flakey_flow fails with 12 or 24 messages unacknowledged.

[petersilva]

• there are two polls configured to share responsibility for a directory during the test.
• as part of the test the broker is repeatedly stopped and started (to observe robustness to that event.)
• as part of the test the active poll is swapped ever time the broker is restarted.

the flakey_tests on github often fail with 12 or 24 messages unacked, but are otherwise correct. It seems to be a problem with:

• flowcb/gather/message/ gather() is called by poll flow to get messages posted in order to update it's recent files cache.
• the flowcb/scheduled/poll.py has a gather routine that pauses... waiting for next polling interval.

so after reading a batch of messages, we then pause until the next scheduled polling interval... then we continue processing and eventually ack them.

It would seem better to acknolwedge them before we pause.

[petersilva]

[petersilva]

tagging it harmless because there does not seem to be any data loss or actual real-life problem that would result from this. This is an admittedly sub-optimal behaviour, but it results from an obscure condition and torture test that should not cause anything other than display issues in operations.