Properly using Terraform External Data Source - terraform

Question

I am using Terraform from the bash cloud shell in Azure. I am trying to add an external data source to my Terraform configuration file that will use az cli to query for the virtualip object on a Microsoft.Web/hostingEnvironment the template deploys.
AZ CLI command line:
az resource show --ids /subscriptions/<subscription Id>/resourceGroups/my-ilbase-rg/providers/Microsoft.Web/hos
tingEnvironments/my-ilbase/capacities/virtualip
Output when run from command line:
{
"additionalProperties": {
"internalIpAddress": "10.10.1.11",
"outboundIpAddresses": [
"52.224.70.119"
],
"serviceIpAddress": "52.224.70.119",
"vipMappings": []
},
"id": null,
"identity": null,
"kind": null,
"location": null,
"managedBy": null,
"name": null,
"plan": null,
"properties": null,
"sku": null,
"tags": null,
"type": null
}
In my Terraform config I create a variable for the --ids value:
variable ilbase_resourceId {
default = "/subscriptions/<subscription Id>/resourceGroups/my-ilbase-rg/providers/Microsoft.Web/hostingEnvironments/my-ilbase/capacities/virtualip"
}
I then have the data source structured this way:
data "external" "aseVip" {
program = ["az", "resource", "show", "--ids", "${var.ilbase_resourceId}"]
}
When I execute my configuration, I get the error below:
data.external.aseVip: data.external.aseVip: command "az" produced invalid JSON: json: cannot unmarshal object into Go value of type string
Any ideas what I am doing wrong?

Answer 1

I discovered the problem was that the Terraform External Data Source is not yet able to handle the complex structure of what gets returned by the command. I was able to get around this by adding an AZ CLI command block at the beginning of the script I use to deploy the Application Gateway that grabs the IP address and passes it into the Terraform config as a variable. Below is the script block I am using:
ilbase_virtual_ip=$(
az resource show \
--ids "/subscriptions/$subscription_id/resourceGroups/$ilbase_rg_name/providers/Microsoft.Web/hostingEnvironments/$ilbase_name/capacities/virtualip" \
--query "additionalProperties.internalIpAddress"
)

Answer 2

That command will be successful when you are working in a session. I guess that when you run it from your shell, you already have done az login. When terraform executes your command, it is not using your existing session. You would need to create a PS1 script where you would be propmted for login, or where you provide your credentials so your request can be successful.
Whatever your choice is, take into account that the ONLY output that script should have is a JSON. If any other command add something to the output (for example, when you do a login, you have an output with information about your subscription) then you will have the same error as the output is not a proper JSON. You will need to pipeline that kind of extra ouputs to Out-Null making them "silent" and just write to the output the JSON you are receiving from your request.
I hope this can help.

Answer 3

While there is an accepted response, that is actually a good workaround.
The error is because terraform expect an one level json map like { "a" = "b", "c" = "d" } and your az command returns a multi level map. ( a map of maps )
You can improve your az command to limit the return only one map by adding --query
data "external" "aseVip" {
program = ["az", "resource", "show", "--ids", "${var.ilbase_resourceId}" , "--query additionalProperties" ]
}
output "internalIpAddress" {
value = data.external.aseVip.internalIpAddress
}
output "outboundIpAddresses" {
value = data.external.aseVip.outboundIpAddresses
}
I hope this may help other people.