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68 lines
1.5 KiB
Go
68 lines
1.5 KiB
Go
package localstore
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import (
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"errors"
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"sync"
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"time"
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"github.com/ngaut/log"
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"github.com/pingcap/tidb/kv"
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)
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// ErrOverflow is the error returned by CurrentVersion, it describes if
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// there're too many versions allocations in a very short period of time, ID
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// may conflict.
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var ErrOverflow = errors.New("overflow when allocating new version")
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// LocalVersionProvider uses local timestamp for version.
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type LocalVersionProvider struct {
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mu sync.Mutex
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lastTimestamp uint64
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// logical guaranteed version's monotonic increasing for calls when lastTimestamp
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// are equal.
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logical uint64
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}
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const (
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timePrecisionOffset = 18
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)
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func time2TsPhysical(t time.Time) uint64 {
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return uint64((t.UnixNano() / int64(time.Millisecond)) << timePrecisionOffset)
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}
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func version2Second(v kv.Version) int64 {
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return int64(v.Ver>>timePrecisionOffset) / 1000
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}
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// CurrentVersion implements the VersionProvider's GetCurrentVer interface.
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func (l *LocalVersionProvider) CurrentVersion() (kv.Version, error) {
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l.mu.Lock()
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defer l.mu.Unlock()
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for {
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var ts uint64
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ts = time2TsPhysical(time.Now())
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if l.lastTimestamp > ts {
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log.Error("[kv] invalid physical time stamp")
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continue
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}
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if l.lastTimestamp == uint64(ts) {
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l.logical++
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if l.logical >= 1<<timePrecisionOffset {
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return kv.Version{}, ErrOverflow
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}
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return kv.Version{Ver: ts + l.logical}, nil
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}
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l.lastTimestamp = ts
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l.logical = 0
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return kv.Version{Ver: ts}, nil
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}
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}
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func localVersionToTimestamp(ver kv.Version) uint64 {
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return ver.Ver >> timePrecisionOffset
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}
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