feat(api): implement new api handler

cmd/root.go

@@ -1,22 +1,19 @@
 package cmd
 
 import (
-	"errors"
-	"math"
-	"net/http"
 	"os"
 	"os/signal"
-	"strconv"
 	"strings"
+	"sync"
 	"syscall"
 	"time"
 
 	"github.com/containrrr/watchtower/internal/actions"
 	"github.com/containrrr/watchtower/internal/flags"
 	"github.com/containrrr/watchtower/internal/meta"
+	"github.com/containrrr/watchtower/internal/util"
 	"github.com/containrrr/watchtower/pkg/api"
-	apiMetrics "github.com/containrrr/watchtower/pkg/api/metrics"
-	"github.com/containrrr/watchtower/pkg/api/update"
+	"github.com/containrrr/watchtower/pkg/api/updates"
 	"github.com/containrrr/watchtower/pkg/container"
 	"github.com/containrrr/watchtower/pkg/filters"
 	"github.com/containrrr/watchtower/pkg/metrics"
@@ -31,20 +28,16 @@ import (
 var (
 	client            container.Client
 	scheduleSpec      string
-	cleanup           bool
-	noRestart         bool
-	monitorOnly       bool
 	enableLabel       bool
 	disableContainers []string
 	notifier          t.Notifier
-	timeout           time.Duration
-	lifecycleHooks    bool
-	rollingRestart    bool
 	scope             string
-	labelPrecedence   bool
+
+	up = t.UpdateParams{}
 )
 
 var rootCmd = NewRootCommand()
+var localLog = notifications.LocalLog
 
 // NewRootCommand creates the root command for watchtower
 func NewRootCommand() *cobra.Command {
@@ -87,18 +80,18 @@ func PreRun(cmd *cobra.Command, _ []string) {
 	scheduleSpec, _ = f.GetString("schedule")
 
 	flags.GetSecretsFromFiles(cmd)
-	cleanup, noRestart, monitorOnly, timeout = flags.ReadFlags(cmd)
+	up.Cleanup, up.NoRestart, up.MonitorOnly, up.Timeout = flags.ReadFlags(cmd)
 
-	if timeout < 0 {
+	if up.Timeout < 0 {
 		log.Fatal("Please specify a positive value for timeout value.")
 	}
 
 	enableLabel, _ = f.GetBool("label-enable")
 	disableContainers, _ = f.GetStringSlice("disable-containers")
-	lifecycleHooks, _ = f.GetBool("enable-lifecycle-hooks")
-	rollingRestart, _ = f.GetBool("rolling-restart")
+	up.LifecycleHooks, _ = f.GetBool("enable-lifecycle-hooks")
+	up.RollingRestart, _ = f.GetBool("rolling-restart")
 	scope, _ = f.GetString("scope")
-	labelPrecedence, _ = f.GetBool("label-take-precedence")
+	up.LabelPrecedence, _ = f.GetBool("label-take-precedence")
 
 	if scope != "" {
 		log.Debugf(`Using scope %q`, scope)
@@ -110,25 +103,22 @@ func PreRun(cmd *cobra.Command, _ []string) {
 		log.Fatal(err)
 	}
 
+	var clientOpts = container.ClientOptions{}
+
 	noPull, _ := f.GetBool("no-pull")
-	includeStopped, _ := f.GetBool("include-stopped")
-	includeRestarting, _ := f.GetBool("include-restarting")
-	reviveStopped, _ := f.GetBool("revive-stopped")
-	removeVolumes, _ := f.GetBool("remove-volumes")
+	clientOpts.PullImages = !noPull
+	clientOpts.IncludeStopped, _ = f.GetBool("include-stopped")
+	clientOpts.IncludeRestarting, _ = f.GetBool("include-restarting")
+	clientOpts.ReviveStopped, _ = f.GetBool("revive-stopped")
+	clientOpts.RemoveVolumes, _ = f.GetBool("remove-volumes")
 	warnOnHeadPullFailed, _ := f.GetString("warn-on-head-failure")
+	clientOpts.WarnOnHeadFailed = container.WarningStrategy(warnOnHeadPullFailed)
 
-	if monitorOnly && noPull {
+	if up.MonitorOnly && noPull {
 		log.Warn("Using `WATCHTOWER_NO_PULL` and `WATCHTOWER_MONITOR_ONLY` simultaneously might lead to no action being taken at all. If this is intentional, you may safely ignore this message.")
 	}
 
