Fix: Windows Consumption (Y1) correctly supports deployment slots for Azure Functions #1062
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@@ -15,7 +15,7 @@ resource stagingSlot 'Microsoft.Web/sites/slots@2022-09-01' = { | |
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| ``` | ||
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| ## Slot Requirements — App Service | ||
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| | SKU Tier | Slots Supported | | ||
| |----------|-----------------| | ||
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@@ -24,6 +24,83 @@ resource stagingSlot 'Microsoft.Web/sites/slots@2022-09-01' = { | |
| | Standard | 5 | | ||
| | Premium | 20 | | ||
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| ## Slot Requirements — Azure Functions | ||
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| > ⚠️ Slot support for Azure Functions varies by OS and hosting plan. | ||
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| | Hosting Plan | OS | Slots Supported | | ||
| |---|---|---| | ||
| | Flex Consumption (FC1) | Linux | ❌ 0 | | ||
| | Consumption (Y1) | **Windows** | ✅ 1 staging slot | | ||
| | Consumption (Y1) | Linux | ❌ 0 | | ||
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There was a problem hiding this comment. Linux Consumption also supports slots (1 Slot) but should not be considered in light of deprecation |
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| | Elastic Premium (EP1-EP3) | Windows or Linux | ✅ 20 slots | | ||
| | Dedicated (Standard+) | Windows or Linux | ✅ 5–20 slots | | ||
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| > 💡 **For Azure Functions requiring deployment slots:** | ||
| > - **Windows Consumption (Y1)** supports 1 staging slot. This is valid for existing apps or specific Windows requirements, | ||
| > but cold starts on Consumption affect slot swap reliability. | ||
| > - **Elastic Premium** is the recommended plan for Functions with slots: no cold starts, full VNet integration. | ||
| > - **Flex Consumption does not support slots** — use Premium or Dedicated if slots are required for new projects. | ||
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| ### Windows Consumption Function App with Staging Slot (Bicep) | ||
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| ```bicep | ||
| resource functionAppPlan 'Microsoft.Web/serverfarms@2022-09-01' = { | ||
| name: '${resourcePrefix}-funcplan-${uniqueHash}' | ||
| location: location | ||
| sku: { name: 'Y1', tier: 'Dynamic' } | ||
| // No 'reserved: true' — Windows Consumption | ||
| } | ||
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| resource functionApp 'Microsoft.Web/sites@2022-09-01' = { | ||
| name: '${resourcePrefix}-${serviceName}-${uniqueHash}' | ||
| location: location | ||
| kind: 'functionapp' // Windows (no 'linux' suffix) | ||
| identity: { type: 'SystemAssigned' } | ||
| properties: { | ||
| serverFarmId: functionAppPlan.id | ||
| httpsOnly: true | ||
| siteConfig: { | ||
| appSettings: [ | ||
| { name: 'WEBSITE_NODE_DEFAULT_VERSION', value: '~20' } | ||
| { name: 'FUNCTIONS_EXTENSION_VERSION', value: '~4' } | ||
| { name: 'FUNCTIONS_WORKER_RUNTIME', value: 'node' } | ||
| { name: 'WEBSITE_CONTENTAZUREFILECONNECTIONSTRING', value: 'DefaultEndpointsProtocol=https;AccountName=${storageAccount.name};AccountKey=${storageAccount.listKeys().keys[0].value}' } | ||
| { name: 'WEBSITE_CONTENTSHARE', value: '${toLower(serviceName)}-prod' } | ||
| { name: 'AzureWebJobsStorage', value: 'DefaultEndpointsProtocol=https;AccountName=${storageAccount.name};AccountKey=${storageAccount.listKeys().keys[0].value}' } | ||
| { name: 'APPLICATIONINSIGHTS_CONNECTION_STRING', value: applicationInsights.properties.ConnectionString } | ||
| ] | ||
| } | ||
| } | ||
| } | ||
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| // Staging slot — only 1 staging slot supported on Consumption | ||
| resource stagingSlot 'Microsoft.Web/sites/slots@2022-09-01' = { | ||
| parent: functionApp | ||
| name: 'staging' | ||
| location: location | ||
| kind: 'functionapp' | ||
| properties: { | ||
| serverFarmId: functionAppPlan.id | ||
| siteConfig: { | ||
| appSettings: [ | ||
| { name: 'WEBSITE_NODE_DEFAULT_VERSION', value: '~20' } | ||
| { name: 'FUNCTIONS_EXTENSION_VERSION', value: '~4' } | ||
| { name: 'FUNCTIONS_WORKER_RUNTIME', value: 'node' } | ||
| { name: 'WEBSITE_CONTENTAZUREFILECONNECTIONSTRING', value: 'DefaultEndpointsProtocol=https;AccountName=${storageAccount.name};AccountKey=${storageAccount.listKeys().keys[0].value}' } | ||
| { name: 'WEBSITE_CONTENTSHARE', value: '${toLower(serviceName)}-staging' } // MUST differ from production | ||
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There was a problem hiding this comment. This is optional for slots as discussed at https://learn.microsoft.com/en-us/azure/azure-functions/functions-app-settings#website_contentshare |
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| { name: 'AzureWebJobsStorage', value: 'DefaultEndpointsProtocol=https;AccountName=${storageAccount.name};AccountKey=${storageAccount.listKeys().keys[0].value}' } | ||
| { name: 'APPLICATIONINSIGHTS_CONNECTION_STRING', value: applicationInsights.properties.ConnectionString } | ||
| ] | ||
| } | ||
| } | ||
| } | ||
| ``` | ||
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| > ⚠️ `WEBSITE_CONTENTSHARE` **must be unique per slot** on Windows Consumption — each slot needs its own file share. | ||
| > Use slot-sticky settings (via `slotConfigNames`) for `WEBSITE_CONTENTSHARE` and `WEBSITE_CONTENTAZUREFILECONNECTIONSTRING` | ||
| > so these values do not swap with production. | ||
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| ## Deployment Flow | ||
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| 1. Deploy to staging slot | ||
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Y1 also supports the 1 staging slot. We need to decouple the support of slots with our guidance whether to use Y1 or not. While we don't recommend it, if you *need it, it can be done and it has the slot
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Updated in 651b804. The guidance callout now leads with the factual statement ("Windows Consumption Y1 supports 1 staging slot — this is a supported platform capability. If you need it, use it.") and separates that cleanly from the recommendation ("for new projects, prefer Elastic Premium or Dedicated"). The two concerns are now independent.