Fetch service

Short description

A proxy that can be used by Launchpad builders as an alternative to the squid proxy. When used, it keeps track of requests and dependencies for the build.

Detailed description

The fetch service is a proxy service used by Launchpad builders (see Build Farm) that keeps track of dependencies downloaded during a build. This ensures developers have a trustworthy record of all the parts that make up the software being built.

The service contains a set of APIs endpoints that can be distinguished into two groups:

  • Control endpoints (default port 9999): used by Launchpad to manage the fetch service sessions

  • Proxy endpoints (default port 9988): used within the builder to access external resources

The life-cycle of a fetch-service session within Launchpad goes as follows:

  1. Launchpad (specifically, launchpad-buildd-manager) makes a request to the fetch service control endpoint for the creation of a fetch service session, which returns a session ID and a token. Launchpad sends those details to launchpad buildd to be used during the build.

  2. During a build, any external requests go through the fetch service proxy endpoint, using the specific session ID and token. The fetch service keeps track of all requests made during the build to that given session ID.

  3. After the pull-phase or at the end of the build (depending on the configuration of the snap itself within Launchpad), launchpad-buildd makes a request to the fetch service control endpoint to revoke the token, meaning no new external requests can be made during that build.

  4. After the end of the build, when Launchpad gathers the resulting artifacts, Launchpad makes a request to the fetch service control endpoint to gather the metadata from the session (i.e., a file that contains all the requests and dependencies fetched during the build) for the specified session ID.

  5. Launchpad makes a final request to the fetch service control endpoint to end session session ID, which deletes all data for that session that was stored in the fetch service database.

Using the fetch service

Currently, only snaps can use the fetch service.

To do so, a Launchpad admin is required to set the use_fetch_service flag within a snap to true, either in the API or in the UI by accessing the Admin area of a snap.

Requests to use the fetch service shall be made to the Launchpad team through the usual channels (by opening a question, or emailing the team at feedback@launchpad.net).

Fetch service maintainers

The fetch service code itself is not maintained by Launchpad - it is maintained by Canonical’s Starcraft team. Nonetheless, the service was created to be used by Launchpad builders, and that’s currently its purpose.

Launchpad maintains its mojo specs and deployment to its environments.


Git repositories

The following repositories also contain code relevant to how Launchpad uses the fetch service:

Bug trackers


We deploy the fetch service using the specs defined in fetch service mojo specs.


For qastaging deployment, SSH into stg-lp-fetch-service-qastaging@launchpad-bastion-ps5, and run upgrade-qastaging.


For production deployment, SSH into stg-lp-fetch-service@launchpad-bastion-ps5, and run upgrade-production.

Log files


Not set up.


Currently, to access the fetch-service internal logs, one needs to:

  1. SSH into stg-lp-fetch-service-qastaging@launchpad-bastion-ps5.

  2. SSH into the fetch-service juju unit by running juju ssh <unit>, for example juju ssh fetch-service/2.

  3. Run sudo snap logs fetch-service -n 100 -f (where -n sets the number of log lines, and -f keeps up the latest logs up-to-date).


Not set up.

Common support cases

The fetch service is not currently widely used. As such, there haven’t been a lot of support requests made.

More information