snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

internal/xds/xdsclient/requests_counter.go

@@ -0,0 +1,83 @@
+/*
+ *
+ * Copyright 2020 gRPC 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 xdsclient
+
+import (
+	"fmt"
+	"sync"
+	"sync/atomic"
+)
+
+type clusterNameAndServiceName struct {
+	clusterName, edsServiceName string
+}
+
+type clusterRequestsCounter struct {
+	mu       sync.Mutex
+	clusters map[clusterNameAndServiceName]*ClusterRequestsCounter
+}
+
+var src = &clusterRequestsCounter{
+	clusters: make(map[clusterNameAndServiceName]*ClusterRequestsCounter),
+}
+
+// ClusterRequestsCounter is used to track the total inflight requests for a
+// service with the provided name.
+type ClusterRequestsCounter struct {
+	ClusterName    string
+	EDSServiceName string
+	numRequests    uint32
+}
+
+// GetClusterRequestsCounter returns the ClusterRequestsCounter with the
+// provided serviceName. If one does not exist, it creates it.
+func GetClusterRequestsCounter(clusterName, edsServiceName string) *ClusterRequestsCounter {
+	src.mu.Lock()
+	defer src.mu.Unlock()
+	k := clusterNameAndServiceName{
+		clusterName:    clusterName,
+		edsServiceName: edsServiceName,
+	}
+	c, ok := src.clusters[k]
+	if !ok {
+		c = &ClusterRequestsCounter{ClusterName: clusterName}
+		src.clusters[k] = c
+	}
+	return c
+}
+
+// StartRequest starts a request for a cluster, incrementing its number of
+// requests by 1. Returns an error if the max number of requests is exceeded.
+func (c *ClusterRequestsCounter) StartRequest(max uint32) error {
+	// Note that during race, the limits could be exceeded. This is allowed:
+	// "Since the implementation is eventually consistent, races between threads
+	// may allow limits to be potentially exceeded."
+	// https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/upstream/circuit_breaking#arch-overview-circuit-break.
+	if atomic.LoadUint32(&c.numRequests) >= max {
+		return fmt.Errorf("max requests %v exceeded on service %v", max, c.ClusterName)
+	}
+	atomic.AddUint32(&c.numRequests, 1)
+	return nil
+}
+
+// EndRequest ends a request for a service, decrementing its number of requests
+// by 1.
+func (c *ClusterRequestsCounter) EndRequest() {
+	atomic.AddUint32(&c.numRequests, ^uint32(0))
+}