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..c8a7bb0c7cb31ab72cdb0a84c136d1adf8781fd3 100644
--- a/third_party/buildbot_8_4p1/buildbot/process/builder.py
+++ b/third_party/buildbot_8_4p1/buildbot/process/builder.py
@@ -853,12 +853,30 @@ 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 lengths. Old
+        # style functions only take two parameters.
+        if getattr(mergeRequests_fn, 'with_length', False):
+            mergeRequests_with_length_fn = mergeRequests_fn
+        else:
+            mergeRequests_with_length_fn = (
+                lambda a, b, *_ : mergeRequests_fn(a, b))
+
+        # This might not reflect the 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(

[agable, 2016/10/13 17:58:36]

It might be less confusing if the "if fn.with_length" logic were down here, and
then whether you pass two or four arguments is dependent on the result of that
check, rather than always passing four and having to decode the lambda above. Up
to you, though.

[Michael Achenbach, 2016/10/13 19:05:07]

Done.

+                        breq_object,
+                        other_breq_object,
+                        queue_length, 
+                        len(merged_request_objects),
+                    )))
             yield wfd
             if wfd.getResult():
                 merged_request_objects.append(other_breq_object)