Add master_manager_launch script which launches master_manager scripts for each master on a host.

infra/services/master_manager_launcher/__main__.py

Index: infra/services/master_manager_launcher/__main__.py
diff --git a/infra/services/master_manager_launcher/__main__.py b/infra/services/master_manager_launcher/__main__.py
new file mode 100644
index 0000000000000000000000000000000000000000..245c3fab67b456276c782a2036d4bafe3cfc3c64
--- /dev/null
+++ b/infra/services/master_manager_launcher/__main__.py
@@ -0,0 +1,122 @@
+#!/usr/bin/python
+# Copyright 2015 Google Inc. All Rights Reserved.
+# pylint: disable=F0401
+
+"""Launch a master_manager script for every master on a host."""
+
+# pragma: no cover

[agable, 2015/05/07 17:59:31]

I don't think this actually works. Does it? I swear I've tried this and had it
not actually do what I want in the past.

[ghost stip (do not use), 2015/05/07 19:49:39]

again -- since there is no test file associated with this, the entire file is
not tested for coverage, period. the #pragma here is for humans

[agable, 2015/05/08 00:14:53]

Ah, right. Balls :(

+
+import argparse
+import json
+import logging
+import operator
+import os
+import socket
+import subprocess
+import sys
+
+from infra.libs import logs
+from infra.libs.service_utils import daemon
+from infra.services.master_lifecycle import buildbot_state
+from infra.services.master_manager_launcher import desired_state_parser
+
+
+SCRIPT_DIR = os.path.abspath(os.path.dirname(__file__))
+RUNPY = os.path.abspath(os.path.join(
+  SCRIPT_DIR, os.pardir, os.pardir, os.pardir, 'run.py'))
+
+
+def parse_args():
+  parser = argparse.ArgumentParser(
+      description='Launches master_manager for every master on a host. NOTE: '
+                  'does not perform any action unless --prod is set.')
+  parser.add_argument('build_dir', nargs='?',
+      help='location of the tools/build directory')
+  parser.add_argument('--hostname',
+      default=socket.getfqdn(),
+      help='override local hostname (currently %(default)s)')
+  parser.add_argument('--json-location',
+      default='desired_master_state.json',
+      help='desired master state configuration (default: %(default)s)')
+  parser.add_argument('--command-timeout',
+      help='apply a timeout in seconds to each master_manager process')
+  parser.add_argument('--verify', action='store_true',
+      help='verify the desired master state JSON is valid, then exit')
+  parser.add_argument('--prod', action='store_true',
+      help='actually perform actions instead of doing a dry run')
+  logs.add_argparse_options(parser)
+
+  args = parser.parse_args()
+  logs.process_argparse_options(args)
+
+  if not args.verify:
+    if not args.build_dir:
+      parser.error('A build/ directory must be specified.')
+
+  return args
+
+
+def synthesize_master_manager_cmd(master_dict, hostname, prod=False):
+  """Find the current desired state and synthesize a command for the master."""
+  state = desired_state_parser.get_master_state(master_dict['states'])
+  cmd = [
+      RUNPY,
+      'infra.tools.master_manager',
+      master_dict['fulldir'],
+      str(state['desired_state']),
+      str(state['transition_time_utc']),
+      '--hostname', hostname,
+      '--enable-gclient-sync',
+      '--verbose',
+  ]
+
+  if prod:
+    cmd.append('--prod')
+
+  return cmd
+
+
+def log_triggered_ignored(triggered, ignored, hostname):
+  """Outputs for humans which masters will be managed and which won't."""
+  if ignored:
+    logging.info(
+        '%d masters on host %s left unmanaged (no desired state section):\n%s',
+        len(ignored), hostname, '\n'.join(ignored))
+
+  triggered_master_string = '.'
+  if triggered:
+    triggered_master_string = ':\n'
+  triggered_master_string += '\n'.join(m['dirname'] for m in triggered)
+  logging.info(
+      '%d masters managed for host %s%s',
+      len(triggered), hostname, triggered_master_string)
+
+
+def main():
+  args = parse_args()
+
+  desired_state = desired_state_parser.load_desired_state_file(
+      args.json_location)
+
+  if args.verify:
+    return 0  # File checks out, no need to continue.
+
+  triggered, ignored = desired_state_parser.get_masters_for_host(
+      desired_state, args.build_dir, args.hostname)
+  log_triggered_ignored(triggered, ignored, args.hostname)
+
+  commands = [
+      synthesize_master_manager_cmd(m, args.hostname, prod=args.prod)
+      for m in triggered
+  ]
+
+  if args.command_timeout:
+    commands = [daemon.add_timeout(c, args.command_timeout) for c in commands]
+
+  for command in commands:
+    logging.info('running %s' % command)

[agable, 2015/05/07 17:59:31]

This log line will be prettier (and copy-pasteable) if you ' '.join(command).
Otherwise it's gonna print the full list of tokens, which is just annoying.

[ghost stip (do not use), 2015/05/07 19:49:39]

I always worry about doing that because you might have spaces in the command. we
don't right now, but I don't like the idea of people copying/pasting things
which may be subtly broken

[agable, 2015/05/08 00:14:53]

Hmm. That's fair, I suppose. But also makes me want to cry.

+    subprocess.call(command)
+
+
+if __name__ == '__main__':
+  sys.exit(main())