Book Image

Nginx Troubleshooting

By : Alexey Kapranov
Book Image

Nginx Troubleshooting

By: Alexey Kapranov

Overview of this book

Nginx is clearly winning the race to be the dominant software to power modern websites. It is fast and open source, maintained with passion by a brilliant team. This book will help you maintain your Nginx instances in a healthy and predictable state. It will lead you through all the types of problems you might encounter as a web administrator, with a special focus on performance and migration from older software. You will learn how to write good configuration files and will get good insights into Nginx logs. It will provide you solutions to problems such as missing or broken functionality and also show you how to tackle performance issues with the Nginx server. A special chapter is devoted to the art of prevention, that is, monitoring and alerting services you may use to detect problems before they manifest themselves on a big scale. The books ends with a reference to error and warning messages Nginx could emit to help you during incident investigations.
Table of Contents (15 chapters)
Nginx Troubleshooting
About the Author
About the Reviewers
Rare Nginx Error Messages

Solving problems with cache

We spent a lot of time on providing good caching, that is, saving intermediate results and serving saved copies instead of recalculating from scratch for the same requests. This works perfectly only in a perfect world (for example, a pure functional world where functions and, by extension, GET/HEAD HTTP requests do not have side effects). In the real world, two equal requests may sometimes lead to different responses. There are two basic reasons for it: the earlier-mentioned side effects, which change the state despite the perceived idempotence of GET/HEAD, or flawed equality relationship between requests. A good example of this is ignoring wall time when the response depends on it.

Such problems usually manifest themselves as complaints about seeing stale versions of some pages on your website or seeing pages that belong to other users. Although you can tolerate the first type to some extent (for example, as a compromise for performance), the second type is a...