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dedupe.go
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dedupe.go
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/*
Copyright 2018 The Knative 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 activator
import (
"errors"
"net/http"
"sync"
)
var shuttingDownError = ActivationResult{
Endpoint: Endpoint{},
Status: http.StatusInternalServerError,
Error: errors.New("activator shutting down"),
}
var _ Activator = (*dedupingActivator)(nil)
type dedupingActivator struct {
mux sync.Mutex
pendingRequests map[RevisionID][]chan ActivationResult
activator Activator
shutdown bool
}
// NewDedupingActivator creates an Activator that deduplicates
// activations requests for the same revision id and namespace.
func NewDedupingActivator(a Activator) Activator {
return &dedupingActivator{
pendingRequests: make(map[RevisionID][]chan ActivationResult),
activator: a,
}
}
func (a *dedupingActivator) ActiveEndpoint(namespace, name string) ActivationResult {
id := RevisionID{Namespace: namespace, Name: name}
ch := make(chan ActivationResult, 1)
a.dedupe(id, ch)
result := <-ch
return result
}
func (a *dedupingActivator) Shutdown() {
a.activator.Shutdown()
a.mux.Lock()
defer a.mux.Unlock()
a.shutdown = true
for _, reqs := range a.pendingRequests {
for _, ch := range reqs {
ch <- shuttingDownError
}
}
}
func (a *dedupingActivator) dedupe(id RevisionID, ch chan ActivationResult) {
a.mux.Lock()
defer a.mux.Unlock()
if a.shutdown {
ch <- shuttingDownError
return
}
if reqs, ok := a.pendingRequests[id]; ok {
a.pendingRequests[id] = append(reqs, ch)
} else {
a.pendingRequests[id] = []chan ActivationResult{ch}
go a.activate(id)
}
}
func (a *dedupingActivator) activate(id RevisionID) {
result := a.activator.ActiveEndpoint(id.Namespace, id.Name)
a.mux.Lock()
defer a.mux.Unlock()
if reqs, ok := a.pendingRequests[id]; ok {
delete(a.pendingRequests, id)
for _, ch := range reqs {
ch <- result
}
}
}