Highly available WordPress deployment on Azure

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WordPress is the leading content management system today owning more than 50% of the market share. WordPress on Microsoft Azure is becoming a very popular offering with the ability to host WordPress as an Azure WebApp. While Microsoft has made the process of spinning up a WordPress site very easy with built in gallery images, running business critical applications on a cloud platform also introduces challenges in terms on availability and scalability.

WordPress Architecture

A typical WordPress deployment consists of the following two tiers:

  • Web Frontend – PHP web site
  • Backend Data store
    • Relational data store – Hierarchical entity store
    • Object data store – Used to store uploaded images and other artefacts

In order to guarantee high availability and scalability, we need to ensure that each of these service tiers are decoupled and can be separately managed.

Web frontend

Windows Azure supports WordPress to be deployed as an Azure WebApp. Azure WebApp is a part of the Azure App Services offering, a fully managed service which can host mission critical web applications.

Azure WebApps natively supports scaling which can be achieved by increasing the number of instances of the hosting WebApp. The native Azure load balancer takes care of distributing the traffic amongst these instances in a ‘round robin’ manner. WebApps also support schedule-driven and automatic scaling.

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Azure Portal can be used to configure scaling rules for the WebApp.

Azure WebApps offers an uptime of 99.95% for basic, standard and premium tiers even with a single instance of deployment . Azure Load Balancer takes care of managing failover amongst instances within a region. To achieve higher availability, the application front end can be deployed across different geographical regions and Azure Traffic manager can be employed to handle load balancing, network performance optimization and failover.

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Backend Store

WordPress back consists of two data stores. One, a relational data store which is used to store WordPress entities along with their hierarchies and second, an object store used to persist artefacts.

Azure Gallery hosts a prebaked image for Scalable WordPress, which lets you configure a scalable MySQL backend as the relational store and uses Azure Storage as the object store for your WordPress deployment. Scalable WordPress uses Azure Blob store to host uploaded artefacts. This works well for most of the scenarios.

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It is important to understand that by using a MySQL backend for your WordPress site you are engaging with a third party database-as-a-service provider (which in this case is Clear DB). This means that the availability SLA associated with your WordPress backend is not provided by Microsoft. Always check the SLAs associated with your chosen pricing tier with the third party provider.

An alternative is to use Project Nami, which offers a WordPress image configured to run against Azure SQL Database as the back end. You can deploy the WordPress site with a Project Nami image either from the Azure gallery or from project’s website. Nami supports WordPress version 4.4.2 with a fully configurable Azure SQL Database backend. Once deployed, the WordPress instance can be configured to use Azure Storage as the object store by employing Windows Azure Storage for WordPress plugin.

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Using SQL Azure and Azure Storage as backend for your WordPress site has the following key advantages

  • Eligibility for Microsoft SLA – A minimum uptime of 99.9% is guaranteed on Azure Storage and an uptime of 99.99% is guaranteed on Basic, Standard, or Premium tiers of Microsoft Azure SQL Database.
  • Easily manageable – Azure SQL databased can be provisioned and managed using Azure Resource Manager templates or through the portal.
  • On-demand scaling – Azure SQL database supports on-demand scaling to meet changing business demands and traffic.
  • More secure – Azure SQL databases offers better support around auditing and compliance apart from offering highly secure connections.
Conclusion

To conclude, you can deploy a highly available WordPress site in Microsoft Azure by ensuring that the front end and backend tiers are fault tolerant and designed for failure. The deployment strategy can be influenced by the following factors:

  • Choice of technology for the backend – Microsoft (SQL Azure)/Non-Microsoft (MySQL)
  • SLA requirements
  • Logging and Auditing requirements
  • Scaling, security and manageability requirements
References

Project Nami – http://projectnami.org/

Scalable WordPress – https://azure.microsoft.com/en-us/marketplace/partners/wordpress/scalablewordpress/

 

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