Add json body check for sqs message

[kaiyan-sheng]

What does this PR do?

I suspect sometimes AWS SQS message is not an invalid JSON format. This PR is to add check on it and improving error message for better debugging.

For example:

2020-08-26T10:05:10.780Z        ERROR   [s3]    s3/input.go:257 handleSQSMessage failed: json unmarshal sqs message body failed: invalid character 'e' in literal true (expecting 'r')

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Related issues

• Relates [Filebeat] json unmarshal error in S3 input #21726

[elasticmachine]

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Build stats

• Build Cause: Pull request #21727 updated

• Start Time: 2020-12-03T16:43:24.768+0000

• Duration: 43 min 56 sec

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Test	Results
Failed	0
Passed	1979
Skipped	259
Total	2238

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Passed	1979
Skipped	259
Total	2238

[elasticmachine]

Pinging @elastic/integrations-platforms (Team:Platforms)

[kaiyan-sheng]

@exekias I have a question about this: When json body check json.Valid failed, should this SQS message be deleted from the queue? Right now with this PR, it will not be removed. This means the visibility timeout will be updated and the message will eventually go back into the queue and get processed again later. But if the json body is invalid, it will not pass json.Valid check next time around either.

[exekias]

Sorry I miss this notification 🙏 , two things:

• Calling Valid here is the same as handling the Unmarshall error, but Valid will add more processing, you are basically reading the message twice. It would be better just to do the logging when the error happens.
• An invalid JSON message is permanent to us, so I think it would make sense to remove it from the queue, is there any way to retrieve it later after removing it? I guess the answer is no

[kaiyan-sheng]

@exekias Thank you for the input!!

• Calling Valid here is the same as handling the Unmarshall error, but Valid will add more processing, you are basically reading the message twice. It would be better just to do the logging when the error happens.

Good point, will remove the extra Valid here.

• An invalid JSON message is permanent to us, so I think it would make sense to remove it from the queue, is there any way to retrieve it later after removing it? I guess the answer is no

Yeah there is no way to retrieve it later after removing.

[elasticmachine]

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Test stats 🧪

Test	Results
Failed	0
Passed	1947
Skipped	259
Total	2206