I am supposed to write a C application in Unix such that N children processes will be forked from the parent process and I will send messages to these children and children are supposed to send messages each other.
However the problem is, I need to send messages to a specific target child process. i.e. parent will send to child 1, child 1 will send to child 2, ... and child n will send to 1 (circularly).
The problem is, if I create only one message queue, any of n children may dequeue the message (since any of them may run after parent process due to kernel scheduler) therefore the message will be dequeued in wrong process!
In my application, there will be max. 1 message in the queue at a time. The only solution comes to my mind is to create n different message queues and pass messages to appropriate queue so that a specific target process can receive it. But I think there must me a more legitimate solution.
Any ideas?
Contraints: Pipes between processes are not allowed, I know that mq is inefficient here. I'll also implement them, both are required. P.S. This is kinda homework (damn I am the creator of http://canyoudomyhomework.com), however this is not just a homework, a challenging question IMHO.)
Depending on the performance requirements, a brokered (router) solution feels most appropriate.
The parent could act as the router, or could spawn a specific process to do this job.
Define a simple message structure that has its first element as the intended target, we can also designate the parent process as zero.
Each process has only one queue, between itself and the broker. All messages are processed and routed in one place, thereby avoiding the NxN fan-out you mention.
Good Luck