Diagnosing WordPress: What to do when things go wrong

Diagnosing WordPress
Presented by Tim Butler
What do to when things go wrong

Who am I?
● IT professional with 20 years experience
● Head of infrastructure at Conetix
● NGINX Cookbook author
● Certified beer judge
Infrequent ramblings on Twitter: @timbutler
Probably seen more errors than Stack Overflow!

About this talk….
Aimed at developers and agencies
Just as applicable to business owners
Start with the basics and work our way up

One quick takeaway….
Make sure you have a backup!!

How you usually find out there’s a
problem...

“WHY IS MY WEBSITE DOWN!!!!”

Additional management “assistance”

Software equivalent of what you’re facing

The path to Zen
Where we’ll be focussing

Preparation
● Having a known state to compare to
○ Known plugins and versions installed
○ Known errors or PHP warnings
https://en-au.wordpress.org/plugins/stream/
● Ability to track changes

Monitoring
Forearmed is forewarned

Monitoring
● You want to know of issues before your clients
● System MUST have a point of presence in Australia
https://statuscake.com https://www.panopta.com/

Diagnostics
OR
Catastrophic error…..

Diagnostics - Server Logs
Let's look in the logs...

80% of your issues will be identified in the logs
wp-content/plugins/tims-shady-plugin/tims-shady-plugin.php

Consider centralised logging
SaaS Open Source
(host yourself)
https://papertrailapp.com/ https://www.graylog.org/

24 hour snapshot

Diagnostics
Hard failures = easy to find
“Sometimes the site is slow to load”
“Two out of the 5,000 products in my store have an issue”
“My site seems slower this month”
“My site works perfectly for my customers but wp-admin takes forever”
Soft failures = harder...

Diagnostics - WordPress Debugging
Great way to see more info on soft failures eg,
“Two out of the 5,000 products in my store have an issue”

PHP / WordPress Log levels
Normal Debug enabled

Enable via management tools:
Or in the wp-config.php:
define('WP_DEBUG', true);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', false);

By default: wp-content/debug.log
[23-Jul-2018 06:32:09 UTC] PHP Notice: Undefined index: country in
/var/www/vhosts/wcsyd2.conetixtest.com/httpdocs/wp-content/plugins/woocommerce/includes/class-wc-geolite-integration.php on line 60
[23-Jul-2018 06:32:09 UTC] PHP Stack trace:
[23-Jul-2018 06:32:09 UTC] PHP 1. {main}() /var/www/vhosts/wcsyd2.conetixtest.com/httpdocs/index.php:0
[23-Jul-2018 06:32:09 UTC] PHP 2. require() /var/www/vhosts/wcsyd2.conetixtest.com/httpdocs/index.php:17
[23-Jul-2018 06:32:09 UTC] PHP 3. require_once() /var/www/vhosts/wcsyd2.conetixtest.com/httpdocs/wp-blog-header.php:13
[23-Jul-2018 06:32:09 UTC] PHP 4. require_once() /var/www/vhosts/wcsyd2.conetixtest.com/httpdocs/wp-load.php:37
[23-Jul-2018 06:32:09 UTC] PHP 5. require_once() /var/www/vhosts/wcsyd2.conetixtest.com/httpdocs/wp-config.php:80
[23-Jul-2018 06:32:09 UTC] PHP 6. do_action() /var/www/vhosts/wcsyd2.conetixtest.com/httpdocs/wp-settings.php:450
[23-Jul-2018 06:32:09 UTC] PHP 7. WP_Hook->do_action() /var/www/vhosts/wcsyd2.conetixtest.com/httpdocs/wp-includes/plugin.php:453
[23-Jul-2018 06:32:09 UTC] PHP 8. WP_Hook->apply_filters() /var/www/vhosts/wcsyd2.conetixtest.com/httpdocs/wp-includes/class-wp-hook.php:310
[23-Jul-2018 06:32:09 UTC] PHP 9. WooCommerce->init() /var/www/vhosts/wcsyd2.conetixtest.com/httpdocs/wp-includes/class-wp-hook.php:286
[23-Jul-2018 06:32:09 UTC] PHP 10. WC_Customer->__construct()
/var/www/vhosts/wcsyd2.conetixtest.com/httpdocs/wp-content/plugins/woocommerce/includes/class-woocommerce.php:480
[23-Jul-2018 06:32:09 UTC] PHP 11. WC_Data_Store->read()
/var/www/vhosts/wcsyd2.conetixtest.com/httpdocs/wp-content/plugins/woocommerce/includes/class-wc-customer.php:116
[23-Jul-2018 06:32:09 UTC] PHP 12. WC_Customer_Data_Store_Session->read()
/var/www/vhosts/wcsyd2.conetixtest.com/httpdocs/wp-content/plugins/woocommerce/includes/class-wc-data-store.php:156
[23-Jul-2018 06:32:09 UTC] PHP 13. WC_Customer_Data_Store_Session->set_defaults()
…...

