mirror of https://github.com/k3s-io/k3s
103 lines
3.8 KiB
Go
103 lines
3.8 KiB
Go
/*
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Copyright 2018 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package etcd3
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import (
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"context"
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"sync"
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"time"
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"github.com/ibuildthecloud/kvsql/clientv3"
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)
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// leaseManager is used to manage leases requested from etcd. If a new write
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// needs a lease that has similar expiration time to the previous one, the old
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// lease will be reused to reduce the overhead of etcd, since lease operations
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// are expensive. In the implementation, we only store one previous lease,
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// since all the events have the same ttl.
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type leaseManager struct {
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client *clientv3.Client // etcd client used to grant leases
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leaseMu sync.Mutex
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prevLeaseID clientv3.LeaseID
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prevLeaseExpirationTime time.Time
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// The period of time in seconds and percent of TTL that each lease is
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// reused. The minimum of them is used to avoid unreasonably large
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// numbers. We use var instead of const for testing purposes.
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leaseReuseDurationSeconds int64
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leaseReuseDurationPercent float64
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}
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// newDefaultLeaseManager creates a new lease manager using default setting.
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func newDefaultLeaseManager(client *clientv3.Client) *leaseManager {
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return newLeaseManager(client, 60, 0.05)
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}
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// newLeaseManager creates a new lease manager with the number of buffered
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// leases, lease reuse duration in seconds and percentage. The percentage
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// value x means x*100%.
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func newLeaseManager(client *clientv3.Client, leaseReuseDurationSeconds int64, leaseReuseDurationPercent float64) *leaseManager {
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return &leaseManager{
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client: client,
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leaseReuseDurationSeconds: leaseReuseDurationSeconds,
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leaseReuseDurationPercent: leaseReuseDurationPercent,
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}
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}
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// setLeaseReuseDurationSeconds is used for testing purpose. It is used to
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// reduce the extra lease duration to avoid unnecessary timeout in testing.
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func (l *leaseManager) setLeaseReuseDurationSeconds(duration int64) {
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l.leaseMu.Lock()
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defer l.leaseMu.Unlock()
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l.leaseReuseDurationSeconds = duration
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}
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// GetLease returns a lease based on requested ttl: if the cached previous
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// lease can be reused, reuse it; otherwise request a new one from etcd.
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func (l *leaseManager) GetLease(ctx context.Context, ttl int64) (clientv3.LeaseID, error) {
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now := time.Now()
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l.leaseMu.Lock()
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defer l.leaseMu.Unlock()
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// check if previous lease can be reused
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reuseDurationSeconds := l.getReuseDurationSecondsLocked(ttl)
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valid := now.Add(time.Duration(ttl) * time.Second).Before(l.prevLeaseExpirationTime)
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sufficient := now.Add(time.Duration(ttl+reuseDurationSeconds) * time.Second).After(l.prevLeaseExpirationTime)
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if valid && sufficient {
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return l.prevLeaseID, nil
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}
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// request a lease with a little extra ttl from etcd
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ttl += reuseDurationSeconds
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lcr, err := l.client.Lease.Grant(ctx, ttl)
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if err != nil {
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return clientv3.LeaseID(0), err
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}
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// cache the new lease id
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l.prevLeaseID = lcr.ID
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l.prevLeaseExpirationTime = now.Add(time.Duration(ttl) * time.Second)
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return lcr.ID, nil
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}
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// getReuseDurationSecondsLocked returns the reusable duration in seconds
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// based on the configuration. Lock has to be acquired before calling this
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// function.
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func (l *leaseManager) getReuseDurationSecondsLocked(ttl int64) int64 {
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reuseDurationSeconds := int64(l.leaseReuseDurationPercent * float64(ttl))
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if reuseDurationSeconds > l.leaseReuseDurationSeconds {
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reuseDurationSeconds = l.leaseReuseDurationSeconds
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}
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return reuseDurationSeconds
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}
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