Upon the release of Holberton School’s System Engineering & Dev Ops project 0x19, an outage occurred on an isolated Ubuntu 14.04 container running an Apache web server. GET requests on the server led to 500 Internal Server Error
's, when the expected response was an HTML file defining a simple Holberton WordPress site .
Debugging Process
1 : Checked running processes using ps aux
. Two apache2
processes - root
and www-data
- were properly running.
2 : Looked in the sites-available
folder of the /etc/apache2/
directory. Determined that the web server was serving content located in /var/www/html/
.
3 : In one terminal, ran strace
on the PID of the root
Apache process. In another, curled the server. Expected great things... only to be disappointed. strace
gave no useful information.
4 : Repeated step 3, except on the PID of the www-data
process. Kept expectations lower this time... but was rewarded! strace
revelead an -1 ENOENT (No such file or directory)
error occurring upon an attempt to access the file /var/www/html/wp-includes/class-wp-locale.phpp
.
5 : Looked through files in the /var/www/html/
directory one-by-one, using Vim pattern matching to try and locate the erroneous .phpp
file extension. Located it in the wp-settings.php
file. (Line 137, require_once( ABSPATH . WPINC . '/class-wp-locale.php' );
).
6 : Removed the trailing p
from the line.
7 : Tested another curl
on the server. 200 A-ok!
8 : Wrote a Puppet manifest to automate fixing of the error.
Summation
In short, a typo. Gotta love’em. In full, the WordPress app was encountering a critical error in wp-settings.php
when trying to load the file class-wp-locale.phpp
. The correct file name, located in the wp-content
directory of the application folder, was class-wp-locale.php
.
Patch involved a simple fix on the typo, removing the trailing p
.
Prevention
This outage was not a web server error, but an application error. To prevent such outages moving forward, please keep the following in mind.
Test the application before deploying. This error would have arisen and could have been addressed earlier had the app been tested.
Note that in response to this error, I wrote a Puppet manifest 0-strace_is_your_friend.pp to automate fixing of any such identitical errors should they occur in the future. The manifest replaces any phpp
extensions in the file /var/www/html/wp-settings.php
with php
.
But of course, it will never occur again, because we’re programmers, and we never make errors!
Thanks for reading!!