github.com/pingcap/tiflow@v0.0.0-20240520035814-5bf52d54e205/dm/syncer/safe-mode/mode.go (about)

     1  // Copyright 2019 PingCAP, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package mode
    15  
    16  import (
    17  	"sync"
    18  
    19  	"github.com/pingcap/tidb/pkg/util/filter"
    20  	tcontext "github.com/pingcap/tiflow/dm/pkg/context"
    21  	"github.com/pingcap/tiflow/dm/pkg/terror"
    22  	"github.com/pingcap/tiflow/dm/pkg/utils"
    23  	"go.uber.org/zap"
    24  )
    25  
    26  // SafeMode controls whether enable safe-mode through a mechanism similar to reference-count
    27  // indicates enabled excepting the count is 0.
    28  type SafeMode struct {
    29  	mu     sync.RWMutex
    30  	count  int32
    31  	tables map[string]struct{}
    32  }
    33  
    34  // NewSafeMode creates a new SafeMode instance.
    35  func NewSafeMode() *SafeMode {
    36  	return &SafeMode{
    37  		tables: make(map[string]struct{}),
    38  	}
    39  }
    40  
    41  // Add adds n to the count, n can be negative.
    42  func (m *SafeMode) Add(tctx *tcontext.Context, n int32) error {
    43  	m.mu.Lock()
    44  	defer m.mu.Unlock()
    45  	return m.setCount(tctx, m.count+n)
    46  }
    47  
    48  // IncrForTable tries to add 1 on the count if the table not added before
    49  // can only be desc with DescForTable.
    50  func (m *SafeMode) IncrForTable(tctx *tcontext.Context, table *filter.Table) error {
    51  	tableID := utils.GenTableID(table)
    52  
    53  	m.mu.Lock()
    54  	defer m.mu.Unlock()
    55  	if _, ok := m.tables[tableID]; !ok {
    56  		m.tables[tableID] = struct{}{}
    57  		return m.setCount(tctx, m.count+1)
    58  	}
    59  	return nil
    60  }
    61  
    62  // DescForTable tries to add -1 on the count if the table added before.
    63  func (m *SafeMode) DescForTable(tctx *tcontext.Context, table *filter.Table) error {
    64  	tableID := utils.GenTableID(table)
    65  
    66  	m.mu.Lock()
    67  	defer m.mu.Unlock()
    68  	if _, ok := m.tables[tableID]; ok {
    69  		delete(m.tables, tableID)
    70  		return m.setCount(tctx, m.count-1)
    71  	}
    72  	return nil
    73  }
    74  
    75  // Reset resets to the state of not-enable.
    76  func (m *SafeMode) Reset(tctx *tcontext.Context) {
    77  	m.mu.Lock()
    78  	defer m.mu.Unlock()
    79  
    80  	//nolint:errcheck
    81  	m.setCount(tctx, 0)
    82  	m.tables = make(map[string]struct{})
    83  }
    84  
    85  // Enable returns whether is enabled currently.
    86  func (m *SafeMode) Enable() bool {
    87  	m.mu.RLock()
    88  	defer m.mu.RUnlock()
    89  	return m.count != 0
    90  }
    91  
    92  // setCount sets the count, called internal.
    93  func (m *SafeMode) setCount(tctx *tcontext.Context, n int32) error {
    94  	if n < 0 {
    95  		return terror.ErrSyncUnitSafeModeSetCount.Generatef("set negative count (%d) for safe-mode not valid", m.count)
    96  	}
    97  
    98  	prev := m.count
    99  	m.count = n
   100  	tctx.L().Info("change count", zap.Int32("previous count", prev), zap.Int32("new count", m.count))
   101  	return nil
   102  }