Merge "Update infra-prod limit semaphore to a max of 4"

zuul.d/infra-prod.yaml

@@ -12,15 +12,11 @@
 # This semaphore limits the total number of production playbook
 # jobs that can run on bridge at one time. We want things to run in
 # parallel but we have a lot of jobs (particularly in the periodic
-# pipeline) that we don't want to run all at once.
+# pipeline) that we don't want to run all at once to avoid overwhelming
+# the bastion host.
 - semaphore:
     name: infra-prod-playbook-limit
-    # TODO(clarkb) this semaphore allows us to stage the rollout of
-    # parallel infra-prod job exceution in two steps. First we reorganize
-    # everything but roughly keep the same behaviors as before (max: 1).
-    # When we are happy with that we can bump this to 2 or higher and see
-    # things run in parallel.
-    max: 2
+    max: 4
 
 - job:
     name: infra-prod-bootstrap-bridge