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Subject: RE: RE: [tosca] 答复: [tosca] 答复: InstantiationLevel discussion paper
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Yes, we need to make sure that we keep instance model support and TOSCA template support consistent when we add support for multiple instances. Chris From: zhang.maopeng1@zte.com.cn <zhang.maopeng1@zte.com.cn>
As I know, this email focus on how to express the multi-node instances based on one node-template. In my mind, this issue will effect both TOSCA-Instance-Model and Yaml profile. I agree that the YAML profile definition may be at first discussed. Thanks. BR Maopeng
原始邮件 发件人：DerekPalma <dpalma@vnomic.com> 收件人：张茂鹏10030173;lishitao@huawei.com <lishitao@huawei.com> 抄送人：Chris Lauwers <lauwers@ubicity.com>arturo.martin-de-nicolas@ericsson.com
<arturo.martin-de-nicolas@ericsson.com>claude.noshpitz@att.com <claude.noshpitz@att.com>mrutkows@us.ibm.com
<mrutkows@us.ibm.com>priya.g@netcracker.com <priya.g@netcracker.com>thinh.nguyenphu@nokia.com
<thinh.nguyenphu@nokia.com>tosca@lists.oasis-open.org <tosca@lists.oasis-open.org>calin.curescu@ericsson.com
<calin.curescu@ericsson.com> 日
期
：2018年03月26日 20:42 主
题
：RE: [tosca]
答复: [tosca]
答复: InstantiationLevel discussion paper The instance model describes the structure and state of a deployment (after orchestration has completed) enabling reasoning over the topology so that additional automation and management
operations can be performed on it. From what I can see, these issues are about how to express and realize specific relationship cardinalities and semantics (and contextual nuances) in the service topology. So this
still fits into the area of deployment which is where the YAML profile discussions have focused. Derek From:
tosca@lists.oasis-open.org <tosca@lists.oasis-open.org>
On Behalf Of zhang.maopeng1@zte.com.cn Hi all is the concern same with TOSCA-Instance-Model? There is a document: "http://docs.oasis-open.org/tosca/TOSCA-Instance-Model/v1.0/TOSCA-Instance-Model-v1.0.html". BR Maopeng
原始邮件
发件人：Lishitao <lishitao@huawei.com>
收件人：Chris Lauwers <lauwers@ubicity.com>Arturo Martin De Nicolas <arturo.martin-de-nicolas@ericsson.com>claude.noshpitz@att.com
<claude.noshpitz@att.com>Matthew Rutkowski (mrutkows@us.ibm.com) <mrutkows@us.ibm.com>Priya
T G <priya.g@netcracker.com>Nguyenphu, Thinh(Nokia - US/Irving) (thinh.nguyenphu@nokia.com) <thinh.nguyenphu@nokia.com>tosca@lists.oasis-open.org
<tosca@lists.oasis-open.org>
抄送人：Calin Curescu <calin.curescu@ericsson.com>
日
期
：2018年03月26日 10:29
主
题
：[tosca]
答复: InstantiationLevel discussion paper Hi Chris and Arturo I think Chris has pointed out some interesting and important issues for the multiple instances design. I agree we need to take this
as one of the high priority feature to be support in v1.3. Regards shitao 发件人: Chris Lauwers [mailto:lauwers@ubicity.com]
Hi Arturo, Thanks for putting this together. We’ll use it as the basis for further discussion. Comments in-line:
From: Arturo Martin De Nicolas [mailto:arturo.martin-de-nicolas@ericsson.com]
Hello all,
As already discussed, there is no clear equivalent to the NFV instantiation level in the TOSCA Simple Profile in YAML (i.e. a property that indicates how many instances of each node template should be instantiated at deployment of the service template). I
think this is a candidate feature for 1.3. Yes, there is currently no language support for allowing the same node template to be instantiated multiple times. Your proposal circumvents this by
making it the responsibility of the “create” operation to create multiple instances (based on the instantiation level data structure). While this will work, it means that the orchestrator (and any ongoing operational management systems) has no knowledge
of the individual instances. I fully support your suggestion that we should address this in Version 1.3. You have previously proposed to support the ‘occurrences’ keyname in node
templates. This is likely the correct starting point, but we need to think through the implications on the rest of the topology template. Specifically:
1.
If node template A supports multiple occurrences, and node template B supports multiple occurrences, and we have a relationship between A and B, what is the desired cardinality of the relationship between
A and B? Full mesh from all instances of A to all instances of B? Single relationship between one instance of A and one instance of B? What if A and B don’t have the same number of occurrences? We need to document the various use cases and then decide which
grammar is required to create those use cases.
2.
If node template A supports multiple occurrences, and some of A’s properties are initialized using get_input statements, how do we specify that a list of values must be provided for each named input? How
do we specify which value in that list goes to which instance of A?
3.
If node template A supports multiple occurrences, and node template B uses a { get_property, [A, <property_of_A> ] }, then which specific instance of A will be used in the corresponding property value of
B?
4.
If node template A supports multiple occurrences, and node template A is “realized” through substitution mapping, do we need any extensions to the substitution _mapping grammar to accommodate this? I’m sure there are other potential issues, but we can start with these.
I have uploaded a discussion paper related to this issue. The intention of the paper is not to propose a solution for 1.3, but something that ETSI NFV could use in the meantime, using the mechanisms available in YAML 1.1 or 1.2.
One of the concerns you point out is that, independent of multiple occurrences, the get_property syntax can get cumbersome when complex data types are
used. I’m not sure that this is necessarily a problem, but I agree that we need to do a better job of clarifying what the appropriate syntax is for various scenarios that involve list, map, or complex data. Specifically:
1.
For properties of type list, how do we specify the index of a specific entry in the list?
2.
For properties of type map, how do we specify the entry that corresponds to a specific key value
3.
For multiple instances of a requirement, how do we specify the index of a specific requirement instance in the list
4.
It is currently not possible to use get_property to retrieve property values of relationships
As the instantiationLevel is a complex type and there is a need to pass information from one node template to another, the grammar becomes unclear. I am looking for advice if this may be a base for a solution. The mechanism for passing information from one node template to another is through the ‘substitution_mapping’ grammar. I agree, that this grammar can
get confusing, since in the v1.2 spec we’re overloading this grammar for two completely different purposes:
1.
Mapping: specify how properties, attributes, capabilities, requirements, and interfaces from one node template are mapped
to corresponding entities in a substituting service template.
2.
Matching: when the orchestrator finds multiple service templates that can be used to substitute a node template, how does
the orchestrator select the best match? The examples in Chapter 14 do not properly highlight these two purposes. I strongly believe we need to more clearly separate them. In my opinion, substitution
mapping grammar should be used exclusively to specify the intended mappings. Different grammar should then be used to drive matching. Since we use node filters in other parts of the spec for similar purposes, I suggest we investigate the use of node filters
to guide matching decisions when multiple possible substituting template are found.
Claude and Matt, is it possible to add this discussion to the agenda for tomorrow’s meeting?
TOSCA_InstantiationLevel_Discussion.docx
Best regards,
Arturo
Chris
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