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Async Blob Storage: Retention and Lifecycle Management

Attribute Value
Version 1.1
Last Updated 2026-05-21
Owner SimpleL7Proxy maintainers
Review Cycle Quarterly

Summary

SimpleL7Proxy writes one blob per async request to Azure Blob Storage. Blobs do not expire automatically. Operators MUST configure a storage lifecycle management policy to prevent unbounded storage growth and cost. BlobRetentionDays sets the retention window; StorageDbContainerName identifies the container the policy MUST target.

TL;DR

  • BlobRetentionDays (default: 7) sets the days-since-last-modification threshold for automatic deletion.
  • A lifecycle management policy MUST be created in the Azure Storage account targeting StorageDbContainerName (default: Requests).
  • Three equivalent provisioning methods are available: Azure Portal, Azure CLI, and Bicep.

Warning

Setting BlobRetentionDays in the proxy configuration alone does NOT delete blobs. The Azure Storage lifecycle management policy MUST be created independently in the storage account.

Scope & Applicability

In scope: Lifecycle management policy configuration for async request blobs written by SimpleL7Proxy. Out of scope: Blob Storage authentication and connection string setup (see AsyncOperation.md); blob container creation (the proxy creates the container automatically at startup). Dependencies: AsyncModeEnabled=true; AsyncBlobStorageConfig set with a valid storage account URI.

Reference — Variables

Variable Default Description
BlobRetentionDays 7 Days after last modification before a blob is eligible for automatic deletion. Set to 0 to disable.
StorageDbContainerName Requests Container name where async request blobs are stored. The lifecycle rule MUST target this name exactly.

Note

Azure Blob Storage lifecycle management policies run once per day. Blobs are not deleted immediately when the retention period elapses — deletion occurs on the next daily policy evaluation.

Configuring Blob Storage Lifecycle Management

The following three methods are equivalent. Operators MUST use exactly one.

Option 1: Azure Portal

  1. Navigate to your storage account in the Azure Portal.
  2. Select Lifecycle Management under Data management.
  3. Create a new rule with these settings:
    • Rule name: DeleteExpiredAsyncBlobs
    • Rule scope: Apply to containers matching prefix {StorageDbContainerName} (default: Requests)
    • If blob was last modified more than (days ago): {BlobRetentionDays} (default: 7)
    • Then delete the blob: Checked

Option 2: Azure CLI

STORAGE_ACCOUNT="your-storage-account-name"
RESOURCE_GROUP="your-resource-group"
CONTAINER_NAME="Requests"
RETENTION_DAYS=7

az storage account management-policy create \
  --account-name $STORAGE_ACCOUNT \
  --resource-group $RESOURCE_GROUP \
  --policy @- << EOF
{
  "rules": [
    {
      "name": "DeleteExpiredAsyncBlobs",
      "type": "Lifecycle",
      "definition": {
        "filters": {
          "blobTypes": ["blockBlob"],
          "prefixMatch": ["$CONTAINER_NAME"]
        },
        "actions": {
          "baseBlob": {
            "delete": {
              "daysAfterModificationGreaterThan": $RETENTION_DAYS
            }
          }
        }
      }
    }
  ]
}
EOF

Option 3: Bicep

resource storageAccount 'Microsoft.Storage/storageAccounts@2021-08-01' = {
  // ...existing storage account properties...

  resource managementPolicies 'managementPolicies' = {
    name: 'default'
    properties: {
      policy: {
        rules: [
          {
            name: 'DeleteExpiredAsyncBlobs'
            type: 'Lifecycle'
            definition: {
              filters: {
                blobTypes: [
                  'blockBlob'
                ]
                prefixMatch: [
                  containerName
                ]
              }
              actions: {
                baseBlob: {
                  delete: {
                    daysAfterModificationGreaterThan: retentionDays
                  }
                }
              }
            }
          }
        ]
      }
    }
  }
}

Validation & Compliance

Check Method Expected Result
Lifecycle policy exists Azure Portal → Storage Account → Lifecycle Management DeleteExpiredAsyncBlobs rule is present and enabled
Target container correct Inspect rule's prefix filter Matches StorageDbContainerName value exactly
Blobs deleted after retention Wait BlobRetentionDays days after async requests complete Blobs absent from container on next daily evaluation
Container exists Azure Portal → Storage Account → Containers {StorageDbContainerName} container is present

Version History

Version Date Changes Author
1.1 2026-05-21 Added H1 title, metadata, TL;DR, Summary, Scope & Applicability, Validation & Compliance, Version History; fixed Bicep code block language tag; standardized variable table SimpleL7Proxy maintainers
1.0 — Initial version (no document title or intro) SimpleL7Proxy maintainers