virajjasani commented on a change in pull request #1690:
URL: https://github.com/apache/hbase/pull/1690#discussion_r424880212



##########
File path: 
hbase-server/src/test/java/org/apache/hadoop/hbase/master/TestMasterShutdown.java
##########
@@ -151,19 +152,46 @@ public void 
testMasterShutdownBeforeStartingAnyRegionServer() throws Exception {
       hbaseCluster = new LocalHBaseCluster(htu.getConfiguration(), 
options.getNumMasters(),
         options.getNumRegionServers(), options.getMasterClass(), 
options.getRsClass());
       final MasterThread masterThread = hbaseCluster.getMasters().get(0);
+
       masterThread.start();
-      // Switching to master registry exacerbated a race in the master 
bootstrap that can result
-      // in a lost shutdown command (HBASE-8422, HBASE-23836). The race is 
essentially because
-      // the server manager in HMaster is not initialized by the time 
shutdown() RPC (below) is
-      // made to the master. The suspected reason as to why it was uncommon 
before HBASE-18095
-      // is because the connection creation with ZK registry is so slow that 
by then the server
-      // manager is usually init'ed in time for the RPC to be made. For now, 
adding an explicit
-      // wait() in the test, waiting for the server manager to become 
available.
-      final long timeout = TimeUnit.MINUTES.toMillis(10);
-      assertNotEquals("Timeout waiting for server manager to become 
available.",
-        -1, Waiter.waitFor(htu.getConfiguration(), timeout,
-          () -> masterThread.getMaster().getServerManager() != null));
-      htu.getConnection().getAdmin().shutdown();
+      final CompletableFuture<Void> shutdownFuture = 
CompletableFuture.runAsync(() -> {
+        // Switching to master registry exacerbated a race in the master 
bootstrap that can result
+        // in a lost shutdown command (HBASE-8422, HBASE-23836). The race is 
essentially because
+        // the server manager in HMaster is not initialized by the time 
shutdown() RPC (below) is
+        // made to the master. The suspected reason as to why it was uncommon 
before HBASE-18095
+        // is because the connection creation with ZK registry is so slow that 
by then the server
+        // manager is usually init'ed in time for the RPC to be made. For now, 
adding an explicit
+        // wait() in the test, waiting for the server manager to become 
available.
+        final long timeout = TimeUnit.MINUTES.toMillis(10);
+        assertNotEquals("timeout waiting for server manager to become 
available.", -1,
+          htu.waitFor(timeout, () -> 
masterThread.getMaster().getServerManager() != null));
+
+        // Master has come up far enough that we can terminate it without 
creating a zombie.
+        LOG.debug("Attempting to establish connection.");
+        try {
+          // HBASE-24327 : (Resolve Flaky connection issues)
+          // shutdown() RPC can have flaky ZK connection issues.
+          // e.g
+          // ERROR 
[RpcServer.priority.RWQ.Fifo.read.handler=1,queue=1,port=53033]
+          // master.HMaster(2878): ZooKeeper exception trying to set cluster 
as down in ZK
+          // org.apache.zookeeper.KeeperException$SystemErrorException:
+          // KeeperErrorCode = SystemError
+          //
+          // However, even when above flakes happen, shutdown call does get 
completed even if
+          // RPC call has failure. Hence, subsequent retries will never 
succeed as HMaster is
+          // already shutdown. Hence, it can fail. To resolve it, after making 
one shutdown()
+          // call, we are ignoring IOException.
+          htu.getConnection().getAdmin().shutdown();
+          LOG.info("Shutdown RPC sent.");
+        } catch (IOException | CompletionException e) {
+          LOG.warn("Failed to establish connection.", e);

Review comment:
       Thanks @ndimiduk 
   Let me put the code reference of the link that I mentioned. This is what I 
had in my first commit:
   
   ```
             } catch (IOException|CompletionException e) {
               LOG.error("Failed to establish connection.");
               if (connectionFailedWithMaster(e)) {
                 return true;
               }
             }
   ```
   
   ```
     private boolean connectionFailedWithMaster(Exception e) {
       if (e instanceof RetriesExhaustedException) {
         Throwable cause = e.getCause();
         if (cause instanceof MasterRegistryFetchException) {
           cause = cause.getCause();
           if (cause instanceof RetriesExhaustedException) {
             final String message = cause.getMessage();
             return message != null && message
               .startsWith("Failed contacting masters after 1 attempts");
           }
         }
       }
       return false;
     }
   ```
   
   `return true` in the first code block indicates returning true to waitFor().




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