Ironic Python Agent¶
Ironic Python Agent (also often called IPA or just agent) is a Python-based agent which handles ironic bare metal nodes in a variety of actions such as inspect, configure, clean and deploy images. IPA is distributed over nodes and runs, inside of a ramdisk, the process of booting this ramdisk on the node.
For more information see the ironic-python-agent documentation.
Starting with the Kilo release all deploy interfaces (except for fake ones) are using IPA. For nodes using the Direct deploy interface, the conductor prepares a swift temporary URL or a local HTTP URL for the image. IPA then handles the whole deployment process: downloading an image from swift, putting it on the machine and doing any post-deploy actions.
Using IPA requires it to be present and configured on the deploy ramdisk, see Building or downloading a deploy ramdisk image
Using proxies for image download¶
When using the Direct deploy, IPA supports using proxies for downloading the user image. For example, this could be used to speed up download by using a caching proxy.
Steps to enable proxies¶
Configure the proxy server of your choice (for example Squid, Apache Traffic Server). 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), 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.
[glance]swift_temp_url_cache_enabledin 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).
[glance]swift_temp_url_expected_download_start_delayoption 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_durationoption 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=1200then 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
Add one or more of
image_no_proxyto driver_info properties in each node that will use the proxy.
Out-of-band vs. in-band power off on deploy¶
After deploying an image onto the node’s hard disk, Ironic will reboot
the machine into the new image. By default this power action happens
in-band, meaning that the ironic-conductor will instruct the IPA
ramdisk to power itself off.
Some hardware may have a problem with the default approach and
would require Ironic to talk directly to the management controller
to switch the power off and on again. In order to tell Ironic to do
that, you have to update the node’s
driver_info field and set the
deploy_forces_oob_reboot parameter with the value of True. For
example, the below command sets this configuration in a specific node:
baremetal node set <UUID or name> --driver-info deploy_forces_oob_reboot=True