feat: Add basic periodic metric INFO logger#496
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kodiakhq[bot] merged 2 commits intocloudquery:mainfrom Dec 24, 2022
shimonp21:periodic_metric_logger
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feat: Add basic periodic metric INFO logger#496kodiakhq[bot] merged 2 commits intocloudquery:mainfrom shimonp21:periodic_metric_logger
kodiakhq[bot] merged 2 commits intocloudquery:mainfrom
shimonp21:periodic_metric_logger
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yevgenypats
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Dec 17, 2022
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Few changes needed to make it work
plugins/source_scheduler_dfs.go
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| // We start a goroutine that logs the metrics periodically. | ||
| // It needs its own waitgroup | ||
| var logWg sync.WaitGroup | ||
| logWg.Add(1) |
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I don't think you need the waitgroup here
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- Here is the race I am worried about:
- A sync starts and finishes, and
syncDfsreturns. However, periodic-metric-logger is still running (maybe he's still summing up in TotalResourcesAtomic, so not looking atctxright now. - A new sync starts (maybe we are in
grpc-mode?), andmetrics.InitWithClientsis called. periodicMetricLoggeris still running and summing up stuff from the map, so golang panics withconcurrent reads and writes to map!
See the following code-snippet for a toy reproduction:
https://gist.github.com/shimonp21/dda9ee70434ad5da25f3c3ecf5149b40
This produces a panic:
fatal error: concurrent map read and map write
fatal error: concurrent map read and map write
goroutine 31 [running]:
main.mapReader(0x0?)
/Users/shimonp/projects/etc/main.go:25 +0x4e
created by main.main
/Users/shimonp/projects/etc/main.go:12 +0x6e
goroutine 1 [runnable]:
main.main()
/Users/shimonp/projects/etc/main.go:12 +0x8f
goroutine 17 [runnable]:
main.mapWriter(0xc0000547b8?)
/Users/shimonp/projects/etc/main.go:18 +0x6c
created by main.main
/Users/shimonp/projects/etc/main.go:8 +0x65
- because logCancel is a child-context of
ctx- it will be cancelled if the parent is cancelled. I don't want to put it in adefer, because, as mentioned in point 1 - I think we need to synchronously wait for the priodiclogger to finish.
Agree is a far-fetched race, but AFAIU it can definitly happen, so I'd rather err on the side of "no races in the code".
- Logs very basic stats about the sync every 30 seconds. - Used `ctx` and a new waitgroup - because it's importat to shut it down gracefully (concurrent map read-writes are dangerous in golang). - Used `TotalResourcesAtomic` - see this stackoverflow answer: https://stackoverflow.com/a/46557083
yevgenypats
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Dec 24, 2022
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Not sure I understood the write-up on the race condition but this looks fine to me now once it moved to the right place.
kodiakhq bot
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Dec 27, 2022
🤖 I have created a release *beep* *boop* --- ## [1.14.0](v1.13.1...v1.14.0) (2022-12-27) ### Features * Add basic periodic metric INFO logger ([#496](#496)) ([8d1d32e](8d1d32e)) ### Bug Fixes * **destinations:** Stop writing resources when channel is closed ([#460](#460)) ([5590845](5590845)) * Don't hide errors in destination server ([#529](#529)) ([d91f94f](d91f94f)) --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).
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ctxand a new waitgroup - because it's importat to shut it down gracefully (concurrent map read-writes are dangerous in golang).TotalResourcesAtomic- see this stackoverflow answer: https://stackoverflow.com/a/46557083