github.com/pingcap/tiflow@v0.0.0-20240520035814-5bf52d54e205/dm/pkg/log/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 log
    15  
    16  import (
    17  	"context"
    18  
    19  	"go.uber.org/zap"
    20  )
    21  
    22  type logCtxKeyType string
    23  
    24  var logCtxKey = logCtxKeyType("zap-fields")
    25  
    26  func getZapFieldsFromCtx(ctx context.Context) []zap.Field {
    27  	// Use a pointer to key to save one allocation.
    28  	fields := ctx.Value(&logCtxKey)
    29  	if fields == nil {
    30  		return nil
    31  	}
    32  	// Note that the value is a pointer to slice, to save allocation.
    33  	return *fields.(*[]zap.Field)
    34  }
    35  
    36  // AppendZapFieldToCtx attaches new fields to the context, which can be then
    37  // used with log.WithCtx().
    38  func AppendZapFieldToCtx(ctx context.Context, newFields ...zap.Field) context.Context {
    39  	fields := getZapFieldsFromCtx(ctx)
    40  	if fields == nil {
    41  		// 8 fields should be enough for most situations.
    42  		fields = make([]zap.Field, 0, 8)
    43  	}
    44  	fields = append(fields, newFields...)
    45  
    46  	return context.WithValue(ctx, &logCtxKey, &fields)
    47  }