Create proper wrapper scripts to decouple from swarm_client.

scripts/slave/swarming/trigger_swarm_shim.py

+#!/usr/bin/env python
+# Copyright 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""This script acts as the liason between the master and the swarming_client
+code.
+
+This helps with master restarts and when swarming_client is updated. It helps
+support older versions of the client code, without having to complexify the
+master code.
+"""
+
+import optparse
+import os
+import subprocess
+import sys
+
+from common import chromium_utils
+from common import find_depot_tools  # pylint: disable=W0611
+
+from slave.swarming import swarming_utils
+
+# From depot tools/
+import fix_encoding
+
+
+def v0(client, options):
+  """Compatible up to the oldest swarm_client code."""
+  cmd = [
+    sys.executable,
+    os.path.join(client, 'swarm_trigger_step.py'),
+    '--swarm-url', options.swarming,
+    '--data-server', options.isolate_server,
+    '--os_image', options.os,
+    '--test-name-prefix', options.task_prefix,
+  ]
+  for i in options.tasks:
+    cmd.append('--run_from_hash')
+    cmd.extend(i)
+
+  print ' '.join(cmd)
+  return subprocess.call(cmd, cwd=client)
+
+
+def determine_version_and_run_handler(client, options):
+  """Executes the proper handler based on the code layout and --version support.
+  """
+  # TODO(maruel): Determine version.
+  return v0(client, options)
+
+
+def process_build_properties(options):
+  """Converts build properties and factory properties into expected flags."""
+  options.task_prefix = '%s-%s-' % (
+      options.build_properties.get('buildername'),
+      options.build_properties.get('buildnumber'),
+  )
+  # target_os is not defined when using a normal builder (and it's not
+  # needed since the OS match), it's defined in builder/tester configurations.
+  options.os = options.build_properties.get('target_os', options.os)
+
+
+def main():
+  """Note: this is solely to run the current master's code and can totally
+  differ from the underlying script flags.
+
+  To update these flags:
+  - Update the following code to support both the previous flag and the new
+    flag.
+  - Change scripts/master/factory/swarm_commands.py to pass the new flag.
+  - Restart all the masters using swarming.
+  - Remove the old flag from this code.
+  """
+  client = swarming_utils.find_client(os.getcwd())
+  if not client:
+    print >> sys.stderr, 'Failed to find swarm(ing)_client'
+    return 1
+
+  parser = optparse.OptionParser()
+  parser.add_option(
+      '--os', default=sys.platform,
+      help='it\'s possible to trigger a task on an OS while the client code '
+           'runs on another OS')
+  parser.add_option('--swarming')
+  parser.add_option('--isolate-server')
+  parser.add_option('--task-prefix', help='task name prefix')
+  parser.add_option(
+      '--task', nargs=4, action='append', default=[], dest='tasks')
+  chromium_utils.AddPropertiesOptions(parser)
+  options, args = parser.parse_args()
+  if args:
+    parser.error('Unsupported args: %s' % args)
+
+  if options.build_properties:
+    # Loads the other flags implicitly.
+    process_build_properties(options)
+
+  return determine_version_and_run_handler(client, options)
+
+
+if __name__ == '__main__':
+  fix_encoding.fix_encoding()
+  sys.exit(main())