-	client = container.NewClient(container.ClientOptions{
-		PullImages:        !noPull,
-		IncludeStopped:    includeStopped,
-		ReviveStopped:     reviveStopped,
-		RemoveVolumes:     removeVolumes,
-		IncludeRestarting: includeRestarting,
-		WarnOnHeadFailed:  container.WarningStrategy(warnOnHeadPullFailed),
-	})
+	client = container.NewClient(clientOpts)
 
 	notifier = notifications.NewNotifier(cmd)
 	notifier.AddLogHook()
@@ -137,13 +127,16 @@ func PreRun(cmd *cobra.Command, _ []string) {
 // Run is the main execution flow of the command
 func Run(c *cobra.Command, names []string) {
 	filter, filterDesc := filters.BuildFilter(names, disableContainers, enableLabel, scope)
+	up.Filter = filter
 	runOnce, _ := c.PersistentFlags().GetBool("run-once")
-	enableUpdateAPI, _ := c.PersistentFlags().GetBool("http-api-update")
+	enableUpdateAPI, _ := c.PersistentFlags().GetBool("http-api-updates")
 	enableMetricsAPI, _ := c.PersistentFlags().GetBool("http-api-metrics")
 	unblockHTTPAPI, _ := c.PersistentFlags().GetBool("http-api-periodic-polls")
 	apiToken, _ := c.PersistentFlags().GetString("http-api-token")
 	healthCheck, _ := c.PersistentFlags().GetBool("health-check")
 
+	enableScheduler := !enableUpdateAPI || unblockHTTPAPI
+
 	if healthCheck {
 		// health check should not have pid 1
 		if os.Getpid() == 1 {
@@ -153,61 +146,97 @@ func Run(c *cobra.Command, names []string) {
 		os.Exit(0)
 	}
 
-	if rollingRestart && monitorOnly {
+	if up.RollingRestart && up.MonitorOnly {
 		log.Fatal("Rolling restarts is not compatible with the global monitor only flag")
 	}
 
 	awaitDockerClient()
 
-	if err := actions.CheckForSanity(client, filter, rollingRestart); err != nil {
+	if err := actions.CheckForSanity(client, up.Filter, up.RollingRestart); err != nil {
 		logNotifyExit(err)
 	}
 
 	if runOnce {
 		writeStartupMessage(c, time.Time{}, filterDesc)
-		runUpdatesWithNotifications(filter)
+		runUpdatesWithNotifications(up)
 		notifier.Close()
 		os.Exit(0)
 		return
 	}
 
-	if err := actions.CheckForMultipleWatchtowerInstances(client, cleanup, scope); err != nil {
+	if err := actions.CheckForMultipleWatchtowerInstances(client, up.Cleanup, scope); err != nil {
 		logNotifyExit(err)
 	}
 
-	// The lock is shared between the scheduler and the HTTP API. It only allows one update to run at a time.
-	updateLock := make(chan bool, 1)
-	updateLock <- true
+	// The lock is shared between the scheduler and the HTTP API. It only allows one updates to run at a time.
+	updateLock := sync.Mutex{}
 
 	httpAPI := api.New(apiToken)
 
 	if enableUpdateAPI {
-		updateHandler := update.New(func(images []string) {
-			metric := runUpdatesWithNotifications(filters.FilterByImage(images, filter))
-			metrics.RegisterScan(metric)
-		}, updateLock)
-		httpAPI.RegisterFunc(updateHandler.Path, updateHandler.Handle)
-		// If polling isn't enabled the scheduler is never started and
-		// we need to trigger the startup messages manually.
-		if !unblockHTTPAPI {
-			writeStartupMessage(c, time.Time{}, filterDesc)
-		}
+		httpAPI.EnableUpdates(func(paramsFunc updates.ModifyParamsFunc) t.Report {
+			apiUpdateParams := up
+			paramsFunc(&apiUpdateParams)
+			if up.MonitorOnly && !apiUpdateParams.MonitorOnly {
+				apiUpdateParams.MonitorOnly = true
+				localLog.Warn("Ignoring request to disable monitor only through API")
+			}
+			report := runUpdatesWithNotifications(apiUpdateParams)
+			metrics.RegisterScan(metrics.NewMetric(report))
+			return report
+		}, &updateLock)
 	}
 
 	if enableMetricsAPI {
-		metricsHandler := apiMetrics.New()
-		httpAPI.RegisterHandler(metricsHandler.Path, metricsHandler.Handle)
+		httpAPI.EnableMetrics()
 	}
 
-	if err := httpAPI.Start(enableUpdateAPI && !unblockHTTPAPI); err != nil && !errors.Is(err, http.ErrServerClosed) {
+	if err := httpAPI.Start(); err != nil {
 		log.Error("failed to start API", err)
 	}
 
-	if err := runUpgradesOnSchedule(c, filter, filterDesc, updateLock); err != nil {
-		log.Error(err)
+	var firstScan time.Time
+	var scheduler *cron.Cron
+	if enableScheduler {
+		var err error
+		scheduler, err = runUpgradesOnSchedule(up, &updateLock)
+		if err != nil {
+			log.Errorf("Failed to start scheduler: %v", err)
+		} else {
+			firstScan = scheduler.Entries()[0].Schedule.Next(time.Now())
+		}
 	}
 
