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Merge pull request #14658 from ahrtr/double_barrier_3.5

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[3.5] clientv3: fix the implementation of double barrier
This commit is contained in:
Hitoshi Mitake
2022-11-02 23:16:11 +09:00
committed by GitHub
parent 27707209ae 8e26a1fff1
commit cc6a082f9e
2 changed files with 109 additions and 10 deletions
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53
client/v3/experimental/recipes/double_barrier.go
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@@ -45,25 +45,46 @@ func NewDoubleBarrier(s *concurrency.Session, key string, count int) *DoubleBarr
// Enter waits for "count" processes to enter the barrier then returns
func (b *DoubleBarrier) Enter() error {
client := b.s.Client()
// Check the entered clients before creating the UniqueEphemeralKey,
// fail the request if there are already too many clients.
if resp1, err := b.enteredClients(client); err != nil {
return err
} else if len(resp1.Kvs) >= b.count {
return ErrTooManyClients
}
ek, err := newUniqueEphemeralKey(b.s, b.key+"/waiters")
if err != nil {
return err
}
b.myKey = ek
resp, err := client.Get(b.ctx, b.key+"/waiters", clientv3.WithPrefix())
// Check the entered clients after creating the UniqueEphemeralKey
resp2, err := b.enteredClients(client)
if err != nil {
return err
}
if len(resp2.Kvs) >= b.count {
lastWaiter := resp2.Kvs[b.count-1]
if ek.rev > lastWaiter.CreateRevision {
// delete itself now, otherwise other processes may need to wait
// until these keys are automatically deleted when the related
// lease expires.
if err = b.myKey.Delete(); err != nil {
// Nothing to do here. We have to wait for the key to be
// deleted when the lease expires.
}
return ErrTooManyClients
}
if len(resp.Kvs) > b.count {
return ErrTooManyClients
}
if len(resp.Kvs) == b.count {
// unblock waiters
_, err = client.Put(b.ctx, b.key+"/ready", "")
return err
if ek.rev == lastWaiter.CreateRevision {
// TODO(ahrtr): we might need to compare ek.key and
// string(lastWaiter.Key), they should be equal.
// unblock all other waiters
_, err = client.Put(b.ctx, b.key+"/ready", "")
return err
}
}
_, err = WaitEvents(
@@ -74,6 +95,18 @@ func (b *DoubleBarrier) Enter() error {
return err
}
// enteredClients gets all the entered clients, which are ordered by the
// createRevision in ascending order.
func (b *DoubleBarrier) enteredClients(cli *clientv3.Client) (*clientv3.GetResponse, error) {
resp, err := cli.Get(b.ctx, b.key+"/waiters", clientv3.WithPrefix(),
clientv3.WithSort(clientv3.SortByCreateRevision, clientv3.SortAscend))
if err != nil {
return nil, err
}
return resp, nil
}
// Leave waits for "count" processes to leave the barrier then returns
func (b *DoubleBarrier) Leave() error {
client := b.s.Client()
@@ -96,7 +129,7 @@ func (b *DoubleBarrier) Leave() error {
}
isLowest := string(lowest.Key) == b.myKey.Key()
if len(resp.Kvs) == 1 {
if len(resp.Kvs) == 1 && isLowest {
// this is the only node in the barrier; finish up
if _, err = client.Delete(b.ctx, b.key+"/ready"); err != nil {
return err