Azure Function for Blob snapshots

A fairly simple node.js Azure Function for snapshotting all files/blobs periodically in given containers within a Storage Account

How it works

Using the @azure/storage-blob npm package, the script contacts the given Storage Account and iterates through all files in containers configured in Azure Function's Application Settings. This is a crontab style timed process (see function.json).

This function does not delete old snapshots, that needs to be configured in the Storage Account's Lifecycle Management.

Also, it's recommended to enable Soft Delete for the Storage Account to achieve full backup-like functionality.

Configuration

The Azure Function needs to have three Application Settings set up:

1. account: The Storage Account name
2. accountKey: one of the access keys for the Storage Account
3. containers: A comma separated list of containers

For a TimerTrigger to work, you provide a schedule in the form of a cron expression in function.json. Azure Functions use 6 part cron expressions, so for example once per hour is 0 0 * * * *.

See this for reference: https://codehollow.com/2017/02/azure-functions-time-trigger-cron-cheat-sheet/

Deployment

I've used VSCode for this during development: https://code.visualstudio.com/tutorials/functions-extension/getting-started Remember to run npm install before deploying.

Example Lifecycle Management rule

This goes into the storage account's Lifecycle Management.

Delete snapsots older than 14 days:

{
    "rules": [
        {
            "enabled": true,
            "name": "snapshotRule",
            "type": "Lifecycle",
            "definition": {
                "actions": {
                    "snapshot": {
                        "delete": {
                            "daysAfterCreationGreaterThan": 14
                        }
                    }
                },
                "filters": {
                    "blobTypes": [
                        "blockBlob"
                    ]
                }
            }
        }
    ]
}