Comments from Openshift QE:
After resources are created, images stream needs to import image tags from registry. Once the tags are generated, a build will be automatically invoked. Importing image tag from registry needs time, so it spends several minutes to start build. I think this is acceptable.

Not true in this case, image streams were created prior to creating templates.

Even if that is the case, it doesn't explain why it takes random time between a second and 2 minutes.

Here is possibly what is happening:

1. image stream is created
2. image stream tags are imported
3. build config is created
4. because the image stream tags were already imported, the build config doesn't get any trigger for an image stream update
5. after 2 minutes, the build's image change controller re-examines the image streams (it uses a reflector with a resync period of 2 minutes, which means it reprocesses all streams every 2 minutes)
6. the image change controller sees the tag now, so it kicks off a build

1.Create a django-psql-example template using https://raw.githubusercontent.com/openshift/django-ex/master/openshift/templates/django-postgresql.json file
2.Create an app using django-psql-example template from GUI
3.Now no build is invoked since no imagestreamtag.
4.Create python imagestream
5.Build is invoked in a second after importing imagestreamtag
6.Change something in python image, and push,then import python imagestream again
7.Build is invoked in a second after importing imagestreamtag.

So can't reproduce this issue in devenv-fedora_2287, will mark this bug as verified.

Sorry to verify this bug on wrong env.
Test in ose env
openshift-3.0.1.0-1.git.529.dcab62c.el7ose.x86_64
openshift-master-3.0.1.0-1.git.529.dcab62c.el7ose.x86_64

Build will be invoked in a second after importing imagestreamtag.

This fix is available in OpenShift Enterprise 3.1.