infra-specs/specs/unified_mirrors.rst

Copyright 2015 Hewlett Packard Enterprise Development Company, L.P.

This work is licensed under a Creative Commons Attribution 3.0
Unported License.
http://creativecommons.org/licenses/by/3.0/legalcode

Unified Mirrors

This spec captures the work necessary to provide multiple mirror types to the openstack build infrastructure, without requiring the creation of a new node for each mirror.

Problem Description

The package mirrors available in our infra regions are python specific, both due to their names (pypi.<region>.openstack.org), and because the mirror is hosted at the root directory of the webserver. This prevents us from reusing the host for different package mirrors.

At the same time, there is new demand for different mirrors, including (but not restricted to) pypi-wheel, EPEL, UCA...

Proposed Change

The existing pypi.<region>.openstack.org mirrors will be renamed to mirror.<region>.openstack.org, and the current existing pypi mirror will be moved into a subdirectory of the http root. Furthermore, each mirror will also be named based on the hosting cloud provider. The eventual goal is URI paths similar to the following:

• http://mirror.<region>.<provider>.openstack.org/pypi
• http://mirror.<region>.<provider>.openstack.org/wheel
• http://mirror.<region>.<provider>.openstack.org/centos
• http://mirror.<region>.<provider>.openstack.org/ubuntu

In order to reduce the complexity and storage requirements of the mirror hosts, the mirror content will be written into AFS. When mirror updates are performed, the AFS volume hosting the mirror will be "released" (that is, replicated into fault-toleranet read-only volumes). Each of the mirror hosts will serve the same content from those read-only volumes, but will be configured with a substantial local cache so that ultimately most content will be served directly from local disk.

Alternative 1: Per-language mirror hosts

Rather than using one host for all mirrors, we could create one host per mirror. This is possible, however it increases the maintenance overhead, consumes unnecessary resources, and introduces additional points of failure.

Alternative 2: In-flight updates of mirrors

Rather than provisioning new hosts, we could live-modify the existing hosts. Building new hosts is more labor intensive, however it results in zero downtime, and also permits us to upgrade the operating system for those instances still running Ubuntu precise.

Alternative 3: The status quo

Rather than creating more mirrors, we can simply maintain the status quo. This discards potential speed improvements from having our own wheel mirrors, and makes our builds vulnerable to downtimes in upstream repositories.

Implementation

Assignee(s)

• Michael Krotscheck (Mirror Rename)
• Greg Haynes (Wheel Mirror)

Support from infra root will be required to provision servers, rsync packages, and update DNS records.

Gerrit Topic

Use the 'unified_mirror' gerrit topics for all patches related to this spec:

git-review -t unified_mirror

Work Items

The following work items will need to be completed in order to facilitate the rename. Goal: http://mirror.<region>.<cloud>.openstack.org/pypi

1. New hosts will be provisioned for each region, and DNS records created, named mirror.<region>.<cloud>.openstack.org. These should all run ubuntu trusty.
2. A new host, mirror-update.openstack.org will be provisioned to run the bandersnatch process. It will write into AFS, and upon the completion of each successful run, it will release the volume to read-only replicas.
3. Each mirror server will be configured to serve files out of AFS via the read-only replica path.
4. The existing pypi_mirror.pp manifest should defer its vhost creation, and data directory location, to its including manifest.
5. A new mirror.pp manifest should be created that provides the new data directory to pypi_mirror.pp, hosted at /pypi. This should be used by an entry in site.pp used by mirror.<region>.<cloud>.openstack.org.
6. Once our new mirror have had a successful puppet run, they should be manually tested to ensure they function correctly.
7. Nodepool slaves should be instructed to use the new mirror urls.
8. Builds should be manually checked to ensure that they are using the new mirrors.
9. The old pypi.<region>.openstack.org hosts should be terminated, as well as their DNS entries.
10. All old mirror references and manifests, should be deleted from system-config.

The following work items will need to be completed in order to create a wheel mirror. Goal: http://mirror.<region>.<cloud>.openstack.org/wheel

1. A new wheel_mirror.pp manifest should be added to mirror.pp to provide room for our built wheels, hosted at /wheel.
2. A wheel build job should be created, to build our wheels from the global upper-constraint requirements and write the output into AFS.
3. A volume release job should be created to release the data to read-write AFS volumes if the wheel update is successful.
4. Our nodepool slaves should be instructed to use the new wheel mirror in addition to our pypi mirror.

Repositories

No new repositories are required.

Servers

• New hosts will be provisioned for each region, named mirror.<region>.<cloud>.openstack.org. These should all run trusty.
• 100-200GB of disk space will need to be provided for an AFS cache. The AFS cache size will be set at 50GB. For mirrors where Cinder is available, a 100GB volume should be provisioned to start with. Where Cinder is not available, a flavor with 200GB of local storage should be used.

DNS Entries

New DNS entries will be required for mirror.<region>.<cloud>.openstack.org. Old DNS entries for pypi.<region>.openstack.org will need to be removed.

Documentation

Existing documentation in the infra manual should be updated to indicate new mirror locations.

Security

No security concerns anticipated other than those already addressed.

Testing

Manual testing of the new mirrors should be performed before they are used.

Dependencies

There are no dependencies.