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clientv3/concurrency: don't poll in mutex lock on early prior key delete 

Lock would get the prior key on retry using WithRev(myRev - 1) instead of
using the latest revision; the Watch() would return immediately and Lock
devolves into polling.
release-2.3
Anthony Romano 2016-03-03 09:46:46 -08:00
parent e3b755e9e0
commit 6d3f172c6e
1 changed files with 2 additions and 25 deletions
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27
clientv3/concurrency/mutex.go
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@ -44,31 +44,8 @@ func (m *Mutex) Lock(ctx context.Context) error {
}
// put self in lock waiters via myKey; oldest waiter holds lock
m.myKey, m.myRev, err = NewUniqueKey(ctx, m.client, m.pfx, v3.WithLease(s.Lease()))
// wait for lock to become available
for err == nil {
// find oldest element in waiters via revision of insertion
var resp *v3.GetResponse
resp, err = m.client.Get(ctx, m.pfx, v3.WithFirstRev()...)
if err != nil {
break
}
if m.myRev == resp.Kvs[0].CreateRevision {
// myKey is oldest in waiters; myKey holds the lock now
return nil
}
// otherwise myKey isn't lowest, so there must be a pfx prior to myKey
opts := append(v3.WithLastRev(), v3.WithRev(m.myRev-1))
resp, err = m.client.Get(ctx, m.pfx, opts...)
if err != nil {
break
}
lastKey := string(resp.Kvs[0].Key)
// wait for release on prior pfx
err = waitUpdate(ctx, m.client, lastKey, v3.WithRev(m.myRev))
// try again in case lastKey left the wait list before acquiring the lock;
// myKey can only hold the lock if it's the oldest in the list
}
// wait for deletion revisions prior to myKey
err = waitDeletes(ctx, m.client, m.pfx, v3.WithPrefix(), v3.WithRev(m.myRev-1))
// release lock key if cancelled
select {
case <-ctx.Done():