Server: Add standard liveness/readiness check endpoints

Signed-off-by: Michael Mayer <michael@photoprism.app>

internal/config/config.go

@@ -33,6 +33,7 @@ import (
 	"runtime"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/dustin/go-humanize"
@@ -78,6 +79,7 @@ type Config struct {
 	serial    string
 	env       string
 	start     bool
+	ready     atomic.Bool
 }
 
 func init() {
@@ -266,10 +268,16 @@ func (c *Config) Init() error {
 
 	// Show log message.
 	log.Debugf("config: successfully initialized [%s]", time.Since(start))
+	c.ready.Store(true)
 
 	return nil
 }
 
+// IsReady checks if the application has been successfully initialized.
+func (c *Config) IsReady() bool {
+	return c.ready.Load()
+}
+
 // Propagate updates config options in other packages as needed.
 func (c *Config) Propagate() {
 	FlushCache()
@@ -599,6 +607,9 @@ func (c *Config) SetLogLevel(level logrus.Level) {
 
 // Shutdown shuts down the active processes and closes the database connection.
 func (c *Config) Shutdown() {
+	// App is no longer accepting requests.
+	c.ready.Store(false)
+
 	// Send cancel signal to all workers.
 	mutex.CancelAll()
 

internal/server/start.go

@@ -111,12 +111,27 @@ func Start(ctx context.Context, conf *config.Config) {
 	// Register application routes.
 	registerRoutes(router, conf)
 
-	// Register "GET /health" route so clients can perform health checks.
-	router.GET(conf.BaseUri("/health"), func(c *gin.Context) {
+	// Register standard health check endpoints to determine whether the server is running.
+	isLive := func(c *gin.Context) {
 		c.Header(header.CacheControl, header.CacheControlNoStore)
 		c.Header(header.AccessControlAllowOrigin, header.Any)
 		c.String(http.StatusOK, "OK")
-	})
+	}
+	router.Any(conf.BaseUri("/livez"), isLive)
+	router.Any(conf.BaseUri("/health"), isLive)
+	router.Any(conf.BaseUri("/healthz"), isLive)
+
+	// Register "/readyz" endpoint to check if the server has been successfully initialized.
+	isReady := func(c *gin.Context) {
+		c.Header(header.CacheControl, header.CacheControlNoStore)
+		c.Header(header.AccessControlAllowOrigin, header.Any)
+		if conf.IsReady() {
+			c.String(http.StatusOK, "OK")
+		} else {
+			c.String(http.StatusServiceUnavailable, "Service Unavailable")
+		}
+	}
+	router.Any(conf.BaseUri("/readyz"), isReady)
 
 	// Create a new HTTP server instance with no read or write timeout, except for reading the headers:
 	// https://pkg.go.dev/net/http#Server