github.com/insionng/yougam@v0.0.0-20170714101924-2bc18d833463/libraries/pingcap/tidb/store/tikv/oracle/oracles/local.go (about)

     1  // Copyright 2016 PingCAP, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package oracles
    15  
    16  import (
    17  	"sync"
    18  	"time"
    19  
    20  	"github.com/insionng/yougam/libraries/pingcap/tidb/store/tikv/oracle"
    21  )
    22  
    23  const epochShiftBits = 18
    24  
    25  var _ oracle.Oracle = &localOracle{}
    26  
    27  type localOracle struct {
    28  	mu              sync.Mutex
    29  	lastTimeStampTs int64
    30  	n               int64
    31  }
    32  
    33  // NewLocalOracle creates an Oracle that uses local time as data source.
    34  func NewLocalOracle() oracle.Oracle {
    35  	return &localOracle{}
    36  }
    37  
    38  func (l *localOracle) IsExpired(lockTs uint64, TTL uint64) (bool, error) {
    39  	beginMs := lockTs >> epochShiftBits
    40  	return uint64(time.Now().UnixNano()/int64(time.Millisecond)) >= (beginMs + TTL), nil
    41  }
    42  
    43  func (l *localOracle) GetTimestamp() (uint64, error) {
    44  	l.mu.Lock()
    45  	defer l.mu.Unlock()
    46  	ts := (time.Now().UnixNano() / int64(time.Millisecond)) << epochShiftBits
    47  	if l.lastTimeStampTs == ts {
    48  		l.n++
    49  		return uint64(ts + l.n), nil
    50  	}
    51  	l.lastTimeStampTs = ts
    52  	l.n = 0
    53  	return uint64(ts), nil
    54  }