php performance tuning for drupal 8

©2016 Acquia Inc. — Confidential and Proprietary

Erin Rasmussen, Support Engineer,

Acquia

PHP Performance

Tuning

for Drupal 8


Make that Drupal 8 site fly!!

– Brief glance over Best Practices for Performance

Tuning.

– PHP tuning including Opcache, Interned strings and

apcu

– Varnish, Memcache, and Database tips

– The Software Stack, with Drupal 8 integration tips.


Mitigate against Failure by planning for Success!!

– Test, test and then Test again! (Include Load & Security

Testing!)

– Performance Review is Key: Understand the factors

that Affect your Site’s Performance

– Incorporate these strategies in your Continuous

Improvement Process

We want your project to succeed as much as you do!


This is an example stack, there

are multiple ways configure

them, your software may be

different.

Note: Development environments are

almost always Different than

Production environments.

Know the Stack, Love the Stack

Balancer / Varnish

Memcached

Apache PHP/FPM

MySQL

File System

Code Repo


Multi-Tier, the Stack gets bigger

With multi-tier, these the

software stack can be split

among server instances.

With redundancy and

failover.

Balancer / Varnish

Balancer / Varnish

Memcached

Apache PHP/FPM

Apache PHP/FPM

MySQL & File System

MySQL & File System

Code Repo

Server AMI Type #Cores Date Time 1m 5m 15m

bal-1*5*8 m3.2xlarge 8 2017-02-20 00:08:21 0.00 0.03 0.08

bal-1*5*9 m3.2xlarge 8 2017-02-20 00:08:22 0.33 0.29 0.25

web-18**7 c3.large 2 2017-02-20 00:08:21 0.02 0.03 0.05

web-18**8 c3.large 2 2017-02-20 00:08:21 0.00 0.01 0.05

fsdb-1**25 c3.large 2 2017-02-20 00:08:22 0.07 0.05 0.05

fsdb-1**26 c3.large 2 2017-02-20 00:08:23 0.03 0.04 0.05


Balancers / Caching a short intro

Drupal 7, has URL-based page caching

and empties the page cache for every edited piece of content!

2009-2011 Varnish wasn’t widely used, so Drupal 7 caches

pages, but doesn’t invalidate them intelligently.

Cache-Control = public, max-age=300

Works great – until there’s a DDOS or back-end server issue

Cache-Control = public, max-age=31536000

Works great – until content updates aren’t reflected on the site.


Drupal 8 Caching is re-architected

• Has a proper internal cache API, allows tagging of cache

items.

• Each single item is described with tags.

Tags "bubble" up to all rendering parents.

These tags are stored in the cache API.

Cache::invalidateTags(["tag"])

CacheTagsListenersInterface

The content API's call ::invalidateTags().

The render and page caches are transparently invalidated.


Varnish https://varnish-cache.org

Support for Drupal 8 Cache Tags with Varnish

Acquia Purge for Drupal 8 is a fully-featured API

and you plug in a 'purger' to it, to support your CDN


PHP / FPM http://php.net https://php-fpm.org

– Memory Limits

– Max Execution Time

– Zend OPcache

– APC user cache

– Memory Allocation Math


PHP Memory Limit http://php.net/manual/en/ini.core.php#ini.memory-

limit

The PHP memory_limit is the maximum number of M (in

integers) that a single PHP/FPM proc can consume, by

default memory_limit =128M

Clear signs this is set too low:

– php-errors.log: [20-Feb-2017 19:26:10 America/New_York] PHP Fatal error: Allowed memory

size of 268435456 bytes exhausted (tried to allocate 15990062 bytes) in

docroot/includes/database/database.inc on line 2227

– PHP WSOD errors or “Temporarily Unavailable” errors.


Max Execution Time

http://php.net/manual/en/features.connection-handling.php

The amount of time a single PHP process can run (in

seconds) max_execution_time

– Resolve this problems by identifying slow processes

and resolving the request or set_time_limit() function.

Clear signs that your processes are taking too long

–fpm-error.log max_children errors

–White Screen of Death (Temporary Unavailable) errors.

http://php.net/manual/en/function.set-time-limit.php


OPcache (opcode cache) http://php.net/manual/en/intro.opcache.php

Caches pre-compiled bytecode. Faster than using PHP of

load & parse each script for each & every HTTP request.

key variable: opcache.memory_consumption(128M)

Needs to be large enough to store compiled code for your

applications PHP scripts Clear sign that this is too small:

– php-errors.log Warning: require_once() [function.require-once]: Unable to allocate memory for

pool.

