InVisionApp/go-health

package main

import (
    "log"
    "net/http"
    "net/url"
    "os"
    "time"

    "github.com/InVisionApp/go-health/v2"
    "github.com/InVisionApp/go-health/v2/checkers"
    "github.com/InVisionApp/go-health/v2/handlers"
)

var svcLogger *log.Logger

// HealthCheckStatusListener is the implementation of the IStatusListener interface
type HealthCheckStatusListener struct{}

// HealthCheckFailed is triggered when a health check fails the first time
func (sl *HealthCheckStatusListener) HealthCheckFailed(entry *health.State) {
    svcLogger.Printf("State for failed health check: %+v", entry)
}

// HealthCheckRecovered is triggered when a health check recovers
func (sl *HealthCheckStatusListener) HealthCheckRecovered(entry *health.State, recordedFailures int64, failureDurationSeconds float64) {
    svcLogger.Printf("Recovering from %d contiguous errors, lasting %1.2f seconds: %+v", recordedFailures, failureDurationSeconds, entry)
}

func init() {
    svcLogger = log.New(os.Stderr, "service: ", 0)
}

func main() {
    // Create a new health instance
    h := health.New()
    // disable logging from health lib
    h.DisableLogging()
    testURL, _ := url.Parse("http://0.0.0.0:8081")

    // Create a couple of checks
    httpCheck, _ := checkers.NewHTTP(&checkers.HTTPConfig{
        URL: testURL,
    })

    // Add the checks to the health instance
    h.AddChecks([]*health.Config{
        {
            Name:     "dependency-check",
            Checker:  httpCheck,
            Interval: time.Duration(2) * time.Second,
            Fatal:    true,
        },
    })

    // set status listener
    sl := &HealthCheckStatusListener{}
    h.StatusListener = sl

    //  Start the healthcheck process
    if err := h.Start(); err != nil {
        svcLogger.Fatalf("Unable to start healthcheck: %v", err)
    }

    svcLogger.Println("Server listening on :8080")

    // Define a healthcheck endpoint and use the built-in JSON handler
    http.HandleFunc("/healthcheck", handlers.NewJSONHandlerFunc(h, nil))
    http.ListenAndServe(":8080", nil)
}