Scaling a WordPress server horizontally in a self-managed environment is no small feat, especially when you’re not leveraging fully managed cloud services like AWS, Azure, or GCP. This was one of the most challenging and rewarding projects I undertook during my time at Robu.in. By configuring and optimizing virtual machines (VMs) on DigitalOcean, we achieved high scalability and improved performance for our WordPress-based platform.
This article details the challenges we faced, the innovative solutions implemented, and the lessons learned throughout the process.
Understanding the Goal: Why Horizontal Scaling?
Horizontal scaling involves distributing traffic and workloads across multiple servers, ensuring better performance, reliability, and availability. At Robu, our objective was to handle growing traffic efficiently while maintaining a seamless user experience. However, achieving this in a self-managed environment added an extra layer of complexity.
Key Challenges and Solutions
Here are the significant challenges we faced and how we tackled them:
1. Separating WordPress PHP Code and Database
- Challenge: Decoupling the WordPress PHP code and its database to optimize resource allocation.
- Solution: We deployed the WordPress application on one server and the MySQL database on another, ensuring dedicated resources for each layer. This separation improved flexibility and scalability.
2. Sharing Storage Across WordPress Instances
- Challenge: Ensuring all WordPress instances had access to the same themes, plugins, and uploads directories.
- Solution:
- Implemented Network File Sharing (NFS) to synchronize storage across instances.
- Moved uploads directories to external block storage, allowing independent scaling as needed.
3. Session Persistence
- Challenge: Maintaining user sessions across multiple WordPress instances.
- Solution: Integrated Redis to synchronize sessions, ensuring a consistent user experience regardless of the server handling the request.
4. Routing Backend Traffic
- Challenge: Heavy backend requests often slowed down the frontend, affecting user experience.
- Solution:
- Dedicated specific WordPress instances to handle backend traffic.
- Modified staff device host files to route traffic to designated instances for backend operations.
5. Health and Log Monitoring
- Challenge: Proactively identifying and resolving performance issues.
- Solution:
- Deployed monitoring tools like Grafana, Prometheus, and Netdata.
- Created a lightweight PHP script to check application health and response time every 1-2 seconds.
- Developed a custom shell script to automatically restart the PHP-FPM service in case of crashes.
6. NAT Gateway Implementation
- Challenge: Consolidating multiple public-facing IPs into a single IP for better management.
- Solution: Configured a NAT gateway, exposing a single public IP to the internet while keeping internal IPs private.
7. Nginx Load Balancer
- Challenge: Effectively distributing traffic across multiple WordPress instances.
- Solution:
- Configured Nginx as a load balancer to route requests based on predefined rules.
- Set up multiple server blocks for different instances handling frontend, backend, and API requests.
Collaboration and Credits
A project of this magnitude couldn’t have been achieved without teamwork. I want to acknowledge my former colleague Prasoon Gupta, whose collaboration was instrumental. Together, after two attempts, we finally implemented a successful solution.
Lessons Learned from Initial Failures
Our first attempt at horizontal scaling didn’t go as planned. We underestimated the complexity of synchronizing storage and managing session persistence. However, these challenges taught us the importance of meticulous planning, thorough testing, and adapting quickly to unforeseen issues.
Looking Ahead: Scaling with Cloud-Native Solutions
While our self-managed approach was successful, cloud-native solutions like AWS, with managed services for auto-scaling, load balancing, and database management, offer even more efficiency. In future articles, I’ll share insights on implementing horizontal scaling on AWS and compare the two approaches.
Final Thoughts
Scaling WordPress horizontally in a self-managed environment required creativity, persistence, and a willingness to learn. For those exploring similar challenges, I hope this article provides valuable insights and inspiration.
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