-	os.Exit(1)
+	writeStartupMessage(c, firstScan, filterDesc)
+
+	// Graceful shut-down on SIGINT/SIGTERM
+	interrupt := make(chan os.Signal, 1)
+	signal.Notify(interrupt, os.Interrupt)
+	signal.Notify(interrupt, syscall.SIGTERM)
+
+	recievedSignal := <-interrupt
+	localLog.WithField("signal", recievedSignal).Infof("Got shutdown signal. Gracefully shutting down...")
+	if scheduler != nil {
+		scheduler.Stop()
+	}
+
+	updateLock.Lock()
+	go func() {
+		time.Sleep(time.Second * 3)
+		updateLock.Unlock()
+	}()
+
+	waitFor(httpAPI.Stop(), "Waiting for HTTP API requests to complete...")
+	waitFor(&updateLock, "Waiting for running updates to be finished...")
+
+	localLog.Info("Shutdown completed")
+}
+
+func waitFor(waitLock *sync.Mutex, delayMessage string) {
+	if !waitLock.TryLock() {
+		log.Info(delayMessage)
+		waitLock.Lock()
+	}
 }
 
 func logNotifyExit(err error) {
@@ -221,48 +250,9 @@ func awaitDockerClient() {
 	time.Sleep(1 * time.Second)
 }
 
-func formatDuration(d time.Duration) string {
-	sb := strings.Builder{}
-
-	hours := int64(d.Hours())
-	minutes := int64(math.Mod(d.Minutes(), 60))
-	seconds := int64(math.Mod(d.Seconds(), 60))
-
-	if hours == 1 {
-		sb.WriteString("1 hour")
-	} else if hours != 0 {
-		sb.WriteString(strconv.FormatInt(hours, 10))
-		sb.WriteString(" hours")
-	}
-
-	if hours != 0 && (seconds != 0 || minutes != 0) {
-		sb.WriteString(", ")
-	}
-
-	if minutes == 1 {
-		sb.WriteString("1 minute")
-	} else if minutes != 0 {
-		sb.WriteString(strconv.FormatInt(minutes, 10))
-		sb.WriteString(" minutes")
-	}
-
-	if minutes != 0 && (seconds != 0) {
-		sb.WriteString(", ")
-	}
-
-	if seconds == 1 {
-		sb.WriteString("1 second")
-	} else if seconds != 0 || (hours == 0 && minutes == 0) {
-		sb.WriteString(strconv.FormatInt(seconds, 10))
-		sb.WriteString(" seconds")
-	}
-
-	return sb.String()
-}
-
 func writeStartupMessage(c *cobra.Command, sched time.Time, filtering string) {
 	noStartupMessage, _ := c.PersistentFlags().GetBool("no-startup-message")
-	enableUpdateAPI, _ := c.PersistentFlags().GetBool("http-api-update")
+	enableUpdateAPI, _ := c.PersistentFlags().GetBool("http-api-updates")
 
 	var startupLog *log.Entry
 	if noStartupMessage {
@@ -285,11 +275,11 @@ func writeStartupMessage(c *cobra.Command, sched time.Time, filtering string) {
 	startupLog.Info(filtering)
 
 	if !sched.IsZero() {
-		until := formatDuration(time.Until(sched))
+		until := util.FormatDuration(time.Until(sched))
 		startupLog.Info("Scheduling first run: " + sched.Format("2006-01-02 15:04:05 -0700 MST"))
 		startupLog.Info("Note that the first check will be performed in " + until)
 	} else if runOnce, _ := c.PersistentFlags().GetBool("run-once"); runOnce {
-		startupLog.Info("Running a one time update.")
+		startupLog.Info("Running a one time updates.")
 	} else {
 		startupLog.Info("Periodic runs are not enabled.")
 	}
@@ -309,25 +299,19 @@ func writeStartupMessage(c *cobra.Command, sched time.Time, filtering string) {
 	}
 }
 
-func runUpgradesOnSchedule(c *cobra.Command, filter t.Filter, filtering string, lock chan bool) error {
-	if lock == nil {
-		lock = make(chan bool, 1)
-		lock <- true
-	}
-
+func runUpgradesOnSchedule(updateParams t.UpdateParams, updateLock *sync.Mutex) (*cron.Cron, error) {
 	scheduler := cron.New()
 	err := scheduler.AddFunc(
 		scheduleSpec,
 		func() {
-			select {
-			case v := <-lock:
-				defer func() { lock <- v }()
-				metric := runUpdatesWithNotifications(filter)
-				metrics.RegisterScan(metric)
-			default:
+			if updateLock.TryLock() {
+				defer updateLock.Unlock()
+				result := runUpdatesWithNotifications(updateParams)
+				metrics.RegisterScan(metrics.NewMetric(result))
+			} else {
 				// Update was skipped
 				metrics.RegisterScan(nil)
-				log.Debug("Skipped another update already running.")
+				log.Debug("Skipped another updates already running.")
 			}
 
 			nextRuns := scheduler.Entries()
@@ -337,47 +321,28 @@ func runUpgradesOnSchedule(c *cobra.Command, filter t.Filter, filtering string,
 		})
 
 	if err != nil {
-		return err
+		return nil, err
 	}
 
-	writeStartupMessage(c, scheduler.Entries()[0].Schedule.Next(time.Now()), filtering)
-
 	scheduler.Start()
 
