I needed to prevent two copies of a node program from running concurrently
on a host. There appears to be no support for
fcntl(2) F_SETLK file
locking in node at the moment, so I fell back on this module.
Please note that there are obvious denial-of-service issues with this module: if you pick a non-privileged port for locking then any process can open that port (even one that isn't yours) and prevent your process from starting up. With that said, it's a simple solution that should work on systems with only trusted users.
var LOCKING_PORT = 43002;var PortMutex = PortMutex;var mtx = LOCKING_PORT 1000;mtx;mtx;