[Pulp-dev] Proposal: merge the content-app & streamer

Dennis Kliban dkliban at redhat.com
Mon Dec 3 22:24:31 UTC 2018

It was pointed out on IRC that plugins that have to supply their own
content app (such as docker) currently need to supply 2 implementations of
it in order to support on-demand use cases. One using django and another
using aiohttp.

We should not burden plugin writers in such a way. We really have to make
the proposed change.

On Mon, Dec 3, 2018 at 3:24 PM Dana Walker <dawalker at redhat.com> wrote:

> In light of the efficiency gains and lack of significant drawbacks, I'm +1
> on this proposal.
> --Dana
> Dana Walker
> Associate Software Engineer
> Red Hat
> <https://www.redhat.com>
> <https://red.ht/sig>
> On Mon, Dec 3, 2018 at 2:40 PM Dennis Kliban <dkliban at redhat.com> wrote:
>> I like the idea of combining the two applications for all the reasons
>> already outlined on this thread. The user experience is going to be
>> simplified by this change. However, I want to point out that it will also
>> alter the plugin writer experience. Plugin writers that want to have their
>> own content app will now need to provide it as a plugin for the content app
>> (which is not a Django project). We should be able to clearly document this
>> for plugin writers. pulp_docker plugin will need to adopt this change. For
>> that reason I'd like us to make a decision on this soon.
>> On Fri, Nov 30, 2018 at 4:59 PM Jeff Ortel <jortel at redhat.com> wrote:
>>> The pulp3 content app and the streamer (in-progress) currently have a
>>> lot of duplicate code and functionality.  At the very least, I think there
>>> is a opportunity to refactor both and share code.  But, this would leave us
>>> with two components with significant overlap in functionality.
>>> The functionality exclusive to the content-app:
>>>   - Optionally delegate file serving to a web server. (Eg:
>>> mod_xsendfile).
>>>   - Optional redirect to the streamer.
>>> The functionality exclusive to the streamer:
>>>   - Using the Remote & RemoteArtifact to download the file and stream on
>>> demand.
>>> Not much difference which raises the question: "Why do we have both?"  I
>>> think the answer may be that we don't.
>>> Let's pull the content-app out and merge it with the streamer.  The new
>>> content (app) would have *streamer* architecture & functionality.  When
>>> a requested artifact has not been downloaded, it would download/streamed
>>> instead of REDIRECT.  This does mean that deployments and development
>>> environments would need to run an additional service to serve content.  The
>>> /pulp/content endpoint would be on a different port than the API.  I see
>>> this separation as a healthy thing.  There is significant efficiency to be
>>> gained as well.  Let's start with eliminating the REDIRECTs.  Cutting the
>>> GET requests in half is a win for both the client, the network and the Pulp
>>> web stack.  Next is database queries.  Since both applications needed to
>>> perform many of the same queries, combining the applications will roughly
>>> cut them in half as well.  Since the streamer is based on asyncio and so
>>> would the merged app.
>>> There are probably lots of other pros/cons I have not considered but it
>>> seems relatively straight forward.
>>> I'm thinking the new content app/service would be named: *pulp-content*.
>>> Thoughts?
>>> _______________________________________________
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