Unify port fallback logic to a single place

core/src/main/scala/org/apache/spark/HttpServer.scala

@@ -19,6 +19,7 @@ package org.apache.spark
 
 import java.io.File
 
+import org.apache.spark.network.PortManager
 import org.eclipse.jetty.util.security.{Constraint, Password}
 import org.eclipse.jetty.security.authentication.DigestAuthenticator
 import org.eclipse.jetty.security.{ConstraintMapping, ConstraintSecurityHandler, HashLoginService, SecurityHandler}
@@ -47,7 +48,7 @@ private[spark] class HttpServer(resourceBase: File,
   private var server: Server = null
   private var port: Int = localPort
 
-  private def startOnPort(startPort: Int): Tuple2[Server,Int] = {
+  private def startOnPort(startPort: Int): Server = {
     val server = new Server()
     val connector = new SocketConnector
     connector.setMaxIdleTime(60*1000)
@@ -78,34 +79,15 @@ private[spark] class HttpServer(resourceBase: File,
     server.start()
     val actualPort = server.getConnectors()(0).getLocalPort()
 
-    return (server, actualPort)
-  }
-
-  private def startWithIncrements(startPort: Int, maxRetries: Int): Tuple2[Server,Int] = {
-    for( offset <- 0 to maxRetries) {
-      try {
-        val (server, actualPort) = startOnPort(startPort + offset)
-        return (server, actualPort)
-      } catch {
-        case e: java.net.BindException => {
-          if (!e.getMessage.contains("Address already in use") ||
-            offset == (maxRetries-1)) {
-            throw e
-          }
-          logInfo("Could not bind on port: " + (startPort + offset))
-        }
-        case e: Exception => throw e
-      }
-    }
-    return (null, -1)
+    server
   }
 
   def start() {
     if (server != null) {
       throw new ServerStateException("Server is already started")
     } else {
       logInfo("Starting HTTP Server")
-      val (actualServer, actualPort) = startWithIncrements(localPort, 3)
+      val (actualServer, actualPort) = PortManager.startWithIncrements(localPort, 3, startOnPort)
       server = actualServer
       port = actualPort
     }

core/src/main/scala/org/apache/spark/network/ConnectionManager.scala

@@ -102,24 +102,11 @@ private[spark] class ConnectionManager(port: Int, conf: SparkConf,
   serverChannel.socket.setReuseAddress(true)
   serverChannel.socket.setReceiveBufferSize(256 * 1024)
 
-  def bindWithIncrement(port: Int, maxTries: Int = 3) {
-    for( offset <- 0 until maxTries ) {
-      try {
-        serverChannel.socket.bind(new InetSocketAddress(port + offset))
-        return
-      } catch {
-        case e: java.net.BindException => {
-          if(!e.getMessage.contains("Address already in use") ||
-             offset == maxTries) {
-            throw e
-          }
-          logInfo("Could not bind on port: " + (port + offset))
-        }
-        case e: Exception => throw e
-      }
-    }
+  private def startService(port: Int) = {
+    serverChannel.socket.bind(new InetSocketAddress(port))
+    serverChannel
   }
-  bindWithIncrement(port, 3)
+  PortManager.startWithIncrements(port, 3, startService)
   serverChannel.register(selector, SelectionKey.OP_ACCEPT)
 
   val id = new ConnectionManagerId(Utils.localHostName, serverChannel.socket.getLocalPort)

core/src/main/scala/org/apache/spark/network/PortManager.scala

@@ -0,0 +1,61 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.apache.spark.network
+
+import java.net.InetSocketAddress
+
+import org.apache.spark.{Logging, SparkException}
+import org.eclipse.jetty.server.Server
+
+private[spark] object PortManager extends Logging
+{
+
+  /**
+   * Start service on given port, or attempt to fall back to the n+1 port for a certain number of
+   * retries
+   *
+   * @param startPort
+   * @param maxRetries Maximum number of retries to attempt.  A value of e.g. 3 will cause 4
+   *                   total attempts, on ports n, n+1, n+2, and n+3
+   * @param startService Function to start service on a given port.  Expected to throw a java.net
+   *                     .BindException if the port is already in use
+   * @tparam T
+   * @throws SparkException When unable to start service in the given number of attempts
+   * @return
+   */
+  def startWithIncrements[T](startPort: Int, maxRetries: Int, startService: Int => T):
+      (T, Int) = {
+    for( offset <- 0 to maxRetries) {
+      val tryPort = startPort + offset
+      try {
+        val service: T = startService(tryPort)
+        return (service, tryPort)
+      } catch {
+        case e: java.net.BindException => {
+          if (!e.getMessage.contains("Address already in use") ||
+            offset == (maxRetries-1)) {
+            throw e
+          }
+          logInfo("Could not bind on port: " + tryPort + ". Attempting port " + (tryPort+1))
+        }
+        case e: Exception => throw e
+      }
+    }
+    throw new SparkException(s"Couldn't start service on port $startPort")
+  }
+}