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oracle.go
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oracle.go
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// Copyright 2021 TiKV 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.
// NOTE: The code in this file is based on code from the
// TiDB project, licensed under the Apache License v 2.0
//
// https://github.com/pingcap/tidb/tree/cc5e161ac06827589c4966674597c137cc9e809c/store/tikv/oracle/oracle.go
//
// 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,
// 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 oracle
import (
"context"
"time"
)
// Option represents available options for the oracle.Oracle.
type Option struct {
TxnScope string
}
// Oracle is the interface that provides strictly ascending timestamps.
type Oracle interface {
GetTimestamp(ctx context.Context, opt *Option) (uint64, error)
GetTimestampAsync(ctx context.Context, opt *Option) Future
GetLowResolutionTimestamp(ctx context.Context, opt *Option) (uint64, error)
GetLowResolutionTimestampAsync(ctx context.Context, opt *Option) Future
GetStaleTimestamp(ctx context.Context, txnScope string, prevSecond uint64) (uint64, error)
IsExpired(lockTimestamp, TTL uint64, opt *Option) bool
UntilExpired(lockTimeStamp, TTL uint64, opt *Option) int64
Close()
}
// Future is a future which promises to return a timestamp.
type Future interface {
Wait() (uint64, error)
}
const (
physicalShiftBits = 18
logicalBits = (1 << physicalShiftBits) - 1
// GlobalTxnScope is the default transaction scope for a Oracle service.
GlobalTxnScope = "global"
)
// ComposeTS creates a ts from physical and logical parts.
func ComposeTS(physical, logical int64) uint64 {
return uint64((physical << physicalShiftBits) + logical)
}
// ExtractPhysical returns a ts's physical part.
func ExtractPhysical(ts uint64) int64 {
return int64(ts >> physicalShiftBits)
}
// ExtractLogical return a ts's logical part.
func ExtractLogical(ts uint64) int64 {
return int64(ts & logicalBits)
}
// GetPhysical returns physical from an instant time with millisecond precision.
func GetPhysical(t time.Time) int64 {
return t.UnixNano() / int64(time.Millisecond)
}
// GetTimeFromTS extracts time.Time from a timestamp.
func GetTimeFromTS(ts uint64) time.Time {
ms := ExtractPhysical(ts)
return time.Unix(ms/1e3, (ms%1e3)*1e6)
}
// GoTimeToTS converts a Go time to uint64 timestamp.
func GoTimeToTS(t time.Time) uint64 {
ts := (t.UnixNano() / int64(time.Millisecond)) << physicalShiftBits
return uint64(ts)
}
// GoTimeToLowerLimitStartTS returns the min start_ts of the uncommitted transaction.
// maxTxnTimeUse means the max time a Txn May use (in ms) from its begin to commit.
func GoTimeToLowerLimitStartTS(now time.Time, maxTxnTimeUse int64) uint64 {
return GoTimeToTS(now.Add(-time.Duration(maxTxnTimeUse) * time.Millisecond))
}