Schema-based answer to how to populate an @odata.id

slotain
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Posts: 19

Schema-based answer to how to populate an @odata.id Nov 2, 2021 20:32:20 GMT

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Post by slotain on Nov 2, 2021 20:32:20 GMT

TLDR; Is there a programmatic way to determine the URI path that we see in DSP2046_2021 Redfish Resource and Schema Guide, for example, can I compute the the @odata.id, including the {Curly_Braces} part, by using only the schema. Let's say for Fan 1.1.0, can I compute this value that I found in the DSP2046?

6.39.2 URIs

/redfish/v1/Chassis/{ChassisId}/ThermalSubsystem/Fans/{FanId}

I'm writing changes to the generator in Redfish-Interface-Emulator/infragen/generate_template.py to suit my purpose of generating a template JSON that is fully populated with jinja replacement strings like "{{property}}" for some `property` in the schema.

This generate_template.py program will crawl the web for schema files on redfish.org/schemas and prompt the user for input about how to fill in a generated template.

When the generator asks about an @odata.id value, it just asks for a string. So basically I'm wondering how to know where in the spec a certain @odata.id attribute should be populated. And hopefully there's a place in the schema that I can read from this python file to compute this.

For example, if I look in the DSP2043_2021.2 Mockups Bundle, and I find a fan's mockup JSON, I see an attribute for "@odata.id": "/redfish/v1/Chassis/1U/ThermalSubsystem/Fans/Bay1",

Obviously, the Fan implements the Fan resource schema underneath the Fans collection, and Bay1 is just an identifier that could be replaced with {{id}}. I can, using the generator, create a template string to easily replace that.

Does the schema (specifically schema files under DSP8010, which are published online at redfish.org/schemas) define the full URI path with curly braces and all?

For example, Chassis is a root-level collection, but I don't see any enforcement Chassis resources inside that collection as defined in the schema require that @odata.id have a substring "/redfish/v1/Chassis/" in it which some Redfish implementation appends {ChassisId} at the end.

Last Edit: Nov 2, 2021 20:59:54 GMT by slotain

mraineri
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Posts: 1,132

Schema-based answer to how to populate an @odata.id Nov 2, 2021 20:58:27 GMT slotain likes this

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Post by mraineri on Nov 2, 2021 20:58:27 GMT

There are terms in the schemas themselves that describe the allowable URI patterns for a given resource. The OpenAPI definitions tend to be more standardized in terms of how tools process schema files and build the URI paths to different elements, but in theory you can construct the same sort of tooling with JSON Schema and CSDL.

For example, in the CSDL definition of "Fan" (defined in Fan_v1.xml), there is a "Redfish.Uris" term that lists the allowable URI patterns (in the case of this resource, it's a single pattern).

        <Annotation Term="Redfish.Uris">
          <Collection>
            <String>/redfish/v1/Chassis/{ChassisId}/ThermalSubsystem/Fans/{FanId}</String>
          </Collection>
        </Annotation>

Each schema format has its own representation for encoding these strings, but essentially the strings themselves all follow the above format.

There is still the problem of how to glue this with the other resources that lead to the Fan resource, and as you've pointed out this is largely going to depend on how the service is constructed. But with the syntax of the string, the terms in the curly braces are parameters for the URI. Some resources have many allowable URI patterns since they're used in many different places. Port is probably one of the extreme cases, but the same pattern still applies: the curly braces are parameters into the URI path that a client can replace with identifiers.

slotain
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Posts: 19

Schema-based answer to how to populate an @odata.id Nov 2, 2021 21:17:08 GMT

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Post by slotain on Nov 2, 2021 21:17:08 GMT

That's exactly what I'm looking for!

DSP8010_2021.2-redfish-schema/json-schema $ grep -r '"uris"'

Every result of this grep, and there's exactly one for every schema, is a unique collection of URIs for the resource/collection/whatever-else-I'm-still-learning.

That's perfect. My implementation can pick which answer is correct, and use that in the template generation for @odata.id, and it will be schema conforming.