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<div class="moz-cite-prefix">On 07/01/14 06:25, Susaant Kondapaneni
wrote:<br>
</div>
<blockquote
cite="mid:CALR54ZMV_z6OoqVDUbcVigON8+3mnD1Vns+AcNWbC4Go3bREAw@mail.gmail.com"
type="cite">
<div dir="ltr">
<div>Hi Steve,</div>
<div><br>
</div>
<div>I am trying to understand the software config
implementation. Can you clarify the following:</div>
<div><br>
</div>
<div>i. To use Software config and deploy in a template,
instance resource MUST always be accompanied by user_data.
User_data should specify how to bootstrap CM tool and signal
it. Is that correct?</div>
<div><br>
</div>
</div>
</blockquote>
Yes, currently the user_data contains cfn-init formatted metadata
which tells os-collect-config how to poll for config changes. What
happens when new config is fetched depends on the os-apply-config
templates and os-refresh-config scripts which are already on that
image (or set up with cloud-init).<br>
<blockquote
cite="mid:CALR54ZMV_z6OoqVDUbcVigON8+3mnD1Vns+AcNWbC4Go3bREAw@mail.gmail.com"
type="cite">
<div dir="ltr">
<div>ii. Supposing we were to use images which do not have
cloud-init packaged in them, (and a custom CM tool that won't
require bootstrapping on the instance itself), can we still
use software config and deploy resources to deploy software on
such instances? </div>
<div><br>
</div>
</div>
</blockquote>
Currently os-collect-config is more of a requirement than
cloud-init, but as Clint said cloud-init does a good job of boot
config so you'll need to elaborate on why you don't want to use it.<br>
<blockquote
cite="mid:CALR54ZMV_z6OoqVDUbcVigON8+3mnD1Vns+AcNWbC4Go3bREAw@mail.gmail.com"
type="cite">
<div dir="ltr">
<div>iii. If ii. were possible who would signal the deployment
resource to indicate that the instance is ready for the
deployment? <br>
</div>
</div>
</blockquote>
os-collect-config polls for the deployment data, and triggers the
resulting deployment/config changes. One day this may be performed
by a different agent like the unified agent that has been discussed.
Currently os-collect-collect polls via a heat-api-cfn metadata call.
This too may be done in any number of ways in the future such as
messaging or long-polling.<br>
<br>
So you *could* consume the supplied user_data to know what to poll
for subsequent config changes without cloud-init or
os-collect-config, but you would have to describe what you're doing
in detail for us to know if that sounds like a good idea.<br>
<br>
<blockquote
cite="mid:CALR54ZMV_z6OoqVDUbcVigON8+3mnD1Vns+AcNWbC4Go3bREAw@mail.gmail.com"
type="cite">
<div dir="ltr">
<div><br>
</div>
<div>Thanks</div>
<div>Susaant</div>
</div>
<div class="gmail_extra">
<br>
<br>
<div class="gmail_quote">On Fri, Dec 13, 2013 at 3:46 PM, Steve
Baker <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:sbaker@redhat.com" target="_blank">sbaker@redhat.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> I've been working on
a POC in heat for resources which perform software
configuration, with the aim of implementing this spec <a
moz-do-not-send="true"
href="https://wiki.openstack.org/wiki/Heat/Blueprints/hot-software-config-spec"
target="_blank">https://wiki.openstack.org/wiki/Heat/Blueprints/hot-software-config-spec</a><br>
<br>
The code to date is here:<br>
<a moz-do-not-send="true"
href="https://review.openstack.org/#/q/topic:bp/hot-software-config,n,z"
target="_blank">https://review.openstack.org/#/q/topic:bp/hot-software-config,n,z</a><br>
<br>
What would be helpful now is reviews which give the
architectural approach enough of a blessing to justify
fleshing this POC out into a ready to merge changeset.<br>
<br>
Currently it is possible to:<br>
- create templates containing OS::Heat::SoftwareConfig and
OS::Heat::SoftwareDeployment resources<br>
- deploy configs to OS::Nova::Server, where the deployment
resource remains in an IN_PROGRESS state until it is
signalled with the output values<br>
- write configs which execute shell scripts and report
back with output values that other resources can have
access to.<br>
<br>
What follows is an overview of the architecture and
implementation to help with your reviews.<br>
<br>
REST API<br>
========<br>
Like many heat resources, OS::Heat::SoftwareConfig and
OS::Heat::SoftwareDeployment are backed by "real"
resources that are invoked via a REST API. However in this
case, the API that is called is heat itself.<br>
<br>
The REST API for these resources really just act as
structured storage for config and deployments, and the
entities are managed via the REST paths
/{tenant_id}/software_configs and
/{tenant_id}/software_deployments:<br>
<a moz-do-not-send="true"
href="https://review.openstack.org/#/c/58878/7/heat/api/openstack/v1/__init__.py"
target="_blank"> </a><a moz-do-not-send="true"
href="https://review.openstack.org/#/c/58878/"
target="_blank">https://review.openstack.org/#/c/58878/</a><br>
RPC layer of REST API:<br>
<a moz-do-not-send="true"
href="https://review.openstack.org/#/c/58877/"
target="_blank">https://review.openstack.org/#/c/58877/</a><br>
DB layer of REST API:<br>
<a moz-do-not-send="true"
href="https://review.openstack.org/#/c/58876"
target="_blank">https://review.openstack.org/#/c/58876</a><br>
heatclient lib access to REST API:<br>
<a moz-do-not-send="true"
href="https://review.openstack.org/#/c/58885"
target="_blank">https://review.openstack.org/#/c/58885</a><br>
<br>
This data could be stored in a less structured datastore
like swift, but this API has a couple of important
implementation details which I think justify it existing:<br>
- SoftwareConfig resources are immutable once created.
