Locks are used for mutual exclusion. When you want to ensure that a piece of code is atomic, put a lock around it. You could theoretically use a binary semaphore to do this, but that’s a special case. Semaphores and condition variables build on top of the mutual exclusion provide by locks and are used … Read more
You can keep your separate timestamp columns and still use an exclusion constraint on an expression: CREATE TABLE tbl ( tbl_id serial PRIMARY KEY , starts_at timestamp , ends_at timestamp , EXCLUDE USING gist (tsrange(starts_at, ends_at) WITH &&) — no overlap ); Constructing a tsrange value without explicit bounds as tsrange(starts_at, ends_at) assumes default bounds: … Read more
Well, most of PHP runs in a different process space (there are few threading implementations). The easy one is flock. It’s guaranteed to work on all platforms. However, if you compile in support, you can use a few other things such as the Semaphore extension. (Compile PHP with –enable-sysvsem). Then, you can do something like … Read more
The difference is that you can lock and unlock a std::unique_lock. std::lock_guard will be locked only once on construction and unlocked on destruction. So for use case B you definitely need a std::unique_lock for the condition variable. In case A it depends whether you need to relock the guard. std::unique_lock has other features that allow … Read more
The following code should do the job, it is cross-platform and runs on Python 2.4-3.2. I tested it on Windows, OS X and Linux. from tendo import singleton me = singleton.SingleInstance() # will sys.exit(-1) if other instance is running The latest code version is available singleton.py. Please file bugs here. You can install tend using … Read more