[Trilug-ontopic] perl and threads

[Brian Weaver]

Greg,

I don't know about using threads, but if you want multiple instances with each working on a single device then why not use a master-child process model? Have the master fork off N children and maintain a link using anonymous pipes, unix sockets, or some other IPC mechanism. The master can inform each child on what system to query and then receive a status back from the child when it's done.

Instead of writing the status to a log file the child process could simply write the status back to the parent's communication channel. The master process can then write to the log file without any fear of multiple writers.

-- Brian


On Mar 10, 2011, at 5:07 PM, Greg Brown wrote:

> Ok, I've GOT to get my scripts using threads.  Here's what I've got and what I'd like to do:
> 
> source: a 3000 line file with hostnames, IP addrs, etc.
> 
> what script does: logs into each device using Net::SSH::Expect that makes configuration changes to IOS devices (uses Net::SSH::Expect rather than expect.pm because one of our NMS servers is a windows box and the scripts have to run across all NMS servers.. sigh)
> 
> how script does it: the guts of the script, the real work, is all done in a subscript.  The main portion of the script opens the file and creates a foreach loop to process each line (and device) one at at time.  As you might imagine this script takes a long time to complete.  The subscript returns a message to the main script that is written to a log file ("login failed", "change implemented", etc).
> 
> what I'd like to do: take a group of devices, say five at at time, and launch the subscript as a thread so I can process more than one device at a time.  I would imagine this would involve some kind of flock on the log file so two threads couldn't return at the same time.  John B. sent me some instructions how to thread a perl script a while back but now I can't find it.  
> 
> Does anyone know of a perl book with good and clear examples that use threads?
> 
> Greg
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