Yongjun Zhang created HADOOP-15530:
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Summary: RPC could stuck at senderFuture.get()
Key: HADOOP-15530
URL: https://issues.apache.org/jira/browse/HADOOP-15530
Project: Hadoop Common
Issue Type: Bug
Components: common
Reporter: Yongjun Zhang
In Client.java, sendRpcRequest does the following
{code}
/** 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);
}
}
}
}
{code}
It's observed that the call can be stuck at {{senderFuture.get();}}
Given that we support rpcTimeOut, we could chose the second method of Future
below:
{code}
/**
* 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;
{code}
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.
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