pattern-deploy-resources.json

{
    "properties": {
        "displayName": "Deploy network watcher when virtual networks are created",
        "mode": "Indexed",
        "description": "This policy creates a network watcher resource in regions with virtual networks. You need to ensure existence of a resource group named networkWatcherRG, which will be used to deploy network watcher instances.",
        "metadata": {
            "category": "Network"
        },
        "parameters": {},
        "policyRule": {
            "if": {
                "field": "type",
                "equals": "Microsoft.Network/virtualNetworks"
            },
            "then": {
                "effect": "DeployIfNotExists",
                "details": {
                    "type": "Microsoft.Network/networkWatchers",
                    "resourceGroupName": "networkWatcherRG",
                    "existenceCondition": {
                        "field": "location",
                        "equals": "[field('location')]"
                    },
                    "roleDefinitionIds": [
                        "/providers/Microsoft.Authorization/roleDefinitions/4d97b98b-1d4f-4787-a291-c67834d212e7"
                    ],
                    "deployment": {
                        "properties": {
                            "mode": "incremental",
                            "template": {
                                "$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json",
                                "contentVersion": "1.0.0.0",
                                "parameters": {
                                    "location": {
                                        "type": "string"
                                    }
                                },
                                "resources": [{
                                    "apiVersion": "2016-09-01",
                                    "type": "Microsoft.Network/networkWatchers",
                                    "name": "[concat('networkWacher_', parameters('location'))]",
                                    "location": "[parameters('location')]"
                                }]
                            },
                            "parameters": {
                                "location": {
                                    "value": "[field('location')]"
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}