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From "Ming Ma (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-7009) No enough retry during DN's initial handshake with NN
Date Sat, 06 Sep 2014 00:08:28 GMT
Ming Ma created HDFS-7009:
-----------------------------

             Summary: No enough retry during DN's initial handshake with NN
                 Key: HDFS-7009
                 URL: https://issues.apache.org/jira/browse/HDFS-7009
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: Ming Ma


To follow up on https://issues.apache.org/jira/browse/HDFS-6478, in most cases, given DN sends
HB and BR to NN regularly, if a specific RPC call fails, it isn't a big deal.

However, there are cases where DN fails to register with NN during initial handshake due to
exceptions not covered by RPC client's connection retry. When this happens, the DN won't talk
to that NN until the DN restarts.

{noformat}
BPServiceActor

  public void run() {
    LOG.info(this + " starting to offer service");

    try {
      // init stuff
      try {
        // setup storage
        connectToNNAndHandshake();
      } catch (IOException ioe) {
        // Initial handshake, storage recovery or registration failed
        // End BPOfferService thread
        LOG.fatal("Initialization failed for block pool " + this, ioe);
        return;
      }

      initialized = true; // bp is initialized;
      
      while (shouldRun()) {
        try {
          offerService();
        } catch (Exception ex) {
          LOG.error("Exception in BPOfferService for " + this, ex);
          sleepAndLogInterrupts(5000, "offering service");
        }
      }
...
{noformat}


Here is an example of the call stack.

{noformat}
java.io.IOException: Failed on local exception: java.io.IOException: Response is null.; Host
Details : local host is: "xxx"; destination host is: "yyy":8030;
        at org.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:761)
        at org.apache.hadoop.ipc.Client.call(Client.java:1239)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:202)
        at com.sun.proxy.$Proxy9.registerDatanode(Unknown Source)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:606)
        at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:164)
        at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:83)
        at com.sun.proxy.$Proxy9.registerDatanode(Unknown Source)
        at org.apache.hadoop.hdfs.protocolPB.DatanodeProtocolClientSideTranslatorPB.registerDatanode(DatanodeProtocolClientSideTranslatorPB.java:146)
        at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.register(BPServiceActor.java:623)
        at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.connectToNNAndHandshake(BPServiceActor.java:225)
        at org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:664)
        at java.lang.Thread.run(Thread.java:745)
Caused by: java.io.IOException: Response is null.
        at org.apache.hadoop.ipc.Client$Connection.receiveResponse(Client.java:949)
        at org.apache.hadoop.ipc.Client$Connection.run(Client.java:844)
{noformat}

This will create discrepancy between active NN and standby NN in terms of live nodes.
 
Here is a possible scenario of missing blocks after failover.

1. DN A, B set up handshakes with active NN, but not with standby NN.
2. A block is replicated to DN A, B and C.
3. From standby NN's point of view, given A and B are dead nodes, the block is under replicated.
4. DN C is down.
5. Before active NN detects DN C is down, it fails over.
6. The new active NN considers the block is missing. Even though there are two replicas on
DN A and B.






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