github.com/pingcap/tiflow@v0.0.0-20240520035814-5bf52d54e205/cdc/async/async_initializer.go (about)

     1  // Copyright 2024 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 async
    15  
    16  import (
    17  	"context"
    18  	"sync"
    19  
    20  	"github.com/pingcap/log"
    21  	"github.com/pingcap/tiflow/pkg/errors"
    22  	"github.com/pingcap/tiflow/pkg/workerpool"
    23  	"go.uber.org/atomic"
    24  	"go.uber.org/zap"
    25  )
    26  
    27  // Initializer is a helper struct to initialize a changefeed asynchronously.
    28  type Initializer struct {
    29  	// state related fields
    30  	initialized  *atomic.Bool
    31  	initializing *atomic.Bool
    32  	initError    *atomic.Error
    33  
    34  	// func to cancel the changefeed initialization
    35  	cancelInitialize context.CancelFunc
    36  	initialWaitGroup sync.WaitGroup
    37  }
    38  
    39  // NewInitializer creates a new initializer.
    40  func NewInitializer() *Initializer {
    41  	return &Initializer{
    42  		initialized:  atomic.NewBool(false),
    43  		initializing: atomic.NewBool(false),
    44  		initError:    atomic.NewError(nil),
    45  	}
    46  }
    47  
    48  // TryInitialize tries to initialize the module asynchronously.
    49  // returns true if the module is already initialized or initialized successfully.
    50  // returns false if the module is initializing or failed to initialize.
    51  // returns error if the module failed to initialize.
    52  // It will only initialize the module once.
    53  // It's not thread-safe.
    54  func (initializer *Initializer) TryInitialize(ctx context.Context,
    55  	initFunc func(ctx context.Context) error,
    56  	pool workerpool.AsyncPool,
    57  ) (bool, error) {
    58  	if initializer.initialized.Load() {
    59  		return true, nil
    60  	}
    61  	if initializer.initializing.CompareAndSwap(false, true) {
    62  		initialCtx, cancelInitialize := context.WithCancel(ctx)
    63  		initializer.initialWaitGroup.Add(1)
    64  		initializer.cancelInitialize = cancelInitialize
    65  		log.Info("submit async initializer task to the worker pool")
    66  		err := pool.Go(initialCtx, func() {
    67  			defer initializer.initialWaitGroup.Done()
    68  			if err := initFunc(initialCtx); err != nil {
    69  				initializer.initError.Store(errors.Trace(err))
    70  			} else {
    71  				initializer.initialized.Store(true)
    72  			}
    73  		})
    74  		if err != nil {
    75  			log.Error("failed to submit async initializer task to the worker pool", zap.Error(err))
    76  			initializer.initialWaitGroup.Done()
    77  			return false, errors.Trace(err)
    78  		}
    79  	}
    80  	if initializer.initError.Load() != nil {
    81  		return false, errors.Trace(initializer.initError.Load())
    82  	}
    83  	return initializer.initialized.Load(), nil
    84  }
    85  
    86  // Terminate terminates the initializer.
    87  // It will cancel the initialization if it is initializing. and wait for the initialization to finish.
    88  // It's not thread-safe.
    89  func (initializer *Initializer) Terminate() {
    90  	if initializer.initializing.Load() {
    91  		if initializer.cancelInitialize != nil {
    92  			initializer.cancelInitialize()
    93  		}
    94  		initializer.initialWaitGroup.Wait()
    95  	}
    96  	initializer.initializing.Store(false)
    97  	initializer.initialized.Store(false)
    98  	initializer.initError.Store(nil)
    99  }