Order gang scheduled jobs based on time of arrival

[adam-marek]

What this PR does / why we need it:
The ordering of equal priority gang scheduled jobs is currently based on the job's namespace/name which is unintuitive when multiple users schedule jobs competing for the same resources.
Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #454

Special notes for your reviewer:

Release note:

Equal priority gang scheduled jobs will be ordered by their time of creation.

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[adam-marek]

I am a member of the CNCF Intel Corporation group. My email is adam.marek@intel.com

[TravisBuddy]

Travis tests have failed

Hey @adam-marek,
Please read the following log in order to understand the failure reason.
It'll be awesome if you fix what's wrong and commit the changes.

1st Build

View build log

make verify

go build -o _output/bin/deepcopy-gen ./cmd/deepcopy-gen/
_output/bin/deepcopy-gen -i ./pkg/apis/scheduling/v1alpha1/ -O zz_generated.deepcopy
hack/verify-gofmt.sh
diff -u ./pkg/scheduler/plugins/gang/gang.go.orig ./pkg/scheduler/plugins/gang/gang.go
--- ./pkg/scheduler/plugins/gang/gang.go.orig	2018-11-01 22:23:59.289164644 +0000
+++ ./pkg/scheduler/plugins/gang/gang.go	2018-11-01 22:23:59.289164644 +0000
@@ -122,7 +122,7 @@
 		if !lReady && !rReady {
 			if lv.PodGroup.GetCreationTimestamp().Time.Equal(rv.PodGroup.GetCreationTimestamp().Time) {
 				if lv.UID < rv.UID {
-					return -1;
+					return -1
 				}
 			} else if lv.PodGroup.GetCreationTimestamp().Time.Before(rv.PodGroup.GetCreationTimestamp().Time) {
 				return -1
make: *** [verify] Error 1

TravisBuddy Request Identifier: 50fc6850-de27-11e8-b084-61188e6c7303

[k82cn]

hm... we need to add a new field into JobInfo, the creation-timestamp is from PodGroup or PDB. And we will check jobInfo's creation time here. We need to support PDB as tf-operator is using it, we will remove it at least after 0.4 release.

[adam-marek]

Something along these lines ? (3f0dfd8)

[TravisBuddy]

Hey @adam-marek,
Something went wrong with the build.

TravisCI finished with status errored, which means the build failed because of something unrelated to the tests, such as a problem with a dependency or the build process itself.

View build log

TravisBuddy Request Identifier: 5954b640-e08b-11e8-90db-29214a2b47d8

[k82cn]

LGTM overall! let’s get it merged when CI is happy :)

[k82cn]

please sign cla

[k82cn]

/approve
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: adam-marek, k82cn

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[adam-marek]

CLA should be signed now