket sock = new ServerSocket(0);
+      sockets[i] = sock;
+      ports[i] = sock.getLocalPort();
+    }
+    for (ServerSocket sock : sockets) {
+      sock.close();
+    }
+    return ports;
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -169,6 +169,9 @@ Release 2.7.4 - UNRELEASED
     HDFS-10301. Remove FBR tracking state to fix false zombie storage
     detection for interleaving block reports. (Vinitha Gankidi via shv)
 
+    HDFS-9444. Add utility to find set of available ephemeral ports to
+    ServerSocketUtil. (Masatake Iwasaki via Brahma Reddy Battula)
+
 Release 2.7.3 - 2016-08-25
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestEditLogTailer.java

@@ -19,8 +19,11 @@ package org.apache.hadoop.hdfs.server.namenode.ha;
 
 import static org.junit.Assert.assertTrue;
 
+import static org.junit.Assert.fail;
+
 import java.io.File;
 import java.io.IOException;
+import java.net.BindException;
 import java.net.URI;
 
 import org.apache.commons.logging.impl.Log4JLogger;
@@ -37,6 +40,7 @@ import org.apache.hadoop.hdfs.server.namenode.FSImage;
 import org.apache.hadoop.hdfs.server.namenode.NNStorage;
 import org.apache.hadoop.hdfs.server.namenode.NameNode;
 import org.apache.hadoop.hdfs.server.namenode.NameNodeAdapter;
+import org.apache.hadoop.net.ServerSocketUtil;
 import org.apache.hadoop.test.GenericTestUtils;
 import org.apache.log4j.Level;
 import org.junit.Test;
@@ -120,17 +124,32 @@ public class TestEditLogTailer {
     // Roll every 1s
     conf.setInt(DFSConfigKeys.DFS_HA_LOGROLL_PERIOD_KEY, 1);
     conf.setInt(DFSConfigKeys.DFS_HA_TAILEDITS_PERIOD_KEY, 1);
-    
-    // Have to specify IPC ports so the NNs can talk to each other.
-    MiniDFSNNTopology topology = new MiniDFSNNTopology()
-      .addNameservice(new MiniDFSNNTopology.NSConf("ns1")
-        .addNN(new MiniDFSNNTopology.NNConf("nn1").setIpcPort(10031))
-        .addNN(new MiniDFSNNTopology.NNConf("nn2").setIpcPort(10032)));
 
-    MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf)
-      .nnTopology(topology)
-      .numDataNodes(0)
-      .build();
+    MiniDFSCluster cluster = null;
+    for (int i = 0; i < 5; i++) {
+      try {
+        // Have to specify IPC ports so the NNs can talk to each other.
+        int[] ports = ServerSocketUtil.getPorts(2);
+        MiniDFSNNTopology topology = new MiniDFSNNTopology()
+            .addNameservice(new MiniDFSNNTopology.NSConf("ns1")
+                .addNN(new MiniDFSNNTopology.NNConf("nn1")
+                    .setIpcPort(ports[0]))
+                .addNN(new MiniDFSNNTopology.NNConf("nn2")
+                    .setIpcPort(ports[1])));
+
+        cluster = new MiniDFSCluster.Builder(conf)
+            .nnTopology(topology)
+            .numDataNodes(0)
+            .build();
+        break;
+      } catch (BindException e) {
+        // retry if race on ports given by ServerSocketUtil#getPorts
+        continue;
+      }
+    }
+    if (cluster == null) {
+      fail("failed to start mini cluster.");
+    }
     try {
       cluster.transitionToActive(activeIndex);
       waitForLogRollInSharedDir(cluster, 3);