fspubsub is a very simple streaming event store, good to demonstrate the
basics of event publishing and subscription. It publishes events directly to the
filesystem, with the subscriber listening to the publishing location with
inotify. It also has facilities to pull the entire current store, and a single
event.
Note that the hook on inotify events currently means that this package is supported on Linux only.
Streams are named for the type of event they support. An event is a type, although realistically, it is probably a struct:
type TestEvent struct {
Text string
}
Using the above type, you can start a stream by creating a publisher for the event you will be publishing to:
p, err := pub.NewPublisher("./", TestEvent{})
if err != nil {
return log.Fatalf("[FATAL] Could not create stream: %s", err)
}
Note that the struct that you pass to the event in NewPublisher does not need
to have data in it, and in fact is ignored if there is any.
After the publisher is created, sending the event is as easy as sending the struct along:
e := &TestEvent{Text: "Foo"}
id, err := p.Publish(e)
if err != nil {
return log.Fatalf("[FATAL] Could not publish event: %s", err)
}
To listen for events on the stream, create a new subscriber via NewSubscriber.
You can then use Queue to get a channel where you can watch for events, and
Done to get a channel that will close when the stream is done or fails for
some other reason. The error will be in Error when done, if any.
s, err := sub.NewSubscriber(wd, TestEvent{})
if err != nil {
log.Fatalf("[FATAL] Cannot create subscriber: %s", err)
}
go func() {
for {
select {
case event := <-s.Queue():
// Do something with event here
case <-s.Done():
return
}
}
}()
<-s.Done()
if s.Error() != nil {
log.Fatalf("[FATAL] Error while listening to events: %s", s.Error())
}
For full details, see the GoDoc.
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