Enable merging buildbot builds dependent on queue length

third_party/buildbot_8_4p1/buildbot/process/builder.py

 # This file is part of Buildbot.  Buildbot is free software: you can
 # redistribute it and/or modify it under the terms of the GNU General Public
 # License as published by the Free Software Foundation, version 2.
 #
 # This program is distributed in the hope that it will be useful, but WITHOUT
 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 # FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 # details.
 #
 # You should have received a copy of the GNU General Public License along with
 # this program; if not, write to the Free Software Foundation, Inc., 51
 # Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 #
 # Copyright Buildbot Team Members
 
 
-import random, weakref
+import inspect, random, weakref
 from zope.interface import implements
 from twisted.python import log, failure
 from twisted.spread import pb
 from twisted.application import service, internet
 from twisted.internet import defer
 
 from buildbot import interfaces
 from buildbot.status.progress import Expectations
 from buildbot.status.builder import RETRY
 from buildbot.status.buildrequest import BuildRequestStatus
@@ skipping 818 matching lines @@
         # we'll need BuildRequest objects, so get those first
         wfd = defer.waitForDeferred(
             defer.gatherResults(
                 [ self._brdictToBuildRequest(brdict)
                   for brdict in unclaimed_requests ]))
         yield wfd
         unclaimed_request_objects = wfd.getResult()
         breq_object = unclaimed_request_objects.pop(
                 unclaimed_requests.index(breq))
 
+        # Make sure the merge-requests function can take the queue length. Old

[tandrii(chromium), 2016/10/13 13:35:22]

...queue length and len(merged_requests). 

[Michael Achenbach, 2016/10/13 13:53:35]

wrote "lengths" now

+        # style functions only take two parameters.
+        mergeRequests_with_length_fn = lambda a, b, *_ : mergeRequests_fn(a, b)

[tandrii(chromium), 2016/10/13 13:35:22]

inspect on bound class functions or on functions with kwargs or *args will not
quite work in all cases as intended. I'd do the usual python way: try and see
what happens.
def wrapper(a,b,c,d):
  try:
    return mergeRequests_fn(a,b)
  except TypeError:
    return mergeRequests_fn(a,b,c,d)

[Michael Achenbach, 2016/10/13 13:53:35]

Good catch. Now implemented your suggestion to use an extra attribute and got
rid of inspect.

+        try:
+            n_args = len(inspect.getargspec(mergeRequests_fn).args)
+            if n_args > 3:
+                # New style function that accepts total and merged parameters.
+                mergeRequests_with_length_fn = mergeRequests_fn
+        except Exception as e:
+          log.err(e, 'Exception analyzing mergeRequests function.')
+
+        # This might not reflect exact number of items that could be merged
+        # (this depends on the canBeMergedWith algorithm), but it can help
+        # indicating how loaded this builder is.
+        queue_length = len(unclaimed_request_objects)
+
         # gather the mergeable requests
         merged_request_objects = [breq_object]
         for other_breq_object in unclaimed_request_objects:
             wfd = defer.waitForDeferred(
                 defer.maybeDeferred(lambda :
-                    mergeRequests_fn(breq_object, other_breq_object)))
+                    mergeRequests_with_length_fn(
+                        breq_object,
+                        other_breq_object,
+                        queue_length, 
+                        len(merged_request_objects),
+                    )))
             yield wfd
             if wfd.getResult():
                 merged_request_objects.append(other_breq_object)
 
         # convert them back to brdicts and return
         merged_requests = [ br.brdict for br in merged_request_objects ]
         yield merged_requests
 
     def _brdictToBuildRequest(self, brdict):
         """
@@ skipping 107 matching lines @@
         d = defer.DeferredList(dl)
         d.addCallback(self._gatherPingResults)
         return d
 
     def _gatherPingResults(self, res):
         for ignored,success in res:
             if not success:
                 return False
         return True