Cesar Chew at 17:32, 24 November 2014

2014-11-24T17:32:28Z

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{{Cat|Nginx}}

<slideshow style="nobleprog" headingmark="⌘" incmark="…" scaled="true" font="Trebuchet MS" >
;title: Troubleshooting
;author: Bernard Szlachta (NobleProg Ltd)
</slideshow>

=== Troubleshooting ⌘===
* Before you assume it's an nginx problem, take a step back and look at the issue
* Automated script to help problem diagnosis - What's Wrong?
:* https://github.com/BashtonLtd/whatswrong

=== nginx Troubleshooting ⌘===
* Always syntax check your config
service nginx configtest
* Check the error log
:* By default, /var/log/nginx/error_log

=== nginx error logs ⌘===
* Can sometimes be a little cryptic
* Google helps of course..

=== Common errors (1) ⌘===
;
2012/11/29 06:31:42 [error] 2589#0: *6437 client intended to send too
large body: 13106010 bytes, client: 127.0.0.1, server: , request:
"POST /upload/ HTTP/1.1", host: "www.example.com", referrer:
"http://www.example.com/file_upload/"

* Client attempted to upload a file bigger than the maximum POST size

=== Common errors (1) ⌘===
;
2012/11/29 06:31:42 [error] 2589#0: *6437 client intended to send too
large body: 13106010 bytes, client: 127.0.0.1, server: , request:
"POST /upload/ HTTP/1.1", host: "www.example.com", referrer:
"http://www.example.com/file_upload/"

=== Common errors (2) ⌘===
;
2012/10/14 19:51:22 [emerg] 3969#0: "proxy_pass" cannot have
URI part in location given by regular expression, or inside
named location, or inside "if" statement, or inside
"limit_except" block in /etc/nginx/conf.d/proxy.conf:16

=== Common errors (2)⌘===
;
2012/10/14 19:51:22 [emerg] 3969#0: "proxy_pass" cannot have
URI part in location given by regular expression, or inside
named location, or inside "if" statement, or inside
"limit_except" block in /etc/nginx/conf.d/proxy.conf:16

* nginx won't start to to configuration syntax error
* Line containing error shown
* If you attempted to reload nginx with this config, it will continue to run with the old config

=== Common errors (3) ⌘===
;
2012/10/14 18:46:54 [emerg] 2593#0: unknown directive
"client_body_temp_path" in /etc/nginx/conf.d/vhost.conf:6

=== Common errors (3) ⌘===
;
2012/10/14 18:46:54 [emerg] 2593#0: unknown directive
"client_body_temp_path" in /etc/nginx/conf.d/vhost.conf:6

* client_body_temp_path is actually a valid directive
* .. but it's being used in the wrong place
* Because nginx is modular, each module's directives are known only inside the section that module configures

=== Common errors (4) ⌘===
;
2012/10/16 20:56:31 [emerg] 3039#0: "try_files" directive is not allowed
here in /opt/nginx/conf/vhost.conf:16

=== Common errors (4) ⌘===
;
2012/10/16 20:56:31 [emerg] 3039#0: "try_files" directive is not allowed
here in /etc/nginx/conf.d/vhost.conf:16

* nginx can sometimes hint when you've used something valid for the module, but in the wrong place

=== Common errors (5) ⌘===
;
2012/10/16 20:56:42 [emerg] 3043#0: host not found in upstream "tickets.
example.com" in /opt/nginx/conf.d/proxy.conf:22

=== Common errors (5) ⌘===
;
2012/10/16 20:56:42 [emerg] 3043#0: host not found in upstream "tickets.
example.com" in /opt/nginx/conf.d/proxy.conf:22

* Your configuration is valid, but there is a DNS problem looking up
tickets.example.com

=== Common errors (6) ⌘===
;
2012/10/29 18:59:26 [emerg] 2287#0: unexpected "}" in /etc/nginx/conf.d/
vhost.conf:40

=== Common errors (6) ⌘===
;
2012/10/29 18:59:26 [emerg] 2287#0: unexpected "}" in /etc/nginx/conf.d/
vhost.conf:40

* Simple syntax error
* Too many closing brackets
=== Common errors (7) ===
;
2012/10/29 18:59:26 [emerg] 2287#0: unexpected end of file, expecting "}"
in /etc/nginx/conf.d/ vhost.conf:40

=== Common errors (7) ⌘===
;
2012/10/29 18:59:26 [emerg] 2287#0: unexpected end of file, expecting "}"
in /etc/nginx/conf.d/ vhost.conf:40

* Simple syntax error
* Insufficient closing brackets

=== Debugging with custom logs ⌘===
* Not sure if a section of config is getting called, or what a variable is set to?
* Log data into the access logs with the `log_format` directive

=== Debugging with custom logs example ⌘===
;
http {
log_format sentlog '[$time_local] "$request" $status $body_bytes_sent ';
log_format imagelog '[$time_local] $image_file $image_type ' '$body_bytes_sent $status';
log_format authlog '[$time_local] $remote_addr $remote_user ' '"$request" $status';
server {
server_name .example.com;
root /home/www;
location / {
access_log logs/example.com-access.log combined;
access_log logs/example.com-root_access.log sentlog;
rewrite ^/(.*)\.(png|jpg|gif)$ /images/$1.$2;
set $image_file $1;
set $image_type $2;
}
location /images {
access_log logs/example.com-images_access.log imagelog;
}
location /auth {
auth_basic "authorized area";
auth_basic_user_file conf/htpasswd;
deny all;
access_log logs/example.com-auth_access.log authlog;
}
}
}

== Miscellaneous ⌘==
=== Be careful what you believe on the Internet ⌘===
* nginx still relatively young
* There have been many changes to configuration syntax and features since release
* Many blog/forum posts you will find via Google telling you how to do something are outdated or just plain wrong

=== Common mis-use ⌘===
* Commonly seen on forums/blogs:
location / {
if (!-f $request_filename) {
include fastcgi_params;
proxy_pass 127.0.0.1:8000;
break;
}
}

=== Common mis-use - the right way ⌘===
* A better performing way to achieve the same result:
location / {
try_files $uri $uri/ @proxy;
}

location @proxy {
proxy_pass 127.0.0.1:8000;
}
=== More commonly seen bad advice ⌘===
;
server {
server_name .example.com;
root /var/www/html;
if ($host ~* ^example\.com) {
rewrite ^/(.*)$ http://www.example.com/$1 redirect;
}
}

=== The right way ⌘===
;
server {
server_name example.com;
return 301 http://www.example.com;
}

=== In-place upgrades ⌘===
* nginx has a nice feature to switch binaries while running
* installing an upgraded package leaves the old version of nginx running
* simply run `service nginx upgrade` to switch to the new version with 0 downtime

=== nginx status module ⌘===
* nginx has module which can provide status details vi a URL
location /nginx_status {
stub_status on;
access_log off;
allow 127.0.0.1;
deny all;
}
=== Status module output ⌘===
;
$ curl -s http://localhost/nginx_status
Active connections: 2532
server accepts handled requests
1476737983 1476737983 3553635810
Reading: 93 Writing: 13 Waiting: 2426

Troubleshooting - Revision history

Cesar Chew at 17:32, 24 November 2014