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https://issues.apache.org/jira/browse/FLINK-11046?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16721314#comment-16721314
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Tzu-Li (Gordon) Tai commented on FLINK-11046:
---------------------------------------------
Ah ...., I think I understand the deadlock now.
It's because the we're calling the user provided
{{ActionRequestFailureHandler.onFailure(...)}} inside the {{afterBulk}}
callback. The lock is only released when the {{afterBulk}} method returns.
So, the deadlock is:
1. The {{BulkProcessor}} flushes, and one of the document indexing failed,
which invokes the user's {{ActionRequestFailureHandler.onFailure(...)}}. At
this point, the lock on {{BulkProcessor}} isn't released yet, because the
{{onFailure}} call is part of the bulk processor's flush callback.
2. Within {{ActionRequestFailureHandler.onFailure(...)}}, in your case you
added some new documents to be indexed. Upon adding, the {{BulkProcessor}}
would try to flush again, but the lock wasn't released yet and therefore
deadlock.
So, the re-indexing thread (i.e. the async callback) should have been blocked
on:
[https://github.com/elastic/elasticsearch/blob/v6.3.1/server/src/main/java/org/elasticsearch/action/bulk/BulkRequestHandler.java#L60]
While the main task thread should have been blocked on:
[https://github.com/elastic/elasticsearch/blob/v6.3.1/server/src/main/java/org/elasticsearch/action/bulk/BulkRequestHandler.java#L86]
Could you confirm this and see if the analysis makes sense to you?
[~luoguohao]
> 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
> Priority: Major
>
> 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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