e6e4a04b10
This blueprint adds support for dynamically generating iPXE configuration files when booting a node. Change-Id: I443d969638ce56beb5bc9b8484b65fdac4bc469a
6.2 KiB
iPXE Dynamic Configuration
https://blueprints.launchpad.net/ironic/+spec/ipxe-dynamic-config
This blueprint adds support for dynamically generating iPXE configuration files when booting a node.
Problem description
The current iPXE support depends on configuration files to be cached
on the disk. This creates a dependency between a given
ironic-conductor and a given node (even without a conductor
lock on a node) because that ironic-conductor is the only
one able to boot that node. This also makes take-over more complicated
because the new ironic-conductor will need to regenerate
the iPXE configuration files for the new nodes it's now managing and
update the DHCP server accordingly.
Proposed change
The proposed implementation consists of creating a new
Driver Vendor Passthru method called
ipxe_config that will dynamically generate the iPXE
configuration files for a given node UUID or mac address depending on
the node's provision state.
When Neutron is used with iPXE enabled, it will configure the DHCP
server to make a request to the Driver Vendor Passthru
endpoint using the node's UUID when booting a node, e.g:
http://<Ironic API Address>:6385/v1/drivers/<driver_name>/vendor_passthru/ipxe_config?node_uuid=<node UUID>Ironic will then check the provision_state of the node
and generate the iPXE configuration file for that state. Say, the node
provision_state is DEPLOYING, we then will return an iPXE
configuration to boot the deploy ramdisk and kernel. If the node
provision_state is ACTIVE, we then return an iPXE
configuration to boot from the image ramdisk and kernel (If local boot
and/or full disk image is not specified). For an unknown
provision_state we just return an iPXE configuration file
that prints out an error explaining the problem on the node's console
log and a warning message in the Ironic log.
If an operator wants to have an external DHCP server (standalone
version) but still benefit from dynamically generated iPXE script files
(instead of using static files) it will be possible by making the same
Driver Vendor Passthru endpoint to support passing the MAC
address of one of the node's port as parameter, e.g:
http://<Ironic API Address>:6385/v1/drivers/<driver_name>/vendor_passthru/ipxe_config?port_address=<port address>When scripting iPXE allows expanding variables
so that an operator can create a single iPXE script pointing to the
Ironic API (and expanding the ${mac} variable) when
configuring their external DHCP server allowing them to have dynamically
generated iPXE configuration for their environment even when Neutron is
not used.
This work can get even more powerful when the images are set to boot
from http1, as then the iPXE drive won't need
to save any state on the disk. As a future work, it would be also
possible to add support for creating a Swift Temporary URL
when booting images being served by Glance with a
Swift storage backend.
Alternatives
Continue doing what we are doing, generate the configuration files and saving it to the disk.
Data model impact
None
State Machine Impact
None
REST API impact
A new Driver Vendor Passthru method called
ipxe_config that supports GET HTTP.
Client (CLI) impact
None
RPC API impact
Currently the RPC method for vendor_passthru and
driver_vendor_passthru returns a tuple with the return
value and a boolean indicating if the method is asynchronous. We will
need another flag to indicate if the value should be returned as a
static file that will be served by the Ironic API instead of a response
body message.
Driver API impact
None
Nova driver impact
None
Security impact
The new Vendor Passthru method endpoint needs to be part
of the public API, so that iPXE can get the configuration file from
without authentication. This is the same as the methods
heartbeat or lookup for the agent driver2.
Other end user impact
None
Scalability impact
A stateless driver can scale better since it won't depend on any information to be saved on the local conductor.
Performance Impact
None
Other deployer impact
None
Developer impact
None
Implementation
Assignee(s)
- Primary assignee:
-
lucasagomes <lucasagomes@gmail.com>
Other contributors:
Work Items
- Create the new
ipxe_configmethod for the PXEVendorPassthru interface. - Change the PXE configuration options passed to the DHCP server to
point to the
v1/drivers/<driver name>/vendor_passthru/ipxe_config?node_uuid=<node UUID>endpoint in the Ironic API instead of pointing to the URL to download the boot.ipxe script (the script won't be need anymore and will be deleted). - Extend the
vendor_passthruanddriver_vendor_passthruRPC methods to return a flag indicating whether the return value should be attached to the response object as a file or returned as a response message. - Update the methods
prepare_ramdiskandclean_up_ramdiskfrom the IPXEBoot interface to not attempt to create or delete the iPXE configuration files.
Dependencies
- New
boot interface: This spec is refactoring the boot logic out of the
current Ironic
deploydrivers into a new boot interface.
Testing
Unittests will be added.
Upgrades and Backwards Compatibility
None
Documentation Impact
The iPXE documentation will be updated to reflect the changes made by this spec.