Consul Health Check

consul_healthcheck.go

package main

import (
	"encoding/json"
	"fmt"
	"github.com/urfave/cli"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"strings"
)

type ServiceHealth struct {
	ServiceName string `json:"ServiceName"`
	Node        string `json:"Node"`
	Status      string `json:"Status"`
}

var (
	consulHealthEndpoint = "/v1/health/checks/"
	httpProto            = "http://"
	instanceCounter      int
	failedCounter        int
	isBad                = false
)

func main() {
	app := cli.NewApp()
	app.Name = "Consul Service Health Checker"
	app.Description = "Get health status from Consul for named service(s)"
	app.Version = "0.0.1"

	app.Flags = []cli.Flag{
		cli.StringFlag{
			Name:  "consul, c",
			Usage: "Host + port of Consul service (e.g., 'localhost:8500')",
		},
		cli.BoolFlag{
			Name:  "secure, s",
			Usage: "Use HTTPS instead of HTTP",
		},
		cli.StringSliceFlag{
			Name:  "name, n",
			Usage: "Name or names of services to check, (e.g., 'apache2')",
		},
	}

	app.Action = func(c *cli.Context) error {
		// Set HTTP or HTTPS
		if c.Bool("secure") {
			httpProto = "https://"
		}

		if c.String("consul") == "" {
			os.Exit(2)
		}

		// Check Consul host is valid
		_, err := http.Get(httpProto + c.String("consul"))
		if err != nil {
			fmt.Printf("COMMUNICATION ERROR:%v\n", httpProto+c.String("consul"))
			os.Exit(2)
		}

		// Retrieve each service status
		for _, serviceName := range c.StringSlice("name") {

			// Retrieve Consul health status
			res, err := http.Get(httpProto + c.String("consul") + consulHealthEndpoint + serviceName)
			if err != nil {
				panic(err.Error())
			}

			body, err := ioutil.ReadAll(res.Body)
			if err != nil {
				panic(err.Error())
			}

			var data []ServiceHealth
			err = json.Unmarshal(body, &data)
			if err != nil {
				panic(err.Error())
			}

			// Validate if each instance passing health checks
			instanceCounter = 0
			failedCounter = 0

			for _, instance := range data {
				status := string(strings.ToLower(instance.Status))

				if status != "passing" {
					isBad = true
					failedCounter++
				}
				instanceCounter++
			}

			healthyInstances := instanceCounter - failedCounter

			// Bad service name will return a valid JSON object, but this works for a validation check
			if healthyInstances == 0 {
				isBad = true
				fmt.Printf("NAME:%v:ERROR:BADVALUE\n", strings.ToUpper(serviceName))
			}

			// Display the total number of healthy, working instances in output
			if isBad {
				fmt.Printf("NAME:%s:PASS:COUNT:%v:FAIL:%v\n", strings.ToUpper(serviceName), healthyInstances, failedCounter)
			} else {
				fmt.Printf("NAME:%s:PASS:COUNT:%v:FAIL:0\n", strings.ToUpper(serviceName), instanceCounter)
			}

		}

		if isBad {
			fmt.Print("FAILED SERVICE HEALTH CHECK ENCOUNTERED\n")
			os.Exit(2)
		} else {

		}

		return nil
	}

	err := app.Run(os.Args)
	if err != nil {
		log.Fatal(err)
	}

}