-	// Graceful shut-down on SIGINT/SIGTERM
-	interrupt := make(chan os.Signal, 1)
-	signal.Notify(interrupt, os.Interrupt)
-	signal.Notify(interrupt, syscall.SIGTERM)
-
-	<-interrupt
-	scheduler.Stop()
-	log.Info("Waiting for running update to be finished...")
-	<-lock
-	return nil
+	return scheduler, nil
 }
 
-func runUpdatesWithNotifications(filter t.Filter) *metrics.Metric {
+func runUpdatesWithNotifications(updateParams t.UpdateParams) t.Report {
 	notifier.StartNotification()
-	updateParams := t.UpdateParams{
-		Filter:          filter,
-		Cleanup:         cleanup,
-		NoRestart:       noRestart,
-		Timeout:         timeout,
-		MonitorOnly:     monitorOnly,
-		LifecycleHooks:  lifecycleHooks,
-		RollingRestart:  rollingRestart,
-		LabelPrecedence: labelPrecedence,
-	}
+
 	result, err := actions.Update(client, updateParams)
 	if err != nil {
 		log.Error(err)
 	}
 	notifier.SendNotification(result)
-	metricResults := metrics.NewMetric(result)
-	notifications.LocalLog.WithFields(log.Fields{
-		"Scanned": metricResults.Scanned,
-		"Updated": metricResults.Updated,
-		"Failed":  metricResults.Failed,
+
+	localLog.WithFields(log.Fields{
+		"Scanned": len(result.Scanned()),
+		"Updated": len(result.Updated()),
+		"Failed":  len(result.Failed()),
 	}).Info("Session done")
-	return metricResults
+
+	return result
 }

internal/util/duration.go

@@ -0,0 +1,47 @@
+package util
+
+import (
+	"math"
+	"strconv"
+	"strings"
+	"time"
+)
+
+func FormatDuration(d time.Duration) string {
+	sb := strings.Builder{}
+
+	hours := int64(d.Hours())
+	minutes := int64(math.Mod(d.Minutes(), 60))
+	seconds := int64(math.Mod(d.Seconds(), 60))
+
+	if hours == 1 {
+		sb.WriteString("1 hour")
+	} else if hours != 0 {
+		sb.WriteString(strconv.FormatInt(hours, 10))
+		sb.WriteString(" hours")
+	}
+
+	if hours != 0 && (seconds != 0 || minutes != 0) {
+		sb.WriteString(", ")
+	}
+
+	if minutes == 1 {
+		sb.WriteString("1 minute")
+	} else if minutes != 0 {
+		sb.WriteString(strconv.FormatInt(minutes, 10))
+		sb.WriteString(" minutes")
+	}
+
+	if minutes != 0 && (seconds != 0) {
+		sb.WriteString(", ")
+	}
+
+	if seconds == 1 {
+		sb.WriteString("1 second")
+	} else if seconds != 0 || (hours == 0 && minutes == 0) {
+		sb.WriteString(strconv.FormatInt(seconds, 10))
+		sb.WriteString(" seconds")
+	}
+
+	return sb.String()
+}

pkg/api/api.go

@@ -1,8 +1,14 @@
 package api
 
 import (
-	"fmt"
+	"context"
+	"errors"
+	"github.com/containrrr/watchtower/pkg/api/metrics"
+	"github.com/containrrr/watchtower/pkg/api/middleware"
+	"github.com/containrrr/watchtower/pkg/api/prelude"
+	"github.com/containrrr/watchtower/pkg/api/updates"
 	"net/http"
+	"sync"
 
 	log "github.com/sirupsen/logrus"
 )
@@ -11,46 +17,52 @@ const tokenMissingMsg = "api token is empty or has not been set. exiting"
 
 // API is the http server responsible for serving the HTTP API endpoints
 type API struct {
-	Token       string
-	hasHandlers bool
+	Token          string
+	hasHandlers    bool
+	mux            *http.ServeMux
+	server         *http.Server
+	running        *sync.Mutex
+	router         router
+	authMiddleware prelude.Middleware
+	registered     bool
 }
 
 // New is a factory function creating a new API instance
 func New(token string) *API {
 	return &API{
-		Token:       token,
-		hasHandlers: false,
+		Token:          token,
+		hasHandlers:    false,
+		mux:            http.NewServeMux(),
+		running:        &sync.Mutex{},
+		router:         router{},
+		authMiddleware: middleware.RequireToken(token),
+		registered:     false,
 	}
 }
 
