opendev/system-config
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Add info on reverse proxy caches

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This includes some basic info on the new mirror host reverse proxy
caches for resources that aren't simple/easy/practical for proper
mirroring.

Change-Id: If71fa6bf1769ef82ab3a4d2c8a5e78005fc6d7e5
This commit is contained in:
Clark Boylan 2017-04-04 09:03:56 -07:00 committed by Ian Wienand
parent f4e3118709
commit fb5391b142
1 changed files with 27 additions and 0 deletions
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doc/source/afs.rst
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@ -398,3 +398,30 @@ If you need to remove a mirror, you can do the following:
vos remove -server afs02.dfw.openstack.org -partition a -id mirror.foo
Reverse Proxy Cache
^^^^^^^^^^^^^^^^^^^
* `modules/openstack_project/templates/mirror.vhost.erb
<https://git.openstack.org/cgit/openstack-infra/system-config/tree/modules/openstack_project/templates/mirror.vhost.erb>`__
Each of the region-local mirror hosts exposes a limited reverse HTTP
proxy on port 8080. These proxies run within the same Apache setup as
used to expose AFS mirror contents. `mod_cache
<https://httpd.apache.org/docs/2.4/mod/mod_proxy.html>`__ is used to
expose a white-listed set of resources (currently just RDO).
Currently they will cache data for up to 24 hours (Apache default)
with pruning performed by ``htcacheclean`` once an hour to keep the
cache size at or under 2GB of disk space.
The reverse proxy is provided because there are some hosted resources
that are not currently able to be practically mirrored. Examples of
this include RDO (rsync from RDO is slow and they update frequently)
and docker images (which require specialized software to run a docker
registry and then sorting out how to run that on a shared filesystem).
Apache was chosen because we already had configuration management in
place for Apache on these hosts. This avoids management overheads of
a completely new service deployment such as Squid or a caching docker
registry daemon.