Add support for repeated keys in TaskRequest.

appengine/swarming/server/task_queues.py

Index: appengine/swarming/server/task_queues.py
diff --git a/appengine/swarming/server/task_queues.py b/appengine/swarming/server/task_queues.py
index 2e5f4068ca1971e8e56a888736ca33086e1cc4ad..dff2d9ee023f6ac50961a43a8e9a2c05c9e31a4c 100644
--- a/appengine/swarming/server/task_queues.py
+++ b/appengine/swarming/server/task_queues.py
@@ -238,8 +238,8 @@ class TaskDimensions(ndb.Model):
 
   def match_request(self, dimensions):
     """Confirms that this instance actually stores this set."""
-    return self._match_request_flat(
-        u'%s:%s' % (k, v) for k, v in dimensions.iteritems())
+    assert isinstance(dimensions, list), repr(dimensions)
+    return self._match_request_flat(u'%s:%s' % (k, v) for k, v in dimensions)
 
   def match_bot(self, bot_dimensions):
     """Returns the TaskDimensionsSet that matches this bot_dimensions, if any.
@@ -405,13 +405,28 @@ def _rebuild_bot_cache(bot_dimensions, bot_root_key):
 
 
 def _get_task_dims_key(dimensions_hash, dimensions):
-  if u'id' in dimensions:
-    return ndb.Key(
-        TaskDimensionsRoot, u'id:%s' % dimensions['id'],
-        TaskDimensions, dimensions_hash)
-  return ndb.Key(
-      TaskDimensionsRoot, u'pool:%s' % dimensions['pool'],
-      TaskDimensions, dimensions_hash)
+  """Return the ndb.Key() for the request dimensions.
+
+  The dimensions may have at most one 'id' key but may have multiple 'pool'. In
+  the case of 'pool', return the first value in sorted order. This means that
+  for a request with both 'pool:bar' and 'pool:foo', the request is rooted at
+  'pool:bar'.
+
+  Arguments:
+  - dimensions: sorted list(tuple(unicode, unicode))
+  """
+  assert isinstance(dimensions, list), repr(dimensions)
+  # Search for ID.
+  for key, value in dimensions:
+    if key == u'id':
+      return ndb.Key(
+          TaskDimensionsRoot, u'id:%s' % value, TaskDimensions, dimensions_hash)
+    # 'pool' comes after 'id'.
+    if key == u'pool':
+      return ndb.Key(
+          TaskDimensionsRoot, u'pool:%s' % value,
+          TaskDimensions, dimensions_hash)
+  raise datastore_errors.BadValueError(u'invalid request')
 
 
 def _hash_data(data):
@@ -507,14 +522,15 @@ def hash_dimensions(dimensions):
   """Returns a 32 bits int that is a hash of the request dimensions specified.
 
   Arguments:
-    dimensions: dict(str, str)
+    dimensions: sorted list(tuple(unicode, unicode))
 
   The return value is guaranteed to be non-zero so it can be used as a key id in
   a ndb.Key.
   """
+  assert isinstance(dimensions, list), repr(dimensions)
   # This horrible code is the product of micro benchmarks.
   data = ''
-  for k, v in sorted(dimensions.items()):
+  for k, v in dimensions:
     data += k.encode('utf8')
     data += '\000'
     data += v.encode('utf8')
@@ -613,7 +629,7 @@ def assert_task(request):
   # If this task specifies an 'id' value, updates the cache inline since we know
   # there's only one bot that can run it, so it won't take long. This permits
   # tasks like 'terminate' tasks to execute faster.
-  if request.properties.dimensions.get(u'id'):
+  if any(k == u'id' for k, _ in request.properties.dimensions):
     rebuild_task_cache(payload)
     return
 
@@ -688,7 +704,7 @@ def rebuild_task_cache(payload):
   dimensions = data[u'dimensions']
   dimensions_hash = int(data[u'dimensions_hash'])
   valid_until_ts = utils.parse_datetime(data[u'valid_until_ts'])
-  dimensions_flat = sorted(u'%s:%s' % (k, v) for k, v in dimensions.iteritems())
+  dimensions_flat = sorted(u'%s:%s' % (k, v) for k, v in dimensions)
 
   now = utils.utcnow()
   updated = 0