Diagnostics - Diving a little deeper

Diagnostics
Make sure you have a backup!
Next items - run on staging / dev copy

Diagnostics - Diving a little deeper
https://en-au.wordpress.org/plugins/query-monitor/
What if there’s no errors in the logs?

Diagnostics - Query Monitor
● Shows database queries
● See WordPress hooks
● See Theme templates used
● See HTTP calls
● … And more!

0.06 second page load
3.8MB peak memory
0.003 second db queries
19 database queries

Database

Templates

HTTP Calls

“Something’s loading JQuery twice….”

What’s the impact of WooCommerce?

“Admin is slower..”
Some premium plugins can have issues refreshing,
with a 30 second timeout
HTTP Calls

Diagnostics
Warning: These examples require root access to a server
(your dev server!) or a localised, development install.

Diagnostics - Digging Deeper
Option 1 - XDebug
“Xdebug is an extension for PHP to assist with debugging and development. It contains a
single step debugger to use with IDEs; it upgrades PHP's var_dump() function; it adds
stack traces for Notices, Warnings, Errors and Exceptions; it features functionality for
recording every function call and variable assignment to disk; it contains a profiler; and
it provides code coverage functionality for use with PHPUnit.”
https://xdebug.org/

Diagnostics - XDebug
Debugging WordPress with xDebug
2:10 pm - Alex Bishop

If it’s compiled in:
zend_extension=xdebug.so
xdebug.profiler_enable_trigger=1
xdebug.profiler_enable_trigger_value=wordcamptest

“My website is slow”
Not database queries…. Must be code

Creates /tmp/cachegrind.out.26139.07d29e

Diagnostics - XDebug KCachegrind / QCachegrind
Webgrind
IDE (PHPStorm)
72.45% time was in apply_filters
This was a single call to excellent_coding
In this function was 100 calls to
password_hash

z
Really shouldn’t let this developer near an editor
wp-content/plugins/tims-shady-plugin/tims-shady-plugin.php

Diagnostics - Digging Deeper
Option 2 - New Relic / APM
https://newrelic.com/
“A complete view of your applications and operating environment”
APM = Application Performance Management

Diagnostics - New Relic
WordPress specific Tools
Other APM’s also available

Diagnostics - New Relic (Lite)
Option 2 - New Relic

Diagnostics - New Relic (Lite)

Diagnostics - New Relic (Essentials)
Hooks

Plugins and Themes

Database

Two quick, get out of jail free cards

Get out of Jail free cards
Check wp_options table for expired transients
Check WordPress core files via WP-CLI
wp core verify-checksums

Summary
1. Remember your path to Zen
2. Find your server log locations
3. Familiarise yourself with the tools before you need them

One final reminder...
Make sure you have a backup!!

Questions?
Feel free to ask in person
or via @timbutler

Diagnosing WordPress: What to do when things go wrong

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