From ec6487f3a70a5067f6d8fc601437160bb4fa753f Mon Sep 17 00:00:00 2001 From: Nat Goodspeed Date: Thu, 27 Sep 2018 14:57:03 -0400 Subject: DRTVWR-474: Make LLEventMailDrop pass all saved events to listener. Previously, LLEventMailDrop would send only the first queued event to a newly-connected listener. If you wanted to flush all queued events, you'd have to "pump" the queue by repeatedly disconnecting and reconnecting -- with no good way to know when you'd caught up. The new behavior makes LLEventMailDrop resemble a multi-valued future: a rendezvous between producer and consumer that, once connected, pushes values rather than requiring them to be pulled (as with a simple queue) -- regardless of the relative order in which post() and listen() are called. --- indra/llcommon/llevents.h | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) (limited to 'indra/llcommon/llevents.h') diff --git a/indra/llcommon/llevents.h b/indra/llcommon/llevents.h index 1d51c660ed..5d60c63810 100644 --- a/indra/llcommon/llevents.h +++ b/indra/llcommon/llevents.h @@ -650,15 +650,21 @@ public: * LLEventMailDrop *****************************************************************************/ /** - * LLEventMailDrop is a specialization of LLEventStream. Events are posted normally, - * however if no listeners return that they have handled the event it is placed in - * a queue. Subsequent attaching listeners will receive stored events from the queue - * until a listener indicates that the event has been handled. In order to receive - * multiple events from a mail drop the listener must disconnect and reconnect. + * LLEventMailDrop is a specialization of LLEventStream. Events are posted + * normally, however if no listener returns that it has handled the event + * (returns true), it is placed in a queue. Subsequent attaching listeners + * will receive stored events from the queue until some listener indicates + * that the event has been handled. + * + * LLEventMailDrop completely decouples the timing of post() calls from + * listen() calls: every event posted to an LLEventMailDrop is eventually seen + * by all listeners, until some listener consumes it. The caveat is that each + * event *must* eventually reach a listener that will consume it, else the + * queue will grow to arbitrary length. * * @NOTE: When using an LLEventMailDrop (or LLEventQueue) with a LLEventTimeout or - * LLEventFilter attaching the filter downstream using Timeout's constructor will - * cause the MailDrop to discharge any of it's stored events. The timeout should + * LLEventFilter attaching the filter downstream, using Timeout's constructor will + * cause the MailDrop to discharge any of its stored events. The timeout should * instead be connected upstream using its listen() method. * See llcoro::suspendUntilEventOnWithTimeout() for an example. */ -- cgit v1.2.3