On 03/12/2015 03:08 PM, John Dickinson wrote:
I'd like a little more info here.
Is Horizon relying on the X-Timestamp header for reads (GET/HEAD)? If so, I
think that's somewhat odd, but not hugely problematic. Swift has been returning
an X-Timestamp header since patch b20264c9d3196 (which landed 3 years ago --
April 2012).
OK, so there is a documentation bug here that X-Timestamp should be part
of the Swift REST API. It currently is not documented that X-Timestamp
is a non-optional HTTP Header, and therefore the RadosGW folks did not
send X-Timestamp headers back in the container response.
The X-Timestamp header is certainly part of the Swift API. It is required for
container-sync functionality (implemented in early 2011) so that two clusters
can communicate about the proper timestamp of the objects.
OK. Sounds like an implementation detail leaking out of the API to me.
In other words, RadosGW (which is attempting to expose a Swift API in
front of Ceph backend storage) needs to expose this X-Timestamp header
even if it implements container-sync using an entirely difference
mechanism...
I'm not sure if this actually matters for Horizon in this specific case. But
it's certainly true that Swift requires and used the X-Timestamp header for
implementing core functionality. Anyone talking to a Swift endpoint can assume
that there is an X-Timestamp header in the response and use it as they see fit.
Anyone talking to an upstream Swift *implementation* can assume that
header will be there :) But, the header is not actually documented in
the Swift *API* and therefore one cannot make this assumption.
Thus the confusion. :)
Anyway, sounds like X-Timestamp should be documented as part of the
official Swift API. What about the X-Object-Meta-Mtime header in the
related bug? That, too, is problematic for a similar reason. Is that
header part of the Swift API as well?
Best,
-jay
--John
On Mar 9, 2015, at 12:53 PM, Anne Gentle <annegen...@justwriteclick.com> wrote:
On Mon, Mar 9, 2015 at 2:32 PM, Matthew Farina <m...@mattfarina.com> wrote:
David,
FYI, the last time I chatted with John Dickinson I learned there are numerous
API elements not documented. Not meant to be private but the docs have not kept
up. How should we handle that?
I've read through this thread and the bug comments and searched through the
docs and I'd like more specifics: which docs have not kept up? Private API docs
for swift internal workings? Or is this a header that could be in _some_ swift
(not ceph) deployments?
Thanks,
Anne
Thanks,
Matt Farina
On Sat, Mar 7, 2015 at 5:25 PM, David Lyle <dkly...@gmail.com> wrote:
I agree that Horizon should not be requiring optional headers. Changing status
of bug.
On Tue, Mar 3, 2015 at 5:51 PM, Jay Pipes <jaypi...@gmail.com> wrote:
Added [swift] to topic.
On 03/03/2015 07:41 AM, Matthew Farina wrote:
Radoslaw,
Unfortunately the documentation for OpenStack has some holes. What you
are calling a private API may be something missed in the documentation.
Is there a documentation bug on the issue? If not one should be created.
There is no indication that the X-Timestamp or X-Object-Meta-Mtime HTTP headers
are part of the public Swift API:
http://developer.openstack.org/api-ref-objectstorage-v1.html
I don't believe this is a bug in the Swift API documentation, either. John
Dickinson (cc'd) mentioned that the X-Timestamp HTTP header is required for the
Swift implementation of container replication (John, please do correct me if
wrong on that).
But that is the private implementation and not part of the public API.
In practice OpenStack isn't a specification and implementation. The
documentation has enough missing information you can't treat it this
way. If you want to contribute to improving the documentation I'm sure
the documentation team would appreciate it. The last time I looked there
were a number of undocumented public swift API details.
The bug here is not in the documentation. The bug is that Horizon is coded to rely on HTTP
headers that are not in the Swift API. Horizon should be fixed to use
<DICT>.get('X-Timestamp') instead of doing <DICT>['X-Timestamp'] in its view
pages for container details. There are already patches up that the Horizon developers have,
IMO erroneously, rejected stating this is a problem in Ceph RadosGW for not properly
following the Swift API).
Best,
-jay
Best of luck,
Matt Farina
On Tue, Mar 3, 2015 at 9:59 AM, Radoslaw Zarzynski
<rzarzyn...@mirantis.com <mailto:rzarzyn...@mirantis.com>> wrote:
Guys,
I would like discuss a problem which can be seen in Horizon: breaking
the boundaries of public, well-specified Object Storage API in favour
of utilizing a Swift-specific extensions. Ticket #1297173 [1] may serve
as a good example of such violation. It is about relying on
non-standard (in the terms of OpenStack Object Storage API v1) and
undocumented HTTP header provided by Swift. In order to make
Ceph RADOS Gateway work correctly with Horizon, developers had to
inspect sources of Swift and implement the same behaviour.
From my perspective, that practise breaks the the mission of OpenStack
which is much more than delivering yet another IaaS/PaaS implementation.
I think its main goal is to provide a universal set of APIs covering all
functional areas relevant for cloud computing, and to place that set
of APIs in front as many implementations as possible. Having an open
source reference implementation of a particular API is required to prove
its viability, but is secondary to having an open and documented API.
I have full understanding that situations where the public OpenStack
interfaces are insufficient to get the work done might exist.
However, introduction of dependency on implementation-specific feature
(especially without giving the users a choice via e.g. some
configuration option) is not the proper way to deal with the problem.
From my point of view, such cases should be handled with adoption of
new, carefully designed and documented version of the given API.
In any case I think that Horizon, at least basic functionality, should
work with any storage which provides Object Storage API.
That being said, I'm willing to contribute such patches, if we decide
to go that way.
Best regards,
Radoslaw Zarzynski
[1] https://bugs.launchpad.net/horizon/+bug/1297173
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