| /* |
| Copyright 2018 The Kubernetes Authors. |
| |
| Licensed under the Apache License, Version 2.0 (the "License"); |
| you may not use this file except in compliance with the License. |
| You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, software |
| distributed under the License is distributed on an "AS IS" BASIS, |
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| See the License for the specific language governing permissions and |
| limitations under the License. |
| */ |
| |
| package etcd3 |
| |
| import ( |
| "context" |
| "sync" |
| "time" |
| |
| "github.com/coreos/etcd/clientv3" |
| ) |
| |
| // leaseManager is used to manage leases requested from etcd. If a new write |
| // needs a lease that has similar expiration time to the previous one, the old |
| // lease will be reused to reduce the overhead of etcd, since lease operations |
| // are expensive. In the implementation, we only store one previous lease, |
| // since all the events have the same ttl. |
| type leaseManager struct { |
| client *clientv3.Client // etcd client used to grant leases |
| leaseMu sync.Mutex |
| prevLeaseID clientv3.LeaseID |
| prevLeaseExpirationTime time.Time |
| // The period of time in seconds and percent of TTL that each lease is |
| // reused. The minimum of them is used to avoid unreasonably large |
| // numbers. We use var instead of const for testing purposes. |
| leaseReuseDurationSeconds int64 |
| leaseReuseDurationPercent float64 |
| } |
| |
| // newDefaultLeaseManager creates a new lease manager using default setting. |
| func newDefaultLeaseManager(client *clientv3.Client) *leaseManager { |
| return newLeaseManager(client, 60, 0.05) |
| } |
| |
| // newLeaseManager creates a new lease manager with the number of buffered |
| // leases, lease reuse duration in seconds and percentage. The percentage |
| // value x means x*100%. |
| func newLeaseManager(client *clientv3.Client, leaseReuseDurationSeconds int64, leaseReuseDurationPercent float64) *leaseManager { |
| return &leaseManager{ |
| client: client, |
| leaseReuseDurationSeconds: leaseReuseDurationSeconds, |
| leaseReuseDurationPercent: leaseReuseDurationPercent, |
| } |
| } |
| |
| // setLeaseReuseDurationSeconds is used for testing purpose. It is used to |
| // reduce the extra lease duration to avoid unnecessary timeout in testing. |
| func (l *leaseManager) setLeaseReuseDurationSeconds(duration int64) { |
| l.leaseMu.Lock() |
| defer l.leaseMu.Unlock() |
| l.leaseReuseDurationSeconds = duration |
| } |
| |
| // GetLease returns a lease based on requested ttl: if the cached previous |
| // lease can be reused, reuse it; otherwise request a new one from etcd. |
| func (l *leaseManager) GetLease(ctx context.Context, ttl int64) (clientv3.LeaseID, error) { |
| now := time.Now() |
| l.leaseMu.Lock() |
| defer l.leaseMu.Unlock() |
| // check if previous lease can be reused |
| reuseDurationSeconds := l.getReuseDurationSecondsLocked(ttl) |
| valid := now.Add(time.Duration(ttl) * time.Second).Before(l.prevLeaseExpirationTime) |
| sufficient := now.Add(time.Duration(ttl+reuseDurationSeconds) * time.Second).After(l.prevLeaseExpirationTime) |
| if valid && sufficient { |
| return l.prevLeaseID, nil |
| } |
| // request a lease with a little extra ttl from etcd |
| ttl += reuseDurationSeconds |
| lcr, err := l.client.Lease.Grant(ctx, ttl) |
| if err != nil { |
| return clientv3.LeaseID(0), err |
| } |
| // cache the new lease id |
| l.prevLeaseID = lcr.ID |
| l.prevLeaseExpirationTime = now.Add(time.Duration(ttl) * time.Second) |
| return lcr.ID, nil |
| } |
| |
| // getReuseDurationSecondsLocked returns the reusable duration in seconds |
| // based on the configuration. Lock has to be acquired before calling this |
| // function. |
| func (l *leaseManager) getReuseDurationSecondsLocked(ttl int64) int64 { |
| reuseDurationSeconds := int64(l.leaseReuseDurationPercent * float64(ttl)) |
| if reuseDurationSeconds > l.leaseReuseDurationSeconds { |
| reuseDurationSeconds = l.leaseReuseDurationSeconds |
| } |
| return reuseDurationSeconds |
| } |