How do you make sure the concurrent issue?

[dawei101]

golongpoll/longpoll.go

Line 652 in 033d1fa

delete(subCategoryClients, disconnected.ClientUUID)

I see there is no lock when remove and add item from map, this will case crash.

[jcuga]

Hello,

I believe the map usage is always run in the same goroutine, which uses channels to receive actions from the http goroutintes. This is the subscription manager's run() function running in it's own goroutine.

See:

golongpoll/longpoll.go

Line 282 in 72ba13b

go subManager.run()

	go subManager.run()

Where the run function has:

golongpoll/longpoll.go

Line 531 in 72ba13b

func (sm *subscriptionManager) run() error {

		select {
		case newClient := <-sm.clientSubscriptions:
			sm.handleNewClient(newClient)
			sm.seeIfTimeToPurgeStaleCategories()
		case disconnected := <-sm.ClientTimeouts:
			sm.handleClientDisconnect(disconnected)
			sm.seeIfTimeToPurgeStaleCategories()
		case event := <-sm.Events:
			// Optional hook on publish
			if sm.AddOn != nil {
				sm.AddOn.OnPublish(event)
			}
			sm.handleNewEvent(event)
			sm.seeIfTimeToPurgeStaleCategories()

Then, when other goroutines handling HTTP need to tell the subscription manager about a new client, a new event, or a disconnect, they send data to the manager via channels which are concurrent-safe.

for example:
sending new subscription over channel to run():

golongpoll/longpoll.go

Line 444 in 72ba13b

subscriptionRequests <- subscription

client disconnect:

golongpoll/longpoll.go

Line 474 in 72ba13b

clientTimeouts <- &subscription.clientCategoryPair

event publish:

golongpoll/longpoll.go

Line 90 in 72ba13b

m.eventsIn <- &Event{timeToEpochMilliseconds(time.Now()), category, data, u}

Conversely, the manager's goroutine will send data back to clients via channels:

golongpoll/longpoll.go

Line 619 in 72ba13b

newClient.Events <- events

If you see any code that is accessing maps across multiple goroutines, or if you have encountered any errors, please point them out and I will try to fix them. But I think all map access is limited to the manager's run() goroutine and the functions called by run() which are still within the same goroutine. All cross-go-routine sharing of data is done via channels.

[dawei101]

Thanks for so rich reply, get it 💯