Non Blocking Lock [Support Thread]

[lhungil]

Non Blocking Lock
Non Blocking Lock (LOCK) provides a non-blocking method for developers to obtain locks on shared resources (across multiple processes / threads).


Features

• Non blocking methods for obtaining and releasing locks
• Timeouts can be configured and renewed for locks
• Automatically releases acquired locks when the PHP process ends

Requirements

• Working installation of Zen Cart 1.5.x
• FTP access to the Zen Cart installation (Secure FTP is recommended)
• A account to access Zen Cart's administrative interface (super user is recommended)

[lat9]

Sound intriguing, lhungil. Would you give an example of a scenario where this would be used?

[lhungil]

Some Exaples: Generating a cache (generated content such as images, category listings, and product listings), theme optimization (LESS pre-processing, minify, compress etc), avoiding race conditions wih longer running blocks of code (such as check, generate, update), only allowing one "click" (or download) at a time, and the list goes on. Basically anytime one wants only a single process performing a task at the same time (or accessing a particular shared resource).


The code uses the database to maintain lock information (works cross platform) and when available uses MEMORY tables for performance reasons). By not blocking, the executing code continues running and can perform other tasks (and optionally attempt to acquire the lock later). One can also code a loop to check and sleep if not available (blocking while waiting for a lock).


I am currently working on a new Zen Cart module and needed the ability to work with Non Blocking Locks. I decided some other modules (old and new) could potentially benefit from the locking code, so added some abstraction and decided to release the locking code as a standalone module.