Oh, just one more point. Consider this statement in the documentation:
"When a |PUB| socket enters the mute state due to having reached the
high water mark for a subscriber, then any messages that would be sent
to the subscriber in question shall instead be dropped until the mute
state ends."
When the mute state ends, which messages does the subscriber receive?
Those that were in the queue when the mute state began or those that the
publisher sent after the mute state ended? From Bill Torpey's answer, I
got the impression that it's the messages sent after the ending of the
mute state. This would be the preferable behaviour for my particular
application. For my purposes, the latest messages are more valuable than
the old ones. This question affects the way how I need to represent the
connection in PROMELA.
Cheers,
John
On 16.10.2020 14.44, John Lång wrote:
Hi Kevin,
Thanks for the clarification!
Best regards,
John
On 16.10.2020 14.39, Kevin Sapper wrote:
Hi John,
* SHALL create a queue when initiating an outgoing connection
to a subscriber, and SHALL maintain the queue whether or not
the connection is established.
This action is taken when a SUB socket binds to an address and the
PUB socket connects to it.
* SHALL create a queue when a subscriber connects to it. If
this subscriber disconnects, the PUB socket SHALL destroy its
queue and SHALL discard any messages it contains.
This action is taken when a PUB socket binds to an address and the
SUB socket connects to it.
What is the difference between initiating an outgoing connection
to a subscriber and a subscriber connecting to a publisher? In
the C++ source code of my system, a publisher binds to a PUB
socket and a subscriber connects to the address of a publisher. I
guess this sounds more like the second point, but I'm not certain.
Yes, the second point!
Did I understand correctly that this message queue between a
publisher and a subscriber works FIFO? It says that for outgoing
messages, "SHALL silently drop the message if the queue for a
subscriber is full." Does this imply that those messages that fit
in the queue are delivered in the order they were sent in? I take
it that the queue being full means that the high water mark has
been exceeded.
When a PUB socket enters the mute state due to having reached the
high water mark for a subscriber, then any messages that would be
sent to the subscriber in question shall instead be dropped until the
mute state ends. The send function does never block for this socket
type.
What is a binary comparison? Is it the same as bitwise
comparison? To me, "binary comparison" sounds like just comparing
two things with each other.
It means that the byte content of the first frame is compared against
the bytes of a subscription. Hence a subscription can use any binary
prefix not just characters.
//Kevin
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