Issue 1267 - Provide a way to run some command on multiple hosts

run.py

+#!/usr/bin/env python
+# coding: utf-8
+
+import sys
+import os
+import re
+import subprocess
+import getopt
+import yaml
+
+def usage():
+  print >>sys.stderr, '''
+Usage: %s [-u <user>] [-h <host>|<group>] [-i] ... <command>
+
+Runs a command on the given hosts or groups of hosts.
+
+Options:
+  -u <user>       User name to use with the SSH command
+  -h <host|group> Host or group to run the command on (can be specified multiple times)
+  -i              If specified, command will be executed on all hosts despite errors
+''' % sys.argv[0]
+
+def parseOptions(args):
+  try:
+    options, args = getopt.getopt(args, 'u:h:i')
+  except getopt.GetoptError, e:
+    print >>sys.stderr, e
+    usage()
+    sys.exit(1)
+
+  user = None
+  hosts = []
+  ignore_errors = False
+  for option, value in options:
+    if option == '-u':
+      user = value
+    elif option == '-h':
+      hosts.append(value)
+    elif option == '-i':
+      ignore_errors = True
+
+  return user, hosts, ignore_errors, args
+
+def readMonitoringConfig():
+  # Use Puppet's parser to convert monitoringserver.pp into YAML
+  manifest = os.path.join(os.path.dirname(__file__), 'manifests', 'monitoringserver.pp')
+  parseScript = '''
+    require 'puppet'
+    require 'puppet/parser'
+    parser = Puppet::Parser::Parser.new(Puppet[:environment])
+    Puppet.settings[:ignoreimport] = true
+    parser.file = ARGV[0]
+    print ZAML.dump(parser.parse)
+  '''
+  data, dummy = subprocess.Popen(['ruby', '', manifest],
+                  stdin=subprocess.PIPE,
+                  stdout=subprocess.PIPE).communicate(parseScript)
+
+  # See http://stackoverflow.com/q/8357650/785541 on parsing Puppet's YAML
+  yaml.add_multi_constructor(u"!ruby/object:", lambda loader, suffix, node: loader.construct_yaml_map(node))
+  yaml.add_constructor(u"!ruby/sym", lambda loader, node: loader.construct_yaml_str(node))
+  return yaml.load(data)
+
+def getValidHosts():
+  def processNode(node, hosts=None, groups=None):
+    if hosts == None:
+      hosts = set()
+    if groups == None:
+      groups = {}
+
+    if 'context' in node and 'code' in node['context']:
+      node = node['context']['code']
+
+    if node.get('type', None) == 'nagios_hostgroup':
+      data = node['instances']['children'][0]
+      title = data['title']['value']
+      members = filter(lambda c: c['param'] == 'members', data['parameters']['children'])[0]['value']['value']
+      members = re.split(r'\s*,\s*', members)
+      groups[title] = members
+    elif node.get('type', None) == 'nagios_host':
+      data = node['instances']['children'][0]
+      title = data['title']['value']
+      hosts.add(title)
+
+    for child in node['children']:
+      processNode(child, hosts, groups)
+    return hosts, groups
+
+  monitoringConfig = readMonitoringConfig()
+  if not monitoringConfig:
+    print >>sys.stderr, "Failed to parse monitoring configuration"
+    return [[], []]
+  # Extract hosts and groups from monitoring config
+  return processNode(monitoringConfig)
+
+def resolveHostList(hosts):
+  validHosts, validGroups = getValidHosts()
+  if not validHosts:
+    print "Warning: No valid hosts found, not validating"
+    return hosts
+
+  result = set()
+  for param in hosts:
+    if param in validGroups:
+      for host in validGroups[param]:
+        if host == '*':
+          result = result | validHosts
+        else:
+          result.add(host)
+    elif param in validHosts:
+      result.add(param)
+    elif '%s.adblockplus.org' % param in validHosts:
+      result.add('%s.adblockplus.org' % param)
+    else:
+      print >>sys.stderr, 'Warning: failed to recognize host or group %s' %param
+  return result
+
+def runCommand(user, host, command, ignore_errors=False):
+  if not isinstance(command, list):
+    command = [command]
+  command = ["ssh"] + (["-l", user] if user else []) + [host] + command
+  if ignore_errors:
+    subprocess.call(command)
+  else:
+    subprocess.check_call(command)
+
+if __name__ == "__main__":
+  user, hosts, ignore_errors, args = parseOptions(sys.argv[1:])
+  selectedHosts = resolveHostList(hosts)
+  if len(selectedHosts) == 0:
+    print >>sys.stderr, 'No valid hosts or groups specified, nothing to do'
+    sys.exit(0)
+  for host in selectedHosts:
+    print 'Running on %s...' % host

[mathias, 2014/08/25 16:21:25]

If all logging would be printed to >>stderr (just like it's intended to) instead
of polluting >>stdout, one could re-use the output of the command properly.

If the host information is required, one could prefix each line instead of
printing host notifications (triggered by a -p flag, for example), which is much
easier to process by scripts (|piped or via log file) or even manually
(shell/editor) later on.

This behavior could even be kept when e.g. deciding to implement parallelization
(similar to Fabric, see http://docs.fabfile.org/).

[Wladimir Palant, 2014/08/29 22:11:15]

I'm not usually using scripts on the output. And there might not even be any
output - I simply want to see the current progress when running a command on
twenty servers.
It's not that easy IMHO. Piping command output in Python while the command is
running requires a second thread - I'm not ready to go there for this simple
tool. An external tool like awk could do it as well, this adds a dependency
however. In the end, maybe I can simply pipe it into a second Python process -
but that's something to consider when I actually need this functionality.
I don't think I want to go there just yet :)

+    runCommand(user, host, args, ignore_errors=ignore_errors)