TEZ-4397 Open Tez Input splits asynchronously #195
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rbalamohan
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Mar 15, 2022
| curReader = wrappedInputFormat.getRecordReader( | ||
| groupedSplit.wrappedSplits.get(idx), job, reporter); | ||
| curReader = initedReaders.poll().get(); | ||
| submitInitReaders(1); |
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From the next stage onwards (i.e after the init part), this will start executing in sequential order as it requests for 1 additional reader. It will be good to init next set of readers in parallel.
rbalamohan
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Mar 16, 2022
| RecordReader<K, V> reader = wrappedInputFormat.getRecordReader(s, job, reporter); | ||
| LOG.debug("Init Thread processed reader number {} initialization", index); | ||
| return reader; | ||
| } catch(IOException e) { |
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If thread is interrupted, it should cancel other pending tasks?
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This should be done for all exceptions as well.
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jfsii
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Mar 17, 2022
jfsii
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Added two comments - I learned a bit reading about ThreadPools and garbage collection
| throw new RuntimeException(e); | ||
| } catch (InterruptedException e) { | ||
| Thread.currentThread().interrupt(); | ||
| for (Future<RecordReader<K,V>> f : initedReaders) { |
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probably want to cancel on any exception and thread interrupt only on InterruptedException.
| TezSplitGrouper.TEZ_GROUPING_SPLIT_INIT_THREADS_DEFAULT); | ||
| this.numReaders = conf.getInt(TezSplitGrouper.TEZ_GROUPING_SPLIT_INIT_NUM_RECORDREADERS, | ||
| TezSplitGrouper.TEZ_GROUPING_SPLIT_INIT_NUM_RECORDREADERS_DEFAULT); | ||
| this.initReaderExecService = Executors.newFixedThreadPool(numThreads, |
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I think we will want to somehow make this static (to share between usages of TezGroupedSplitsRecordReader) or figure out how to call shutdown in a reliable manner. Otherwise I think a long lived process that uses multiple TezGroupedSplitsRecordReaders throughout its life will end up having a large number of unused threads since they will not auto shutdown and thus not garbage collected.
https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ThreadPoolExecutor.html
See finalization section.
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I'm not sure about the context, but if the goal is to properly shutdown a global resource somehow, it can done by the shutdownhandler, somewhere here: https://github.com/apache/tez/blob/master/tez-dag/src/main/java/org/apache/tez/dag/app/DAGAppMaster.java#L954
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Thanks @rbalamohan @jfsii and @abstractdog for the reviews. |
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Latest patch LGTM. +1 |
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Tez input splits can be opened asynchronously. This will reduce the amount of time spent for s3 to prepare the connection and opening the object