-// RequireToken is wrapper around http.HandleFunc that checks token validity
-func (api *API) RequireToken(fn http.HandlerFunc) http.HandlerFunc {
-	return func(w http.ResponseWriter, r *http.Request) {
-		auth := r.Header.Get("Authorization")
-		want := fmt.Sprintf("Bearer %s", api.Token)
-		if auth != want {
-			w.WriteHeader(http.StatusUnauthorized)
-			return
-		}
-		log.Debug("Valid token found.")
-		fn(w, r)
-	}
-}
-
-// RegisterFunc is a wrapper around http.HandleFunc that also sets the flag used to determine whether to launch the API
-func (api *API) RegisterFunc(path string, fn http.HandlerFunc) {
-	api.hasHandlers = true
-	http.HandleFunc(path, api.RequireToken(fn))
+func (api *API) route(route string) methodHandlers {
+	return api.router.route(route)
 }
 
-// RegisterHandler is a wrapper around http.Handler that also sets the flag used to determine whether to launch the API
-func (api *API) RegisterHandler(path string, handler http.Handler) {
-	api.hasHandlers = true
-	http.Handle(path, api.RequireToken(handler.ServeHTTP))
+func (api *API) registerHandlers() {
+	if api.registered {
+		return
+	}
+	for path, route := range api.router {
+		if len(route) < 1 {
+			continue
+		}
+		api.hasHandlers = true
+		api.mux.Handle(path, api.authMiddleware(route.Handler))
+	}
+	api.registered = true
+	return
 }
 
 // Start the API and serve over HTTP. Requires an API Token to be set.
-func (api *API) Start(block bool) error {
+func (api *API) Start() error {
+
+	api.registerHandlers()
 
 	if !api.hasHandlers {
 		log.Debug("Watchtower HTTP API skipped.")
@@ -61,16 +73,49 @@ func (api *API) Start(block bool) error {
 		log.Fatal(tokenMissingMsg)
 	}
 
-	if block {
-		runHTTPServer()
-	} else {
+	api.running.Lock()
+	go func() {
+		defer api.running.Unlock()
+		api.server = &http.Server{
+			Addr:    ":8080",
+			Handler: api.mux,
+		}
+
+		if err := api.server.ListenAndServe(); !errors.Is(err, http.ErrServerClosed) {
+			log.Errorf("HTTP Server error: %v", err)
+		}
+	}()
+
+	return nil
+}
+
+// Stop tells the api server to shut down (if its running) and returns a sync.Mutex that is locked
+// until the server has handled all remaining requests and shut down
+func (api *API) Stop() *sync.Mutex {
+
+	if api.server != nil {
 		go func() {
-			runHTTPServer()
+			if err := api.server.Shutdown(context.Background()); err != nil && !errors.Is(err, http.ErrServerClosed) {
+				log.Errorf("Error stopping HTTP Server: %v", err)
+			}
 		}()
 	}
-	return nil
+
+	return api.running
+}
+
+// Handler is used to get a http.Handler for testing
+func (api *API) Handler() http.Handler {
+	api.registerHandlers()
+	return api.mux
+}
+
+// EnableUpdates registers the `updates` endpoints
+func (api *API) EnableUpdates(f updates.InvokedFunc, updateLock *sync.Mutex) {
+	api.route("/v1/updates").post(updates.PostV1(f, updateLock))
 }
 
-func runHTTPServer() {
-	log.Fatal(http.ListenAndServe(":8080", nil))
+// EnableMetrics registers the `metrics` endpoints
+func (api *API) EnableMetrics() {
+	api.route("/v1/metrics").get(metrics.GetV1())
 }

pkg/api/metrics/metrics.go

@@ -1,27 +1,14 @@
 package metrics
 
 import (
+	. "github.com/containrrr/watchtower/pkg/api/prelude"
 	"github.com/containrrr/watchtower/pkg/metrics"
-	"net/http"
-
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
-// Handler is an HTTP handle for serving metric data
-type Handler struct {
-	Path    string
-	Handle  http.HandlerFunc
-	Metrics *metrics.Metrics
-}
-
-// New is a factory function creating a new Metrics instance
-func New() *Handler {
-	m := metrics.Default()
-	handler := promhttp.Handler()
-
-	return &Handler{
-		Path:    "/v1/metrics",
-		Handle:  handler.ServeHTTP,
-		Metrics: m,
-	}
+// GetV1 creates a new metrics http handler
+func GetV1() HandlerFunc {
+	// Initialize watchtower metrics
+	metrics.Init()
+	return WrapHandler(promhttp.Handler().ServeHTTP)
 }

pkg/api/metrics/metrics_test.go

@@ -12,7 +12,6 @@ import (
 	. "github.com/onsi/gomega"
 
 	"github.com/containrrr/watchtower/pkg/api"
-	metricsAPI "github.com/containrrr/watchtower/pkg/api/metrics"
 	"github.com/containrrr/watchtower/pkg/metrics"
 )
 
