tidb allocator 源码
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
}
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