Azure Custom resource provider - custom error message to ARM template - azure

Question

If my custom resource provider wants to return a custom failure message to ARM, what should be my response body?
I have a custom resource provider backed by a JavaScript Azure function
I tried the following
body = {
error: {
code: "Failed",
message: "A custom error message'."
}
};
httpStatus = 200;
context.res = {
status: httpStatus,
headers: {
'Content-Type': 'application/json'
},
body: body
};
The ARM template deployment fails with error -
{
"error": {
"code": "ResourceDeploymentFailure",
"message": "The response for resource had empty or invalid content."
}
I also tried
body = {
properties: {
provisioningState: "Failed",
error: {
code: "Failed",
message: "A custom error message'."
}
}
};
httpStatus = 200;
context.res = {
status: httpStatus,
headers: {
'Content-Type': 'application/json'
},
body: body
};
The ARM template deployment fails with error
"The resource operation completed with terminal provisioning state 'Failed"
I want the ARM template deployment to fail with a custom error message I return form the Azure function - "A custom error message'."
Edited:
Here is my ARM template
{
"$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"parameters": {
"resourcePrefix": {
"type": "string",
"defaultValue": "prfx-",
"maxLength": 6,
"metadata": {
"description": "The prefix of HLF resource."
}
},
"randomGuid": {
"defaultValue": "[newGuid()]",
"type": "string",
"metadata": {
"description": "New random GUID"
}
}
},
"variables": {
"funcName": "[concat(parameters('resourcePrefix'), substring(parameters('randomGuid'), 0, 5))]",
"myResourceProvider": "my-custom-provider",
"location": "[resourceGroup().location]"
},
"resources": [
{
"apiVersion": "2018-09-01-preview",
"type": "Microsoft.CustomProviders/resourceProviders",
"name": "[variables('myResourceProvider')]",
"location": "[variables('location')]",
"properties": {
"resourceTypes": [
{
"name": "deploy",
"routingType": "Proxy",
"endpoint": "<azure-func-url>"
}
]
}
},
{
"apiVersion": "2018-09-01-preview",
"type": "Microsoft.CustomProviders/resourceProviders/deploy",
"name": "[concat(variables('myResourceProvider'), '/', variables('funcName'))]",
"location": "[variables('location')]",
"dependsOn": [
"[concat('Microsoft.CustomProviders/resourceProviders/',variables('myResourceProvider'))]"
]
}
],
"outputs": {
}
}

Answer 1

Proxying the error message as is, is not currently supported for Custom Providers. The custom error message would be nested as details under a standard message.
However, it looks like there is a bug that is stopping the propagation of the error through the ARM template. This should be fixed soon!

Answer 2

#jjbfour is right. The custom message is nested under "Downstream" label in the propagated message. But that is fine for me. The following works
body = {
error: {
code: "Failed",
message: "A custom error message'."
}
};
httpStatus = 400;
context.res = {
status: httpStatus,
headers: {
'Content-Type': 'application/json'
},
body: body
};
The mistake I was making earlier was not setting the HTTP status correctly.