Introduce poll-interval-variance option #431
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tomgi
commented
Sep 20, 2024
| @@ -275,7 +275,7 @@ def assert_poll(priorities:, locked:) | |||
| assert_equal false, poller.should_poll? | |||
| end | |||
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| it "should be false if the number of jobs returned from the last poll was less than the lowest priority request, but the poll_interval has elapsed" do | |||
| it "should be true if the number of jobs returned from the last poll was less than the lowest priority request, but the poll_interval has elapsed" do | |||
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That was a typo, the test is actually checking assert_equal true, which is the expected behavior.
tomgi
commented
Sep 24, 2024
| job_ids = 5.times.map { Que::Job.enqueue.que_attrs[:id] } | ||
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| result = poller.poll(priorities: { 500 => 7 }, held_locks: Set.new) | ||
| assert_equal job_ids, result.map(&:id) | ||
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| poller.instance_variable_set(:@last_polled_at, Time.now - 30) | ||
| assert_equal true, poller.should_poll? | ||
| Timecop.freeze(Time.now + 30) do |
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This change makes the spec less coupled with implementation details.
Instead of setting private instance variables, it 'time travels' 30 seconds into the future, after the poll_interval has already elapsed.
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Context
We run multiple ECS tasks of que that are all started almost exactly at the same time during every deployment.
That means that they also start polling at the same time, and continue doing so in such a synchronized fashion.
More specifically, in our case:
poll-intervalis set to 20sMeaning that on average we poll every 5s, but in reality, we poll 4 times every 20s 🙂
We would like to introduce a random variance to the polling interval, so that the polling is more evenly distributed.
Changes
Add optional
poll-interval-varianceCLI parameter defaulting to 0.0.It is used to make each individual poll time slightly randomised within the range of
poll-interval +/- poll-interval-variance.This way tasks started at the same time won't continue always polling at the same time.
Backward-compatibility
When the new
poll-interval-varianceparameter is not provided, there's no change compared to the current behaviour.