Details
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Bug
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Status: Open
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Major
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Resolution: Unresolved
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None
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None
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None
Description
In Client.java, sendRpcRequest does the following
/** Initiates a rpc call by sending the rpc request to the remote server.
* Note: this is not called from the Connection thread, but by other
* threads.
* @param call - the rpc request
*/
public void sendRpcRequest(final Call call)
throws InterruptedException, IOException {
if (shouldCloseConnection.get()) {
return;
}
// Serialize the call to be sent. This is done from the actual
// caller thread, rather than the sendParamsExecutor thread,
// so that if the serialization throws an error, it is reported
// properly. This also parallelizes the serialization.
//
// Format of a call on the wire:
// 0) Length of rest below (1 + 2)
// 1) RpcRequestHeader - is serialized Delimited hence contains length
// 2) RpcRequest
//
// Items '1' and '2' are prepared here.
RpcRequestHeaderProto header = ProtoUtil.makeRpcRequestHeader(
call.rpcKind, OperationProto.RPC_FINAL_PACKET, call.id, call.retry,
clientId);
final ResponseBuffer buf = new ResponseBuffer();
header.writeDelimitedTo(buf);
RpcWritable.wrap(call.rpcRequest).writeTo(buf);
synchronized (sendRpcRequestLock) {
Future<?> senderFuture = sendParamsExecutor.submit(new Runnable() {
@Override
public void run() {
try {
synchronized (ipcStreams.out) {
if (shouldCloseConnection.get()) {
return;
}
if (LOG.isDebugEnabled()) {
LOG.debug(getName() + " sending #" + call.id
+ " " + call.rpcRequest);
}
// RpcRequestHeader + RpcRequest
ipcStreams.sendRequest(buf.toByteArray());
ipcStreams.flush();
}
} catch (IOException e) {
// exception at this point would leave the connection in an
// unrecoverable state (eg half a call left on the wire).
// So, close the connection, killing any outstanding calls
markClosed(e);
} finally {
//the buffer is just an in-memory buffer, but it is still polite to
// close early
IOUtils.closeStream(buf);
}
}
});
try {
senderFuture.get();
} catch (ExecutionException e) {
Throwable cause = e.getCause();
// cause should only be a RuntimeException as the Runnable above
// catches IOException
if (cause instanceof RuntimeException) {
throw (RuntimeException) cause;
} else {
throw new RuntimeException("unexpected checked exception", cause);
}
}
}
}
It's observed that the call can be stuck at senderFuture.get(); with the following stack
"Thread-13" #40 prio=5 os_prio=0 tid=0x000000000fb0d000 nid=0xf189c waiting on condition [0x00007f697c582000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x00000006187e5ec0> (a java.util.concurrent.FutureTask) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.FutureTask.awaitDone(FutureTask.java:429) at java.util.concurrent.FutureTask.get(FutureTask.java:191) at org.apache.hadoop.ipc.Client$Connection.sendRpcRequest(Client.java:1088) - locked <0x00000006215c1e08> (a java.lang.Object) at org.apache.hadoop.ipc.Client.call(Client.java:1483) at org.apache.hadoop.ipc.Client.call(Client.java:1441) at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:230) at com.sun.proxy.$Proxy10.getBlockLocations(Unknown Source) at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.getBlockLocations(ClientNamenodeProtocolTranslatorPB.java:266) at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:258) at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:104) at com.sun.proxy.$Proxy11.getBlockLocations(Unknown Source) at org.apache.hadoop.hdfs.DFSClient.callGetBlockLocations(DFSClient.java:1323) at org.apache.hadoop.hdfs.DFSClient.getLocatedBlocks(DFSClient.java:1310) at org.apache.hadoop.hdfs.DFSClient.getLocatedBlocks(DFSClient.java:1298) at org.apache.hadoop.hdfs.DFSInputStream.fetchLocatedBlocksAndGetLastBlockLength(DFSInputStream.java:309) at org.apache.hadoop.hdfs.DFSInputStream.openInfo(DFSInputStream.java:275) - locked <0x00000006187e5530> (a java.lang.Object) at org.apache.hadoop.hdfs.DFSInputStream.<init>(DFSInputStream.java:267) at org.apache.hadoop.hdfs.DFSClient.open(DFSClient.java:1629) at org.apache.hadoop.hdfs.DistributedFileSystem$4.doCall(DistributedFileSystem.java:338) at org.apache.hadoop.hdfs.DistributedFileSystem$4.doCall(DistributedFileSystem.java:334) at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81) at org.apache.hadoop.hdfs.DistributedFileSystem.open(DistributedFileSystem.java:334)
Given that we support rpcTimeOut, we could chose the second method of Future below:
/**
* Waits if necessary for the computation to complete, and then
* retrieves its result.
*
* @return the computed result
* @throws CancellationException if the computation was cancelled
* @throws ExecutionException if the computation threw an
* exception
* @throws InterruptedException if the current thread was interrupted
* while waiting
*/
V get() throws InterruptedException, ExecutionException;
/**
* Waits if necessary for at most the given time for the computation
* to complete, and then retrieves its result, if available.
*
* @param timeout the maximum time to wait
* @param unit the time unit of the timeout argument
* @return the computed result
* @throws CancellationException if the computation was cancelled
* @throws ExecutionException if the computation threw an
* exception
* @throws InterruptedException if the current thread was interrupted
* while waiting
* @throws TimeoutException if the wait timed out
*/
V get(long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException;
In theory, since the RPC at client is serialized, we could just use the main thread to do the execution, instead of using a threadpool to create new thread. This can be discussed in a separate jira.
And why the RPC is not processed and returned by NN is another topic (HADOOP-15538).
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