Add fallover increment logic for HttpServer

Author: ash211

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

@@ -47,40 +47,63 @@ private[spark] class HttpServer(resourceBase: File,
   private var server: Server = null
   private var port: Int = localPort
 
+  private def startOnPort(startPort: Int) {
+    val server = new Server()
+    val connector = new SocketConnector
+    connector.setMaxIdleTime(60*1000)
+    connector.setSoLingerTime(-1)
+    connector.setPort(startPort)
+    server.addConnector(connector)
+
+    val threadPool = new QueuedThreadPool
+    threadPool.setDaemon(true)
+    server.setThreadPool(threadPool)
+    val resHandler = new ResourceHandler
+    resHandler.setResourceBase(resourceBase.getAbsolutePath)
+
+    val handlerList = new HandlerList
+    handlerList.setHandlers(Array(resHandler, new DefaultHandler))
+
+    if (securityManager.isAuthenticationEnabled()) {
+      logDebug("HttpServer is using security")
+      val sh = setupSecurityHandler(securityManager)
+      // make sure we go through security handler to get resources
+      sh.setHandler(handlerList)
+      server.setHandler(sh)
+    } else {
+      logDebug("HttpServer is not using security")
+      server.setHandler(handlerList)
+    }
+
+    server.start()
+    val actualPort = server.getConnectors()(0).getLocalPort()
+
+    return (server, actualPort)
+  }
+
+  private def startWithIncrements(startPort: Int, maxTries: Int) {
+    for( tryPort <- startPort until (startPort+maxTries)) {
+      try {
+        val (server, actualPort) = startOnPort(startPort)
+        return (server, actualPort)
+      } catch {
+        case e: java.net.BindException => {
+          if (!e.getMessage.contains("Address already in use")) {
+            throw e
+          }
+          logInfo("Could not bind on port: " + (tryPort))
+        }
+        case e: Exception => throw e
+      }
+    }
+  }
+
   def start() {
     if (server != null) {
       throw new ServerStateException("Server is already started")
     } else {
       logInfo("Starting HTTP Server")
-      server = new Server()
-      val connector = new SocketConnector
-      connector.setMaxIdleTime(60*1000)
-      connector.setSoLingerTime(-1)
-      connector.setPort(localPort)
-      server.addConnector(connector)
-
-      val threadPool = new QueuedThreadPool
-      threadPool.setDaemon(true)
-      server.setThreadPool(threadPool)
-      val resHandler = new ResourceHandler
-      resHandler.setResourceBase(resourceBase.getAbsolutePath)
-
-      val handlerList = new HandlerList
-      handlerList.setHandlers(Array(resHandler, new DefaultHandler))
-
-      if (securityManager.isAuthenticationEnabled()) {
-        logDebug("HttpServer is using security")
-        val sh = setupSecurityHandler(securityManager)
-        // make sure we go through security handler to get resources
-        sh.setHandler(handlerList)
-        server.setHandler(sh)
-      } else {
-        logDebug("HttpServer is not using security")
-        server.setHandler(handlerList)
-      }
-
-      server.start()
-      port = server.getConnectors()(0).getLocalPort()
+      (server, port) = startWithIncrements(localPort, 3)
     }
   }