[openstack-dev] [heat] Changing the default Server/SoftwareDeployment transports?

Pavlo Shchelokovskyy pshchelokovskyy at mirantis.com
Fri Jan 22 11:26:11 UTC 2016

+1 from me.

Somewhat related, would also be nice to switch the default for
"user_data_format" in OS::Nova::Server to RAW someday, as now it defaults

Best regards,

On Fri, Jan 22, 2016 at 11:38 AM Steven Hardy <shardy at redhat.com> wrote:

> Hi all,
> Wanted to start some discussion re $subject, context is:
> https://bugs.launchpad.net/heat/+bug/1507568
> Here, we're hitting issues because by default OS::Nova::Server uses the
> POLL_SERVER_CFN transport.  This made sense back when the
> SoftwareDeployment stuff was first implemented, but now we have other
> options, and there are some negative consequenses of choosing this default:
> 1. All heat deployments rely on the heat-api-cfn service by default, when
> this should really be a CFN compatibility layer.
> 2. Related to (1) we then require the keystone ec2tokens extension to be
> enabled
> 3. The cfn API action DescribeStackResource is used to retrieve server
> metadata.  Because that API has no action to only show the metadata, we get
> *all* data for that resource - and recent changes to show all attributes by
> default have made this *much* higher overhead than it once was.
> 4. As mentioned in the bug above, trying to resolve all the attributes
> doesn't work, because we're using stack domain user credentials to poll the
> CFN API, which don't have access to the related nova API for the server
> resource.  This can probably be fixed, but an alternative is just don't use
> this API.
> So, my question is, now that we have other (better) alternatives, can we
> consider switching the Server transport e.g to POLL_SERVER_HEAT by default,
> and relatedly the SoftwareDeployment signal_transport to HEAT_SIGNAL?
> http://docs.openstack.org/developer/heat/template_guide/openstack.html#OS::Nova::Server-prop-software_config_transport
> http://docs.openstack.org/developer/heat/template_guide/openstack.html#OS::Heat::SoftwareDeployment-prop-signal_transport
> The advantage of this is it only requires the native heat-api service, when
> all other options require some other service/API to exist.
> Long term, we should probably consider deprecating the CFN transport for
> these (native) resources, but switching the default would be the first step
> - what do people think?
> Thanks,
> Steve
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Dr. Pavlo Shchelokovskyy
Senior Software Engineer
Mirantis Inc
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