go-http-server-with-otel/pkg/srv/http_health.go

package srv

import (
	"context"
	"errors"
	"math/rand"
	"net/http"
	"sync"
	"time"

	"github.com/rs/zerolog"
)

type HealthCheckFunc func(context.Context) error

func handleHealthCheckFunc(ctx context.Context, hcFuncs ...HealthCheckFunc) func(w http.ResponseWriter, r *http.Request) {
	// Return http handle func
	return func(w http.ResponseWriter, r *http.Request) {
		var (
			healthChecksFailed bool
			errs               error
			hcWg               sync.WaitGroup
		)

		if len(hcFuncs) < 1 {
			zerolog.Ctx(ctx).Warn().Msg("no health checks given responding with dummy 200")
			hcFuncs = append(hcFuncs, dummyHealthCheck)
		}

		// Run all health check funcs concurrently
		// log all errors
		hcWg.Add(len(hcFuncs))
		for _, hc := range hcFuncs {
			go func() {
				defer hcWg.Done()
				errs = errors.Join(errs, hc(ctx))
			}()
		}
		hcWg.Wait()

		if errs != nil {
			healthChecksFailed = true
		}

		if healthChecksFailed {
			w.WriteHeader(http.StatusInternalServerError)
		}

		if errs != nil {
			w.Write([]byte(errs.Error()))
		} else {
			w.Write([]byte("ok"))
		}
	}
}

func dummyHealthCheck(ctx context.Context) error {
	workFor := rand.Intn(750)
	ticker := time.NewTicker(time.Duration(time.Duration(workFor) * time.Millisecond))

	select {
	case <-ticker.C:
		return nil
	case <-ctx.Done():
		return ctx.Err()
	}
}