main.go

package main

import (
	"context"
	goerrors "errors"
	"os"
	"os/signal"
	"syscall"

	"github.com/ONSdigital/log.go/v2/log"
	"github.com/pkg/errors"

	"github.com/ONSdigital/dis-search-upstream-stub/config"
	"github.com/ONSdigital/dis-search-upstream-stub/service"

	dpotelgo "github.com/ONSdigital/dp-otel-go"
)

const serviceName = "dis-search-upstream-stub"

var (
	// BuildTime represents the time in which the service was built
	BuildTime string
	// GitCommit represents the commit (SHA-1) hash of the service that is running
	GitCommit string
	// Version represents the version of the service that is running
	Version string

	// TODO: remove below explainer before committing
	/* NOTE: replace the above with the below to run code with for example vscode debugger.
	BuildTime string = "1601119818"
	GitCommit string = "6584b786caac36b6214ffe04bf62f058d4021538"
	Version   string = "v0.1.0"
	*/
)

func main() {
	log.Namespace = serviceName
	ctx := context.Background()

	if err := run(ctx); err != nil {
		log.Fatal(ctx, "fatal runtime error", err)
	}
}

func run(ctx context.Context) error {
	signals := make(chan os.Signal, 1)
	signal.Notify(signals, os.Interrupt, syscall.SIGTERM)

	// Run the service, providing an error channel for fatal errors
	svcErrors := make(chan error, 1)
	svcList := service.NewServiceList(&service.Init{})

	log.Info(ctx, "dis-search-upstream-stub version", log.Data{"version": Version})

	// Read config
	cfg, err := config.Get()
	if err != nil {
		return errors.Wrap(err, "error getting configuration")
	}

	if cfg.OtelEnabled {
		// Set up OpenTelemetry
		otelConfig := dpotelgo.Config{
			OtelServiceName:          cfg.OTServiceName,
			OtelExporterOtlpEndpoint: cfg.OTExporterOTLPEndpoint,
			OtelBatchTimeout:         cfg.OTBatchTimeout,
		}

		otelShutdown, oErr := dpotelgo.SetupOTelSDK(ctx, otelConfig)
		if oErr != nil {
			log.Fatal(ctx, "error setting up OpenTelemetry - hint: ensure OTEL_EXPORTER_OTLP_ENDPOINT is set", oErr)
		}
		// Handle shutdown properly so nothing leaks.
		defer func() {
			err = goerrors.Join(err, otelShutdown(context.Background()))
		}()
	}

	// Start service
	svc, err := service.Run(ctx, cfg, svcList, BuildTime, GitCommit, Version, svcErrors)
	if err != nil {
		return errors.Wrap(err, "running service failed")
	}

	// blocks until an os interrupt or a fatal error occurs
	select {
	case err := <-svcErrors:
		// TODO: call svc.Close(ctx) (or something specific)
		//  if there are any service connections like Kafka that you need to shut down
		return errors.Wrap(err, "service error received")
	case sig := <-signals:
		log.Info(ctx, "os signal received", log.Data{"signal": sig})
	}
	return svc.Close(ctx)
}