There is no update API to modify an existing config. This
gives confidence that a config can have a long lifecycle
without changing, and a certainty of what exactly is
deployed on a server with a given config.<br>
- Fetching all the deployments and configs for a given
server is an operation done repeatedly throughout the
lifecycle of the stack, so is optimized to be able to do
in a single operation. This is called by using the
deployments index API call,
/{tenant_id}/software_deployments?server_id=<server_id>.
The resulting list of deployments include the their
associated config data[1].<br>
<br>
OS::Heat::SoftwareConfig resource<br>
=================================<br>
OS::Heat::SoftwareConfig can be used directly in a
template, but it may end be more frequently used in a
resource provider template which provides a resource aimed
at a particular configuration management tool.<br>
<a moz-do-not-send="true"
href="http://docs-draft.openstack.org/79/58879/7/check/gate-heat-docs/911a250/doc/build/html/template_guide/openstack.html#OS::Heat::SoftwareConfig"
target="_blank">http://docs-draft.openstack.org/79/58879/7/check/gate-heat-docs/911a250/doc/build/html/template_guide/openstack.html#OS::Heat::SoftwareConfig</a><br>
The contents of the config property will depend on the CM
tool being used, but at least one value in the config map
will be the actual script that the CM tool invokes. An
inputs and outputs schema is also defined here. The group
property is used when the deployments data is actually
delivered to the server (more on that later).<br>
<br>
Since a config is immutable, any changes to a
OS::Heat::SoftwareConfig on stack update result in
replacement.<br>
<br>
OS::Heat::SoftwareDeployment resource<br>
=====================================<br>
OS::Heat::SoftwareDeployment joins a
OS::Heat::SoftwareConfig resource with a OS::Nova::Server
resource. It allows server-specific input values to be
specified that map to the OS::Heat::SoftwareConfig inputs
schema. Output values that are signaled to the deployment
resource are exposed as resource attributes, using the
names specified in the outputs schema. The
OS::Heat::SoftwareDeployment resource remains in an
IN_PROGRESS state until it receives a signal (containing
any outputs) from the server.<br>
<a moz-do-not-send="true"
href="http://docs-draft.openstack.org/79/58879/7/check/gate-heat-docs/911a250/doc/build/html/template_guide/openstack.html#OS::Heat::SoftwareDeployment"
target="_blank">http://docs-draft.openstack.org/79/58879/7/check/gate-heat-docs/911a250/doc/build/html/template_guide/openstack.html#OS::Heat::SoftwareDeployment</a><br>
<br>
A deployment has its own actions and statuses that are
specific to what a deployment does, and
OS::Heat::SoftwareDeployment maps this to heat resource
statuses and actions:<br>
actions:<br>
DEPLOY -> CREATE<br>
REDEPLOY -> UPDATE<br>
UNDEPLOY -> DELETE<br>
<br>
status (these could use some bikeshedding):<br>
WAITING -> IN_PROGRESS<br>
RECEIVED -> COMPLETE<br>
FAILED -> FAILED<br>
<br>
In the config outputs schema there is a special flag for
error_output. If the signal response contains any value
for any of these error_output outputs then the deployment
resource is put into the FAILED state.<br>
<br>
The SoftwareDeployment class subclasses SignalResponder
which means that a SoftwareDeployment creates an
associated user and ec2 keypair. Since the
SoftwareDeployment needs to use the resource_id for the
deployment resource uuid, the user_id needs to be stored
in resource-date instead. This non-wip change enables
that:<br>
<a moz-do-not-send="true"
href="https://review.openstack.org/#/c/61902/"
target="_blank">https://review.openstack.org/#/c/61902/</a><br>
<br>
During create, the deployment REST API is polled until
status goes from WAITING to RECEIVED. When handle_signal
is called, the deployment is updated via the REST API to
set the status to RECEIVED (or FAILED), along with any
output values that were received.<br>
<br>
One alarming consequence of having a deployments API is
that any tenant user can create a deployment for any
heat-created nova server and that software will be
deployed to that server, which is, um, powerful.<br>
<br>
There will need to be a deployment policy (probably an
OS::Nova::Server property) which limits to scope of what
deployments are allowed on that server. This could default
to deployments in the same stack, but could still allow
deployments from anywhere.<br>
<br>
OS::Nova::Server support<br>
========================<br>
<a moz-do-not-send="true"
href="https://review.openstack.org/#/c/58880"
target="_blank">https://review.openstack.org/#/c/58880</a><br>
A new user_data_format=SOFTWARE_CONFIG is currently used
to denote that this server is configured via software
