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

internal/xds/balancer/outlierdetection/callcounter.go

@@ -0,0 +1,66 @@
+/*
+ *
+ * Copyright 2022 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 outlierdetection
+
+import (
+	"sync/atomic"
+)
+
+type bucket struct {
+	numSuccesses uint32
+	numFailures  uint32
+}
+
+func newCallCounter() *callCounter {
+	cc := &callCounter{
+		inactiveBucket: &bucket{},
+	}
+	cc.activeBucket.Store(&bucket{})
+	return cc
+}
+
+// callCounter has two buckets, which each count successful and failing RPC's.
+// The activeBucket is used to actively count any finished RPC's, and the
+// inactiveBucket is populated with this activeBucket's data every interval for
+// use by the Outlier Detection algorithm.
+type callCounter struct {
+	// activeBucket updates every time a call finishes (from picker passed to
+	// Client Conn), so protect pointer read with atomic load of the pointer
+	// so picker does not have to grab a mutex per RPC, the critical path.
+	activeBucket   atomic.Pointer[bucket]
+	inactiveBucket *bucket
+}
+
+func (cc *callCounter) clear() {
+	cc.activeBucket.Store(&bucket{})
+	cc.inactiveBucket = &bucket{}
+}
+
+// "When the timer triggers, the inactive bucket is zeroed and swapped with the
+// active bucket. Then the inactive bucket contains the number of successes and
+// failures since the last time the timer triggered. Those numbers are used to
+// evaluate the ejection criteria." - A50.
+func (cc *callCounter) swap() {
+	ib := cc.inactiveBucket
+	*ib = bucket{}
+	ab := cc.activeBucket.Swap(ib)
+	cc.inactiveBucket = &bucket{
+		numSuccesses: atomic.LoadUint32(&ab.numSuccesses),
+		numFailures:  atomic.LoadUint32(&ab.numFailures),
+	}
+}