openstack/fuel-specs
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Merge "Copied and updated image based provisioning spec"

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This work is licensed under a Creative Commons Attribution 3.0 Unported
License.
http://creativecommons.org/licenses/by/3.0/legalcode
================================================================
Substitution native OS installation process with image based one
================================================================
https://blueprints.launchpad.net/fuel/+spec/image-based-provisioning [1]_
Problem description
===================
First, we use plenty of customizations of OS installation process. It is not
always possible to customize native OS installers such as debian-installer and
anaconda on that level of customization we need. Besides, supporting
customizations requires engineering resources. If you need to support
just one set of customization scripts instead of two completely different
sets of customizations for anaconda and debian-installer, it requires
2 times less of engineering resources.
Second, assembling root file system from scratch on every node during OS
provisioning takes a lot of time. It is much more effective to build OS root
filesystem just once and then copy it throughout nodes. It is going to take up
to 10 times faster than installation process using so called native installers.
Proposed change
===============
The first aspect of the issue is going to be addressed by implementing fully
customizable python script which is supposed to be an installation agent which
will do nothing more than making disk partitions, retrieving OS images
and copying them on a hard drive.
As far as MOS has plenty of customizations even for core CentOS and Ubuntu
packages, we need to implement building bare OS images from scratch using
anaconda and debootstrap.
Those images are supposed to have cloud-init installed and we
suggest to use cloud-init built-in capabilities to install and configure
puppet and mcollective after first reboot.
In the future we'll probably use diskimage-builder to build custom
OS images based on those which are distributed by Canonical [2]_
and Red Hat [3]_. OpenStack diskimage-builder is a community tool which
is actively developed and potentially can give us a great advantage.
Openstack Ironic nowadays seems to be mature enough to be used as a
provisioning tool instead of Cobbler. Ironic's scope, however, is strictly
limited to cloud environments. It is not going to support hardware without IPMI
as well as supporting disk partitioning and other important stuff. Besides,
Ironic python agent and Ironic agent driver are not
production ready yet. As a result, we suggest to
implement disk image based provisioning process mostly on the agent
side fully independent on Ironic. It means we are going to implement our
own agent partly based on Ironic python agent. We also suggest to use Cobbler
as a tool for managing tftp and dhcp services but not for
templating kickstarts.
As far as we are going to use our own OS installation agent and this agent is
supposed to be as simple as possible, we don't need to reboot a node before
starting provisioning. Additionally, this approach does not require
Cobbler capability to reboot a node into a different profile.
Discovery/Installation flow diagram is as follows
::
Nailgun Astute Agent Cobbler
+ + + +
| | | PXE boot |
| | | |
| | | <--------+ |
| | | |
| Discovery data | |
| | | |
| <-----------------------+ | |
| | | |
| Provision task | |
| | | |
| +---------> | | |
| | | |
| Provisioning config |
| | | |
| | +---------> | |
| | | |
| Launch provisioning |
| | | |
| | +---------> | |
| | | |
| | Download image |
| | + |
| | | |
| | Partitioning |
| | + |
| | | |
| | Prepare configdrive |
| | + |
| | | |
| Finish provisioning |
| | | |
| | <---------+ | |
| | | |
| | Disable PXE boot |
| | | |
| | +----------------------> |
| | | |
| | Reboot | |
| | | |
| | +---------> | |
| | | |
| Provisioning task finished| |
| | | |
| <---------+ | | |
+ + + +
Our suggestion is to put all agent related code into fuel-web/fuel_agent
python package and implement provision script as a setuptools entry point:
- /usr/bin/provision
It is supposed to use mcollective agents uploadfile for uploading provision
data (/tmp/provision.json) and then use execute_shell_command for launching
provision. Provision data are supposed to come from nailgun provision
serializer. We'll change it as little as possible. Perhaps only information
about available OS images will be needed to append.
Provision script will make partitions according to configuration, download
OS images, copy them on a hard drive, prepare configdrive and copy
configdrive on a hard drive.
Configdrive is a set of configuration files for cloud-init. We assume puppet
and mcollective will be configured right after first reboot by cloud-init.
So, agent needs to be able to get parameters given in a serialized
provisioning data set and put them into a configdrive in the format that
cloud-init is able to read.
Configdrive is supposed to be put on a separate partition in the end of one of
hard drives on a node during provisioning stage. Configdirve is just a file
system which has at least the following structure
- openstack/latest/meta_data
- openstack/latest/user_data
where user_data is supposed to be a multipart mime file [4]_.
This file will contain puppet and mcollective configurations as well as
the executable script implementing all that stuff which now exists
as a set of cobbler snippets [6]_.
Cloud-init should be configured so as to have so called NoCloud data source as
it's only data source (configdrive). Cloud-init configuration file example
is here [5]_.
Astute provision method will add node records into cobbler, but only to prevent
them to boot into bootstrap mode. When adding a node (a system in term of
cobbler) cobbler creates MAC<->IP binding on DHCP server for a node
and modifies TFTP server configuration creating enforcing a node to boot
into installer OS (anaconda or debian-installer). We are planning not to reboot
a node until provisioning process is done. Then we will send an additional RPC
call to cobbler so as to modify TFTP server configuration in such a way to
boot a node with chain loader which tries to find hard drives and boot a
node from first of them. Astute provision method should be re-written so as
to run provision script on nodes and provide this script with serialized
provisioning data generated by nailgun.
We are planning to add provision method radio button on "Settings" tab of
Fuel web interface, so as to make it possible for user to choose between two
provisioning methods "Classic" (anaconda or debian-installer) or "Image"
(copying images on a hard drive). It is also planned to extend cluster
attributes with the the information about available OS images
which are supposed to be built and put on ISO.
