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/*
*
* 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, edsServcieName 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,
edsServcieName: 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))
}
// ClearCounterForTesting clears the counter for the service. Should be only
// used in tests.
func ClearCounterForTesting(clusterName, edsServiceName string) {
src.mu.Lock()
defer src.mu.Unlock()
k := clusterNameAndServiceName{
clusterName: clusterName,
edsServcieName: edsServiceName,
}
c, ok := src.clusters[k]
if !ok {
return
}
c.numRequests = 0
}
// ClearAllCountersForTesting clears all the counters. Should be only used in
// tests.
func ClearAllCountersForTesting() {
src.mu.Lock()
defer src.mu.Unlock()
src.clusters = make(map[clusterNameAndServiceName]*ClusterRequestsCounter)
}
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