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 the problem of an idle upstream

We devoted a great deal of content to the concept of upstreams. Just to remind you, upstreams are entities that generate HTTP responses that Nginx sends to the clients. Usually, an upstream contains several (or at least one) servers speaking one of the supported protocols, such as FastCGI or plain HTTP. Nginx uses sophisticated client code to very efficiently proxy the communication between the clients and the upstream in a transparent way by also optimizing the number of idle connections and wasted memory. There are a number of algorithms that Nginx uses to balance the client load on all the members of an upstream block, and one of those algorithms is known to bite the unsuspecting web administrators.

The configuration under discussion looks like this:

proxy_pass http://backend;

upstream backend {

The first line sets up the handling of some...