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pubsub.go
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pubsub.go
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// Copyright © 2021 The Things Network Foundation, The Things Industries B.V.
//
// 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 basic
import (
"context"
"runtime/trace"
"sync"
"go.thethings.network/lorawan-stack/v3/pkg/events"
"go.thethings.network/lorawan-stack/v3/pkg/ttnpb"
)
// PubSub is a basic event PubSub implementation.
type PubSub struct {
mu sync.RWMutex
subscriptions []events.Subscription
}
// NewPubSub returns a new basic event PubSub.
func NewPubSub() *PubSub {
return &PubSub{}
}
// Subscribe starts a subscription for events that match name and identifiers.
// The subscription lasts until the context is canceled.
// The handler will be notified of matching events and must not block.
func (e *PubSub) Subscribe(ctx context.Context, names []string, identifiers []*ttnpb.EntityIdentifiers, hdl events.Handler) error {
s, err := NewSubscription(ctx, names, identifiers, hdl)
if err != nil {
return err
}
e.AddSubscription(s)
go func() {
<-ctx.Done()
e.RemoveSubscription(s)
}()
return nil
}
// AddSubscription adds an event subscription to the PubSub. The exact same
// subscription must be used in RemoveSubscription.
func (e *PubSub) AddSubscription(s events.Subscription) {
e.mu.Lock()
defer e.mu.Unlock()
subscriptions := make([]events.Subscription, 0, len(e.subscriptions)+1)
for _, sub := range e.subscriptions {
subscriptions = append(subscriptions, sub)
}
e.subscriptions = append(subscriptions, s)
}
// RemoveSubscription removes an event subscription to the PubSub. This method
// expects the exact same subscription that was previously used in AddSubscription.
func (e *PubSub) RemoveSubscription(s events.Subscription) {
e.mu.Lock()
defer e.mu.Unlock()
subscriptions := make([]events.Subscription, 0, len(e.subscriptions))
for _, sub := range e.subscriptions {
if sub != s {
subscriptions = append(subscriptions, sub)
}
}
e.subscriptions = subscriptions
}
// Publish publishes an event, which will notify all matching subscriptions.
func (e *PubSub) Publish(evt events.Event) {
defer trace.StartRegion(evt.Context(), "publish event").End()
e.mu.RLock()
subscriptions := e.subscriptions
e.mu.RUnlock()
for _, sub := range subscriptions {
if sub.Match(evt) {
sub.Notify(evt)
}
}
}