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Azure Functions Hosting Options and Best Practices

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The process for creating Azure Functions is straightforward on the Azure Portal. The only confusing option you have to consider during the function creation is which hosting model to choose from the available choices. There are four different hosting plans to choose from, where you will also be able to determine which OS to host your functions. In this blog post, I’ll have a review of different choices and what suits you best. This is what you will see on Azure Portal when choosing your hosting plan:

Azure Functions hosting plans for each OS.

Consumption plan

Consumption plan is open on both Windows and Linux plans (Linux currently in the public preview). If you are new to the Azure Functions or need the function just up and running, I would recommend picking this plan, as it will make your life easier and you can get to the coding part rapidly. With this option, the function will dynamically allocate enough compute power or in other words, hosts to run your code and scale up or down automatically as needed. You will pay only for the use and not when for idle time. The bill is based aggregated from all functions within an app on the number of executions, execution time and memory used.

App Service Plan

App Service Plan is the second choice both available on Windows and Linux OS. This plan will dedicate you a virtual machine to run your functions. If you have long-running, continuous, CPU and memory consumable algorithms, this is the option you want to choose to have the most cost-effective hosting plan for the function operation. This plan makes it available to choose from Basic, Standard, Premium, and Isolated SKUs application plans and also connect to your on-premises VNET/VPN networks to communicate with your site data. In this plan, the function will not consume any more than the cost of the VM instance that is allocated. Azure App Service Plans can be found from Microsoft’s official documentation.

An excellent example for choosing the App Service Plan is when the system needs continuously crawl for certain data eighter from on-premises or the internet and save the information to Azure Blob Storage for further processing.

Containers
Azure Functions also supports having custom Linux images and containers. I’ll dedicate a blog post for that option shortly.

Timeouts

The function app timeout duration for Consumption plan by default is five minutes and can be increased to ten minutes in both version one and two. For the App Service plan version one has an unlimited timeout by default but the time out for version two of functions is 30 minutes which can be scaled to unlimited if needed.

After creating the function with a particular hosting plan, you cannot change it afterwards, and the only way is to recreate the Function App. The current hosting plan on the Azure Portal is available under the Overview tab when clicking on the function name. More information about pricing can be found from the Azure functions pricing page.

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Azure Functions, Serverless architecture in action

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One of the most popular Azure features is Azure App Services and the Platform as a Service (PaaS) architecture approach. It merely removes the overhead of setting up additional infrastructure, speeds up to get apps up and running and is an economical solution for hosting user faced web apps or API solutions for the web or mobile apps. For the last few years, App Services has played a significant role in the architecture and services I design for the customers.

As the need for background processes increased, Microsoft introduced Azure WebJobs as a part of Azure Web Apps, and it was the first step towards the functional serverless architecture. A WebJob is a workflow step which has a trigger based on time or, e.g. Azure storage features to undertake a specific logical task. WebJobs are a powerful tool to process data and create further actions based on business rules. The downside is that it has a poor modification, monitoring and laborious logging features from the UI compared to Azure Functions.

By publishing the Functions to Azure, it was a game changer in architectural plans and the way handling background processes in the Microsoft cloud. Azure Functions are hosted on-top of Azure Web Apps architecture and can trigger by HTTP requests, time schedules, events in Azure Storage, Service Bus or Azure Event Hub. The full introduction to Functions is available on Microsoft’s documentation.

Functions Apps can be created using developers prefered programming languages like C# or JavaScript either from the Azure Portal using the web editor or using Visual Studio. Cross-platform developers can use the Visual Studio Code for development using their non-windows environments.

Azure Functions have two runtime versions, and there are significant differences between versions one and two. Version 2.X is running in a sandbox, and it will limit access to some specific libraries in C# and .net core. As an example, if your function is manipulating images or videos, you don’t have access to the framework GUI libraries, and you will face exceptions. The version 1.X uses the .NET Framework 4.7 and is a powerful and alternative runtime for processes where full access to .NET Framework libraries are needed. The full list of supported languages and runtimes are available on the Microsft’s documentation.

Here is an example of the usage of Functions:
A client has financial data in different file formats and needs to process the information. The client receives most of the data in text-based PDF format. Using Functions is a perfect way to process textual context from PDF files to create data for search and Artificial intelligence. The following drawing illustrates the architecture.

  1. Azure blob storage to host files and PDF documents
  2. Azure Function which will be triggered as a new file is added to a container
  3. Azure Cosmosdb to save the content of the PDF file as JSON format
  4. Azure Cognitive Services to process textual context
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