OPcache Status monitor: https://github.com/rlerdorf/opcache-status

http://php.net/manual/en/intro.opcache.php


OPcache http://php.net/manual/en/book.opcache.php

Interned Strings - the amount of memory (M) used to store

identical strings (detected by PHP). By default this is a shared

buffer allowing all Drupal PHP processes to reference it across multiple

PHP/FPM procs - saving memory.

Clear sign that this is set too low:

– Fpm-error.log: Warning Interned string buffer overflow

More indepth information: http://jpauli.github.io/2015/03/05/opcache.html


APC User Cache http://php.net/manual/en/intro.apcu.php

APC User cache is PHP APC minus OPcache, rarely

used in Drupal 7 (apc.shm_size= 8M is ok), increase for

Drupal 8 (apc.shm_size=16 or 32M)

Clear sign that the APC User cache is set too small:– In php-errors.log : [20-Feb-2017 13:54:16 America/New_York] PHP Warning: apcu_store(): Unable to allocate

memory for pool. in /mnt/www/html/somenamedev/docroot/core/lib/Drupal/Core/Cache/ApcuBackend.php on line

177

Get usage Details!: use apc.php script in the docroot and

view in your browser: note: the charts are less accurate than the text

http://php.net/manual/en/intro.apcu.php


APC User Cache

Drupal 8.3 will reduce the amount stored in APC user

cache in response to community issues:

– Rationalize use of the 'discovery' cache bin, since it's stored in the limited

size APCu by default https://www.drupal.org/node/2765271

– Change ViewsData to use the default cache bin instead of discovery

https://www.drupal.org/node/2824547

https://www.drupal.org/node/2765271


PHP Procs and PHP Memory Math

Total RAM 3860

OS 50

MySQL 1930

Memcache 64

Sites 4

Sitename Memory Limit Opcache APCu FPM

d7sitedev 256 128 8 1

d7sitestg 256 128 8 1

d8sitedev 128 96 16 1

d8sitestg 128 96 16 1

Calculate the available

memory for PHP (Total - OS - MySQL -Memcache )

Memory use by 1 Process:

– Use top

– memory_get_peak_usage()

– Devel (Drupal 7 & 8)

Calculate how many procs

you can afford.


PHP/FPM max_children errors

When there are more incoming requests than PHP/FPM

can handle you get max_children errors.Clear sign that the site is exhausting PHP/FPM procs:

– fpm-error.log srv-**35m notice [22-Feb-2017 16:32:38] WARNING: [pool someuser]

server reached max_children setting (27), consider raising it.

Causes are Varied – Large amount of HTTP traffic,

PHP/FPM procs that are looping, or not terminating effectively. Or calls to External Services

hanging/timing out


Adding the Impact of Traffic

What happens when the new site launches – or it gets

retweeted a million times:


What’s in that Traffic?


Memcached https://memcached.org

Is a open source, high-performance, distributed memory object caching system

Drupal 8 Memcache Module is Alpha

https://www.drupal.org/project/memcache

The Drupal 8 module will make GETS and SETS with

properly configured Memcached, and supports

key_prefixing.

However, Memcached slabs are not encrypted by default

Community Development is needed for a Stable Release

of the Memcahed Drupal modue

https://www.drupal.org/project/memcache


Keep the Database Layer Happy

– Enable Syslog, disable database Watchdog Logging.

– Caching to the Database does not always Scale, keep

an eye on your capacity and I/O errors.

– Optimize queries, and keep an eye on database tables.

Even the most efficient Views query will be slow on a 50 Gb table.


Keep the Front End Performant

– Compress Site Images, PDFs and other Files before

uploading them to the site. (Even a cached 7MB photo is a major

performance hog when used 27 times on a site.)

– Compress your CSS, and minify your JS.

– Keep an eye on External calls. Use timeouts, and allow your

application to fail gracefully when those resources cannot be reached.


Thank you! Drupal

✩ Modern PHP: New Features and Good Practices by

Josh Lockhart http://shop.oreilly.com/product/0636920033868.do

✩ Drupal 8 Cache API https://www.drupal.org/docs/8/api/cache-api/cache-

api

✩ Acquia Purge https://www.drupal.org/project/acquia_purge

✩ Drupal’s PHP requirements https://www.drupal.org/docs/7/system-

requirements/php

http://shop.oreilly.com/product/0636920033868.do

https://www.drupal.org/docs/8/api/cache-api/cache-api

https://www.drupal.org/project/acquia_purge

https://www.drupal.org/docs/7/system-requirements/php

php performance tuning for drupal 8

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