2015-04-13 tosca_elk_DRAFT_CSAR: issues with capabilities

A second set of issues in the latest CSAR has to do with capabilities. I’ll use the logstash example again. The Logstash node type defines the following capabilities:

 

node_types:

  tosca.nodes.SoftwareComponent.Logstash:

    derived_from: tosca.nodes.SoftwareComponent

    capabilities:

      collectd_endpoint:

         type: tosca.capabilities.Endpoint

      rsyslog_endpoint:

         type: tosca.capabilities.Endpoint

 

The problem here is that the collectd_endpoint and rsyslog_endpoint capabilities are semantically identical since they both have the same type and (presumably)
 the same valid_source_nodes. The only thing that distinguishes them is their (symbolic) name.

 

The problem becomes obvious when we look at the app_collectd and app_rsyslog node templates that use these capabilities:

 

    app_collectd:

      type: tosca.nodes.SoftwareComponent.Collectd

      requirements:

        - host: app_server

        - collectd_endpoint: logstash

 

   app_rsyslog:

      type: tosca.nodes.SoftwareComponent.Rsyslog

      requirements:

        - host: app_server

        - rsyslog_endpoint: logstash

 

Based on the requirement assignments, either capability in the Logstash node type can be used to satisfy either requirement.

 

We could fix this specific use case by augmenting the requirement assignment with the symbolic name of the specific capability that’s needed, as follows:

 

   app_rsyslog:

      type: tosca.nodes.SoftwareComponent.Rsyslog

      requirements:

        - host: app_server

        - rsyslog_endpoint:

            node: logstash

            capability: rsyslog_endpoint

 

 

However, it believe it is bad practice to rely on symbolic names to differentiate between things that are semantically different. If the collectd_endpoint and
 rsyslog_endpoint capabilities are different, they should have different types. Relying on symbolic names only also makes it impossible to do “requirements fulfillment” dynamically (i.e. have the orchestrator dynamically match nodes to requirements).

 

 

Chris

 

 

From: Sahdev P Zala [mailto:]

Sent: Monday, April 13, 2015 4:42 PM

To: Chris Lauwers

Cc: 

Subject: RE: [tosca] Groups - 2015-04-13 tosca_elk_DRAFT_CSAR.zip uploaded

 

Hi Chris, sounds great!

Thanks!!

Regards, 

Sahdev Zala 

From:        Chris Lauwers <>

To:        Sahdev P Zala/Durham/IBM@IBMUS

Cc:        "" <>

Date:        04/13/2015 07:17 PM

Subject:        RE: [tosca] Groups - 2015-04-13 tosca_elk_DRAFT_CSAR.zip uploaded

Sent by:        <>

Thanks Sahdev, I’ll start with an email, since a number of the issues will likely need some discussion. Based on the discussion, I can upload edited YAML files.

 

I’ll work on this later today and tomorrow.

 

Thanks,

 

Chris

 

 

From: Sahdev P Zala [mailto:]

Sent: Monday, April 13, 2015 4:15 PM

To: Chris Lauwers

Cc: 

Subject: RE: [tosca] Groups - 2015-04-13 tosca_elk_DRAFT_CSAR.zip uploaded

  

Hi Chris, 

Thank you so much for the review. I am looking forward to have your comments. 

I think email probably is a good way or may be you can upload them as a doc at the same place we have CSAR? I will make changes per your comments unless I have questions or need to have a discussion.

Thanks again! 

Regards, 

Sahdev Zala 

From:        Chris Lauwers <>

To:        Sahdev P Zala/Durham/IBM@IBMUS, ""
 <>

Date:        04/13/2015 04:57 PM

Subject:        RE: [tosca] Groups - 2015-04-13 tosca_elk_DRAFT_CSAR.zip uploaded

Sent by:        <>

Hi Sahdev, 

 

Thanks for the update. I finally managed to run this test case through my validator, and it turns out there are many issues with the YAML files in this package. In particular, many of the “requirements” sections (in Node Templates as well as in Node Types)
 do not conform to the spec. 

 

What is the best way for me to submit my comments so we can get this package updated?

 

Best regards, 

 

Chris 

 

 

 

From: 
 [mailto:]
On Behalf Of Sahdev Zala

Sent: Monday, April 13, 2015 7:10 AM

To: 

Subject: [tosca] Groups - 2015-04-13 tosca_elk_DRAFT_CSAR.zip uploaded

 

Submitter's message

Document for InterOp. SC review.

Thanks to Matt and Christopher Kaufmann for their initial comments, update the draft with some minor changes. Thanks!

-- Sahdev Zala 

Document Name:
2015-04-13 tosca_elk_DRAFT_CSAR.zip

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Submitter: Sahdev Zala

Group: OASIS Topology and Orchestration Specification for Cloud Applications (TOSCA) TC

Folder: Working Documents

Date submitted: 2015-04-13 07:09:19