Azure deployment what-if denoiser

This tool helps reduce false positive predictions in the result of az deployment what-if (ARM, Bicep) by filtering out unnecessary changes.

False positive predictions contained in the result of az deployment what-if

As indicated in the initial part of the result, the response from Deployment - What-If API may contain false positive predictions.

> Note: The result may contain false positive predictions (noise).
> You can help us improve the accuracy of the result by opening an issue here: https://aka.ms/WhatIfIssues

For instance, the what-if result with Bicep code below indicates changes every time, even when the resource has not changed.

``bicep
param location string = resourceGroup().location
param functionAppName string
param appServicePlanName string

resource appServicePlan 'Microsoft.Web/serverfarms@2022-09-01' = {
name: appServicePlanName
location: location
sku: {
name: 'B1'
}
kind: 'FunctionApp'
}

resource functionApp 'Microsoft.Web/sites@2022-09-01' = {
name: functionAppName
location: location
kind: 'functionapp'
properties: {
serverFarmId: appServicePlan.id
siteConfig: {
appSettings: [
{
name: 'FUNCTIONS_EXTENSION_VERSION'
value: '~4'
}
{
name: 'FUNCTIONS_WORKER_RUNTIME'
value: 'node'
}
]
}
}
}
`

The what-if execution is:

`bash
az deployment group what-if --template-file false-positive-example.bicep --name test-deployment --resource-group test-rg --parameters functionAppName=test-func-denoise appServicePlanName=test-plan
`

The result is:

`
Note: The result may contain false positive predictions (noise).
You can help us improve the accuracy of the result by opening an issue here: https://aka.ms/WhatIfIssues

Resource and property changes are indicated with these symbols:
+ Create
~ Modify
= Nochange

The deployment will update the following scope:

Scope: /subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/test-rg

~ Microsoft.Web/sites/test-func-denoise [2022-09-01]
+ properties.siteConfig.localMySqlEnabled: false
+ properties.siteConfig.netFrameworkVersion: "v4.6"

= Microsoft.Web/serverfarms/test-plan [2022-09-01]

Resource changes: 1 to modify, 1 no change.
`

Changes (creation of properties.siteConfig.localMySqlEnabled and properties.siteConfig.netFrameworkVersion) are shown just after az deployment create.

How to use

$3

`bash
npm install -g az-deployment-denoise


or


yarn global add az-deployment-denoise
`

$3

Define rules in az-deployment-denoise.json to filter changes.
Alternatively, you can define rules using YAML in az-deployment-denoise.yml.
To specify your own file name, use the -f option.

You can use the following conditions.

| Key | Meaning | Example |
|:-------------------|:-------------------------------------------------------------------------------|:----------------------------------------|
| resourceGroupName | resource group name | test-rg |
| providerNamespace | provider namespace | Microsoft.Web |
| resourceType | resource type | sites |
| resourceName | resource name | test-func-denoise |
| resourceNameRegex | resource name (regex) | ^[^-]+-func-denoise$ |
| propertyChangeType | type of property change type (Create \| Delete \| Modify \| Array \| NoEffect) | Delete |
| propertyPath | propety path joined with . | properties.siteConfig.localMySqlEnabled |

If you want to filter the resource /subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/test-rg/Microsoft.Web/sites/test-func-denoise, you can define a rule like below.

`json
{
"rules": [
{
"resourceName": "test-func-denoise"
}
]
}
`

Or, you can filter the creation of properties.siteConfig.localMySqlEnabled in any Azure Functions resource with a rule like below.

`json
{
"rules": [
{
"providerNamespace": "Microsoft.Web",
"resourceType": "sites",
"propertyPath": "properties.siteConfig.localMySqlEnabled"
}
]
}
`

$3

Execute az deployment with --no-pretty-print and input its output to az-deployment-denoise.

`bash
az deployment group what-if --resource-group YOUR_RESOURCE_GROUP --template-file YOUR_TEMPLATE_FILE --no-pretty-print | az-deployment-denoise
`

You can show available options with --help.

`bash
az-deployment-denoise --help
`

$3

You can also execute this tool using Docker like below.

`bash
az deployment group what-if --resource-group YOUR_RESOURCE_GROUP --template-file YOUR_TEMPLATE_FILE --no-pretty-print | docker run --rm -i -v $PWD:/config ottijp/az-deployment-denoise:latest -f /config/az-deployment-denoise.json
`

Development

$3

`
npm install
`

$3

`
npm run build
npm start

for debugging


npm run debug
`

$3

`
npm run lint

lint and fix


npm run lint:fix
`

$3

`
npm test

for watching

npm run test:watch

for debugging

npm run test:debug
`

$3

`
npm run clean
``

License

MIT