[openstack-dev] [heat] Sofware Config progress

Steve Baker sbaker at redhat.com
Thu Jan 16 03:46:28 UTC 2014

On 15/01/14 06:21, Clint Byrum wrote:
> Hey Steve, it has taken me about a month to get enough time to go
> through this. Thanks for doing it, comments in-line.
> Excerpts from Steve Baker's message of 2013-12-13 15:46:48 -0800:
>> I've been working on a POC in heat for resources which perform software
>> configuration, with the aim of implementing this spec
>> https://wiki.openstack.org/wiki/Heat/Blueprints/hot-software-config-spec
>> The code to date is here:
>> https://review.openstack.org/#/q/topic:bp/hot-software-config,n,z
>> 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.
>> Currently it is possible to:
>> - create templates containing OS::Heat::SoftwareConfig and
>> OS::Heat::SoftwareDeployment resources
>> - deploy configs to OS::Nova::Server, where the deployment resource
>> remains in an IN_PROGRESS state until it is signalled with the output values
>> - write configs which execute shell scripts and report back with output
>> values that other resources can have access to.
>> What follows is an overview of the architecture and implementation to
>> help with your reviews.
>> ========
>> 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.
>> 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:
>> <https://review.openstack.org/#/c/58878/7/heat/api/openstack/v1/__init__.py>https://review.openstack.org/#/c/58878/
>> RPC layer of REST API:
>> https://review.openstack.org/#/c/58877/
>> DB layer of REST API:
>> https://review.openstack.org/#/c/58876
>> heatclient lib access to REST API:
>> https://review.openstack.org/#/c/58885
>> 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:
>> - 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.
>> - 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].
> I'm curious if we can use the existing Metadata for this. That would
> be attractive to me, as that would keep the software deployments data
> available to CFN-API based tools. For instance ohai can read the CFN
> API already, but not the Heat native in-instance API (since such a thing
> basically does not exist).
> I'm not suggesting they should both work at the same time. But I can't
> see a time where they need to, so it seems logical enough to me to just
> have the deployments bit populate the resource metadata, albeit with a
> bit more structure. I understand that means updating resource metadata
> after booting the server which may be the very reason not having them be
> the same thing is simpler.
I *think* you've just describe exactly how it works. There is no
Metadata property in the HOT spec, but it is still in the model and
polling metadata via cfn-api is how the instance triggers deployment
work.  One important point is that only the metadata for the server
resource needs to be polled, since this returns the deployment data for
all the deployments on that server.
>> OS::Heat::SoftwareConfig resource
>> =================================
>> 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.
>> http://docs-draft.openstack.org/79/58879/7/check/gate-heat-docs/911a250/doc/build/html/template_guide/openstack.html#OS::Heat::SoftwareConfig
>> 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).
> Can you elaborate on "the actual script that the CM tool invokes" ?
In this context it means the CM tool's own configuration syntax, such as
a puppet manifest or a chef recipe.
> I have an extremely strong desire to never embed script code in an
> orchestration template as it quickly becomes a quagmire of formatting
> problems and poorly defined interfaces, IMO. 
Totally agreed, that is why I've been sidetracked recently on
implementing the get-file blueprint[1]. It is an inclusion mechanism for
getting non-heat syntax content from their own files into heat requests
using a new intrinsic function get_file.
> Also my whole reason for
> doing golden image based deployment is to have code all live in the
> image and stay immutable through the deployed servers' life time.
> So I want to make sure I don't _have_ to do the script for some reason.
No, you don't have to. For tools which just need a configuration data
structure like OAC then that data structure would be the "script" in
that case.
>> Since a config is immutable, any changes to a OS::Heat::SoftwareConfig
>> on stack update result in replacement.
>> OS::Heat::SoftwareDeployment resource
>> =====================================
>> 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.
>> http://docs-draft.openstack.org/79/58879/7/check/gate-heat-docs/911a250/doc/build/html/template_guide/openstack.html#OS::Heat::SoftwareDeployment
>> 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:
>> actions:
>> status (these could use some bikeshedding):
>> 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.
>> 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:
>> https://review.openstack.org/#/c/61902/
>> 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.
>> 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.
> Seems like there is a whole policy can of worms there that all OpenStack
> services probably need to address. AFAIK, any same-tenant user can just
> delete any other user in the same tenant's servers, right? I'm sure
> somebody with Keystone knowledge (I'm looking at you Mr. Hardy) would be
> able to tell us if such things exist now and whether or not we could
> make a stronger bond between user and stack.
Maybe for implementation zero we punt on the policy and add a check
which says a deployment resource must exist in the same stack as the
server resource (although it would be nice to support deployment and
server being in the same nested stack tree).
>> 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.
>> OS::Nova::Server support
>> ========================
>> https://review.openstack.org/#/c/58880
>> 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.
>> 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.
> \o/
>> 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.
> I do like that very much. :)
>> An actual template
>> ==================
>> http://paste.openstack.org/show/54988/
>> This template contains:
>> - a config resource
>> - 2 deployments which deploy that config with 2 different sets of inputs
>> - stack outputs which output the results of the deployments
>> - a server resource
>> - an os-refresh-config script delivered via cloud-config[2] which
>> executes config scripts with deployment inputs and signals outputs to
>> the provided webhook.
> You have demonstrated exactly what I need here. One config definition, two
> deployments of it on the same server with different parameters.  Huzzah!
> I'm a little confused how the config.script gets access to $bar and $foo
> though. ?
In http://paste.openstack.org/show/54988/
<http://paste.openstack.org/show/54988/#120> the orc script on line 120
takes the
deployment inputs and builds the shell environment from that.  Hooks for
different CM tools would do something else, such as building up a
invocation which transforms the inputs to invocation parameters.
>> /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.
>> 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.
>> Next steps
>> ==========
>> 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:
>> - any feedback which causes churn on many of the current changes I will
>> address
>> - a volunteer is found to take the REST API/RPC/DB/heatclient changes
>> and make them ready to merge
> Using this is a mid-term goal for me, but the Tuskar devs would probably
> love to drop my old terrible merge.py and start working on translating
> the TripleO templates to using this. So you will find a mid-term
> volunteer in me, but you might find a sooner volunteer in them. :)
I'd be happy to help out if anyone decides to tackle this.