@@ -51,10 +50,9 @@ func getWithToken(handler http.Handler) map[string]string {
 
 var _ = Describe("the metrics API", func() {
 	httpAPI := api.New(token)
-	m := metricsAPI.New()
+	httpAPI.EnableMetrics()
 
-	handleReq := httpAPI.RequireToken(m.Handle)
-	tryGetMetrics := func() map[string]string { return getWithToken(handleReq) }
+	tryGetMetrics := func() map[string]string { return getWithToken(httpAPI.Handler()) }
 
 	It("should serve metrics", func() {
 

pkg/api/middleware/middleware_test.go

@@ -1,7 +1,7 @@
-package api
+package middleware
 
 import (
-	"io"
+	"github.com/containrrr/watchtower/pkg/api/prelude"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -11,55 +11,58 @@ import (
 )
 
 const (
-	token  = "123123123"
+	token = "123123123"
 )
 
 func TestAPI(t *testing.T) {
 	RegisterFailHandler(Fail)
-	RunSpecs(t, "API Suite")
+	RunSpecs(t, "Middleware Suite")
 }
 
 var _ = Describe("API", func() {
-	api := New(token)
+	requireToken := RequireToken(token)
 
 	Describe("RequireToken middleware", func() {
 		It("should return 401 Unauthorized when token is not provided", func() {
-			handlerFunc := api.RequireToken(testHandler)
-
 			rec := httptest.NewRecorder()
 			req := httptest.NewRequest("GET", "/hello", nil)
 
-			handlerFunc(rec, req)
+			requireToken(testHandler).ServeHTTP(rec, req)
 
 			Expect(rec.Code).To(Equal(http.StatusUnauthorized))
+			Expect(rec.Body).To(MatchJSON(`{
+				"code":  "MISSING_TOKEN",
+				"error": "No authentication token was supplied"
+			}`))
 		})
 
 		It("should return 401 Unauthorized when token is invalid", func() {
-			handlerFunc := api.RequireToken(testHandler)
-
 			rec := httptest.NewRecorder()
 			req := httptest.NewRequest("GET", "/hello", nil)
 			req.Header.Set("Authorization", "Bearer 123")
 
-			handlerFunc(rec, req)
+			requireToken(testHandler).ServeHTTP(rec, req)
 
 			Expect(rec.Code).To(Equal(http.StatusUnauthorized))
+			Expect(rec.Body).To(MatchJSON(`{
+				"code":  "INVALID_TOKEN",
+				"error": "The supplied token does not match the configured auth token"
+			}`))
 		})
 
 		It("should return 200 OK when token is valid", func() {
-			handlerFunc := api.RequireToken(testHandler)
 
 			rec := httptest.NewRecorder()
 			req := httptest.NewRequest("GET", "/hello", nil)
-			req.Header.Set("Authorization", "Bearer " + token)
+			req.Header.Set("Authorization", "Bearer "+token)
 
-			handlerFunc(rec, req)
+			requireToken(testHandler).ServeHTTP(rec, req)
 
 			Expect(rec.Code).To(Equal(http.StatusOK))
 		})
 	})
 })
 
-func testHandler(w http.ResponseWriter, req *http.Request) {
-	_, _ = io.WriteString(w, "Hello!")
+func testHandler(_ *prelude.Context) prelude.Response {
+	return prelude.OK("Hello!")
 }

pkg/api/middleware/require_token.go

@@ -0,0 +1,24 @@
+package middleware
+
+import (
+	"fmt"
+	. "github.com/containrrr/watchtower/pkg/api/prelude"
+)
+
+// RequireToken returns a prelude.Middleware that checks token validity
+func RequireToken(token string) Middleware {
+	return func(next HandlerFunc) HandlerFunc {
+		want := fmt.Sprintf("Bearer %s", token)
+		return func(c *Context) Response {
+			auth := c.Request.Header.Get("Authorization")
+			if auth == "" {
+				return Error(ErrMissingToken)
+			}
+
+			if auth != want {
+				return Error(ErrInvalidToken)
+			}
+			return next(c)
+		}
+	}
+}

pkg/api/prelude/context.go

@@ -0,0 +1,62 @@
+package prelude
+
+import (
+	"bytes"
+	"fmt"
+	"github.com/sirupsen/logrus"
+	"net/http"
+)
+
+type Context struct {
+	Request *http.Request
+	Log     *logrus.Entry
+	writer  http.ResponseWriter
+}
+
+func newContext(w http.ResponseWriter, req *http.Request) *Context {
+	reqLog := localLog.WithField("endpoint", fmt.Sprintf("%v %v", req.Method, req.URL.Path))
+	return &Context{
+		Log:     reqLog,
+		Request: req,
+		writer:  w,
+	}
+}
+
+func (c *Context) Headers() http.Header {
+	return c.writer.Header()
+}
+
+type contextWrapper struct {
+	context    *Context
+	body       bytes.Buffer
+	statusCode int
+}
+
+func (cw *contextWrapper) Header() http.Header {
+	return cw.context.writer.Header()
+}
+
+func (cw *contextWrapper) Write(bytes []byte) (int, error) {
+	return cw.body.Write(bytes)
+}
+
+func (cw *contextWrapper) WriteHeader(statusCode int) {
+	cw.statusCode = statusCode
+}
+
+func WrapHandler(next http.HandlerFunc) HandlerFunc {
+	return func(c *Context) Response {
+		wrapper := contextWrapper{
+			context: c,
+			body:    bytes.Buffer{},
+		}
+
+		next(&wrapper, c.Request)
+
+		return Response{
+			Status: wrapper.statusCode,
+			Body:   wrapper.body.Bytes(),
+			Raw:    true,
+		}
+	}
+}

