May not be an issue...but trying to understand exact dispy mechanism

[Kekushke]

Awesome project! Tried to execute the following on a client along with multiple server nodes. All machines are identical.

import dispy
cluster = dispy.JobCluster('/bin/hostname')
for i in range(50):
    print i
    cluster.submit(i)

The server nodes are running dispynode.py -d and show the following error. Wanting to understand how this works, and why the extra characters are added? Is it that every node gets unique version; and it tries to copy over the destination path?

OSError: [Errno 13] Permission denied: /bin/hostname_RfaY5X

Thank you!

[pgiri]

Is this with latest version (4.8.7)?

Note that dispy sends the program itself to nodes, so in this case '/bin/hostname' program is sent to nodes which save it under dispy execution directory (such as '/tmp/dispy/node/') and execute that program. This may not work if the nodes are different platform as in this case the program is binary executable.

[Kekushke]

This is with the latest version (4.8.7). All machines are identical in all respects including hardware, os, kernel version etc. Just to check permissions, on one of the nodes, I copied /bin/hostname to /tmp with the same local user privileges of dispynode.py. The execution of /tmp/hostname then worked just fine even when owner and group permissions are same as that of how dispynode.py is run. From the fact that it should copy the file, I think the OSError is baffling. Just to confirm identical nature of executable, I did hash check on binaries of /bin/hostname and they turned out to be all identical.

[pgiri]

I tried this with

cluster = dispy.JobCluster('/bin/hostname', nodes=['192.168.0.5'], cleanup=False, dest_path='test')

and checked on the node at `/tmp/dispy/node/192.168.0.5/test' where 'hostname' is saved (in this client and node are same so '192.168.0.5' in path is also node's address). Nothing should be saved directly in '/tmp'. You can run above and check.

[Kekushke]

@pgiri Thanks again! I figured that there is a mistake in the original post. '/bin/hostname' with a parameter is a request for changing the hostname. Which cannot be accomplished without superuser privileges. Value of i was being sent as a parameter; instead of no parameters at all. Your note above definitely works. Plus, here is a completely working script. Sends fifty /bin/hostname requests to all available nodes and prints out the results:

import dispy
cluster = dispy.JobCluster('/bin/hostname', cleanup=False, dest_path='test')
jobs=[]
for i in range(50):
    job=cluster.submit()
    jobs.append(job)
for j in jobs:
    job()
    print j.stdout