named checks if verbose is used

Signed-off-by: Imran Pochi <imranpochi@microsoft.com>

cmd/agent/app/server.go

@@ -17,6 +17,7 @@ limitations under the License.
 package app
 
 import (
+	"bytes"
 	"context"
 	"crypto/tls"
 	"fmt"
@@ -26,6 +27,7 @@ import (
 	"runtime"
 	runpprof "runtime/pprof"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus/promhttp"
@@ -107,14 +109,38 @@ func (a *Agent) runHealthServer(o *options.GrpcProxyAgentOptions, cs agent.Readi
 	livenessHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		fmt.Fprintf(w, "ok")
 	})
+
+	checks := []agent.HealthChecker{agent.PingHealthz, agent.NewServerConnectedHealthz(cs)}
 	readinessHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if cs.Ready() {
-			w.WriteHeader(http.StatusOK)
-			fmt.Fprintf(w, "ok")
-		} else {
+		var failedChecks []string
+		var individualCheckOutput bytes.Buffer
+		for _, check := range checks {
+			if err := check.Check(r); err != nil {
+				fmt.Fprintf(&individualCheckOutput, "[-]%s failed: %v\n", check.Name(), err)
+				failedChecks = append(failedChecks, check.Name())
+			} else {
+				fmt.Fprintf(&individualCheckOutput, "[+]%s ok\n", check.Name())
+			}
+		}
+
+		// Always be verbose if the check has failed
+		if len(failedChecks) > 0 {
+			klog.V(0).Infoln("%s check failed: \n%v", strings.Join(failedChecks, ","), individualCheckOutput.String())
 			w.WriteHeader(http.StatusServiceUnavailable)
-			fmt.Fprintf(w, "not ready")
+			fmt.Fprintf(w, individualCheckOutput.String())
+			return
 		}
+
+		if _, found := r.URL.Query()["verbose"]; !found {
+			w.WriteHeader(http.StatusOK)
+			fmt.Fprint(w, "ok")
+			return
+		}
+
+		fmt.Fprintf(&individualCheckOutput, "check passed\n")
+
+		w.WriteHeader(http.StatusOK)
+		fmt.Fprint(w, individualCheckOutput.String())
 	})
 
 	muxHandler := http.NewServeMux()

pkg/agent/healthz.go

@@ -0,0 +1,65 @@
+/*
+copyright 2023 the kubernetes authors.
+
+licensed under the apache license, version 2.0 (the "license");
+you may not use this file except in compliance with the license.
+you may obtain a copy of the license at
+
+    http://www.apache.org/licenses/license-2.0
+
+unless required by applicable law or agreed to in writing, software
+distributed under the license is distributed on an "as is" basis,
+without warranties or conditions of any kind, either express or implied.
+see the license for the specific language governing permissions and
+limitations under the license.
+*/
+
+package agent
+
+import (
+	"fmt"
+	"net/http"
+)
+
+type HealthChecker interface {
+	Name() string
+	Check(req *http.Request) error
+}
+
+// ping implements the simplest possible healthz checker.
+type ping struct{}
+
+var PingHealthz HealthChecker = &ping{}
+
+func (p *ping) Name() string {
+	return "ping"
+}
+
+// PingHealthz is a health check that returns true.
+func (p *ping) Check(_ *http.Request) error {
+	return nil
+}
+
+type serverConnected struct {
+	rm ReadinessManager
+}
+
+var ServerConnectedHealthz HealthChecker = &serverConnected{}
+
+func NewServerConnectedHealthz(cs ReadinessManager) HealthChecker {
+	return &serverConnected{
+		rm: cs,
+	}
+}
+
+func (s *serverConnected) Name() string {
+	return "server-connected"
+}
+
+func (s *serverConnected) Check(_ *http.Request) error {
+	if s.rm.Ready() {
+		return nil
+	}
+
+	return fmt.Errorf("no servers connected")
+}