[exporter/prometheusremotewrite] Fix WAL deadlock #37630
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Signed-off-by: Arthur Silva Sens <[email protected]>
Signed-off-by: Arthur Silva Sens <[email protected]>
Signed-off-by: Arthur Silva Sens <[email protected]>
Signed-off-by: Arthur Silva Sens <[email protected]>
Signed-off-by: Arthur Silva Sens <[email protected]>
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dashpole
approved these changes
Feb 3, 2025
Signed-off-by: Arthur Silva Sens <[email protected]>
dashpole
approved these changes
Feb 3, 2025
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I was taking a look over #20875 and hoping to finish it.
Fixes #19363
Fixes #24399
Fixes #15277
As mentioned in #24399 (comment), I used a library to help me understand how the deadlock was happening. (1st commit). It showed that
persistToWalwas trying to acquire the lock, whilereadPrompbFromWalheld it forever.I changed the strategy here and instead of using fs.Notify, and all that complicated logic around it, we're just using a pub/sub strategy between the writer and reader Go routines.
The reader go routine, once finding an empty WAL, will now release the lock immediately and wait for a notification from the writer. While previously it would hold the lock while waiting for a write that would never happen.