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<div class="moz-cite-prefix">On 2/14/20 1:09 PM, David Davis wrote:<br>
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<div>Grant and I met today to discuss importers and exporters[0]
and we'd like some feedback before we proceed with the design.
To sum up this feature briefly: users can export a repository
version from one Pulp instance and import it to another. </div>
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# Master/Detail vs Core
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<div>So one fundamental question is whether we should use a
Master/Detail approach or just have core control the flow but
call out to plugins to get export formats.</div>
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<div>To give some background: we currently define Exporters (ie
FileSystemExporter) in core as Master models. Plugins extend
this model which allows them to configure or customize the
Exporter. This was necessary because some plugins need to
export Publications (along with repository metadata) while
other plugins who don't have Publications or metadata export
RepositoryVersions.</div>
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<div>The other option is to have core handle the workflow. The
user would call a core endpoint and provide a
RepositoryVersion. This would work because for
importing/exporting, you wouldn't ever use Publications
because metadata won't be used for importing back into Pulp.
If needed, core could provide a way for plugin writers to
write custom handlers/exporters for content types.</div>
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<div>If we go with the second option, the question then becomes
whether we should divorce the concept of Exporters and
import/export. Or do we also switch Exporters from
Master/Detail to core only?</div>
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<div># Foreign Keys</div>
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<div>Content can be distributed across multiple tables (eg
UpdateRecord has UpdateCollection, etc). In our export, we
could either use primary keys (UUIDs) or natural keys to
relate records. The former assumes that UUIDs are unique
across Pulp instances. The safer but more complex alternative
is to use natural keys. This would involve storing a set of
fields on a record that would be used to identify a related
record.</div>
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<div># Incremental Exports</div>
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<div>There are two big pieces of data contained in an export:
the dataset of Content from the database and the artifact
files. An incremental export cuts down on the size of an
export by only exporting the differences. However, when
performing an incremental export, we could still export the
complete dataset instead of just a set of differences
(additions/removals/updates). This approach would be simpler
and it would allow us to ensure that the new repo version
matches the exported repo version exactly. It would however
increase the export size but not by much I think--probably
some number of megabytes at most.</div>
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<p>If its simper, i would go with that. Saving even ~100-200 MB
isn't that big of a deal IMO. the biggest savings is in the RPM
content. <br>
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<div>[0] <a href="https://pulp.plan.io/issues/6134"
moz-do-not-send="true">https://pulp.plan.io/issues/6134</a></div>
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<div>David<br>
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