Enable merging buildbot builds dependent on queue length

third_party/buildbot_8_4p1/buildbot/process/builder.py

Index: third_party/buildbot_8_4p1/buildbot/process/builder.py
diff --git a/third_party/buildbot_8_4p1/buildbot/process/builder.py b/third_party/buildbot_8_4p1/buildbot/process/builder.py
index e92e2d1a34fa1e47532343f21a4beca500dd0080..50c64108c8e1f770ce51a27ac008d8fa2b0c5aba 100644
--- a/third_party/buildbot_8_4p1/buildbot/process/builder.py
+++ b/third_party/buildbot_8_4p1/buildbot/process/builder.py
@@ -14,7 +14,7 @@
 # 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
@@ -853,12 +853,26 @@ class Builder(pb.Referenceable, service.MultiService):
         breq_object = unclaimed_request_objects.pop(
                 unclaimed_requests.index(breq))
 
+        # Make sure the merge-requests function can take the queue length.
+        mergeRequests_with_length_fn = lambda a, b, _ : mergeRequests_fn(a, b)
+        try:
+            if len(inspect.getargspec(mergeRequests_fn).args) > 2:
+                mergeRequests_with_length_fn = mergeRequests_fn
+        except Exception:
+          pass
+
+        # 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)))
             yield wfd
             if wfd.getResult():
                 merged_request_objects.append(other_breq_object)

[Michael Achenbach, 2016/10/13 10:36:13]

Thinking more: Now that I'm already changing this code, I could also pass
len(merged_request_objects) to the merge function, so that I could remove the
extra storage hack in there.