config deployments. Like user_data_format=HEAT_CFNTOOLS,
nova_utils.build_userdata is used to build the cloud-init
parts required to support software config. However like
user_data_format=RAW anything specified in user_data will
be parsed as cloud-init data. If user_data is multi-part
data then the parts will be appended to the parts created
in nova_utils.build_userdata.<br>
<br>
The agent used currently is os-collect-config. This is
typically configured to poll for metadata from a
particular heat resource via the CFN API using the
configured ec2 keypair. In the current implementation the
resource which is polled is the OS::Nova::Server itself,
since this is the only resource known to exist at server
boot time (deployment resources depend on server
resources, so have not been created yet). The ec2 keypair
comes from a user created implicitly with the server
(similar to SignalResponder resources). This means the
template author doesn't need to include
User/AccessKey/AccessPolicy resources in their templates
just to enable os-collect-config metadata polling.<br>
<br>
Until now, polling the metadata for a resource just
returns the metadata which has been stored in the stack
resource database. This implementation changes metadata
polling to actually query the deployments API to return
the latest deployments data. This means deployment state
can be stored in one place, and there is no need to keep
various metadata stores updated with any changed state.<br>
<br>
An actual template<br>
==================<br>
<a moz-do-not-send="true"
href="http://paste.openstack.org/show/54988/"
target="_blank">http://paste.openstack.org/show/54988/</a><br>
This template contains:<br>
- a config resource<br>
- 2 deployments which deploy that config with 2 different
sets of inputs<br>
- stack outputs which output the results of the
deployments<br>
- a server resource<br>
- an os-refresh-config script delivered via
cloud-config[2] which executes config scripts with
deployment inputs and signals outputs to the provided
webhook.<br>
<br>
/opt/stack/os-config-refresh/configure.d/55-heat-config-bash
is a hook specific for performing configuration via shell
scripts, and only acts on software config which has
group=Heat::Shell. Each configuration management tool will
have its own hook, and will act on its own group
namespace. Each configuration management tool will also
have its own way of passing inputs and outputs. The hooks
job is to invoke the CM tool with the given inputs and
script, then extract the outputs and signal heat.<br>
<br>
The server needs to have the CM tool and the hook already
installed, either by building a golden image or by using
cloud-config during boot.<br>
<br>
Next steps<br>
==========<br>
There is a lot left to do and I'd like to spread the
development load. What happens next entirely depends on
feedback to this POC, but here is my ideal scenario:<br>
- any feedback which causes churn on many of the current
changes I will address<br>
- a volunteer is found to take the REST
API/RPC/DB/heatclient changes and make them ready to merge<br>
- we continue to discuss and refine the resources, the
changes to OS::Nova::Server, and the example shell hook<br>
- volunteers write hooks for different CM tools, Chef and
Puppet hooks will need to be attempted soon to validate
this approach.<br>
<br>
Vaguely related changes include:<br>
- Some solution for specifying cloud-init config, either
the intrinsic functions or cloud-init heat resources<br>
- Some heatclient file inclusion mechanism - writing that
python hook in a heat yaml template was a bit painful ;)<br>
<br>
Trying for yourself<br>
===================<br>
- Using diskimage-builder, create an ubuntu image with
tripleo-image-elements os-apply-config, os-refresh-config
and os-collect-config<br>
- Create a local heat branch containing <a
moz-do-not-send="true"
href="https://review.openstack.org/#/q/topic:bp/cloud-init-resource,n,z"
target="_blank">https://review.openstack.org/#/q/topic:bp/cloud-init-resource,n,z</a>
and <a moz-do-not-send="true"
href="https://review.openstack.org/#/q/topic:bp/hot-software-config,n,z"
target="_blank">https://review.openstack.org/#/q/topic:bp/hot-software-config,n,z</a><br>
- launch the above template with your created image<br>
<br>
cheers<br>
<br>
[1] <a moz-do-not-send="true"
href="https://review.openstack.org/#/c/58877/7/heat/engine/api.py"
target="_blank">https://review.openstack.org/#/c/58877/7/heat/engine/api.py</a><br>
[2] This relies on these not-merged intrinsic functions <a
moz-do-not-send="true"
href="https://review.openstack.org/#/q/topic:bp/cloud-init-resource,n,z"
target="_blank">https://review.openstack.org/#/q/topic:bp/cloud-init-resource,n,z</a>
</div>
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