introspection: enable readiness endpoint

Signed-off-by: Hank Donnay <hdonnay@redhat.com>

cmd/clair/main.go

@@ -18,6 +18,7 @@ import (
 	yaml "gopkg.in/yaml.v3"
 
 	"github.com/quay/clair/v4/config"
+	"github.com/quay/clair/v4/health"
 	"github.com/quay/clair/v4/httptransport"
 	"github.com/quay/clair/v4/initialize"
 	"github.com/quay/clair/v4/introspection"
@@ -108,6 +109,7 @@ func main() {
 			return fmt.Errorf("http transport configuration failed: %w", err)
 		}
 		down.Add(h.Server)
+		health.Ready()
 		if err := h.ListenAndServe(); err != http.ErrServerClosed {
 			return fmt.Errorf("http transport failed to launch: %w", err)
 		}

health/readinesshandler.go

@@ -3,43 +3,39 @@ package health
 import (
 	"net/http"
 	"sync/atomic"
-
-	je "github.com/quay/claircore/pkg/jsonerr"
 )
 
 var ready *uint32 = new(uint32)
 
-// Ready instructs the ReadinessHandler to begin serving 200OK status
+// Ready instructs the ReadinessHandler to begin serving 200 OK status.
 func Ready() {
 	atomic.StoreUint32(ready, uint32(1))
 }
 
-// NotReady instructs the ReadinessHandler to begin serving 503ServiceUnavailable status
-func UnReady() {
+// Unready instructs the ReadinessHandler to begin serving 503
+// Service Unavailable.
+func Unready() {
 	atomic.StoreUint32(ready, uint32(0))
 }
 
-// ReadinessHandler will return a 200OK or 503ServiceUnavailable status dependent
-// on whether the exported Ready or NotReady methods have been called.
+// ReadinessHandler will return a 200 OK or 503 "Service Unavailable" status
+// depending on whether the Ready or Unready functions have been called.
 //
-// The Ready() method must be called to begin returning 200OK
-func ReadinessHandler() http.HandlerFunc {
-	return func(w http.ResponseWriter, r *http.Request) {
+// The Ready() method must be called to begin returning 200 OK.
+func ReadinessHandler() http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		h := w.Header()
+		h.Set("X-Content-Type-Options", "nosniff")
+		h.Set("Content-Type", "text/plain; charset=utf-8")
+		h.Set("Content-Length", "0")
+		h.Set("Cache-Control", "no-store")
 		if r.Method != http.MethodGet {
-			resp := &je.Response{
-				Code:    "method-not-allowed",
-				Message: "endpoint only allows GET",
-			}
-			je.Error(w, resp, http.StatusMethodNotAllowed)
+			w.WriteHeader(http.StatusMethodNotAllowed)
 			return
 		}
 
-		ready := atomic.LoadUint32(ready)
-		if ready == 1 {
-			w.WriteHeader(http.StatusOK)
-		} else {
+		if atomic.LoadUint32(ready) != 1 {
 			w.WriteHeader(http.StatusServiceUnavailable)
 		}
-		return
-	}
+	})
 }

introspection/server.go

@@ -17,6 +17,7 @@ import (
 	sdktrace "go.opentelemetry.io/otel/sdk/trace"
 
 	"github.com/quay/clair/v4/config"
+	"github.com/quay/clair/v4/health"
 )
 
 const (
@@ -27,6 +28,7 @@ const (
 	Jaeger                   = "jaeger"
 	DefaultJaegerEndpoint    = "localhost:6831"
 	HealthEndpoint           = "/healthz"
+	ReadyEndpoint            = "/readyz"
 	DefaultIntrospectionAddr = ":8089"
 )
 
@@ -122,6 +124,9 @@ func New(ctx context.Context, conf config.Config, health func() bool) (*Server,
 	if err != nil {
 		return nil, fmt.Errorf("error configuring diagnostics: %v", err)
 	}
+	if err := i.withReady(ctx); err != nil {
+		return nil, fmt.Errorf("error configuring ready: %v", err)
+	}
 
 	// attach Introspection to server, this works because we embed http.ServeMux
 	i.Server.Handler = i
@@ -149,6 +154,11 @@ func (i *Server) withDiagnostics(_ context.Context) error {
 	return nil
 }
 
+func (i *Server) withReady(_ context.Context) error {
+	i.ServeMux.Handle(ReadyEndpoint, health.ReadinessHandler())
+	return nil
+}
+
 // withStdOut configures the stdout exporter for distributed tracing
 func (i *Server) withStdOut(_ context.Context, traceOpts []sdktrace.TracerProviderOption) error {
 	exporter, err := stdout.NewExporter()