Hello everyone,
I have run into a design problem when making a subscriber class with a
ring buffer using CZMQ.
CONTEXT:
The class contains a zactor, which then contains a zloop. The zloop has
a reader for the sub socket, and on receiving a message, adds the
message to a ring buffer, using a lock-free mechanism. This moves the
"head" atomic int.
(The built in queue for zmq does not work for me. I need the oldest
messages to be tossed when the queue is full but ZMQ tosses all newest
messages)
The user has the ability to consume data from the buffer, which moves
the "tail" atomic int.
PROBLEM:
I need a function that returns the number of available messages in the
ring buffer, but with a timeout. Ideally, the user has a while loop that
keeps checking the number of available messages, but with a timeout so
it does not burn CPU usage.
I have tried 2 things:
1. zmq_poll and its timeout functionality: it seems that when I call
zmq_poll, it interferes with the zloop's polling and doesn't allow it to
process the messages properly, so i can't poll on the sub socket on the
user's thread.
2. timers in zloop: I have tried to create a zloop timer when the user
asks for available_messages(), which will either timeout and return 0 or
cancel when a message comes in first and return # of messages. The
problem is that at 2048byte message at 30,000/sec, adding a timer slows
down things considerably.
I am considering using some kind of proxy, and the capture socket, but
other than that, am out of ideas.
Any thoughts? Having a completely blocking function is not possible, and
having it return immediately is not either.
Thanks to anyone that can help,
Kevin
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