On 04/06/2018 09:15 AM, Brian Bouterse 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.
Ten lines of trivial set logic hardly seems like a big deal but any duplication is worth exploring.
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.
The additions/removals can be any interable (like generator) and by using ChangeSet.apply() and iterating the returned object, the pluign can "turn the crank" while downloading and processing the metadata. The ChangeSet.apply_and_drain() is just a convenience method. I don't see how this is a limitation of the ChangeSet.
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.
I'm not convinced that these are actual problems/challenges that need to be addressed in the near term.
Thanks! Brian _______________________________________________ Pulp-dev mailing list [email protected] https://www.redhat.com/mailman/listinfo/pulp-dev
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