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database/sql: goroutine leak detection made difficult with sql.DB.Close() #50616

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MichaelSnowden opened this issue Jan 14, 2022 · 0 comments
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@MichaelSnowden
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@MichaelSnowden MichaelSnowden commented Jan 14, 2022

We start a goroutine for connectionOpener like this:

go db.connectionOpener(ctx)

And then it terminates when the context is cancelled:

go/src/database/sql/sql.go

Lines 1224 to 1233 in 4f0c32d

func (db *DB) connectionOpener(ctx context.Context) {
for {
select {
case <-ctx.Done():
return
case <-db.openerCh:
db.openNewConnection(ctx)
}
}
}

Which happens here:

db.stop()

The Close() method then returns after some additional cleanup. Since we don't wait for the actual goroutine to close, after Close() happens, there could still be a goroutine running.

I think we should add something like this to the OpenDB method:

go func() {
  defer db.openerRoutine.Done()
  db.connectionOpener(ctx)
}

and then add this to the Close() method:

db.stop()
db.openerRoutine.Wait()

This would make it easier to use things like goleak with this library. Currently, I have to workaround it somehow, e.g. with a sleep or an ignore.

@seankhliao seankhliao changed the title goroutine leak detection made difficult with sql.DB.Close() database/sql: goroutine leak detection made difficult with sql.DB.Close() Jan 16, 2022
@seankhliao seankhliao added the NeedsInvestigation label Jan 16, 2022
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