Update budget amount on existing budget by bicep file - azure

Question

I have already budgets created by the bicep and work perfectly. But I want to change the amount on an existing budget by bicep file. Is it possible to do that? I'm receiving errors with the date, or is the budget already exist, .... finally I cannot change it. Below my bicep files:
targetScope = 'subscription'
#description('Name of the Budget. It should be unique within a resource group.')
param budgetName string = 'ConsumptionBudget'
#description('The total amount of cost or usage to track with the budget')
param budgetAmount int
#description('Threshold value associated with a notification. Notification is sent when the cost exceeded the threshold. It is always percent and has to be between 0.01 and 1000.')
param firstPercentageThreshold int = 75
#description('First action group name')
param firstActionGroup string
#description('Threshold value associated with a notification. Notification is sent when the cost exceeded the threshold. It is always percent and has to be between 0.01 and 1000.')
param secondPercentageThreshold int = 100
#description('Second action group name')
param secondActionGroup string
#description('Threshold value associated with a notification. Notification is sent when the cost exceeded the threshold. It is always percent and has to be between 0.01 and 1000.')
param thirdPercentageThreshold int = 110
#description('First action group name')
param thirdActionGroup string
#description('The list of email addresses to send the budget notification to when the threshold is exceeded.')
param contactEmails array = []
param contactRoles array = [
'Owner'
]
#description('The start date must be first of the month in YYYY-MM-DD format. Future start date should not be more than three months. Past start date should be selected within the timegrain preiod.')
param startDate string = '${utcNow('yyyy-MM')}-01'
#description('The time covered by a budget. Tracking of the amount will be reset based on the time grain.')
#allowed([
'Monthly'
'Quarterly'
'Annually'
])
param timeGrain string = 'Monthly'
#description('Subscription id on which budget will be created')
param subscriptionId string
#description('Resource group name in which action groups are located - Action groups passed in firstActionGroup, secondActionGroup, thirdActionGroup')
param resourceGroupName string
var category = 'Cost'
var operator = 'GreaterThan'
resource budgetExists 'Microsoft.Consumption/budgets#2021-10-01' existing = {
name: budgetName
}
resource budget 'Microsoft.Consumption/budgets#2021-10-01' = if(budgetExists.id==null){
name: budgetName
properties: {
timePeriod: {
startDate: startDate
}
timeGrain: timeGrain
category: category
amount: budgetAmount
notifications: {
NotificationForExceededBudget1: {
enabled: true
contactEmails: contactEmails
threshold: firstPercentageThreshold
operator: operator
contactRoles: contactRoles
contactGroups: [
'/subscriptions/${subscriptionId}/resourceGroups/${resourceGroupName}/providers/microsoft.insights/actionGroups/${firstActionGroup}'
]
}
NotificationForExceededBudget2: {
enabled: true
contactEmails: contactEmails
threshold: secondPercentageThreshold
operator: operator
contactRoles: contactRoles
contactGroups: [
'/subscriptions/${subscriptionId}/resourceGroups/${resourceGroupName}/providers/microsoft.insights/actionGroups/${secondActionGroup}'
]
}
NotificationForExceededBudget3: {
enabled: true
contactEmails: contactEmails
threshold: thirdPercentageThreshold
operator: operator
contactRoles: contactRoles
contactGroups: [
'/subscriptions/${subscriptionId}/resourceGroups/${resourceGroupName}/providers/microsoft.insights/actionGroups/${thirdActionGroup}'
]
}
}
}
}
resource budgetUpdate 'Microsoft.Consumption/budgets#2021-10-01' = if(budgetExists.id != null) {
name: budgetName
eTag: budgetExists.eTag
properties: {
timePeriod: {
startDate: budgetExists.properties.timePeriod.startDate
endDate: budgetExists.properties.timePeriod.endDate
}
timeGrain: budgetExists.properties.timeGrain
category: budgetExists.properties.category
amount: budgetAmount
filter: {}
notifications: {
NotificationForExceededBudget1: {
enabled: true
contactEmails: contactEmails
threshold: firstPercentageThreshold
operator: operator
contactRoles: contactRoles
contactGroups: [
'/subscriptions/${subscriptionId}/resourceGroups/${resourceGroupName}/providers/microsoft.insights/actionGroups/${firstActionGroup}'
]
}
NotificationForExceededBudget2: {
enabled: true
contactEmails: contactEmails
threshold: secondPercentageThreshold
operator: operator
contactRoles: contactRoles
contactGroups: [
'/subscriptions/${subscriptionId}/resourceGroups/${resourceGroupName}/providers/microsoft.insights/actionGroups/${secondActionGroup}'
]
}
NotificationForExceededBudget3: {
enabled: true
contactEmails: contactEmails
threshold: thirdPercentageThreshold
operator: operator
contactRoles: contactRoles
contactGroups: [
'/subscriptions/${subscriptionId}/resourceGroups/${resourceGroupName}/providers/microsoft.insights/actionGroups/${thirdActionGroup}'
]
}
}
}
}
Below exceptions from pipelines:
nner Errors:
2023-01-31T08:08:56.4475545Z {"code": "InvalidTemplate", "target": "/subscriptions/d955395e-9c5f-4fa0-ad91-c46ea57d4646/providers/Microsoft.Resources/deployments/budget_20230131080855", "message": "Deployment template validation failed: 'The resource 'Microsoft.Consumption/budgets/ConsumptionBudget' at line '1' and column '3675' is defined multiple times in a template. Please see https://aka.ms/arm-syntax-resources for usage details.'.", "additionalInfo": [{"type": "TemplateViolation", "info": {"lineNumber": 1, "linePosition": 3675, "path": "properties.template.resources[0]"}}]}

Answer 1

This is because you cannot define same resource in a deployment twice :) Looking at your bicep Microsoft.Consumption/budgets/ is indeed defined twice, just with a different condition. Having condition doesn't count, it is still a duplicate :|
What is more, the way you check for existence won't work, as 'existing' keyword in bicep is simply translated to subscriptionResourceId('Microsoft.Consumption/budgets', parameters('budgetName') while compiling to ARM, and this will never be NULL as it is just a helper method to calculate full resource ID, not checking its existence.