Ning created BEAM-13627:
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Summary: aws sqs I/O misses to delete some acked messages, output
mutation exception
Key: BEAM-13627
URL: https://issues.apache.org/jira/browse/BEAM-13627
Project: Beam
Issue Type: Bug
Components: io-java-aws
Affects Versions: 2.34.0
Reporter: Ning
Original problem and analysis:
https://stackoverflow.com/questions/70648489/apache-beam-2-34-0-sqsio-illegal-mutation-exception
The I/O is much more complicated in Beam 2.34.0 than 2.31.0. For Beam 2.34.0,
the
[deleteBatch](https://github.com/apache/beam/blob/release-2.34.0/sdks/java/io/amazon-web-services/src/main/java/org/apache/beam/sdk/io/aws/sqs/SqsUnboundedReader.java#L584)
logic **filters** messages **to delete** based on the **inflight** state.
However, there are assumptions in the
[extend](https://github.com/apache/beam/blob/release-2.34.0/sdks/java/io/amazon-web-services/src/main/java/org/apache/beam/sdk/io/aws/sqs/SqsUnboundedReader.java#L756)
logic where the inflight state is modified to **exclude** messages that are
**assumed expired or to be expired**. These messages are **never** explicitly
deleted from sqs.
So in a future pull, sqs could resend messages that are read from
[messagesNotYetRead](https://github.com/apache/beam/blob/release-2.34.0/sdks/java/io/amazon-web-services/src/main/java/org/apache/beam/sdk/io/aws/sqs/SqsUnboundedReader.java#L509).
And
[safeToDeleteIds](https://github.com/apache/beam/blob/release-2.34.0/sdks/java/io/amazon-web-services/src/main/java/org/apache/beam/sdk/io/aws/sqs/SqsUnboundedReader.java#L526)
contains those excluded message ids but never get to delete them.
This will be detected as output mutation exception.
**TL;DR: debugging process**
The mutation was detected in the SqsUnboundedSource, not caused by any other
code in the pipeline.
The code that reports the warning and throws the exception is
[here](https://github.com/apache/beam/blob/release-2.34.0/sdks/java/core/src/main/java/org/apache/beam/sdk/util/MutationDetectors.java#L145).
The only field changed is the Receipt handle. It's documented
[here](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-queue-message-identifiers.html)
that:
> If you receive a message more than once, each time you receive it, you get a
> different receipt handle. You must provide the most recently received receipt
> handle when you request to delete the message (otherwise, the message might
> not be deleted).
There is no
[aws_java_sdk_version](https://github.com/apache/beam/blob/release-2.34.0/buildSrc/src/main/groovy/org/apache/beam/gradle/BeamModulePlugin.groovy#L447)
change between Beam 2.31.0 and Beam 2.34.0. So AWS SDK shouldn't be the
culprit.
There is a significant change between Beam 2.31.0 and Beam 2.34.0 for
[SqsUnboundedReader](https://github.com/apache/beam/blob/release-2.34.0/sdks/java/io/amazon-web-services/src/main/java/org/apache/beam/sdk/io/aws/sqs/SqsUnboundedReader.java).
To receive a message more than once, the message must not have been deleted
since the first time received. The deletion logic is invoked in
[SqsCheckpointMark](https://github.com/apache/beam/blob/release-2.34.0/sdks/java/io/amazon-web-services/src/main/java/org/apache/beam/sdk/io/aws/sqs/SqsCheckpointMark.java).
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