github.com/pingcap/tiflow@v0.0.0-20240520035814-5bf52d54e205/engine/pkg/errctx/ctx.go (about)

     1  // Copyright 2022 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 errctx
    15  
    16  import (
    17  	"context"
    18  	"sync"
    19  )
    20  
    21  type errCtx struct {
    22  	context.Context
    23  
    24  	mu     sync.Mutex
    25  	cancel context.CancelFunc
    26  	err    error
    27  }
    28  
    29  func newErrCtx(parent context.Context) *errCtx {
    30  	ctx, cancel := context.WithCancel(parent)
    31  	return &errCtx{
    32  		Context: ctx,
    33  		cancel:  cancel,
    34  	}
    35  }
    36  
    37  func (c *errCtx) doCancel(err error) {
    38  	if err == nil {
    39  		panic("errctx: internal error: missing cancel error")
    40  	}
    41  
    42  	c.mu.Lock()
    43  	if c.err != nil {
    44  		c.mu.Unlock()
    45  		return // already canceled
    46  	}
    47  
    48  	if c.Context.Err() != nil {
    49  		// Parent context is already canceled.
    50  		c.err = c.Context.Err()
    51  	} else {
    52  		c.err = err
    53  		c.cancel()
    54  	}
    55  	c.mu.Unlock()
    56  }
    57  
    58  func (c *errCtx) Err() error {
    59  	c.mu.Lock()
    60  	defer c.mu.Unlock()
    61  	if c.err != nil {
    62  		return c.err
    63  	}
    64  	return c.Context.Err()
    65  }