52 lines
1.0 KiB
Go
52 lines
1.0 KiB
Go
package pubsub
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import (
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"context"
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"sync"
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)
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// Subscription handles the details of a particular Topic subscription.
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// There may be many subscriptions for a given Topic.
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type Subscription struct {
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topic string
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ch chan *Message
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cancelCh chan<- *Subscription
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ctx context.Context
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err error
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once sync.Once
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}
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// Topic returns the topic string associated with the Subscription
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func (sub *Subscription) Topic() string {
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return sub.topic
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}
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// Next returns the next message in our subscription
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func (sub *Subscription) Next(ctx context.Context) (*Message, error) {
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select {
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case msg, ok := <-sub.ch:
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if !ok {
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return msg, sub.err
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}
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return msg, nil
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case <-ctx.Done():
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return nil, ctx.Err()
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}
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}
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// Cancel closes the subscription. If this is the last active subscription then pubsub will send an unsubscribe
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// announcement to the network.
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func (sub *Subscription) Cancel() {
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select {
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case sub.cancelCh <- sub:
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case <-sub.ctx.Done():
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}
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}
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func (sub *Subscription) close() {
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sub.once.Do(func() {
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close(sub.ch)
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})
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}
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