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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 Pulp Plugin API 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.