[jira] [Created] (FLINK-11046) ElasticSearch6Connector cause thread blocked when index failed with retry

[Shang Yuanchun (Jira)]

luoguohao created FLINK-11046:
---------------------------------

             Summary: ElasticSearch6Connector cause thread blocked when index failed with retry
                 Key: FLINK-11046
                 URL: https://issues.apache.org/jira/browse/FLINK-11046
             Project: Flink
          Issue Type: Bug
          Components: ElasticSearch Connector
    Affects Versions: 1.6.2
            Reporter: luoguohao


When i'm using es6 sink to index into es, bulk process with some exception catched, and  i trying to reindex the document with the call `indexer.add(action)` in the `ActionRequestFailureHandler.onFailure()` method, but things goes incorrect. The call thread stuck there, and with the thread dump, i saw the `bulkprocessor` object was locked by other thread. 
{code:java}
public interface ActionRequestFailureHandler extends Serializable {

 void onFailure(ActionRequest action, Throwable failure, int restStatusCode, RequestIndexer indexer) throws Throwable;

}
{code}
After i read the code implemented in the `indexer.add(action)`, i find that `synchronized` is needed on each add operation.

 

 
{code:java}
private synchronized void internalAdd(DocWriteRequest request, @Nullable Object payload) {
  ensureOpen();
  bulkRequest.add(request, payload);
  executeIfNeeded();
}
{code}
 

 

And, at i also noticed that `bulkprocessor` object would also locked in the bulk process thread. 

the bulk process operation is in the following code:
{code:java}
public void execute(BulkRequest bulkRequest, long executionId) {
    Runnable toRelease = () -> {};
    boolean bulkRequestSetupSuccessful = false;
    try {
        listener.beforeBulk(executionId, bulkRequest);
        semaphore.acquire();
        toRelease = semaphore::release;
        CountDownLatch latch = new CountDownLatch(1);
        retry.withBackoff(consumer, bulkRequest, new ActionListener<BulkResponse>() {
            @Override
            public void onResponse(BulkResponse response) {
                try {
                    listener.afterBulk(executionId, bulkRequest, response);
                } finally {
                    semaphore.release();
                    latch.countDown();
                }
            }

            @Override
            public void onFailure(Exception e) {
                try {
                    listener.afterBulk(executionId, bulkRequest, e);
                } finally {
                    semaphore.release();
                    latch.countDown();
                }
            }
        }, Settings.EMPTY);
        bulkRequestSetupSuccessful = true;
        if (concurrentRequests == 0) {
            latch.await();
        }
    } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
        logger.info(() -> new ParameterizedMessage("Bulk request {} has been cancelled.", executionId), e);
        listener.afterBulk(executionId, bulkRequest, e);
    } catch (Exception e) {
        logger.warn(() -> new ParameterizedMessage("Failed to execute bulk request {}.", executionId), e);
        listener.afterBulk(executionId, bulkRequest, e);
    } finally {
        if (bulkRequestSetupSuccessful == false) {  // if we fail on client.bulk() release the semaphore
            toRelease.run();
        }
    }
}
{code}
As the read line i marked above, i think, that's the reason why the retry operation thread was block, because the the bulk process thread never release the lock on `bulkprocessor`.  and, i also trying to figure out why the field `concurrentRequests` was set to zero. And i saw the the initialize for bulkprocessor in class `ElasticsearchSinkBase`:
{code:java}
protected BulkProcessor buildBulkProcessor(BulkProcessor.Listener listener) {
 ...
 BulkProcessor.Builder bulkProcessorBuilder =      callBridge.createBulkProcessorBuilder(client, listener);

 // This makes flush() blocking
 bulkProcessorBuilder.setConcurrentRequests(0);
 
 ...

 return bulkProcessorBuilder.build();
}
{code}
 this field value was set to zero explicitly. So, all things seems to make sense, but i still wonder why the retry operation is not in the same thread as the bulk process execution, after i read the code, `bulkAsync` method might be the last puzzle.
{code:java}
@Override
public BulkProcessor.Builder createBulkProcessorBuilder(RestHighLevelClient client, BulkProcessor.Listener listener) {
 return BulkProcessor.builder(client::bulkAsync, listener);
}
{code}
So, I hope someone can help to fix this problem, or given some suggestions, and also i can make a try to take it. 
Thanks a lot !



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