swarming: add transaction_id to tasks.new request

appengine/swarming/swarming_rpcs.py

 # Copyright 2015 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """This module defines ProtoRPC types for the Swarming Server handlers."""
 
 from protorpc import message_types
 from protorpc import messages
 
 
@@ skipping 218 matching lines @@
   # separately.
   service_account_token = messages.StringField(8)
 
   # Full topic name to post too, e.g. "projects/<id>/topics/<id>".
   pubsub_topic = messages.StringField(9)
   # Secret string to put into "auth_token" attribute of PubSub message.
   pubsub_auth_token = messages.StringField(10)
   # Will be but into "userdata" fields of PubSub message.
   pubsub_userdata = messages.StringField(11)
 
+  # Global ID of the transaction to create a new task request.
+  # If specified and a task request with the same transaction id was created
+  # recently, the existing request will be returned as is.
+  # If two NewTaskRequests use the same transaction ID, requests must have all
+  # attributes equal.
+  #
+  # Transaction ID can be used to cancel this task request.
+  transaction_id = messages.StringField(12)
+
 
 class TaskRequest(messages.Message):
   """Description of a task request as registered by the server."""
   expiration_secs = messages.IntegerField(1)
   name = messages.StringField(2)
   parent_task_id = messages.StringField(3)
   priority = messages.IntegerField(4)
   properties = messages.MessageField(TaskProperties, 5)
   tags = messages.StringField(6, repeated=True)
   created_ts = message_types.DateTimeField(7)
@@ skipping 321 matching lines @@
 
 
 class DeletedResponse(messages.Message):
   """Indicates whether a bot was deleted."""
   deleted = messages.BooleanField(1)
 
 
 class TerminateResponse(messages.Message):
   """Returns the pseudo taskid to wait for the bot to shut down."""
   task_id = messages.StringField(1)