pkg/api/prelude/errors.go

@@ -0,0 +1,36 @@
+package prelude
+
+import "net/http"
+
+type errorResponse struct {
+	Error  string    `json:"error"`
+	Code   ErrorCode `json:"code"`
+	Status int       `json:"-"`
+}
+
+const internalErrorPayload string = `{ "error": "API internal error, check logs", "code": "API_INTERNAL_ERROR" }`
+
+type ErrorCode string
+
+var (
+	ErrUpdateRunning = errorResponse{
+		Code:   "UPDATE_RUNNING",
+		Error:  "Update already running",
+		Status: http.StatusConflict,
+	}
+	ErrNotFound = errorResponse{
+		Code:   "NOT_FOUND",
+		Error:  "Endpoint is not registered to a handler",
+		Status: http.StatusNotFound,
+	}
+	ErrInvalidToken = errorResponse{
+		Code:   "INVALID_TOKEN",
+		Error:  "The supplied token does not match the configured auth token",
+		Status: http.StatusUnauthorized,
+	}
+	ErrMissingToken = errorResponse{
+		Code:   "MISSING_TOKEN",
+		Error:  "No authentication token was supplied",
+		Status: http.StatusUnauthorized,
+	}
+)

pkg/api/prelude/handler_func.go

@@ -0,0 +1,39 @@
+package prelude
+
+import (
+	log "github.com/sirupsen/logrus"
+	"net/http"
+)
+
+type HandlerFunc func(c *Context) Response
+
+func (hf HandlerFunc) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+
+	w.Header().Set("Content-Type", DefaultContentType)
+	context := newContext(w, req)
+
+	reqLog := context.Log.WithFields(log.Fields{
+		"query": req.URL.RawQuery,
+	})
+	reqLog.Trace("Received API Request")
+
+	res := hf(context)
+
+	status := res.Status
+
+	bytes, err := res.Bytes()
+	if err != nil {
+		context.Log.WithError(err).Errorf("Failed to create JSON payload for response")
+		bytes = []byte(internalErrorPayload)
+		status = http.StatusInternalServerError
+		// Reset the content-type in case the handler changed it
+		w.Header().Set("Content-Type", DefaultContentType)
+	}
+
+	reqLog.WithField("status", status).Trace("Handled API Request")
+
+	w.WriteHeader(status)
+	if _, err = w.Write(bytes); err != nil {
+		localLog.Errorf("Failed to write HTTP response: %v", err)
+	}
+}

pkg/api/prelude/response.go

@@ -0,0 +1,41 @@
+package prelude
+
+import (
+	"encoding/json"
+	log "github.com/sirupsen/logrus"
+	"net/http"
+)
+
+type Response struct {
+	Body   any
+	Status int
+	Raw    bool
+}
+
+func (r *Response) Bytes() ([]byte, error) {
+	if bytes, raw := r.Body.([]byte); raw {
+		return bytes, nil
+	}
+
+	if str, raw := r.Body.(string); raw {
+		return []byte(str), nil
+	}
+
+	return json.MarshalIndent(r.Body, "", "  ")
+}
+
+var localLog = log.WithField("notify", "no")
+
+func OK(body any) Response {
+	return Response{
+		Status: http.StatusOK,
+		Body:   body,
+	}
+}
+
+func Error(err errorResponse) Response {
+	return Response{
+		Status: err.Status,
+		Body:   err,
+	}
+}

pkg/api/prelude/types.go

@@ -0,0 +1,5 @@
+package prelude
+
+type Middleware func(next HandlerFunc) HandlerFunc
+
+const DefaultContentType = "application/json"

pkg/api/router.go

@@ -0,0 +1,34 @@
+package api
+
+import (
+	. "github.com/containrrr/watchtower/pkg/api/prelude"
+	"net/http"
+)
+
+type router map[string]methodHandlers
+
+type methodHandlers map[string]HandlerFunc
+
+func (mh methodHandlers) Handler(c *Context) Response {
+	handler, found := mh[c.Request.Method]
+	if !found {
+		return Error(ErrNotFound)
+	}
+	return handler(c)
+}
+
+func (mh methodHandlers) post(handlerFunc HandlerFunc) {
+	mh[http.MethodPost] = handlerFunc
+}
+func (mh methodHandlers) get(handlerFunc HandlerFunc) {
+	mh[http.MethodGet] = handlerFunc
+}
+
+func (r router) route(route string) methodHandlers {
+	routeMethods, found := r[route]
+	if !found {
+		routeMethods = methodHandlers{}
+		r[route] = routeMethods
+	}
+	return routeMethods
+}

