Commit 003c44cb authored by Kirill Smelkov's avatar Kirill Smelkov

go/zodb: Fix IStorage implementation not to deadlock driver if watcher fails

Before the patch if storage.watcher fails, storage.driver.Close is not
called, and so the driver will continue to send to .drvWatchq, but noone
is receiving from it.

a5dbb92b (go/zodb: Require drivers to close watchq on Close), provides
the guarantee that the driver will stop sending on drvWatchq right after
drv.Close call.
parent 58e0142c
...@@ -168,9 +168,10 @@ type storage struct { ...@@ -168,9 +168,10 @@ type storage struct {
driver IStorageDriver driver IStorageDriver
l1cache *Cache // can be =nil, if opened with NoCache l1cache *Cache // can be =nil, if opened with NoCache
down chan struct{} // ready when no longer operational down chan struct{} // ready when no longer operational
downOnce sync.Once // shutdown may be due to both Close and IO error in watcher|Sync downOnce sync.Once // shutdown may be due to both Close and IO error in watcher|Sync
downErr error // reason for shutdown downErr error // reason for shutdown
drvCloseErr error // err from .driver.Close()
// watcher // watcher
...@@ -193,6 +194,11 @@ func (s *storage) shutdown(reason error) { ...@@ -193,6 +194,11 @@ func (s *storage) shutdown(reason error) {
s.downOnce.Do(func() { s.downOnce.Do(func() {
close(s.down) close(s.down)
s.downErr = fmt.Errorf("not operational due: %s", reason) s.downErr = fmt.Errorf("not operational due: %s", reason)
// - if called by Close or failed Sync: driver.Close will close
// drvWatchq and cause watcher to stop.
// - if called by failed watcher: closing driver will prevent
// drvWatchq<- deadlock in driver because we no longer read from it.
s.drvCloseErr = s.driver.Close()
}) })
} }
...@@ -206,7 +212,7 @@ func (s *storage) Iterate(ctx context.Context, tidMin, tidMax Tid) ITxnIterator ...@@ -206,7 +212,7 @@ func (s *storage) Iterate(ctx context.Context, tidMin, tidMax Tid) ITxnIterator
func (s *storage) Close() error { func (s *storage) Close() error {
s.shutdown(fmt.Errorf("closed")) s.shutdown(fmt.Errorf("closed"))
return s.driver.Close() // this will close drvWatchq and cause watcher stop return s.drvCloseErr
} }
// loading goes through cache - this way prefetching can work // loading goes through cache - this way prefetching can work
......
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