openstack
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ironic
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Add documentation for proxies usage with IPA 

This change adds documentation on setting proxy properties that will
be used by IPA ramdisk to download a disk image.

Closes-bug: #1526222

Change-Id: Ib640da7304e8a5779e74e1f15898229b6f772b11
This commit is contained in:
Vladyslav Drok 2015-11-27 18:15:18 +02:00
parent 37a3486919
commit 26922806ac
1 changed files with 58 additions and 1 deletions
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59
doc/source/drivers/ipa.rst
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@ -43,7 +43,64 @@ image to fit in the node's memory.
.. todo: explain configuring swift for temporary URL's
Requirements
~~~~~~~~~~~~
------------
Using IPA requires it to be present and configured on the deploy ramdisk, see
:ref:`BuildingDeployRamdisk` for details.
Using proxies for image download in agent drivers
=================================================
Overview
--------
IPA supports using proxies while downloading the user image. For example, this
could be used to speed up download by using caching proxy.
Steps to enable proxies
-----------------------
#. Configure the proxy server of your choice (for example
`Squid <http://www.squid-cache.org/Doc/>`_,
`Apache Traffic Server <https://docs.trafficserver.apache.org/en/latest/index.html>`_).
This will probably require you to configure the proxy server to cache the
content even if the requested URL contains a query, and to raise the maximum
cached file size as images can be pretty big. If you have HTTPS enabled in
swift (see `swift deployment guide <http://docs.openstack.org/developer/swift/deployment_guide.html>`_),
it is possible to configure the proxy server to talk to swift via HTTPS
to download the image, store it in the cache unencrypted and return it to
the node via HTTPS again. Because the image will be stored unencrypted in
the cache, this approach is recommended for images that do not contain
sensitive information. Refer to your proxy server's documentation to
complete this step.
#. Set ``[glance]swift_temp_url_cache_enabled`` in the ironic conductor config
file to ``True``. The conductor will reuse the cached swift temporary URLs
instead of generating new ones each time an image is requested, so that the
proxy server does not create new cache entries for the same image, based on
the query part of the URL (as it contains some query parameters that change
each time it is regenerated).
#. Set ``[glance]swift_temp_url_expected_download_start_delay`` option in the
ironic conductor config file to the value appropriate for your hardware.
This is the delay (in seconds) from the time of the deploy request (when
the swift temporary URL is generated) to when the URL is used for the image
download. You can think of it as roughly the time needed for IPA ramdisk to
startup and begin download. This value is used to check if the swift
temporary URL duration is large enough to let the image download begin. Also
if temporary URL caching is enabled this will determine if a cached entry
will still be valid when the download starts. It is used only if
``[glance]swift_temp_url_cache_enabled`` is ``True``.
#. Increase ``[glance]swift_temp_url_duration`` option in the ironic conductor
config file, as only non-expired links to images will be returned from the
swift temporary URLs cache. This means that if
``swift_temp_url_duration=1200`` then after 20 minutes a new image will be
cached by the proxy server as the query in its URL will change. The value of
this option must be greater than or equal to
``[glance]swift_temp_url_expected_download_start_delay``.
#. Add one or more of ``image_http_proxy``, ``image_https_proxy``,
``image_no_proxy`` to driver_info properties in each node that will use the
proxy. Please refer to ``ironic driver-properties`` output of the
``agent_*`` driver you're using for descriptions of these properties.