pkg/api/update/update.go

@@ -1,72 +0,0 @@
-package update
-
-import (
-	"io"
-	"net/http"
-	"os"
-	"strings"
-
-	log "github.com/sirupsen/logrus"
-)
-
-var (
-	lock chan bool
-)
-
-// New is a factory function creating a new  Handler instance
-func New(updateFn func(images []string), updateLock chan bool) *Handler {
-	if updateLock != nil {
-		lock = updateLock
-	} else {
-		lock = make(chan bool, 1)
-		lock <- true
-	}
-
-	return &Handler{
-		fn:   updateFn,
-		Path: "/v1/update",
-	}
-}
-
-// Handler is an API handler used for triggering container update scans
-type Handler struct {
-	fn   func(images []string)
-	Path string
-}
-
-// Handle is the actual http.Handle function doing all the heavy lifting
-func (handle *Handler) Handle(w http.ResponseWriter, r *http.Request) {
-	log.Info("Updates triggered by HTTP API request.")
-
-	_, err := io.Copy(os.Stdout, r.Body)
-	if err != nil {
-		log.Println(err)
-		return
-	}
-
-	var images []string
-	imageQueries, found := r.URL.Query()["image"]
-	if found {
-		for _, image := range imageQueries {
-			images = append(images, strings.Split(image, ",")...)
-		}
-
-	} else {
-		images = nil
-	}
-
-	if len(images) > 0 {
-		chanValue := <-lock
-		defer func() { lock <- chanValue }()
-		handle.fn(images)
-	} else {
-		select {
-		case chanValue := <-lock:
-			defer func() { lock <- chanValue }()
-			handle.fn(images)
-		default:
-			log.Debug("Skipped. Another update already running.")
-		}
-	}
-
-}

pkg/api/updates/updates.go

@@ -0,0 +1,22 @@
+package updates
+
+import (
+	"github.com/containrrr/watchtower/pkg/types"
+	"net/url"
+	"strings"
+)
+
+type ModifyParamsFunc func(up *types.UpdateParams)
+type InvokedFunc func(ModifyParamsFunc) types.Report
+
+func parseImages(u *url.URL) []string {
+	var images []string
+	imageQueries, found := u.Query()["image"]
+	if found {
+		for _, image := range imageQueries {
+			images = append(images, strings.Split(image, ",")...)
+		}
+
+	}
+	return images
+}

pkg/api/updates/updates_v1.go

@@ -0,0 +1,37 @@
+package updates
+
+import (
+	. "github.com/containrrr/watchtower/pkg/api/prelude"
+	"github.com/containrrr/watchtower/pkg/filters"
+	"github.com/containrrr/watchtower/pkg/types"
+	"sync"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// PostV1 creates an API http.HandlerFunc for V1 of updates
+func PostV1(updateFn InvokedFunc, updateLock *sync.Mutex) HandlerFunc {
+	return func(c *Context) Response {
+		log.Info("Updates triggered by HTTP API request.")
+
+		images := parseImages(c.Request.URL)
+
+		if !updateLock.TryLock() {
+			if len(images) > 0 {
+				// If images have been passed, wait until the current updates are done
+				updateLock.Lock()
+			} else {
+				// If a full update is running (no explicit image filter), skip this update
+				log.Debug("Skipped. Another updates already running.")
+				return OK(nil) // For backwards compatibility
+			}
+		}
+
+		defer updateLock.Unlock()
+		_ = updateFn(func(up *types.UpdateParams) {
+			up.Filter = filters.FilterByImage(images, up.Filter)
+		})
+
+		return OK(nil)
+	}
+}

pkg/metrics/metrics.go

@@ -45,12 +45,11 @@ func (metrics *Metrics) Register(metric *Metric) {
 	metrics.channel <- metric
 }
 
-// Default creates a new metrics handler if none exists, otherwise returns the existing one
-func Default() *Metrics {
+// Init creates a new metrics handler if none exists
+func Init() {
 	if metrics != nil {
-		return metrics
+		return
 	}
-
 	metrics = &Metrics{
 		scanned: promauto.NewGauge(prometheus.GaugeOpts{
 			Name: "watchtower_containers_scanned",
@@ -76,6 +75,11 @@ func Default() *Metrics {
 	}
 
 	go metrics.HandleUpdate(metrics.channel)
+}
+
+// Default creates a new metrics handler if none exists, otherwise returns the existing one
+func Default() *Metrics {
+	Init()
 
 	return metrics
 }