How to implement traceid in golang

With the popularity of microservice architecture, calls between services are becoming more and more complex. When we need to troubleshoot a request, we need to be able to trace the entire call link and see how each service handles the request. In order to realize this requirement, we need to introduce the traceid mechanism to connect the logs of each service in the entire calling process for analysis and troubleshooting.

In Golang, we can implement the traceid mechanism through simple code. First, we need to introduce a global link context (context), which will be passed throughout the process, and will continue to increase and pass the traceid with the request. The specific implementation is as follows:

import (
    "context"
    "github.com/google/uuid"
)

const traceIdKey = "traceid"

func WithTraceID(ctx context.Context, traceID string) context.Context {
    return context.WithValue(ctx, traceIdKey, traceID)
}

func GetTraceID(ctx context.Context) string {
    if v, ok := ctx.Value(traceIdKey).(string); ok {
        return v
    } else {
        return ""
    }
}

func NewTraceID() string {
    return uuid.New().String()
}

In the above code, we introduce a traceid constant to store traceid in the context, and provide two functions WithTraceID and GetTraceID, which are used to set and get the traceid in the context respectively. traceid. At the same time, we also provide a function NewTraceID that generates traceid. This function will generate a unique uuid as the traceid of the current request.

Next, in our service, we need to pass the traceid of the current request to the next service in each function that handles the request, and print the traceid in the log for subsequent troubleshooting. The specific implementation is as follows:

func HandlerFunc(w http.ResponseWriter, r *http.Request) {
    traceID := ""
    if traceIDArr := r.Header.Get("X-Trace-ID"); len(traceIDArr) > 0 {
        traceID = traceIDArr[0]
    }
    if traceID == "" {
        traceID = NewTraceID()
    }
    ctx := context.Background()
    ctx = WithTraceID(ctx, traceID)
    
    // 调用下一个服务
    resp := CallNextService(ctx)
    
    // 打印日志
    log.Printf("request traceID=%s\n", traceID)
    
    // 返回数据
    w.Write(resp)
}

func CallNextService(ctx context.Context) []byte {
    traceID := GetTraceID(ctx)
    // 调用下一个服务
    ...
    
    // 打印日志
    log.Printf("call next service traceID=%s\n", traceID)
    
    // 返回数据
    return resp
}

As shown above, in the function that handles the request, we first obtain the traceid of the current request from the request header. If it is not obtained, a new traceid is generated. We then add the traceid to the context and pass the context to the next service when it is called. In the next service, we can get the traceid passed by the previous service through the GetTraceID function and print it out in the log.

Through the above code, we can pass the traceid throughout the request link and print out the corresponding log to facilitate troubleshooting and analysis.

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