Using global logger fails to bind values causing incorrect context values

[jatinrungtaallen]

What happened:

Using a global logger fails to output correct values from the context. It instead creates a background context and fills data with empty values

What you expected to happen:

How to reproduce it (as minimally and precisely as possible):

Because the global logger is of type loggerAppliance, using WithContext causes it to return a new instance without prefix and kvs. This causes the code to not bind values and causes the downstream logger to not have context

Anything else we need to know?:

Environment:

• Kratos version (use kratos -v):
• Go version (use go version):
• OS (e.g: cat /etc/os-release):
• Others:

[kvii]

提供一下最小复现呗？最小复现不是指几张截图，而是一个能完全运行的例子。你可以像这样操作：

1. 创建一个空的 go 项目。只导入 kratos 之类的必要的依赖项。
2. 在 main 方法里用你的方式创建一个 logger。调用这个 logger 的方法，传入你准备的参数。其他和问题无关的代码一行都不要留。
3. 在注释里讲清楚你期望什么结果，实际上的结果是什么。
4. 最后把 main.go 的源码贴到 github 上来，方便别人复制后在本地运行。

比如说这就是一个最小复现：

package main

import (
	"context"

	"github.com/go-kratos/kratos/v2/log"
)

func main() {
	ctx := context.Background()
	ctx = context.WithValue(ctx, traceIdKey{}, "123456")

	global := log.GetLogger()
	logger := log.WithContext(ctx, global)
	// logger = log.With(logger, "traceId", TraceIdValue()) // 看后面的说明
	helper := log.NewHelper(logger)

	helper.Infow("msg", "用户登录", "user", "张三")

	// 期望输出
	// INFO traceId=123456 msg=用户登录 user=张三
	// 实际输出
	// INFO msg=用户登录 user=张三
}

type traceIdKey struct{}

// 看后面的说明
func TraceIdValue() log.Valuer {
	return func(ctx context.Context) any {
		return ctx.Value(traceIdKey{})
	}
}

这只是个例子。如果这个例子刚好能反映你的情况的话。那么问题就简单了。log 库并没有“能把 context 里所有 value 都打印出来” 的能力。想要从 context 里拿数据打印需要自己实现 logger 或者 valuer。比如例子中的 TraceIdValue 就实现了从 context 中提取 trace id 的功能。

[urdarinda]

@kvii
I have reproduced it below

package main

import (
	"context"

	"github.com/go-kratos/kratos/v2/log"
)

func main() {
	ctx := context.Background()
	ctx = context.WithValue(ctx, traceIdKey{}, "123456")


	logger := log.DefaultLogger
	newLogger := log.With(logger, "traceId", TraceIdValue())

	log.SetLogger(newLogger) // setting logger with valuer as global

	helper := log.NewHelper(newLogger)

	helper.WithContext(ctx).Info("This prints the traceID correctly")


	globalLogger := log.NewHelper(log.GetLogger()) // getting the global logger

	globalLogger.WithContext(ctx).Info("This does not print the traceID")

	// INFO traceId=123456 msg=This prints the traceID correctly
	// INFO traceId=<nil> msg=This does not print the traceID
}

type traceIdKey struct{}

func TraceIdValue() log.Valuer {
	return func(ctx context.Context) any {
		return ctx.Value(traceIdKey{})
	}
}

[kvii]

中文省流：因为 log.GetLogger return 的不是 log.SetLogger 存进去的那个 logger。所以导致 log.WithContext 合并 logger 的时候出了问题。最终导致底层的 log.Valuer 取数的时候拿不到 with 的那个 context。解决方案是让 log.GetLogger 返回存进去的那个 logger。

English version:
A minimal reproduce for this issue:

package main

import (
	"context"
	"os"

	"github.com/go-kratos/kratos/v2/log"
)

func main() {
	l1 := log.NewStdLogger(os.Stderr)            // *log.stdLogger
	l2 := log.With(l1, "traceId", traceIdValuer) // *log.logger ctx=Background

	log.SetLogger(l2)     // log.global.Logger = l2
	l3 := log.GetLogger() // log.global not l2 *log.loggerAppliance

	ctx := context.TODO()
	ctx = context.WithValue(ctx, traceIdKey{}, "123456")

	// log.WithContext(ctx,l) only "merge" ctx when l is a *log.logger.
	// and l3 is not.
	l4 := log.WithContext(ctx, l3) // *log.logger (not l2) ctx=ctx
	l4.Log(log.LevelInfo, "msg", "m")

	// want:
	// INFO traceId=123456 msg=m
	// got:
	// INFO traceId=<nil> msg=m

	// solution: Let log.global be a place that only stores values, rather than a Logger.
}

type traceIdKey struct{}

var traceIdValuer log.Valuer = func(ctx context.Context) any {
	return ctx.Value(traceIdKey{})
}

Currently log.SetLogger sets the logger to log.global.Logger. But log.SetLogger returns log.global, not log.global.Logger.
And log.WithContext or log.Helper.WithContext only "merge" context when the parameter is *log.logger.
So the logger that log.GetLogger returned can't be "merged".

kratos/log/global.go

Lines 10 to 39 in 908e625

	// globalLogger is designed as a global logger in current process.
	var global = &loggerAppliance{}
	// loggerAppliance is the proxy of `Logger` to
	// make logger change will affect all sub-logger.
	type loggerAppliance struct {
	lock sync.Mutex
	Logger
	}
	func init() {
	global.SetLogger(DefaultLogger)
	}
	func (a *loggerAppliance) SetLogger(in Logger) {
	a.lock.Lock()
	defer a.lock.Unlock()
	a.Logger = in
	}
	// SetLogger should be called before any other log call.
	// And it is NOT THREAD SAFE.
	func SetLogger(logger Logger) {
	global.SetLogger(logger)
	}
	// GetLogger returns global logger appliance as logger in current process.
	func GetLogger() Logger {
	return global
	}

[shenqidebaozi]

#3455

[kratos-ci-bot]

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#3455