>> - we continue to discuss and refine the resources, the changes to
>> OS::Nova::Server, and the example shell hook
>> - volunteers write hooks for different CM tools, Chef and Puppet hooks
>> will need to be attempted soon to validate this approach.
>> Vaguely related changes include:
>> - Some solution for specifying cloud-init config, either the intrinsic
>> functions or cloud-init heat resources
>> - Some heatclient file inclusion mechanism - writing that python hook in
>> a heat yaml template was a bit painful ;)
> This has been an open question for a long time. Absent golden images, I
> think you just need a simple way to express where to fetch the hooks from.
> That could be hidden behind the SoftwareConfig resource so that the url
> has a default where the cloud operator has put tools. Users could then
> just override that url when they want to write their own hooks.
So one thing which has moved on since I wrote this email is that the
cloud-config intrinsic functions have been ditched, and replaced with
cloud-config SoftwareConfig resources [2]. These are for boot-only
config, so instead of a deployment resource. I'll demonstrate how this
works at a later date, but this could fulfill the above case either by
referencing long-lived software config resources which contain the
hooks, or by defining the config resource in your template and pulling
in the hook with a get_file call to a URL.
>> Trying for yourself
>> ===================
>> - Using diskimage-builder, create an ubuntu image with
>> tripleo-image-elements os-apply-config, os-refresh-config and
>> os-collect-config
>> - Create a local heat branch containing
>> https://review.openstack.org/#/q/topic:bp/cloud-init-resource,n,z and
>> https://review.openstack.org/#/q/topic:bp/hot-software-config,n,z
>> - launch the above template with your created image
> At the time you sent this I think I got this working.
When it is easy to consume I'll send out another email describing how to
try this locally.  The hooks need to be hosted somewhere - I think the
best place for now might be the heat-templates repo. I'll attempt to
come up with a directory structure to contain all the appropriate
templates, hooks, dib elements, READMEs and examples.
> Very excited to help move this forward as much as I can.
Jun Jie Nan has taken over the REST commits [3]. It would be good to get
as much of this as possible into i-2 so reviews on all of the below
would be very helpful.


[1] https://review.openstack.org/#/q/topic:bp/get-file,n,z
[2] https://review.openstack.org/#/c/63214/
[3] https://review.openstack.org/#/q/topic:bp/hot-software-config-rest,n,z

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