Nginx Troubleshooting

Table of Contents

Nginx Troubleshooting

Credits

About the Author

About the Reviewers

www.PacktPub.com

eBooks, discount offers, and more

Why subscribe?

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Downloading the color images of this book

Errata

Piracy

Questions

1. Searching for Problems in Nginx Configuration

Introducing basic configuration syntax, directives, and testing

Simple directives

Multiline directives

Include directive

Testing Nginx configuration

The default configuration directory layout

A quick example of modifying the MIME types registry

Default nginx.conf

The http directive

Common mistakes in configuration

Semicolons and newlines

File permissions

Variables

Regular expressions

Summary

2. Searching for Problems in Log Files

Configuring Nginx logging

Logging POST requests

Conditional logging

Logging big request bodies

Creating infrastructure around logs

Configuring log rotation

Working with a lot of log data

Reading logs

Error log record

Summary

3. Troubleshooting Functionality

Processing a complain

Rolling back

Keeping Nginx configuration under source control

Keeping a case journal

Performing the simplest test

Performing the Internet connection test

Testing the general HTTP response traffic

Detecting a lying application

Working around an integration failure

The try_files directive

Setting up automatic removal from upstream

Configuring the good old SSI

Planning for more complete monitoring

Processing a situation of no traffic

Restarting Nginx properly

Investigating lower than usual traffic

Summary

4. Optimizing Website Performance

Why Nginx is so fast?

Optimizing individual upstreams

Optimizing static files

Optimizing PHP backends

Java backends

Optimizing Python and Ruby backends

Optimizing Perl backends

Using thread pools in Nginx

The caching layer of Nginx

Emitting caching headers

Caching in Nginx upstream modules

Caching static files

Replacing external redirects with internal ones

Summary

5. Troubleshooting Rare Specific Problems

Security warnings

Domain name mismatch

Expired certificates

Insecure warnings for valid certificates

The mixed – content warning

Building a secure proxy for the external content

Solving problems with cache

Obsolete pages and VirtualBox

Apache migration problems

Solving problems with WebSockets

Showing a file upload progress bar

Solving the problem of an idle upstream

Summary

6. Monitoring Nginx

Using ngxtop

Getting statistics from http_stub_status

Monitoring Nginx with Munin

Configuring alerts

Getting more status data from Nginx

Using Nginx Plus alternatives

nginx-module-vts

Luameter

nginx-lua-stats

The upsteam_check module in tengine

The requests/sec patch by Catap

The Ustats module

Summary

7. Going Forward with Nginx

System administration

Linux/Unix operating system as a whole

Modern Internet protocols

Specific backend software used in your company

Modern cloud platforms

Automation

Software development

Summary

A. Rare Nginx Error Messages

Index

Nginx Troubleshooting

Nginx Troubleshooting

Copyright © 2016 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: April 2016

Production reference: 1190416

Published by Packt Publishing Ltd.

Livery Place

35 Livery Street

Birmingham B3 2PB, UK.

ISBN 978-1-78528-865-4

www.packtpub.com

Credits

Author

Alex Kapranoff

Reviewers

Titouan Galopin

Valery Kholodkov

Commissioning Editor

Dipika Gaonkar

Acquisition Editor

Reshma Raman

Content Development Editor

Sanjeet Rao

Technical Editor

Mohit Hassija

Copy Editor

Dipti Mankame

Project Coordinator

Judie Jose

Proofreader

Safis Editing

Indexer

Priya Sane

Graphics

Kirk D'Penha

Production Coordinator

Shantanu N. Zagade

Cover Work

Shantanu N. Zagade

About the Author

Alex Kapranoff is an established IT professional with more than 20 years of experience in roles ranging from a database developer to the CTO of a social search engine start-up to an infrastructure manager of a huge web application with hundreds of millions of users. His background allows him to be more on the developer side of things, and he is happy to share some of that perspective with fellow system administration specialists.