Alternatives
------------
Another possible way is to integrate Ironic into Fuel. Why not? Because Ironic
has a very specific scope which is more about cloud environments when a node
is provisioned and leased by a tenant for a while and then it is supposed to
be returned to repeat that cycle again. This very specific use case makes
Ironic tightly limited in its capabilities. For example, Ironic assumes all
partitioning related stuff will be encapsulated either into an image itself or
into the configuration stage (not provisioning stage). Ironic also is not going
to support OS agent based power management (only IPMI, ILO, DRAC, etc.) That is
why it is better to adderess those issues Fuel currently has that are related
to provisioning customizations independently on Ironic.
Placing partition table into an OS image is going to be a part of DIB
capabilities. Currently cloud OS image is just an image of root file system.
But what if OS image would be an image of a block device with partition table
inside it. It is possible if you use logical volumes which are unlike plain
primary partitions extendable. During image building you create logical volume
which suits exactly the size of unextended root file system and then after
reboot cloud-init will create other primary partitions, place there physical
volumes, attach those physical volumes to root volume group and then extend
root logical volume and extend root file system.
Data model impact
-----------------
* Serialized provisioning data format will be changed so as to contain
information about available OS images.
* It is planned to append provision_metadata json field into nailgun
release database model.
REST API impact
---------------
None
Upgrade impact
--------------
This change assumes that bootstrap-2 distro and bootstrap-2 profile
will be created in Cobbler. bootstrap-2 distro will be bound to initramfs
containing fuel_agent. This bootstrap-2 profile will be used for
the default Cobbler system. It is supposed that upgrade script will also put
two OS images into /var/www/nailgun/targetimages so as to make provision
agent able to download them from a master node. Upgrade script will also
make database migration in order to add provision_metadata json field into
release database model. And it also will patch nailgun provision serializer.
It will be possible to use both cobbler based provisioning scheme or
image based provisioning scheme for different clusters.
Security impact
---------------
None
Notifications impact
--------------------
None
Other end user impact
---------------------
Probably provisioning progress bar is better to be removed
at all as it is going to take as much time as reboot
stage usually takes. Another point is that
we are going to add a radio button on the settings
tab of Fuel UI where user can
choose provison method: image based or classic
(a.k.a anaconda or debian-installer based).
Performance Impact
------------------
Provisioning process is going to take much less time than it usually
takes at the moment.
Other deployer impact
---------------------
As far as we are going to include Ubuntu and Centos OS bare images into ISO,
it is going to become around 700M bigger.
Developer impact
----------------
Probably UI team cooperation will be necessary to remove provisioning
progress bar if it'll be appropriate.
Implementation
==============
Assignee(s)
-----------
Primary assignee:
<vkozhukalov@mirantis.com>
<agordeev@mirantis.com>
Work Items
----------
- Create make scripts for building bare OS images (Centos and Ubuntu)
from scratch and for putting those images into ISO. (Iteration 1)
- Re-implement in terms of cloud-init all that stuff which is currently
implemented in terms of Cobbler snippets. (Iteration 1)
- Create provisioning agent script. (Iteration 1)
* partitioning
* downloading and copying OS image
* preparing and copying configdrive
- Testing and debugging. (Iteration 2)
* add image based provision case into system tests
* make functional tests and integrate them into Fuel CI
- Create upgrade module so as to introduce this feature on
an existing master node. (Iteration 2)
- Create documentation according to this feature
Dependencies
============
None
Testing
=======
Testing approach
- Create VM or allocate hardware node.
- Deploy tftp + pxelinux and configure pxelinux with bootstrap ramdisk
as a default item. Bootstrap ramdisk should contain provisioning script.
- Prepare a set of testing provisioning configurations similar to ones
generated by provisioning serialier in nailgun.
- Run provision script with a set of different configurations one by one,
comparing obtained state with required one.
Testing is supposed to be implemented according to this document [7]_
Acceptance criteria
- OS images built from scratch using MOS repositories must be
available via http on Fuel master node ('http://master_ip:8080/targetimages')
- After master node upgrade Cobbler must have one additional distro
bootstrap-2 and one additional profile bootstrap-2 which are supposed to
provide ramdisk with built-in fuel agent.
- It must be possible to choose one of two provisioning options "cobbler based"
and "image based". Provision method is supposed to be bound to release
database model.
- During image based provisioning fuel agent must make an appropriate
partitioning scheme on a node according to the partitioning data, which is
supposed to have the same format as it currently has.
- Once provisioning process is done, cloud-init must perform initial node
configuration including at least but not limited to network, ssh,
puppet and mcollective, so to make it possible to launch deployment process
on a node.
Documentation Impact
====================
It will be necessary to re-write those parts of Fuel documentation
which mention cobbler and provisioning.
References
==========
.. [1] https://blueprints.launchpad.net/fuel/+spec/image-based-provisioning
.. [2] http://cloud-images.ubuntu.com/
.. [3] http://openstack.redhat.com/Image_resources
.. [4] https://help.ubuntu.com/community/CloudInit
.. [5] http://bazaar.launchpad.net/~cloud-init-dev/cloud-init/trunk/view/head:/config/cloud.cfg
.. [6] https://etherpad.openstack.org/p/BOwAMY9pqy
.. [7] http://docs.mirantis.com/fuel-dev/devops.html

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tox.ini
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@ -8,7 +8,7 @@ usedevelop = True
setenv = VIRTUAL_ENV={envdir}
install_command = pip install -U {opts} {packages}
deps = -r{toxinidir}/requirements.txt
commands = python setup.py testr --slowest --testr-args='{posargs}'
commands = python setup.py testr --slowest --testr-args='{posargs:}'
[testenv:venv]
commands = {posargs}