lockserver

A simple python lockserver with no extra dependencies.

basic usage:

To start the server on the default port simply run lockserver.py

$ python lockserver.py

To use locks in your code

import lockserver

with lockserver.Lock("lock_name"):
    print "doing stuff under lock <lock_name>"

with lockserver.SharedLock("lock_name"):
    print "doing stuff under shared lock <lock_name>"
    
count = lockserver.lockAccessCount("lock_name")
print "there are %d locks currently held for <lock_name>"

You can also use the Lock() class outside of a context manager (and this is required if you wish to test the locks and not wait for them).

When started the server drops the file lockserver.info that the client can use to find the ip address and port of the server. The client looks for this file in the current working directory as it's default manner of finding the server. You can also specify the filename/path of the info file or just specify the host and port when instantiating the Lock() class.

The server is a single threaded select/poll socket server written only with core python libraries. I specifically like writing servers this way because it makes it very difficult to create race conditions and other resource contention problems you get with multithreaded code even if it is often easier to write servers in general in a multithreaded or multiprocess fashion.

I wrote this a while ago when I wanted a basic lockserver that would work across multiple systems without requiring a shared filesystem and without running a database or similar. I did manage to find a few other attempts at python lockservers before writing my own but all of the ones I found had very obvious race conditions that weren't easy to fix. I then built it up for my specific environment but here it is after I've stripped most of that back out to be more general purpose.

Things that it currently doesn't have but would be useful on the server side

ability to set the port and bind address on the command line
ability to try multiple ports
deleting the lockserver.info file on quit.

And on the client

timeouts on locks

Xuth/lockserver

lockserver