APIM - validate-content on consumption tier - azure

Question

I recently changed our APIM instance from the developer tier, to the consumption tier, and am seeing some weird behavior in the validate-content policy. On the developer tier, this policy would work as expected and return a 400 error with the appropriate error message.
Below is the policy:
<validate-content unspecified-content-type-action="prevent" max-size="102400" size-exceeded-action="prevent">
<content type="application/json" validate-as="json" action="prevent" />
</validate-content>
Below is an example from the trace and the response from developer tier (expected behavior):
//Trace
validate-content (0.100 ms)
{
"name": "application/json",
"type": "RequestBody",
"validationRule": "IncorrectMessage",
"details": "Body of the request does not conform to the definition skills-POST-request, which is associated with the content type application/json. Property 'nam' has not been defined and the schema does not allow additional properties. Line: 1, Position: 7",
"action": "Prevented"
}
//Response
HTTP/1.1 400 Bad Request
vary: Origin
{
"statusCode": 400,
"message": "Body of the request does not conform to the definition skills-POST-request, which is associated with the content type application/json. Property 'nam' has not been defined and the schema does not allow additional properties. Line: 1, Position: 7"
}
However, now the same policy on the consumption tier returns the following trace and response (incorrect behavior):
//Trace
validate-content (4.736 ms)
{
"name": "application/json",
"type": "RequestBody",
"validationRule": "IncorrectMessage",
"details": "Body of the request does not conform to the definition skills-POST-request, which is associated with the content type application/json. Property 'nam' has not been defined and the schema does not allow additional properties. Line: 1, Position: 7",
"action": "Prevented"
}
validate-content (0.714 ms)
{
"name": null,
"type": "RequestBody",
"validationRule": "ValidationException",
"details": "Body of the request cannot be validated for the content type application/json. Value cannot be null.\r\nParameter name: key",
"action": "Prevented"
}
validate-content (2.679 ms)
{
"messages": [
"Value cannot be null.\r\nParameter name: key"
]
}
//response
HTTP/1.1 500 Internal Server Error
vary: Origin
{
"statusCode": 500,
"message": "Internal server error",
"activityId": "b3d76aed-fdf0-4240-a5c1-db49fed82105"
}
This looks to be some sort of bug perhaps in the content validation policy for the consumption tier?

Answer 1

I entered a support request with Microsoft and they determined this was a bug in API management. The workaround was to add the following to policy:
errors-variable-name="requestBodyValidation"
So the final policy now looks like:
<validate-content unspecified-content-type-action="prevent" max-size="102400" size-exceeded-action="prevent" errors-variable-name="requestBodyValidation">
<content type="application/json" validate-as="json" action="prevent" />
</validate-content>

Answer 2

As per the Azure documentation,Consumption tier in APIM supports TLS Settings,External Cache,Client Certificate authentication & Graph QL API's only. Therefore validate-content APIM policy doesn’t work for APIM Services running on consumption SKU.