[Pulp-dev] Changesets Challenges

[David Davis]

+1


David

On Fri, Apr 6, 2018 at 10:39 AM, Dennis Kliban <dkliban at redhat.com> wrote:

> On Fri, Apr 6, 2018 at 10:15 AM, Brian Bouterse <bbouters at redhat.com>
> wrote:
>
>> Several plugins have started using the Changesets including pulp_ansible,
>> pulp_python, pulp_file, and perhaps others. The Changesets provide several
>> distinct points of value which are great, but there are two challenges I
>> want to bring up. I want to focus only on the problem statements first.
>>
>> 1. There is redundant "differencing" code in all plugins. The Changeset
>> interface requires the plugin writer to determine what units need to be
>> added and those to be removed. This requires all plugin writers to write
>> the same non-trivial differencing code over and over. For example, you can
>> see the same non-trivial differencing code present in pulp_ansible
>> <https://github.com/pulp/pulp_ansible/blob/d0eb9d125f9a6cdc82e2807bcad38749967a1245/pulp_ansible/app/tasks/synchronizing.py#L217-L306>,
>> pulp_file
>> <https://github.com/pulp/pulp_file/blob/30afa7cce667b57d8fe66d5fc1fe87fd77029210/pulp_file/app/tasks/synchronizing.py#L114-L193>,
>> and pulp_python
>> <https://github.com/pulp/pulp_python/blob/066d33990e64b5781c8419b96acaf2acf1982324/pulp_python/app/tasks/sync.py#L172-L223>.
>> Line-wise, this "differencing" code makes up a large portion (maybe 50%) of
>> the sync code itself in each plugin.
>>
>>
> That is definitely a problem. We should address this.
>
>
>> 2. Plugins can't do end-to-end stream processing. The Changesets
>> themselves do stream processing, but when you call into
>> changeset.apply_and_drain() you have to have fully parsed the metadata
>> already. Currently when fetching all metadata from Galaxy, pulp_ansible
>> takes about 380 seconds (6+ min). This means that the actual Changeset
>> content downloading starts 380 seconds later than it could. At the heart of
>> the problem, the fetching+parsing of the metadata is not part of the stream
>> processing.
>>
>>
> This is the same problem we currently have in Pulp 2. We should address
> this.
>
>
>> Do you see the same challenges I do? Are these the right problem
>> statements? I think with clear problem statements a solution will be easy
>> to see and agree on.
>>
>>
> Yes, I do. You described the problems very well.
>
>
>> Thanks!
>> Brian
>>
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>>
>
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