read-health check endpoint returns success if cluster can serve read requests (#11310)

cmd/erasure-server-pool.go

@@ -1461,6 +1461,40 @@ type HealthResult struct {
 	WriteQuorum   int
 }
 
+// ReadHealth returns if the cluster can serve read requests
+func (z *erasureServerPools) ReadHealth(ctx context.Context) bool {
+	erasureSetUpCount := make([][]int, len(z.serverPools))
+	for i := range z.serverPools {
+		erasureSetUpCount[i] = make([]int, len(z.serverPools[i].sets))
+	}
+
+	diskIDs := globalNotificationSys.GetLocalDiskIDs(ctx)
+	diskIDs = append(diskIDs, getLocalDiskIDs(z))
+
+	for _, localDiskIDs := range diskIDs {
+		for _, id := range localDiskIDs {
+			poolIdx, setIdx, err := z.getPoolAndSet(id)
+			if err != nil {
+				logger.LogIf(ctx, err)
+				continue
+			}
+			erasureSetUpCount[poolIdx][setIdx]++
+		}
+	}
+
+	b := z.BackendInfo()
+	readQuorum := b.StandardSCData[0]
+
+	for poolIdx := range erasureSetUpCount {
+		for setIdx := range erasureSetUpCount[poolIdx] {
+			if erasureSetUpCount[poolIdx][setIdx] < readQuorum {
+				return false
+			}
+		}
+	}
+	return true
+}
+
 // Health - returns current status of the object layer health,
 // provides if write access exists across sets, additionally
 // can be used to query scenarios if health may be lost

cmd/fs-v1.go

@@ -1623,3 +1623,9 @@ func (fs *FSObjects) Health(ctx context.Context, opts HealthOptions) HealthResul
 		Healthy: newObjectLayerFn() != nil,
 	}
 }
+
+// ReadHealth returns "read" health of the object layer
+func (fs *FSObjects) ReadHealth(ctx context.Context) bool {
+	_, err := os.Stat(fs.fsPath)
+	return err == nil
+}

cmd/gateway-unsupported.go

@@ -254,3 +254,8 @@ func (a GatewayUnsupported) IsCompressionSupported() bool {
 func (a GatewayUnsupported) Health(_ context.Context, _ HealthOptions) HealthResult {
 	return HealthResult{}
 }
+
+// ReadHealth - No Op.
+func (a GatewayUnsupported) ReadHealth(_ context.Context) bool {
+	return true
+}

cmd/generic-handlers.go

@@ -216,7 +216,8 @@ func guessIsHealthCheckReq(req *http.Request) bool {
 	return aType == authTypeAnonymous && (req.Method == http.MethodGet || req.Method == http.MethodHead) &&
 		(req.URL.Path == healthCheckPathPrefix+healthCheckLivenessPath ||
 			req.URL.Path == healthCheckPathPrefix+healthCheckReadinessPath ||
-			req.URL.Path == healthCheckPathPrefix+healthCheckClusterPath)
+			req.URL.Path == healthCheckPathPrefix+healthCheckClusterPath ||
+			req.URL.Path == healthCheckPathPrefix+healthCheckClusterReadPath)
 }
 
 // guessIsMetricsReq - returns true if incoming request looks

cmd/healthcheck-handler.go

@@ -64,6 +64,29 @@ func ClusterCheckHandler(w http.ResponseWriter, r *http.Request) {
 	writeResponse(w, http.StatusOK, nil, mimeNone)
 }
 
+// ClusterReadCheckHandler returns if the server is ready for requests.
+func ClusterReadCheckHandler(w http.ResponseWriter, r *http.Request) {
+	ctx := newContext(r, w, "ClusterReadCheckHandler")
+
+	if shouldProxy() {
+		w.Header().Set(xhttp.MinIOServerStatus, unavailable)
+		writeResponse(w, http.StatusServiceUnavailable, nil, mimeNone)
+		return
+	}
+
+	objLayer := newObjectLayerFn()
+
+	ctx, cancel := context.WithTimeout(ctx, globalAPIConfig.getClusterDeadline())
+	defer cancel()
+
+	result := objLayer.ReadHealth(ctx)
+	if !result {
+		writeResponse(w, http.StatusServiceUnavailable, nil, mimeNone)
+		return
+	}
+	writeResponse(w, http.StatusOK, nil, mimeNone)
+}
+
 // ReadinessCheckHandler Checks if the process is up. Always returns success.
 func ReadinessCheckHandler(w http.ResponseWriter, r *http.Request) {
 	if shouldProxy() {

cmd/healthcheck-router.go

@@ -23,11 +23,12 @@ import (
 )
 
 const (
-	healthCheckPath          = "/health"
-	healthCheckLivenessPath  = "/live"
-	healthCheckReadinessPath = "/ready"
-	healthCheckClusterPath   = "/cluster"
-	healthCheckPathPrefix    = minioReservedBucketPath + healthCheckPath
+	healthCheckPath            = "/health"
+	healthCheckLivenessPath    = "/live"
+	healthCheckReadinessPath   = "/ready"
+	healthCheckClusterPath     = "/cluster"
+	healthCheckClusterReadPath = "/cluster/read"
+	healthCheckPathPrefix      = minioReservedBucketPath + healthCheckPath
 )
 
 // registerHealthCheckRouter - add handler functions for liveness and readiness routes.
@@ -38,6 +39,7 @@ func registerHealthCheckRouter(router *mux.Router) {
 
 	// Cluster check handler to verify cluster is active
 	healthRouter.Methods(http.MethodGet).Path(healthCheckClusterPath).HandlerFunc(httpTraceAll(ClusterCheckHandler))
+	healthRouter.Methods(http.MethodGet).Path(healthCheckClusterReadPath).HandlerFunc(httpTraceAll(ClusterReadCheckHandler))
 
 	// Liveness handler
 	healthRouter.Methods(http.MethodGet).Path(healthCheckLivenessPath).HandlerFunc(httpTraceAll(LivenessCheckHandler))

cmd/object-api-interface.go

@@ -155,6 +155,7 @@ type ObjectLayer interface {
 
 	// Returns health of the backend
 	Health(ctx context.Context, opts HealthOptions) HealthResult
+	ReadHealth(ctx context.Context) bool
 
 	// ObjectTagging operations
 	PutObjectTags(context.Context, string, string, string, ObjectOptions) (ObjectInfo, error)