Pubsub - A fast concurrent in memory publish subscribe event bus for golang

Pubsub is an in memory event bus, its goals are to be simple yet powerful intended to be used in highly concurrent environments. While there are already quite a few different implementations in go (see below), all proved to be not a good fit in one way or another.

The implementations tries to be scalable by building on a lock free hashtable and a custom scalable list of subscriptions. Currently golang's sync.Map is used, since there is a bug in the lockfree hashtable.

To avoid dead looks and interference across unrelated topics no locks will be held while calling client code, this also allows callbacks to unsubscribe them selves.~~

Examples

bus := pubsub.NewBus()

// subscribe with callback
sub := bus.Subscribe("topic", func(ev MyEvent) {
   ...
})

// publish
bus.Publish("topic", MyEvent{})

// unsubscribe
bus.Unsubscribe(sub)

// subscribe for at most one callback
sub := bus.SubscribeOnce("topic", func(ev MyEvent) {
   ...
})

// unsubscribe from handler if condition is met
sub := bus.SubscribeOnce("topic", func(ev MyEvent, sub *pubsub.Subscription) {
   if (dontcareanymore) {
      bus.Unsubscribe(sub)
   }
   ...
})

// subscribe by sending events to a channel
ch := make(chan MyEvent, 10)
sub := bus.SubscribeChan("topic", ch, pubsub.CloseOnUnsubscribe)
...
// Unsubscribe will also close the channel in a concurrency safe manner
bus.Unsubscribe(sub)


// Block until an event is received or context is cancelled
ctx context.Context = ...
ev, ok := bus.SubscribeOnceWait("topic", ctx.Done())
if ok { // event was received

}

Similar projects

Here is a selection of some existing similar projects

• EventBus
• Bus