Architecture¶

Pulp’s architecture has three components to it: a REST API, a content serving application, and the tasking system. Each component can be horizontally scaled for both high availability and/or additional capacity for that part of the architecture.

REST API¶

Pulp’s REST API is a Django application that runs under any WSGI server. It serves the following things:

The REST API hosted at /pulp/api/v3/
The browse-able documentation at /pulp/api/v3/docs/
Any viewsets or views provided by plugins
Static content used by Django, e.g. images used by the browse-able API. This is not Pulp content.

Note

A simple, but limited way to run the REST API as a standalone service using the built-in Django runserver. The pulpcore-manager command is manage.py configured with the DJANGO_SETTINGS_MODULE="pulpcore.app.settings". Run the simple webserver with:

$ pulpcore-manager runserver 24817

The REST API can be deployed with any any WSGI webserver like a normal Django application. See the Django deployment docs for more information.

Content Serving Application¶

An aiohttp.server based application that serves content to clients. The content could be Artifacts already downloaded and saved in Pulp, or on-demand content units. When serving on-demand content units the downloading also happens from within this component as well.

Note

Pulp installs a script that lets you run the content serving app as a standalone service as follows::

$ pulp-content

The content serving application can be deployed like any aiohttp.server application. See the aiohttp Deployment docs for more information.

Tasking System (current default)¶

Pulp’s tasking system has two components: a resource manager and workers, all of which are run using rq.

Worker

Pulp workers perform most tasks “run” by the tasking system including long-running tasks like synchronize and short-running tasks like a Distribution update. Each worker handles one task at a time, and additional workers provide more concurrency. Workers auto-name and are auto-discovered, so they can be started and stopped without notifying Pulp.

Resource Manager

A different type of Pulp worker that plays a coordinating role for the tasking system. You must run exactly one of these for Pulp to operate correctly. The resource-manager is identified by configuring using exactly the name resource-manager with the --resource-manager option.

N resource-manager rq processes can be started with 1 being active and N-1 being passive. The N-1 will exit and should be configured to auto-relaunch with either systemd, supervisord, or k8s.

Note

Pulp serializes tasks that are unsafe to run in parallel, e.g. a sync and publish operation on the same repo should not run in parallel. Generally tasks are serialized at the “resource” level, so if you start N workers you can process N repo sync/modify/publish operations concurrently.

Distributed Tasking System (tech-preview)¶

Pulp provides an alternative implementation for the tasking system as a drop in replacement.

Note

This distributed resource-manager free tasking system is still in tech-preview.

The major differences to the prior tasking system is, that tasks are not routed through a resource-manager, and not queued into rq queues. So all necessary information about tasks is stored in Pulp’s Postgres database as a single source of truth. This version of the tasking system consists of a single pulpcore-worker component consequently, and can be scaled by increasing the number of worker processes. Each worker can handle one task at a time, and idle workers will lookup waiting and ready tasks in a distributed manner. If no ready tasks were found a worker enters a sleep state to be notified, once new tasks are available or resources are released.

While this tasking system is designed with better scalability and high availability in mind, it provides the same interfaces to the user via the REST API.

To switch to using this worker model, one needs to set USE_NEW_WORKER_STYLE=True in pulp settings, and start the worker processes via pulpcore-worker instead of calling rq.

Note

Pulp serializes tasks that are unsafe to run in parallel, e.g. a sync and publish operation on the same repo should not run in parallel. Generally tasks are serialized at the “resource” level, so if you start N workers you can process N repo sync/modify/publish operations concurrently.

In case your tasking system get’s jammed, there is a guide to help :ref:debugging_tasks.

Static Content¶

When browsing the REST API or the browsable documentation with a web browser, for a good experience, you’ll need static content to be served.

In Development¶

If using the built-in Django webserver and your settings.yaml has DEBUG: True then static content is automatically served for you.

In Production¶

Collect all of the static content into place using the collectstatic command. The pulpcore-manager command is manage.py configured with the DJANGO_SETTINGS_MODULE="pulpcore.app.settings". Run collectstatic as follows:

$ pulpcore-manager collectstatic