How to populate Azure SignalR Service's upstream code in Bicep - azure

Question

I have a Bicep template to create an Azure SignalR Service per the following script. How can I obtain the upstream's code value within the bicep template and populate the urlTemplate's code value based on it? (the keyword TBD exhibits the exact spot in the following code.)
targetScope = 'resourceGroup'
param location string = resourceGroup().location
param signalRName string
resource signalR 'Microsoft.SignalRService/signalR#2022-02-01' = {
name: signalRName
location: location
kind: 'SignalR'
sku: {
name: 'Free_F1'
tier: 'Free'
capacity: 1
}
properties: {
features: [
{
flag: 'ServiceMode'
value: 'Serverless'
}
{
flag: 'EnableConnectivityLogs'
value: 'true'
}
{
flag: 'EnableMessagingLogs'
value: 'true'
}
{
flag: 'EnableLiveTrace'
value: 'true'
}
]
liveTraceConfiguration: {
enabled: 'true'
categories: [
{
name: 'ConnectivityLogs'
enabled: 'true'
}
{
name: 'MessagingLogs'
enabled: 'true'
}
{
name: 'HttpRequestLogs'
enabled: 'true'
}
]
}
cors: {
allowedOrigins: [
'*'
]
}
upstream: {
templates: [
{
hubPattern: '*'
eventPattern: '*'
categoryPattern: '*'
auth: {
type: 'None'
}
urlTemplate: 'https://${signalRName}.azurewebsites.net/runtime/webhooks/signalr?code=TBD'
}
]
}
}
}

Answer 1

I'm assuming that you are using a function app that has the same name as your signalR service.
Looking at the documentation:
The url always looks like that <Function_App_URL>/runtime/webhooks/signalr?code=<API_KEY>
the API_KEY is a function app systemkey called signalr_extension.
So you should be able to retrieve the key and use it like that:
var signalRKey = listKeys(resourceId('Microsoft.Web/sites/host', signalRName, 'default'), '2022-03-01').systemkeys.signalr_extension
resource signalR 'Microsoft.SignalRService/signalR#2022-02-01' = {
name: signalRName
...
properties: {
...
upstream: {
templates: [
{
...
urlTemplate: 'https://${signalRName}.azurewebsites.net/runtime/webhooks/signalr?code=${signalRKey}'
}
]
}
}
}