[GitHub] [kafka] mumrah commented on a diff in pull request #13169: KAFKA-14658: Do not open broker ports until we are ready to accept traffic

["mumrah (via GitHub)" <gi...@apache.org>]

mumrah commented on code in PR #13169:
URL: https://github.com/apache/kafka/pull/13169#discussion_r1092435602


##########
core/src/main/scala/kafka/network/SocketServer.scala:
##########
@@ -585,23 +616,35 @@ private[kafka] abstract class Acceptor(val socketServer: SocketServer,
   private var currentProcessorIndex = 0
   private[network] val throttledSockets = new mutable.PriorityQueue[DelayedCloseSocket]()
   private var started = false
-  private[network] val startFuture = new CompletableFuture[Void]()
+  private[network] val startedFuture = new CompletableFuture[Void]()
 
   val thread = KafkaThread.nonDaemon(
     s"${threadPrefix()}-kafka-socket-acceptor-${endPoint.listenerName}-${endPoint.securityProtocol}-${endPoint.port}",
     this)
 
-  startFuture.thenRun(() => synchronized {
-    if (!shouldRun.get()) {
-      debug(s"Ignoring start future for ${endPoint.listenerName} since the acceptor has already been shut down.")
-    } else {
+  def start(): Unit = synchronized {
+    try {
+      if (!shouldRun.get()) {
+        throw new ClosedChannelException()

Review Comment:
   How does this happen? If the kafka server is shutdown before the socket server is able to finish starting?



##########
core/src/main/scala/kafka/network/SocketServer.scala:
##########
@@ -573,7 +591,20 @@ private[kafka] abstract class Acceptor(val socketServer: SocketServer,
   private val listenBacklogSize = config.socketListenBacklogSize
 
   private val nioSelector = NSelector.open()
-  private[network] val serverChannel = openServerSocket(endPoint.host, endPoint.port, listenBacklogSize)
+
+  // If the port is configured as 0, we are using a random (ephemeral) port, so we need to open
+  // the socket before we can find out what port we have. If it is set to a nonzero value, defer
+  // opening the socket until we start the Acceptor. The reason for deferring the socket opening
+  // is so that systems which assume that the socket being open indicates readiness are not
+  // confused.
+  private[network] var serverChannel: ServerSocketChannel  = _
+  private[network] val localPort: Int  = if (endPoint.port != 0) {

Review Comment:
   It might be good to log when we are opening the socket server early.



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