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https://issues.apache.org/jira/browse/FLINK-4027?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15344657#comment-15344657
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ASF GitHub Bot commented on FLINK-4027:
---------------------------------------
Github user tillrohrmann commented on a diff in the pull request:
https://github.com/apache/flink/pull/2108#discussion_r68086007
--- Diff:
flink-streaming-connectors/flink-connector-kafka-base/src/main/java/org/apache/flink/streaming/connectors/kafka/FlinkKafkaProducerBase.java
---
@@ -261,7 +298,9 @@ public void invoke(IN next) throws Exception {
} else {
record = new ProducerRecord<>(targetTopic,
partitioner.partition(next, serializedKey, serializedValue, partitions.length),
serializedKey, serializedValue);
}
-
+ if(flushOnCheckpoint) {
+ pendingRecords++;
--- End diff --
The increment and decrement operations are not atomic. Thus, we have to
guard them from concurrent access. Concurrent modifications can happen when
you're in the `invoke` method and a callback is executed at the same time.
> FlinkKafkaProducer09 sink can lose messages
> -------------------------------------------
>
> Key: FLINK-4027
> URL: https://issues.apache.org/jira/browse/FLINK-4027
> Project: Flink
> Issue Type: Bug
> Components: Kafka Connector
> Affects Versions: 1.0.3
> Reporter: Elias Levy
> Assignee: Robert Metzger
> Priority: Critical
>
> The FlinkKafkaProducer09 sink appears to not offer at-least-once guarantees.
> The producer is publishing messages asynchronously. A callback can record
> publishing errors, which will be raised when detected. But as far as I can
> tell, there is no barrier to wait for async errors from the sink when
> checkpointing or to track the event time of acked messages to inform the
> checkpointing process.
> If a checkpoint occurs while there are pending publish requests, and the
> requests return a failure after the checkpoint occurred, those message will
> be lost as the checkpoint will consider them processed by the sink.
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