slocket
A locking socket alternative to file-system mutex locks
Algorithm
to ACQUIRE(lockname)
- create server, listen on lockname
- if enotsock, WATCH(lockname)
- if eaddrinuse,
- CONNECT(lockname)
- unref server
- lock has been acquired via server
! on connection, place sockets in queue
to RELEASE(lockname)
- if acquired via connection
- if connected, disconnect
- else, unlink lockname
- if acquired via server
- send "OK" to front-most connection
- when connection disconnects, RELEASE(lockname)
- if acquired via filename
- unlink file
to CONNECT(lockname)
- net.connect(lockname)
- if econnrefused (socket, but not listening!)
could be that a server process crashed, leaving a dangling
connection that thinks it has the lock.
- WATCH(lockname)
- if enoent or on socket termination, ACQUIRE(lockname)
- when server says "OK",
- lock has been acquired via connection
- on connection disconnect, on release, unlink socket
to WATCH(lockname)
- fs.watch(lockname)
- on change, ACQUIRE(lockname)
USAGE
var slocket = // Only one of these can run in this filesystem space,// even if there are many processes running at once { }
A slocket is like a Promise, so this works:
If you want to use async/await, you can do this, which is nice:
{ var lock = await // now I have an exclusive lock on the fooness! await // all done, release the mutex lock}