inter process communication

aral · 08-03-2006, 11:27 AM

What kind of inter process communication is best suited for several processes sending keep alive timeouts to a wathdog process ? Each keep alive timeout is composed of three fields: PID, Date&time, Sate of process. Are message queues suitable for something like that ?If not , what is best suited for something like that ? What should I use to send the keep alive messages ?

macemoneta · 08-03-2006, 12:08 PM

You could use a sockets-based communication method. The advantage is that the processes can scale to multiple machines without having to change the code.

Alternatively, if the transaction rate is high (the timeout is in milliseconds), you may want to look at using a shared memory implementation instead.

aral · 08-03-2006, 12:22 PM

What do you mean "scale to multiple machines" ? You mean .. if the watchdog process and also the processes which have to send keep alive timeouts are on diferent machines ? it's all on the same machine .. if that's what you meant ..
I don't need the transactions to be at miliseconds intervals .. , so what should I use ?

macemoneta · 08-03-2006, 12:36 PM

Yes, if the watchdog process and the processes which have to send keep alive timeouts are on diferent machines. Sometimes when creating the software you know that the application will grow, and that will change the design choices.

If it's all on the same machine, you want a simple communication path, you can just use file I/O with /dev/shm. Alternatively, you can use SysV IPC. As mentioned earlier, sockets are very popular. The choice is up to you, and to the requirements of your application.

aral · 08-03-2006, 01:25 PM

I thought we weren't suppose to use /dev/shm cause it's used for virtual memory .. . nop ?

macemoneta · 08-03-2006, 01:37 PM

/dev/shm uses virtual memory, it's not used for virtual memory (that's the function of page frames and swap). /dev/shm will go to swap if it is permitted to grow sufficiently large; it's just an in-memory filesystem - I/Os are converted to memory read/write. It is a shared memory communication area, convenient for IPC. I frequently use it even for scripts on laptops, to prevent spinning up the hard drive on I/O.