tidb allocator 代码
文件路径：/br/pkg/lightning/backend/kv/allocator.go
/ Copyright 2019 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.
/ TODO combine with the pkg/kv package outside.
package kv
import (
"context"
"sync/atomic"
"github.com/pingcap/tidb/meta/autoid"
)
/ panickingAllocator is an ID allocator which panics on all operations except Rebase
type panickingAllocator struct {
autoid.Allocator
base *int64
ty autoid.AllocatorType
}
/ NewPanickingAllocators creates a PanickingAllocator shared by all allocation types.
func NewPanickingAllocators(base int64) autoid.Allocators {
sharedBase := &base
return autoid.NewAllocators(
&panickingAllocator{base: sharedBase, ty: autoid.RowIDAllocType},
&panickingAllocator{base: sharedBase, ty: autoid.AutoIncrementType},
&panickingAllocator{base: sharedBase, ty: autoid.AutoRandomType},
)
}
/ Rebase implements the autoid.Allocator interface
func (alloc *panickingAllocator) Rebase(ctx context.Context, newBase int64, allocIDs bool) error {
/ CAS
for {
oldBase := atomic.LoadInt64(alloc.base)
if newBase <= oldBase {
break
}
if atomic.CompareAndSwapInt64(alloc.base, oldBase, newBase) {
break
}
}
return nil
}
/ Base implements the autoid.Allocator interface
func (alloc *panickingAllocator) Base() int64 {
return atomic.LoadInt64(alloc.base)
}
func (alloc *panickingAllocator) GetType() autoid.AllocatorType {
return alloc.ty
}