85 lines
1.9 KiB
Go
85 lines
1.9 KiB
Go
/*
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* MinIO Cloud Storage, (C) 2019 MinIO, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package pubsub
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import (
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"sync"
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)
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// Sub - subscriber entity.
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type Sub struct {
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ch chan interface{}
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filter func(entry interface{}) bool
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}
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// PubSub holds publishers and subscribers
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type PubSub struct {
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subs []*Sub
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sync.RWMutex
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}
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// Publish message to the subscribers.
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// Note that publish is always nob-blocking send so that we don't block on slow receivers.
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// Hence receivers should use buffered channel so as not to miss the published events.
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func (ps *PubSub) Publish(item interface{}) {
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ps.RLock()
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defer ps.RUnlock()
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for _, sub := range ps.subs {
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if sub.filter(item) {
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select {
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case sub.ch <- item:
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default:
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}
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}
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}
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}
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// Subscribe - Adds a subscriber to pubsub system
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func (ps *PubSub) Subscribe(subCh chan interface{}, doneCh chan struct{}, filter func(entry interface{}) bool) {
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ps.Lock()
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defer ps.Unlock()
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sub := &Sub{subCh, filter}
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ps.subs = append(ps.subs, sub)
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go func() {
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<-doneCh
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ps.Lock()
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defer ps.Unlock()
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for i, s := range ps.subs {
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if s == sub {
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ps.subs = append(ps.subs[:i], ps.subs[i+1:]...)
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}
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}
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}()
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}
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// HasSubscribers returns true if pubsub system has subscribers
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func (ps *PubSub) HasSubscribers() bool {
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ps.RLock()
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defer ps.RUnlock()
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return len(ps.subs) > 0
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}
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// New inits a PubSub system
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func New() *PubSub {
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return &PubSub{}
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}
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