On-Demand Downloading¶
Overview¶
Pulp can sync content in a few modes: 'immediate', 'on_demand', and 'streamed'. Each provides a
different behavior on how and when Pulp acquires content. These are set as the policy attribute
of the Remote performing the sync. Policy is an optional parameter and defaults to
immediate.
immediate¶
When performing the sync, download all Artifacts now. Also download all metadata
now to create the content units in Pulp, associated with the
repository version created by the sync. immediate is the default, and
any plugin providing a sync is expected to implement the immediate mode.
on_demand¶
When performing the sync, do not download any Artifacts now. Download all
metadata now to create the content units in Pulp, associated with the
repository version created by the sync. Clients requesting content
trigger the downloading of Artifacts, which are saved into Pulp to be served to
future clients.
This mode is ideal for saving disk space because Pulp never downloads and stores
Artifacts that clients don't need. Units created from this mode are
on-demand content units<on-demand content>.
streamed¶
When performing the sync, do not download any Artifacts now. Download all
metadata now to create the content units in Pulp, associated with the
repository version created by the sync. Clients requesting content
trigger the downloading of Artifacts, which are not saved into Pulp. This
content will be re-downloaded with each client request.
This mode is ideal for content that you especially don't want Pulp to store over time. For
instance, syncing from a nightly repo would cause Pulp to store every nightly ever produced which
is likely not valuable. Units created from this mode are
on-demand content units<on-demand content>.
Does Plugin X Support 'on_demand' or 'streamed'?¶
Unless a plugin has enabled either the 'on_demand' or 'streamed' values for the policy attribute
you will receive an error. Check that plugin's documentation also.
Note
Want to add on-demand support to your plugin? See the On-Demand Support documentation for more details on how to add on-demand support to a plugin.
Associating On-Demand Content with Additional Repository Versions¶
An on-demand content unit can be associated and unassociated from a repository version just like a normal unit. Note that the original Remote will be used to download content should a client request it, even as that content is
made available in multiple places.
Warning
Deleting a Remote that was used in a sync with either the on_demand or streamed
options can break published data. Specifically, clients who want to fetch content that a
Remote was providing access to would begin to 404. Recreating a Remote and
re-triggering a sync will cause these broken units to recover again.