About the Reviewers

Titouan Galopin is a certified PHP/Symfony French web architect from Paris. He currently works for SensioLabs, the company behind the PHP framework Symfony, and he has worked for various other companies, including LIIP, Emakina, Ademis, and Coburo.

Titouan graduated in computer science and information technology from the Paris-Saclay University, and he is currently pursuing an engineering degree at the University of Technology of Compiègne.

First as a web developer and then as a web architect since 2012, Titouan has worked on Nginx intensively for PHP applications and Dockerized environments. Within the few years of his work, he has accumulated a lot of experience with Nginx and shares his experience in this book and in the related one, Nginx High Performance, Packt Publishing.

Valery Kholodkov is a seasoned IT professional with a decade of experience in creating, building, scaling, and maintaining industrial-grade web services, web applications, and mobile application backends. Throughout his career, he has worked for well-known brands such as Yandex, Booking.com, and AVG. He currently works as the CTO of QubiQ Digital, a consumer acquisition agency. Valery has a deep understanding of technology, and he is able to express its essence, advantages, and risks to a layman, which makes him an accomplished author and technical reviewer.

www.PacktPub.com

eBooks, discount offers, and more

Did you know that Packt offers eBook versions of every book published, with PDF and ePub files available? You can upgrade to the eBook version at www.PacktPub.com and as a print book customer, you are entitled to a discount on the eBook copy. Get in touch with us at for more details.

At www.PacktPub.com, you can also read a collection of free technical articles, sign up for a range of free newsletters and receive exclusive discounts and offers on Packt books and eBooks.

https://www2.packtpub.com/books/subscription/packtlib

Do you need instant solutions to your IT questions? PacktLib is Packt's online digital book library. Here, you can search, access, and read Packt's entire library of books.

Why subscribe?

Fully searchable across every book published by Packt

Copy and paste, print, and bookmark content

On demand and accessible via a web browser

Preface

You will learn how to notes problems before your boss calls you about some pages not loading. You will learn how to find those problems using logs and your usual Linux toolbox. You will also learn how to minimize the probability of problems happening again.

Nginx started as a web accelerator reverse proxy inside one of the big Russian web companies of the early 2000s. The main web server software was Apache 1.3, and it started to show architectural problems serving thousands of relatively slow clients using the old process-based model. Smart web engineers were already building two-tier systems of light frontends based on the mod_proxy Apache module or even used the squid caching proxy in the reverse proxy mode.

The early predecessor of Nginx was named mod_accel, and it was also implemented as an Apache module. The mod_accel module gained some popularity among the administrators of some of the busiest websites, but it is nothing compared with what Nginx later enjoyed. Both of them are built on the idea that the additional level of proxying on the server side of a busy website is a good thing, providing both the extra flexibility and separating the job of serving slow clients from the actual response generation.

Nginx took the idea of mod_proxy module to the extreme by being a self-sufficient separate HTTP server with a goal to solve the so-called C10K problem, that is, serving 10,000 concurrent connections. The numbers do not look impressive at all in 2016, but they did in 2007 when Nginx first claimed a significant share of 1% of the Web according to Netcraft.

Since that time, the share grew manifold while Nginx steadily gained new functionality and remained the ideal open source success story project with a single, talented developer devoting his genius to producing free quality software, which the whole Web could benefit from.

In 2011, a commercial enterprise named Nginx, Inc. was founded, which allowed even more freedom for the developers (now a team). The firm provides both support services and a special subscription-based extended version of the software named Nginx Plus. We will mention some of the Nginx Plus features in the sixth chapter.

In 2016, Nginx is a great tool many businesses are built upon. However, it is still just a tool which requires a master to show its full potential. If you want to understand what is going on in your web server, to be able to write correct Nginx configuration files and read Nginx logs, and if you want your web server to be very fast, you will have to become that master.

What this book covers

Chapter 1, Searching for Problems in Nginx Configuration, briefly describes the configuration language of Nginx and presents some of the corner cases and several techniques to search for problems.

