KAFKA-10289 fix failed connect_distributed_test.py (ConnectDistribute…

[chia7712]

issue: https://issues.apache.org/jira/browse/KAFKA-10289

In Python 3, filter functions return iterators rather than list so it can traverse only once. Hence, the following loop only see "empty" and then validation fails.

        src_messages = self.source.committed_messages() # return iterator
        sink_messages = self.sink.flushed_messages()) # return iterator
        for task in range(num_tasks):
            # only first task can "see" the result. following tasks see empty result
            src_seqnos = [msg['seqno'] for msg in src_messages if msg['task'] == task]

reference: https://portingguide.readthedocs.io/en/latest/iterators.html#new-behavior-of-map-and-filter

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[chia7712]

@hachikuji Could you take a look? I have test this patch on my local. It pass.

command

docker rm -f ducker01 ducker02 ducker03 ducker04 ducker05 ducker06 ducker07 ducker08 ducker09 ducker10 ducker11 ducker12 ducker13 ducker14 \
; export _DUCKTAPE_OPTIONS="--subset 0 --subsets 2" \
&& TC_PATHS="tests/kafkatest/tests/connect/connect_distributed_test.py" /bin/bash tests/docker/run_tests.sh

result

SESSION REPORT (ALL TESTS)
ducktape version: 0.8.0
session_id:       2020-12-06--005
run time:         35 minutes 42.481 seconds
tests run:        30
passed:           30
failed:           0
ignored:          0

command

docker rm -f ducker01 ducker02 ducker03 ducker04 ducker05 ducker06 ducker07 ducker08 ducker09 ducker10 ducker11 ducker12 ducker13 ducker14 \
; export _DUCKTAPE_OPTIONS="--subset 1 --subsets 2" \
&& TC_PATHS="tests/kafkatest/tests/connect/connect_distributed_test.py" /bin/bash tests/docker/run_tests.sh

result

SESSION REPORT (ALL TESTS)
ducktape version: 0.8.0
session_id:       2020-12-06--003
run time:         29 minutes 57.771 seconds
tests run:        30
passed:           30
failed:           0
ignored:          0

[hachikuji]

LGTM