go-gin-opentracing

OpenTracing middleware from the Gin http framework.

Based on opentracing-go, this middleware adds an OpenTracing span for every http request, using the inbound requestID (if one exists) and adds the request span to the gin.Context as the key: tracing-context.

Required Reading

In order to understand the Go platform API, one must first be familiar with the OpenTracing project and terminology more specifically.

Installation

$ go get github.com/Bose/go-gin-opentracing

Usage as middleware

package main

import (
    "fmt"
    "os"

    ginopentracing "github.com/Bose/go-gin-opentracing"
    "github.com/gin-gonic/gin"
    "github.com/opentracing/opentracing-go"
)

func main() {
    r := gin.Default()
    hostName, err := os.Hostname()
    if err != nil {
        hostName = "unknown"
    }
    // initialize the global singleton for tracing...
    tracer, reporter, closer, err := ginopentracing.InitTracing(fmt.Sprintf("go-gin-opentracing-example::%s", hostName), "localhost:5775", ginopentracing.WithEnableInfoLog(true))
    if err != nil {
        panic("unable to init tracing")
    }
    defer closer.Close()
    defer reporter.Close()
    opentracing.SetGlobalTracer(tracer)

    // create the middleware
    p := ginopentracing.OpenTracer([]byte("api-request-"))

    // tell gin to use the middleware
    r.Use(p)

    r.GET("/", func(c *gin.Context) {
        c.JSON(200, "Hello world!")
    })

    r.Run(":29090")
}

See the example.go file

Usage within gin.Handler

Within the gin Handler you can access this request span and use it to create additional spans, and/or add span tags.

func HelloWorld(c *gin.Context) {
    if cspan, ok := c.Get("tracing-context"); ok {
        span = tracing.StartSpanWithParent(cspan.(opentracing.Span).Context(), "helloword", c.Request.Method, c.Request.URL.Path)   
    } else {
        span = tracing.StartSpanWithHeader(&c.Request.Header, "helloworld", c.Request.Method, c.Request.URL.Path)
    }
    defer span.Finish()
    c.String(200, "Hello.")
}