Chapter 2, Searching for Problems in Log Files, describes the logging subsystem, log syntax, and what to look for when you troubleshoot. Nginx provides thorough logs of everything it does.

Chapter 3, Troubleshooting Functionality, the central chapter in this book, contains a list of steps you will make while investigating a problem. You will find the types of problems people generally encounter with their Nginx-powered web servers.

Chapter 4, Optimizing Website Performance, is dedicated to all things about performance. Starting with thorough explanation of the basic principles behind the Nginx event-driven processing model, it also touches on caching and even gives some advice on possible upstream optimization.

Chapter 5, Troubleshooting Rare Specific Problems, is devoted to studies of several real cases that you may face, from some of the simplest and easiest cases to fix to more problematic cases. The cases described might not be the most frequent, but they still provide valuable insight on the internals of the software and the methods of troubleshooting.

Chapter 6, Monitoring Nginx, is devoted to the abundance of tools available today that you may use for monitoring. No system is complete without good processes for the detection of emerging problems.

Chapter 7, Going Forward with Nginx, the short final chapter, provides a selection of directions you may choose for your further development as a specialist. The whole industry is very dynamic, and you should never settle.

Appendix, Rare Nginx Error Messages, provides a reference of interesting and not very common error messages that you might encounter in your log files.

What you need for this book

Although modern versions of Nginx support Windows, this configuration is not considered production-ready. Most of the examples in this book will work on your Windows machines, but we still recommend having a Linux or FreeBSD server for experiments.

Nginx itself is pretty stable, so any version released since 2013 will suffice. Some of the newer features are only available in more recent versions, and those cases are marked in the book. We always recommend running modern Nginx from the stable line in production. As of the start of the year 2016, it is 1.8.1.

Who this book is for

The book is for technical specialists who already use Nginx to serve web pages for their users. Whether you are an experienced system administrator or a new professional, this book will help you do your job in the most efficient way.

Conventions

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: The error_page directive installs a handler for an HTTP error based on the famous HTTP status codes.

A block of code is set as follows:

...

simple_command 4 two;

# another_simple_command 0;

special_context {

    some_special_command /new/path;

    multiline_directive param {

        1 2 3 5 8 13;

    }

    include common_parameters;

}

...

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

Cache-Control:max-age=1800

Content-Encoding:gzip

Content-Type:text/html; charset=UTF-8

Date:Sun, 10 Oct 2015 13:42:34 GMT

Expires:Sun, 10 Oct 2015 14:12:34 GMT

Server:nginx

X-Cache:EXPIRED

Any command-line input or output is written as follows:

% sudo nginx -t nginx: [emerg] unexpected end of file, expecting } in /etc/nginx/nginx.conf:1 nginx: configuration file /etc/nginx/nginx.conf test failed

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: You should have a way to reboot an otherwise unreachable server; every sane modern hosting provider has it, whether in the form of a simple menu item Reboot, such as in Amazon EC2 or a whole IPMI console access.

Note

Warnings or important notes appear in a box like this.

Tip

Tips and tricks appear like this.

Reader feedback

Feedback from our readers is always welcome. Let us know what you think about this book—what you liked or disliked. Reader feedback is important for us as it helps us develop titles that you will really get the most out of.

To send us general feedback, simply e-mail <[email protected]>, and mention the book's title in the subject of your message.

If there is a topic that you have expertise in and you are interested in either writing or contributing to a book, see our author guide at www.packtpub.com/authors.

Customer support

Now that you are the proud owner of a Packt book, we have a number of things to help you to get the most from your purchase.

Downloading the example code

You can download the example code files for this book from your account at http://www.packtpub.com. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.

You can download the code files by following these steps:

Log in or register to our website using your e-mail address and password.

Hover the mouse pointer on the SUPPORT tab at the top.

Click on Code Downloads & Errata.

Enter the name of the book in the Search box.

Select the book for which you're looking to download the code files.

Choose from the drop-down menu where you purchased this book from.

Click on Code