🐛 Source Kafka: fix missing data

[alexnikitchuk]

What

Kafka Source does not guarantee "at-least-once" delivery because it drops records in case max_records_process is exceeded.

How

Consume all data returned from each call to poll(long) before closing the consumer.

Recommended reading order

1. x.java
2. y.python

🚨 User Impact 🚨

Are there any breaking changes? What is the end result perceived by the user? If yes, please merge this PR with the 🚨🚨 emoji so changelog authors can further highlight this if needed.

Pre-merge Checklist

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[marcosmarxm]

Hello 👋, first thank you for this amazing contribution.

We really appreciate the effort you've made to improve the project.
We ask you patience for the code review. Last month our team was focused on Hacktoberfest event and that probably left some PR without the proper feedback. And this week, due to the Thanksgiving US Holiday, most our team is out of office with their families. Another important piece of information why code won't be merge this week is: as a safety measure the core team has decided to freeze merging code to main branch to keep the release stable. Next week we'll return to you with the proper code review and update the status of your contribution.

If you have any questions feel free to send me a message in Slack!
Thanks!

[marcosmarxm]

@itaseskii are you going to review this?

[marcosmarxm]

/test connector=connectors/source-kafka

🕑 connectors/source-kafka https://github.com/airbytehq/airbyte/actions/runs/3619654858
✅ connectors/source-kafka https://github.com/airbytehq/airbyte/actions/runs/3619654858
Python tests coverage:

	 Name                                                 Stmts   Miss  Cover   Missing
	 ----------------------------------------------------------------------------------
	 source_acceptance_test/base.py                          12      4    67%   16-19
	 source_acceptance_test/config.py                       140      5    96%   87, 93, 238, 242-243
	 source_acceptance_test/conftest.py                     199     93    53%   35, 41-43, 48, 53, 59, 65, 71, 77-79, 98, 103-105, 111-113, 119-120, 125-126, 131, 137, 146-155, 161-166, 181, 205, 236, 242, 250-255, 263-268, 276-289, 294-300, 307-318, 325-341
	 source_acceptance_test/plugin.py                        69     25    64%   22-23, 31, 36, 120-140, 144-148
	 source_acceptance_test/tests/test_core.py              398    111    72%   53, 58, 87-95, 100-107, 111-112, 116-117, 299, 337-354, 363-371, 375-380, 386, 419-424, 462-469, 512-514, 517, 582-590, 602-605, 610, 666-667, 673, 676, 712-722, 735-760
	 source_acceptance_test/tests/test_incremental.py       158     14    91%   52-59, 64-77, 240
	 source_acceptance_test/utils/asserts.py                 39      2    95%   62-63
	 source_acceptance_test/utils/common.py                  94     10    89%   16-17, 32-38, 72, 75
	 source_acceptance_test/utils/compare.py                 62     23    63%   21-51, 68, 97-99
	 source_acceptance_test/utils/connector_runner.py       112     50    55%   23-26, 32, 36, 39-68, 71-73, 76-78, 81-83, 86-88, 91-93, 96-114, 148-150
	 source_acceptance_test/utils/json_schema_helper.py     107     13    88%   30-31, 38, 41, 65-68, 96, 120, 192-194
	 ----------------------------------------------------------------------------------
	 TOTAL                                                 1569    350    78%

Build Passed

Test summary info:

=========================== short test summary info ============================
SKIPPED [1] ../usr/local/lib/python3.9/site-packages/source_acceptance_test/plugin.py:63: Skipping TestConnection.test_check: not found in the config.
SKIPPED [1] ../usr/local/lib/python3.9/site-packages/source_acceptance_test/plugin.py:63: Skipping TestDiscovery.test_discover: not found in the config.
SKIPPED [1] ../usr/local/lib/python3.9/site-packages/source_acceptance_test/plugin.py:63: Skipping TestBasicRead.test_read: not found in the config.
SKIPPED [1] ../usr/local/lib/python3.9/site-packages/source_acceptance_test/plugin.py:63: Skipping TestFullRefresh.test_sequential_reads: not found in the config.
SKIPPED [1] ../usr/local/lib/python3.9/site-packages/source_acceptance_test/plugin.py:63: Skipping TestIncremental.test_two_sequential_reads: not found in the config.
================= 14 passed, 5 skipped, 21 warnings in 38.19s ==================

[itaseskii]

@itaseskii are you going to review this?

@marcosmarxm don't merge it yet I'll review it today.

[itaseskii]

@alexnikitchuk The fix looks good to me. It makes sense to avoid reading additional records once the max_records count is exceeded which the previous implementation was doing. The additional read shouldn't have been that problematic since the offset wasn't committed and dropped records would have been consumed in the next replication but still it is better to improve efficiency whenever possible 👍

With that in mind I'm unsure if the current implementation is correct when it comes to its constraint about not transmitting more records than specified in max_records. If the poll reads 20 records on initial read whereas the max_records count is set to 10 the records would still be committed/transmitted ignoring the constraint. I'm aware that this was not the point of this task but it is something that maybe we can address in future PR's.

[alexnikitchuk]

@alexnikitchuk The fix looks good to me. It makes sense to avoid reading additional records once the max_records count is exceeded which the previous implementation was doing. The additional read shouldn't have been that problematic since the offset wasn't committed and dropped records would have been consumed in the next replication but still it is better to improve efficiency whenever possible 👍

Consumer close commits all consumed messages. Why do you say it is not committed?

[itaseskii]

@alexnikitchuk The fix looks good to me. It makes sense to avoid reading additional records once the max_records count is exceeded which the previous implementation was doing. The additional read shouldn't have been that problematic since the offset wasn't committed and dropped records would have been consumed in the next replication but still it is better to improve efficiency whenever possible +1

Consumer close commits all consumed messages. Why do you say it is not committed?

because I wasn't aware that close() will auto commit if enable.auto.commit is set to true, which is by default. If that is the case then the issue was bigger than just reconsuming messages on next sync. 👍

[marcosmarxm]

/publish connector=connectors/source-kafka

🕑 Publishing the following connectors:
connectors/source-kafka
https://github.com/airbytehq/airbyte/actions/runs/3630342736

Connector	Did it publish?	Were definitions generated?
connectors/source-kafka	✅	✅

if you have connectors that successfully published but failed definition generation, follow step 4 here ▶️

[marcosmarxm]

Thanks @alexnikitchuk