flightcontrol: protect contention timeouts #5010
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tonistiigi
commented
Jun 10, 2024
| var retryCount int64 | ||
| g := &Group[string]{} | ||
| eg, ctx := errgroup.WithContext(context.Background()) | ||
| for i := 0; i < 1000; i++ { |
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With old configuration this test reaches 15 second limit ~75% with N=100 and ~25% with N=50
New configuration
N=10000 max-backoff=300ms
N=1000, max-backoff=70ms
N=500, max-backoff=40ms
N=100, max-backoff=12ms
These numbers are not exactly correct(and would be different on different machines) as they changed when I removed debug and cleaned up some code. The updated code does not fail as easily anymore if N<100 but the relative difference between the reachable backoff is still same.
tonistiigi
commented
Jun 10, 2024
| if errors.Is(err, errRetryTimeout) { | ||
| atomic.AddInt64(&retryCount, 1) | ||
| } | ||
| return err |
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Returning nil in here changes timing for the test so that it almost never produces the timeout anymore.
Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
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crazy-max
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Jun 10, 2024
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We had a report of #1822 error showing up in some logs.
Possibly important aspect of this race seems to be that callbacks returning errors are handled differently and retry happens right away when previous callback has errored in the beginning of
wait(). This was not handled by previous contention test. With the new test it is easy to reach timeout with ~100 goroutines (and smaller with reduced probability).This patch reduces the backoff factor so it does not increase too quickly and adds a random factor to initial timeout so that when lots of goroutines hit the error at the same time, they do not all retry at the same time as well. This seems to dramatically reduce the maximum backoff that can be reached by generating contention with the new testcase.