What instance of maya is running?

[samgtn]

For times when there is more than one occurrence of maya running on a machine, is there a method of determining an enumeration for each? For example, if two maya's are running on a single machine, the MEL script would be able to return Maya.1 when run on the first instance, and Maya.2 when run from the second instance?

The reason for this is that I have startup scripts on machines that establish commandport numbers. When the second maya runs, it fails to execute anything in it's start script after the commandport() because that port number is already taken (by the first maya instance). I'd like the command port to increment by one for each instance of maya that is running.

Any help, greatly appreciated!

[keilun]

I'm not aware of any mechanism in Maya that might do this, however you could implement something on your own. Perhaps use a shared maya file between the instances. eg. On startup install a file and write out an instance number on one line, while storing that in a global MEL variable. On second startup, write out next instance number on next line and save in global var. On shutdown remove line with given instance number. etc. That should allow you to keep track of instances no? You'll need to be careful that two processes aren't accessing it at the same time. You could implement a locking mechanism via the read-only attribute (if it is read-only no one is accessing it, otherwise someone is).

It's a bit of work, but I think it'd work. I'm just improvising here though.

[macaronikazoo]

you can ask maya for a pid (process id). each process is given a unique pid by windows when it is started. so you could figure out which version of maya is which with that. I'm not sure what the command is tho.

oh, just had a look in the docs, the command is called simply: getpid

[keilun]

Totally forgot about that method. 'Course you'll still need to have some way of determining what other Maya processes are running concurrently. So you'll still need to generate some form of sharing mechanism. In addition, you'll need a way to determine what "instance number" each pid is, if you go that route. It should work too.

[joojaa]

wouldnt it suffice if each maya would write a file with a numbered name in one folder and on exit delete the file then other mayas would know.

offcourse this wouldnt work shuld maya decide to crash! but thenagain it would be hard to take tis into account.

[keilun]

Yeah, that'd work too. All of these suggestions would have the problem of dealing with crashes. I can't think of an easy way of covering that angle apart from writing your own custom program to clean out the directory. But if you're going that far, you might as well write a small server style program to manage Maya instances.

[macaronikazoo]

nah dealing with crashes wouldn't be too hard. basically just have the filename the same as the pid, and the file contents the port which the commandPort is open on. then when maya starts up, it checks to see if the pid exists, then check to see if the commandPort is available. If both these things are correct, that means that iteration of maya is still running. If not, a crash has occurred, and the file should be deleted. easy.

[keilun]

Depending on the OS you're running, you may still need something external to Maya to verify the existence of a PID - specifically Windows. Unless I'm missing something. I'm not familiar with any easy way of checking PIDs on Windows without access to the Win32 API.

Edit: Maybe Cygwin has a Windows based solution for pid checking? Though the 'ps' type calls only retrieve Cygwin processes.

[macaronikazoo]

thats the beauty of it though. You don't need to check pid's... the pid file, contains the port number that commandPort is open on, for the iteration of maya with that pid. so then all you have to do is check the port to see if maya is alive

[keilun]

Sweet. To be honest I didn't know too much about the commandPort command til now. But after reading up more on it, yea that'd work. Nice call.

There's so many parts of MEL that I'm still totally oblivious to, even after 2 years.