The race was detected in CI and locally when running with -race.
It happened between the following calls:
WARNING: DATA RACE
Write at 0x00c0003e6638 by goroutine 1374:
runtime.racewrite()
<autogenerated>:1 +0x1e
github.com/lightninglabs/loop/sweepbatcher.(*batch).Wait()
sweepbatcher/sweep_batch.go:463 +0x6e
github.com/lightninglabs/loop/sweepbatcher.(*Batcher).Run.func1()
sweepbatcher/sweep_batcher.go:272 +0x10e
Previous read at 0x00c0003e6638 by goroutine 1388:
runtime.raceread()
<autogenerated>:1 +0x1e
github.com/lightninglabs/loop/sweepbatcher.(*batch).monitorConfirmations()
sweepbatcher/sweep_batch.go:1144 +0x285
github.com/lightninglabs/loop/sweepbatcher.(*batch).handleSpend()
sweepbatcher/sweep_batch.go:1309 +0x10e4
github.com/lightninglabs/loop/sweepbatcher.(*batch).Run()
sweepbatcher/sweep_batch.go:526 +0xb04
github.com/lightninglabs/loop/sweepbatcher.(*Batcher).spinUpBatch.func1()
sweepbatcher/sweep_batcher.go:455 +0xbd
The race was caused because wg.Add(1) and wg.Wait() were running from different
goroutines (one goroutine was running batch.Run() and another - batcher.Run()).
To avoid this scenario, wg.Wait() call was moved into batch.Run() call, so it
waits itself for its children goroutines, after which the channel b.finished
is closed, and it serves a signal for external waiters (the batcher, calling
batch.Wait()).
Also the channel batch.stopped was renamed to batch.stopping to better reflect
its nature.
Added TestSweepBatcherCloseDuringAdding to make sure adding a sweep during
shutting down does not cause a crash. The test did not catch the original
race condition.
It used to be set to default (defaultBatchConfTarget = 12) which
could in theory affect fee rate if updateRbfRate() and publish()
were not called before the batch was saved. (Unlikely scenario.)
Previously storing an empty batch would make the batcher fail to start
as spinning up a restored batch assumes that there's a primary sweep
added already. As there's no point in spinning up such batch we can just
skip over it.
Furthermore we'll ensure that we won't try to ever publish an empty
batch to avoid setting the fee rate too early.
Previously we'd report the fees per sweep as the total sweep cost of a
batch. With this change the reported cost will be the proportional fee
which should be equal for all sweeps except if there's any rounding
difference in which case that is paid by the sweep belonging to the
first input of the batch tx.
