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From wangsan <wamg...@163.com>
Subject Re:Exception in BucketingSink when cancelling Flink job
Date Wed, 27 Sep 2017 05:33:13 GMT
After digging into the source code, we found that when Flink job is canceled, a TaskCanceler
thread is created.

The TaskCanceler thread calls cancel() on the invokable and periodically interrupts the
task thread until it has terminated.

try {
} catch (Throwable t) {
  logger.error("Error while canceling the task {}.", taskName, t);
}//......executer.interrupt();try {
}catch (InterruptedException e) {  // we can ignore this}//......

Notice that TaskCanceler first send interrupt signal to task thread, and following with join
method. And since the task thread is now try to close DFSOutputStream, which is waiting for
ack, thus InterruptedException is throwed out in task thread.

synchronized (dataQueue) {while (!streamerClosed) {
  checkClosed();  if (lastAckedSeqno >= seqno) {    break;
  }  try {
    dataQueue.wait(1000); // when we receive an ack, we notify on
    // dataQueue
  } catch (InterruptedException ie) {    thrownewInterruptedIOException(        "Interrupted
while waiting for data to be acknowledged by pipeline");

I was confused why TaskCanceler call executer.interrupt() before executer.join(interruptInterval).
Can anyone help?


We are currently using BucketingSink to save data into HDFS in parquet format. But when the
flink job was cancelled, we always got Exception in BucketingSink's  close method. The datailed
exception info is as below:
[ERROR] [2017-09-26 20:51:58,893] [org.apache.flink.streaming.runtime.tasks.StreamTask] -
Error during disposal of stream operator.
java.io.InterruptedIOException: Interrupted while waiting for data to be acknowledged by pipeline
at org.apache.hadoop.hdfs.DFSOutputStream.waitForAckedSeqno(DFSOutputStream.java:2151)
at org.apache.hadoop.hdfs.DFSOutputStream.flushInternal(DFSOutputStream.java:2130)
at org.apache.hadoop.hdfs.DFSOutputStream.closeImpl(DFSOutputStream.java:2266)
at org.apache.hadoop.hdfs.DFSOutputStream.close(DFSOutputStream.java:2236)
at org.apache.hadoop.fs.FSDataOutputStream$PositionCache.close(FSDataOutputStream.java:72)
at org.apache.hadoop.fs.FSDataOutputStream.close(FSDataOutputStream.java:106)
at org.apache.parquet.hadoop.ParquetFileWriter.end(ParquetFileWriter.java:643)
at org.apache.parquet.hadoop.InternalParquetRecordWriter.close(InternalParquetRecordWriter.java:117)
at org.apache.parquet.hadoop.ParquetWriter.close(ParquetWriter.java:301)

at org.apache.flink.api.common.functions.util.FunctionUtils.closeFunction(FunctionUtils.java:43)
at org.apache.flink.streaming.api.operators.AbstractUdfStreamOperator.dispose(AbstractUdfStreamOperator.java:126)
at org.apache.flink.streaming.runtime.tasks.StreamTask.disposeAllOperators(StreamTask.java:429)
at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:334)
at org.apache.flink.runtime.taskmanager.Task.run(Task.java:702)
at java.lang.Thread.run(Thread.java:745)

It seems that DFSOutputStream haven't been closed before task thread is force terminated.
We found a similar problem in http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Changing-timeout-for-cancel-command-td12601.html
, but setting "akka.ask.timeout" to a larger value does not work for us. So how can we make
sure the stream is safely closed when cacelling a job?


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