A Go script that retrieves the Varnish memory consumption and returns it via a RESTful API using GoJi

varnishusage.go

package main

import (
    "strconv"
    "net/http"
    "github.com/zenazn/goji"
    "github.com/zenazn/goji/web"
    "os/exec"
    "encoding/json"
)

func usage(c web.C, w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")
    encoder := json.NewEncoder(w)     
    cmdName := "varnishstat"
    cmdArgs := []string{"-f", "SMA.s0.g_bytes", "-j"}
    cmd := exec.Command(cmdName, cmdArgs...)
    stdout, err := cmd.Output()
    if(err != nil) {
        http.Error(w, err.Error(), 500)
        return
    }    
    var varnishstatInterface interface{}
    err = json.Unmarshal([]byte(stdout), &varnishstatInterface)
    if(err != nil) {
        http.Error(w, err.Error(), 500)
        return
    }
    
    varnishstatMap := varnishstatInterface.(map[string]interface{})
    valueMap := varnishstatMap["SMA.s0.g_bytes"].(map[string]interface{})
    encoder.Encode(strconv.FormatFloat(valueMap["value"].(float64), 'f', 0, 32))  
}

func main() {
    goji.Get("/",usage)
    goji.Serve()
}