source: trunk/packages/invirt-remote/python/remote/monocast.py @ 2495

Last change on this file since 2495 was 2495, checked in by adehnert, 14 years ago

Balance LVM requests (LP: #307361)

  • Add "monocast" method to send remctl requests to exactly one

randomly-selected host.

  • Send LVM requests to randomly-selected host for redundancy and load-balancing (LP: #307361).
File size: 1.3 KB
Line 
1from subprocess import PIPE, Popen
2from invirt.config import structs as config
3import random
4
5hostnames = [ h.hostname for h in config.hosts ]
6
7def monocast(args, hosts = hostnames, randomize = True):
8    """
9    Given a command and a list of hostnames or IPs, issue the command to each
10    node until it connects to one of the nodes.
11
12    Returns:
13        host the command ran on
14        hosts that could not be contacted
15        returncode of remctl
16        stdout of remctl
17        stderr of remctl
18    """
19    if(randomize):
20        hosts = random.sample(hosts, len(hosts))
21    hostsdown = []
22    for host in hosts:
23        pipe = Popen(['remctl', host, 'remote', 'web'] + args, stdout=PIPE, stderr=PIPE)
24        output = pipe.communicate()
25        if pipe.returncode != 0:
26            if output[1].startswith('remctl: cannot connect to %s' % host):
27                hostsdown.append(host)
28            else:
29                #raise RuntimeError("remctl to host %s returned non-zero exit status %d; stderr:\n%s"
30                #                   % (host, pipe.returncode, output[1]))
31                return (host, hostsdown, pipe.returncode,) + output
32        else:
33            return (host, hostsdown, pipe.returncode,) + output
34    raise RuntimeError("Failed to contact any hosts: tried %s" % (hostsdown, ))
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