Subscription patching to duplicate in mongodb should return 409 response

[Eva Balycheva]

What happens:

Now when I try to patch subscription to make it duplicate of other subscription, Zaqar returns 400 response code with body like this:
{
    "title": "Unable to update subscription",
    "description": "Subscription 56c5fe4292d7024058d831fe could not be updated."
}

As you can see it's not very informative for the user. And also there is definitely conflict
And Zaqar server is showing log messages of ERROR level during this event, which is wrong: http://paste.openstack.org/show/JDK4TR2gNG5nLBrJFxnI/

Possible solution:

On such event make Zaqar return response code 409 with body:
{
    "title": "Unable to update subscription",
    "description": "Such subscription already exists"
}

And make zaqar just log this event on DEBUG level.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/279946
Committed: https://git.openstack.org/cgit/openstack/zaqar/commit/?id=f94a9ee4cee28e79fbb4af1da66ab876f2c3079f
Submitter: Jenkins
Branch: master

commit f94a9ee4cee28e79fbb4af1da66ab876f2c3079f
Author: wangxiyuan <email address hidden>
Date: Sun Feb 14 17:30:35 2016 +0800

    Forbid update subscription to duplicate

    Now if users update a subscription in a queue, it doesn't check the
    legality of the new subscriber. We should forbid update subscription to
    duplicate and return 409 response in such case.

    This patch modifies Redis and MongoDB storage controllers and API v2.
    It also adds unit tests for them.

    The functional test will be updated in zaqar client.

    APIimpact
    Closes-Bug: #1545548
    Closes-Bug: #1547131
    Co-Authored-By: wangxiyuan <email address hidden>
    Co-Authored-By: Eva Balycheva <email address hidden>
    Change-Id: I28fe7a114860488c503642417690bf5bfbd99678

[Doug Hellmann (doug-hellmann)]

This issue was fixed in the openstack/zaqar 2.0.0.0rc1 release candidate.