[GitHub] flink pull request #3669: [FLINK-6215] Make the StatefulSequenceSource scala...

[tzulitai <gi...@git.apache.org>]

Github user tzulitai commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3669#discussion_r130080485
  
    --- Diff: flink-streaming-java/src/main/java/org/apache/flink/streaming/api/functions/source/StatefulSequenceSource.java ---
    @@ -61,52 +65,89 @@
     	 * @param end End of the range of numbers to emit.
     	 */
     	public StatefulSequenceSource(long start, long end) {
    +		Preconditions.checkArgument(start <= end);
     		this.start = start;
     		this.end = end;
     	}
     
     	@Override
     	public void initializeState(FunctionInitializationContext context) throws Exception {
     
    -		Preconditions.checkState(this.checkpointedState == null,
    +		Preconditions.checkState(checkpointedState == null,
     			"The " + getClass().getSimpleName() + " has already been initialized.");
     
     		this.checkpointedState = context.getOperatorStateStore().getOperatorState(
     			new ListStateDescriptor<>(
    -				"stateful-sequence-source-state",
    -				LongSerializer.INSTANCE
    +				"stateful-sequence-source-state", 
    +					new TupleSerializer<>(
    +							(Class<Tuple2<Long, Long>>) (Class<?>) Tuple2.class,
    +							new TypeSerializer<?>[] { LongSerializer.INSTANCE, LongSerializer.INSTANCE }
    +					)
     			)
     		);
     
    -		this.valuesToEmit = new ArrayDeque<>();
    +		this.endToNextOffsetMapping = new HashMap<>();
     		if (context.isRestored()) {
    -			// upon restoring
    -
    -			for (Long v : this.checkpointedState.get()) {
    -				this.valuesToEmit.add(v);
    +			for (Tuple2<Long, Long> partitionInfo: checkpointedState.get()) {
    +				Long prev = endToNextOffsetMapping.put(partitionInfo.f0, partitionInfo.f1);
    +				Preconditions.checkState(prev == null,
    +						getClass().getSimpleName() + " : Duplicate entry when restoring.");
     			}
     		} else {
    -			// the first time the job is executed
    -
    -			final int stepSize = getRuntimeContext().getNumberOfParallelSubtasks();
     			final int taskIdx = getRuntimeContext().getIndexOfThisSubtask();
    -			final long congruence = start + taskIdx;
    +			final int parallelTasks = getRuntimeContext().getNumberOfParallelSubtasks();
    +
    +			final long totalElements = Math.abs(end - start + 1L);
    +			final int maxParallelism = getRuntimeContext().getMaxNumberOfParallelSubtasks();
    +			final int totalPartitions = totalElements < Integer.MAX_VALUE ? Math.min(maxParallelism, (int) totalElements) : maxParallelism;
     
    -			long totalNoOfElements = Math.abs(end - start + 1);
    -			final int baseSize = safeDivide(totalNoOfElements, stepSize);
    -			final int toCollect = (totalNoOfElements % stepSize > taskIdx) ? baseSize + 1 : baseSize;
    +			Tuple2<Integer, Integer> localPartitionRange = getLocalRange(totalPartitions, parallelTasks, taskIdx);
    +			int localStartIdx = localPartitionRange.f0;
    +			int localEndIdx = localStartIdx + localPartitionRange.f1;
     
    -			for (long collected = 0; collected < toCollect; collected++) {
    -				this.valuesToEmit.add(collected * stepSize + congruence);
    +			for (int partIdx = localStartIdx; partIdx < localEndIdx; partIdx++) {
    +				Tuple2<Long, Long> limits = getPartitionLimits(totalElements, totalPartitions, partIdx);
    +				endToNextOffsetMapping.put(limits.f1, limits.f0);
     			}
     		}
     	}
     
    +	private Tuple2<Integer, Integer> getLocalRange(int totalPartitions, int parallelTasks, int taskIdx) {
    +		int minPartitionSliceSize = totalPartitions / parallelTasks;
    +		int remainingPartitions = totalPartitions - minPartitionSliceSize * parallelTasks;
    +
    +		int localRangeStartIdx = taskIdx * minPartitionSliceSize + Math.min(taskIdx, remainingPartitions);
    +		int localRangeSize = taskIdx < remainingPartitions ? minPartitionSliceSize + 1 : minPartitionSliceSize;
    +
    +		return new Tuple2<>(localRangeStartIdx, localRangeSize);
    +	}
    +
    +	private Tuple2<Long, Long> getPartitionLimits(long totalElements, int totalPartitions, long partitionIdx) {
    +		long minElementPartitionSize = totalElements / totalPartitions;
    +		long remainingElements = totalElements - minElementPartitionSize * totalPartitions;
    +		long startOffset = start;
    +
    +		for (int idx = 0; idx < partitionIdx; idx++) {
    +			long partitionSize = idx < remainingElements ? minElementPartitionSize + 1L : minElementPartitionSize;
    +			startOffset += partitionSize;
    +		}
    +
    +		long partitionSize = partitionIdx < remainingElements ? minElementPartitionSize + 1L : minElementPartitionSize;
    +		return new Tuple2<>(startOffset, startOffset + partitionSize);
    +	}
    +
     	@Override
     	public void run(SourceContext<Long> ctx) throws Exception {
    -		while (isRunning && !this.valuesToEmit.isEmpty()) {
    -			synchronized (ctx.getCheckpointLock()) {
    -				ctx.collect(this.valuesToEmit.poll());
    +		for (Map.Entry<Long, Long> partition: endToNextOffsetMapping.entrySet()) {
    --- End diff --
    
    nit: empty spaces should surround ":"


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