tidb session_pool 源码
tidb session_pool 代码
文件路径：/ddl/session_pool.go
// Copyright 2018 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 ddl
import (
"fmt"
"sync"
"github.com/ngaut/pools"
"github.com/pingcap/errors"
"github.com/pingcap/tidb/kv"
"github.com/pingcap/tidb/parser/mysql"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/util/logutil"
"github.com/pingcap/tidb/util/mock"
)
// sessionPool is used to new session.
type sessionPool struct {
mu struct {
sync.Mutex
closed bool
}
resPool *pools.ResourcePool
store kv.Storage
}
func newSessionPool(resPool *pools.ResourcePool, store kv.Storage) *sessionPool {
return &sessionPool{resPool: resPool, store: store}
}
// get gets sessionctx from context resource pool.
// Please remember to call put after you finished using sessionctx.
func (sg *sessionPool) get() (sessionctx.Context, error) {
if sg.resPool == nil {
ctx := mock.NewContext()
ctx.Store = sg.store
return ctx, nil
}
sg.mu.Lock()
if sg.mu.closed {
sg.mu.Unlock()
return nil, errors.Errorf("sessionPool is closed")
}
sg.mu.Unlock()
// no need to protect sg.resPool
resource, err := sg.resPool.Get()
if err != nil {
return nil, errors.Trace(err)
}
ctx, ok := resource.(sessionctx.Context)
if !ok {
return nil, fmt.Errorf("sessionPool resource get %v", ctx)
}
ctx.GetSessionVars().SetStatusFlag(mysql.ServerStatusAutocommit, true)
ctx.GetSessionVars().InRestrictedSQL = true
return ctx, nil
}
// put returns sessionctx to context resource pool.
func (sg *sessionPool) put(ctx sessionctx.Context) {
if sg.resPool == nil {
return
}
// no need to protect sg.resPool, even the sg.resPool is closed, the ctx still need to
// put into resPool, because when resPool is closing, it will wait all the ctx returns, then resPool finish closing.
sg.resPool.Put(ctx.(pools.Resource))
}
// close clean up the sessionPool.
func (sg *sessionPool) close() {
sg.mu.Lock()
defer sg.mu.Unlock()
// prevent closing resPool twice.
if sg.mu.closed || sg.resPool == nil {
return
}
logutil.BgLogger().Info("[ddl] closing sessionPool")
sg.resPool.Close()
sg.mu.closed = true
}
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