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From "Yongjun Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Deleted] (HADOOP-14312) RetryInvocationHandler may report ANN as SNN in messages.
Date Mon, 17 Apr 2017 20:25:41 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-14312?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Yongjun Zhang deleted HADOOP-14312:
-----------------------------------


> RetryInvocationHandler  may report ANN as SNN in messages.
> ----------------------------------------------------------
>
>                 Key: HADOOP-14312
>                 URL: https://issues.apache.org/jira/browse/HADOOP-14312
>             Project: Hadoop Common
>          Issue Type: Bug
>            Reporter: Yongjun Zhang
>            Assignee: Yongjun Zhang
>
> When multiple threads use the same DFSClient to make RPC calls, they may report incorrect
NN host name in messages like
>  INFO [pool-3-thread-13] retry.RetryInvocationHandler (RetryInvocationHandler.java:invoke(148))
- Exception while invoking delete of class ClientNamenodeProtocolTranslatorPB over x.y.z/*a.b.c.d*:8020.
Trying to fail over immediately.
> org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.ipc.StandbyException): Operation
category WRITE is not supported in state standby. Visit https://s.apache.org/sbnn-error
> where *a.b.c.d* is the active NN, which confuses user to think failover is not behaving
correctly.
> The reason is that the ProxyDescriptor data field of RetryInvocationHandler may be shared
by multiple threads that do the RPC calls, the failover done by one thread may be visible
to other threads when reporting the above kind of message. 
> As an example, 
> # multiple threads start with the same SNN to do RPC calls, 
> # all threads discover that a failover is needed, 
> # thread X failover first, and changed the ProxyDescriptor's proxyInfo to ANN
> # other threads reports the above message with the proxyInfo changed by thread X, and
reported ANN instead of SNN in the message.
> Some details:
> RetryInvocationHandler does the following when failing over:
> {code}
>   synchronized void failover(long expectedFailoverCount, Method method,
>                                int callId) {
>       // Make sure that concurrent failed invocations only cause a single
>       // actual failover.
>       if (failoverCount == expectedFailoverCount) {
>         fpp.performFailover(proxyInfo.proxy);
>         failoverCount++;
>       } else {
>         LOG.warn("A failover has occurred since the start of call #" + callId
>             + " " + proxyInfo.getString(method.getName()));
>       }
>       proxyInfo = fpp.getProxy();
>     }
> {code}
> and changed the proxyInfo in the ProxyDescriptor.
> While the log method below report message with ProxyDescriotor's proxyinfo:
> {code}
> private void log(final Method method, final boolean isFailover,
>       final int failovers, final long delay, final Exception ex) {
> ......
>    final StringBuilder b = new StringBuilder()
>         .append(ex + ", while invoking ")
>         .append(proxyDescriptor.getProxyInfo().getString(method.getName()));
>     if (failovers > 0) {
>       b.append(" after ").append(failovers).append(" failover attempts");
>     }
>     b.append(isFailover? ". Trying to failover ": ". Retrying ");
>     b.append(delay > 0? "after sleeping for " + delay + "ms.": "immediately.");
> {code}
> and so does  {{handleException}} method do
> {code}
>         if (LOG.isDebugEnabled()) {
>           LOG.debug("Exception while invoking call #" + callId + " "
>               + proxyDescriptor.getProxyInfo().getString(method.getName())
>               + ". Not retrying because " + retryInfo.action.reason, e);
>         }
> {code}
> FailoverProxyProvider
> {code}
>    public String getString(String methodName) {
>       return proxy.getClass().getSimpleName() + "." + methodName
>           + " over " + proxyInfo;
>     }
>     @Override
>     public String toString() {
>       return proxy.getClass().getSimpleName() + " over " + proxyInfo;
>     }
> {code}
>  



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