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.

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:

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

Install from npm

npm install -g az-deployment-denoise
# or
yarn global add az-deployment-denoise

Define filtering rule

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.

{
  "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.

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

Usage

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

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.

az-deployment-denoise --help

Development

Install dependencies

npm install

Build and run

npm run build
npm start

# for debugging
npm run debug

Lint

npm run lint

# lint and fix
npm run lint:fix

Test

npm test

# for watching
npm run test:watch

# for debugging
npm run test:debug

Clean artifacts

npm run clean

License

MIT