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https://issues.apache.org/jira/browse/FLINK-5487?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15880075#comment-15880075
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ASF GitHub Bot commented on FLINK-5487:
---------------------------------------
Github user tzulitai commented on a diff in the pull request:
https://github.com/apache/flink/pull/3358#discussion_r102656903
--- Diff:
flink-connectors/flink-connector-elasticsearch-base/src/main/java/org/apache/flink/streaming/connectors/elasticsearch/ElasticsearchSinkBase.java
---
@@ -211,6 +283,23 @@ public void invoke(T value) throws Exception {
}
@Override
+ public void initializeState(FunctionInitializationContext context)
throws Exception {
+ // no initialization needed
+ }
+
+ @Override
+ public void snapshotState(FunctionSnapshotContext context) throws
Exception {
+ checkErrorAndRethrow();
+
+ if (flushOnCheckpoint) {
+ do {
+ bulkProcessor.flush();
--- End diff --
On a second look, I think my previous statement is incorrect.
To elaborate, this is the way the `BulkProcessor`'s `flush` is implemented:
```
if(this.bulkRequest.numberOfActions() > 0) {
this.execute();
}
```
`execute()` doesn't return until `afterBulk` is called on the listener.
Since we can re-add requests to the bulk processor within `afterBulk`, the
`bulkRequest.numberOfActions() > 0` will be true again and enters the loop.
Therefore, the `bulkProcessor.flush()` can actually just be called once,
and will work with our failure-handler re-adding strategy so that the flush
also waits for re-added requests before returning. We can just check once on
`numPendingRequests` after the flush to make sure the flush works as expected.
> Proper at-least-once support for ElasticsearchSink
> --------------------------------------------------
>
> Key: FLINK-5487
> URL: https://issues.apache.org/jira/browse/FLINK-5487
> Project: Flink
> Issue Type: Bug
> Components: Streaming Connectors
> Reporter: Tzu-Li (Gordon) Tai
> Assignee: Tzu-Li (Gordon) Tai
> Priority: Critical
>
> Discussion in ML:
> http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Fault-tolerance-guarantees-of-Elasticsearch-sink-in-flink-elasticsearch2-td10982.html
> Currently, the Elasticsearch Sink actually doesn't offer any guarantees for
> message delivery.
> For proper support of at-least-once, the sink will need to participate in
> Flink's checkpointing: when snapshotting is triggered at the
> {{ElasticsearchSink}}, we need to synchronize on the pending ES requests by
> flushing the internal bulk processor. For temporary ES failures (see
> FLINK-5122) that may happen on the flush, we should retry them before
> returning from snapshotting and acking the checkpoint. If there are
> non-temporary ES failures on the flush, the current snapshot should fail.
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