Sharing web site config across deployment slots using an ARM template - arm-template

Question

I'm provisioning several webapps in an ARM template, and I'm finding I'm having to have a lot of duplicated code to maintain a single config across multiple deployment slots. Both dependencies and properties have to be duplicated and maintained separately. I looked into using a variable, but a lot of my config is dependent on other resources and cannot be evaluated at the time variables are evaluated.
Ideally I'd like all slots to reference the same 'Microsoft.Web/sites/config' object, but I can't see a way to do that. My current deployment script looks like this (although this has been massively simplified, I have significantly more properties in reality)
{
"name": "[variables('siteName')]",
"type": "Microsoft.Web/sites",
"location": "[resourceGroup().location]",
"apiVersion": "2015-08-01",
"dependsOn": [
"[concat('Microsoft.Web/serverfarms/', variables('serverfarm'))]",
"[resourceid('Microsoft.EventHub/namespaces', variables('fullEventHubNameSpace'))]"
],
"tags": {
"[concat('hidden-related:', resourceGroup().id, '/providers/Microsoft.Web/serverfarms/', parameters('siteName'))]": "Resource"
},
"properties": {
"name": "[variables('siteName')]",
"serverFarmId": "[resourceId('Microsoft.Web/serverfarms/', variables('serverfarm'))]",
"siteConfig": {
"AlwaysOn": true
}
},
"resources": [
{
"name": "appsettings",
"type": "config",
"apiVersion": "2015-08-01",
"dependsOn": [
"[concat('Microsoft.Web/sites/', variables('siteName'))]",
"[concat('Microsoft.Insights/components/', variables('appInsightsSiteName'))]",
"[concat('Microsoft.Web/sites/', variables('otherSiteName'))]",
"[concat('Microsoft.DocumentDb/databaseAccounts/',variables('databaseAccountName'))]",
"[resourceid('Microsoft.EventHub/namespaces', variables('fullEventHubNameSpace'))]"
],
"properties": {
"APPINSIGHTS_INSTRUMENTATIONKEY": "[reference(resourceId('Microsoft.Insights/components', variables('appInsightsName'))).InstrumentationKey]",
"KEYVAULT_PATH": "[parameters('keyVaultPath')]",
"KEYVAULT_SECRET": "[parameters('keyVaultSecret')]",
"OTHER_SITE": "[reference(concat('Microsoft.Web/sites/', variables('otherSiteName'))).hostnames[0]]",
"DB_KEY": "[listKeys(resourceId(concat('Microsoft.DocumentDb/databaseAccounts'),variables('databaseAccountName')),'2015-04-08').primaryMasterKey]",
}
},
{
"apiVersion": "2015-08-01",
"name": "Staging",
"type": "slots",
"location": "[resourceGroup().location]",
"dependsOn": [
"[resourceId('Microsoft.Web/Sites', variables('siteName'))]"
],
"properties": {
},
"resources": [
{
"name": "appsettings",
"type": "config",
"apiVersion": "2015-08-01",
"dependsOn": [
"[concat('Microsoft.Web/sites/', variables('siteName'))]",
"[concat('Microsoft.Insights/components/', variables('appInsightsName'))]",
"[concat('Microsoft.DocumentDb/databaseAccounts/',variables('databaseAccountName'))]",
"[concat('Microsoft.Web/sites/', variables('otherSiteName'))]",
"[resourceid('Microsoft.EventHub/namespaces', variables('fullEventHubNameSpace'))]",
"Staging"
],
"properties": {
"APPINSIGHTS_INSTRUMENTATIONKEY": "[reference(resourceId('Microsoft.Insights/components', variables('appInsightsName'))).InstrumentationKey]",
"KEYVAULT_PATH": "[parameters('keyVaultPath')]",
"KEYVAULT_SECRET": "[parameters('keyVaultSecret')]",
"OTHER_SITE": "[reference(concat('Microsoft.Web/sites/', variables('otherSiteName'))).hostnames[0]]",
"DB_KEY": "[listKeys(resourceId(concat('Microsoft.DocumentDb/databaseAccounts'),variables('databaseAccountName')),'2015-04-08').primaryMasterKey]",
}
}
]
}
]
},
Is there any way to make this template more maintainable?

Answer 1

maybe you can take use of copy in your Template.
Move the section with your slot to root level in your template and add:
"copy": {
"name": "slotcopy",
"count": "[length(parameters('webSiteSlots'))]"
},
The name propperty shlould look like this:
"name": "[concat(parameters('webSiteName'), '/', parameters('webSiteSlots')[copyIndex()].name)]",
With this you say that this resource will be a child of the WebSite resource. More information about this here.
now you can add a parameter with a complex object array to your template:
"webSiteSlots": {
"type": "array",
"minLength": 0,
"defaultValue": []
}
in your parameters file you can now set a collection of slots you want to have with some additional values:
"webSiteSlots": {
"value": [
{
"name": "Staging",
"environment": "Production"
}
]
}
to use these given values you can do something like this:
"properties": {
"ASPNETCORE_ENVIRONMENT": "[parameters('webSiteSlots')[copyIndex()].environment]"
}
This should reduce the dublicated code a fair bit.
Greetings,
KirK