Ally the best two Azure features (Azure function and Azure automation) to support long running process with event triggers

As we can see there are two major features Azure can provide that will help SharePoint online development.

1. Event trigger like Azure function, Flow, Logic Apps. 
2. Back-end long running process like Azure Automation that can run inside Azure on on Hybrid worker. 

The issue for Azure event trigger listed above is they normally cannot run long time, may not support PowerShell, and may be difficult to run against hybrid worker.

The issue for Azure automation is it cannot be triggered by events like queue or SharePoint list item creation. However, Azure automation can utilize hybrid worker to work with SharePoint on-premises as we explained in previous blog.

The hope is if we can combine the event trigger with Azure automation, the sky will be unlimited! Here is the details.

One of the most interesting case to use Azure to handle the events like SharePoint events. If we need to handle the events triggered from SharePoint, we would need to implement some Azure features like Azure function. Here are the triggers supported at this time for Azure function.

·        HTTPTrigger - Trigger the execution of your code by using an HTTP request. For an example, see Create your first function.

·        TimerTrigger - Execute cleanup or other batch tasks on a predefined schedule. For an example, see Create a function triggered by a timer.

·        GitHub webhook - Respond to events that occur in your GitHub repositories. For an example, see Create a function triggered by a GitHub webhook.

·        Generic webhook - Process webhook HTTP requests from any service that supports webhooks. For an example, see Create a function triggered by a generic webhook.

·        CosmosDBTrigger - Process Azure Cosmos DB documents when they are added or updated in collections in a NoSQL database. For an example, see Create a function triggered by Azure Cosmos DB.

·        BlobTrigger - Process Azure Storage blobs when they are added to containers. You might use this function for image resizing. For more information, see Blob storage bindings.

·        QueueTrigger - Respond to messages as they arrive in an Azure Storage queue. For an example, see Create a function triggered by Azure Queue storage.

·        EventHubTrigger - Respond to events delivered to an Azure Event Hub. Particularly useful in application instrumentation, user experience or workflow processing, and Internet of Things (IoT) scenarios. For more information, see Event Hubs bindings.

·        ServiceBusQueueTrigger - Connect your code to other Azure services or on-premises services by listening to message queues. For more information, see Service Bus bindings.

·        ServiceBusTopicTrigger - Connect your code to other Azure services or on-premises services by subscribing to topics. For more information, see Service Bus bindings.

At this time, the most cost effective plan for Azure function is "consumption plan". However, the max timeout for the plan is 10 minutes. If you have long running process, you may have to switch to App Service plan. We found there are may cases we do need to run the process longer then 10 minutes but we still like to leverage the cheaper "consumption plan". Here is the solution - utilize the Azure automation.

The reason most of time we could not use Azure automation directly is there is no trigger like Queue trigger to invoke the Azure automation. This limited the Azure automation usage. However, there is a way to create a webhook on top of the Azure automation. Then this Azure automation can be called from Azure function. The details is described in this blog. As a result, the implementation like this.

1. Create a Azure function to be trigger by desired event
2. Create a Azure automation to do the real work like PowerShell to process report
3. Create Webhook on top of Azure automation
4. Invoke Azure automation Webhook  from Azure function

The architecture is as described below.

The code to invoke the Azure automation in the Azure function like this code.

    ....

    $webhookurl = 'https://s2events.azure-automation.net/webhooks?token=[secrettoken]'

    $body = @{"SITETITLE" = $siteTitle; "SITEURL" = $siteURL}

    $params = @{

        ContentType = 'application/json'

        Headers = @{'from' = 'Harry Chen'; 'Date' = "$(Get-Date)"}

        Body = ($body | convertto-json)

        Method = 'Post'

        URI = $webhookurl

    }

    #Invoking call

    Invoke-RestMethod @params -Verbose

    ....

As a result, we could ally the best two Azure features Azure function and Azure automation to support long running process with cheaper price and still be trigger by events!

Please note other event triggers like Azure flow, Azure Logic Apps can also replace Azure function for your own purpose.