forked from pingcap/tidb
/
pd.go
116 lines (103 loc) · 3.03 KB
/
pd.go
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// Copyright 2016 PingCAP, Inc.
//
// 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package oracles
import (
"sync/atomic"
"time"
"github.com/juju/errors"
"github.com/ngaut/log"
"github.com/pingcap/pd/pd-client"
"github.com/pingcap/tidb/store/tikv/oracle"
"golang.org/x/net/context"
)
var _ oracle.Oracle = &pdOracle{}
const slowDist = 30 * time.Millisecond
// pdOracle is an Oracle that uses a placement driver client as source.
type pdOracle struct {
c pd.Client
lastTS uint64
quit chan struct{}
}
// NewPdOracle create an Oracle that uses a pd client source.
// Refer https://github.com/pingcap/pd/blob/master/pd-client/client.go for more details.
// PdOracle mantains `lastTS` to store the last timestamp got from PD server. If
// `GetTimestamp()` is not called after `updateInterval`, it will be called by
// itself to keep up with the timestamp on PD server.
func NewPdOracle(pdClient pd.Client, updateInterval time.Duration) (oracle.Oracle, error) {
o := &pdOracle{
c: pdClient,
quit: make(chan struct{}),
}
ctx := context.TODO()
go o.updateTS(ctx, updateInterval)
// Initialize lastTS by Get.
_, err := o.GetTimestamp(ctx)
if err != nil {
o.Close()
return nil, errors.Trace(err)
}
return o, nil
}
// IsExpired returns whether lockTS+TTL is expired, both are ms. It uses `lastTS`
// to compare, may return false negative result temporarily.
func (o *pdOracle) IsExpired(lockTS, TTL uint64) bool {
lastTS := atomic.LoadUint64(&o.lastTS)
return oracle.ExtractPhysical(lastTS) >= oracle.ExtractPhysical(lockTS)+int64(TTL)
}
// GetTimestamp gets a new increasing time.
func (o *pdOracle) GetTimestamp(ctx context.Context) (uint64, error) {
ts, err := o.getTimestamp(ctx)
if err != nil {
return 0, errors.Trace(err)
}
o.setLastTS(ts)
return ts, nil
}
func (o *pdOracle) getTimestamp(ctx context.Context) (uint64, error) {
now := time.Now()
physical, logical, err := o.c.GetTS(ctx)
if err != nil {
return 0, errors.Trace(err)
}
dist := time.Since(now)
if dist > slowDist {
log.Warnf("get timestamp too slow: %s", dist)
}
return oracle.ComposeTS(physical, logical), nil
}
func (o *pdOracle) setLastTS(ts uint64) {
lastTS := atomic.LoadUint64(&o.lastTS)
if ts > lastTS {
atomic.CompareAndSwapUint64(&o.lastTS, lastTS, ts)
}
}
func (o *pdOracle) updateTS(ctx context.Context, interval time.Duration) {
ticker := time.NewTicker(interval)
for {
select {
case <-ticker.C:
ts, err := o.getTimestamp(ctx)
if err != nil {
log.Errorf("updateTS error: %v", err)
break
}
o.setLastTS(ts)
case <-o.quit:
ticker.Stop()
return
}
}
}
func (o *pdOracle) Close() {
close(o.quit)
}