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When messages are published i.e. fed into a queue, where are these messages stored ? Does it use the physical memory on the disc ? Is there also some memory sharing i.e. is the memory space split between Master, publishers and subscribers ? If yes, then where are the messages stored ? in Master's memory ?
When messages are published i.e. fed into a queue, where are these messages stored ?
For a typical PC: in RAM.
Does it use the physical memory on the disc ?
No (unless you consider a situation where your OS decides to swap out pages of your virtual memory to disk for some reason and those pages happen to be where some messages are stored).
Is there also some memory sharing i.e. is the memory space split between Master, publishers and subscribers ?
No. Not by default.
And definitely not between the master and publishers/subscribers.
Between pub-sub pairs: maybe, depends on the transport you have configured.
If yes, then where are the messages stored ? in Master's memory ?
Never.
The master is never involved in message exchange, it really only functions as a lookup service.
ok...but lets stay i am feeding messages in a buffer while publishing then does it means these messages are stored in the memory of Publisher and once these topics are subscribed, the memory space of the publisher is free and the subscriber memory is occupied ? @gvdhoorn
@☻gvdhoorn As you mentioned : if a subscriber is subscribing to a topic and then intentionally breaks connection, the subscriber is still publishing (e.g. talker-listener example). Where does these messages go ? must be stored in some memory. Should the Master tell the Publisher to stop publishing
Msg exchange (at some level) is just two processes transmitting bytes to each other over a TCP/IP (or UDP) connection. All the same rules apply as with other TCP/IP connections, so: if a subscribers drops the connection, the publisher is (virtually) immediately aware. The code will then ..
Asked: 2018-04-17 02:38:28 -0500
Seen: 871 times
Last updated: Apr 17 '18
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