Caching and tuning fun for high scalability Wim Godden Cu.be Solutions

Owner of Cu.be Solutions (http://cu.be)

PHP developer since 1997

Developer of OpenX

Zend Certified Engineer

Zend Framework Certified Engineer

MySQL Certified Developer

System/network engineers ?

Managers ?

Caching experience ?

Caching and tuning fun for high scalability Wim Godden Cu.be Solutions

5 visitors/day -> 5 million visitors/day

(Don't expect miracle cure !)

LAMP

LAMP

Architecture

Our test site

Result ?

Caching

What's caching ?

What is caching ? select * from article join user on article.user_id = user.id order by created desc limit 10

Hey, that's frontend !

Theory of caching DB

Theory of caching DB

Blogs

Full pages that don't change

Render -> Store in cache -> retrieve from cache

Usually a small block in a page

Best effect : reused on lots of pages

Resets on every insert/update/delete

free up DB resources for more hits !

XML file parsing

Modification frequency ?

Retrieval frequency ?

Make a complete query log (don't forget to turn it off !)

Check page loading times

Don't rely on it

lots of different queries

Caching SQL queries : preferably not

high latency

locking issues !

-> Hard to scale

Distributed memory caching system

Multiple machines ↔ 1 big memory-based hash-table

Values - max. 1Mbyte

Distributed memory caching system

Multiple machines ↔ 1 big memory-based hash-table

Memcache - where to install

Memcache - where to install

PECL

memcached -d -m <mem> -l <ip> -p <port>

ex. : memcached -d -m 2048 -l 127.0.0.1 -p 11211

Lose session data

Lose shopping cart data

...

Lose session data

Lose shopping cart data

Caching in PHP <?php $memcache = new Memcache(); $memcache->addServer( '172.16.0.1' , 11211); $memcache->addServer( '172.16.0.2' , 11211); $myData = $memcache->get( 'myKey' ); if ($myData === false ) { $myData = GetMyDataFromDB(); // Put it in Memcache as 'myKey', without compression, with no expiration $memcache->set( 'myKey' , $myData, false , 0); } echo $myData;

Let's give that a go ! /** * Retrieves the 10 highest rated articles * @return array List of highest rated articles */ static public function getTopRatedArticleList () { if (!$articleList = $cache->load( 'topRatedArticleList' )) { $articleList = self :: getTopRatedArticleListUncached (); $cache->save($articleList, 'topRatedArticleList' ); } return $articleList; }

Slab 2 : 480 bytes (400 * 1.2)

Each larger slab has room for fewer items (chunks)

-> Store a lot of very large objects

-> Large slabs might be full

-> Rest of slabs might be free

-> Try to store more -> eviction of data !

Use Cacti or other monitoring tools STAT pid 2941 STAT uptime 10878 STAT time 1296074240 STAT version 1.4.5 STAT pointer_size 64 STAT rusage_user 20.089945 STAT rusage_system 58.499106 STAT curr_connections 16 STAT total_connections 276950 STAT connection_structures 96 STAT cmd_get 276931 STAT cmd_set 584148 STAT cmd_flush 0 STAT get_hits 211106 STAT get_misses 65825 STAT delete_misses 101 STAT delete_hits 276829 STAT incr_misses 0 STAT incr_hits 0 STAT decr_misses 0 STAT decr_hits 0 STAT cas_misses 0 STAT cas_hits 0 STAT cas_badval 0 STAT auth_cmds 0 STAT auth_errors 0 STAT bytes_read 613193860 STAT bytes_written 553991373 STAT limit_maxbytes 268435456 STAT accepting_conns 1 STAT listen_disabled_num 0 STAT threads 4 STAT conn_yields 0 STAT bytes 20418140 STAT curr_items 65826 STAT total_items 553856 STAT evictions 0 STAT reclaimed 0

Memcache - backing up

Memcache - deleting <?php $memcache = new Memcache(); $memcache->delete( 'myKey' ); $myData = $memcache->get( 'myKey' ); // $myData === false

Prefix / namespace your keys !

Only letters, numbers and underscore

Document your key names !

Updating data

Updating data

Adding/updating data $memcache->delete( 'ArticleDetails__Toshiba_32C100U_32_Inch' ); $memcache->delete( 'Homepage_Popular_Product_List' );

Adding/updating data

Adding/updating data - Why it crashed

Adding/updating data - Why it crashed

Adding/updating data - Why it crashed

Cache stampeding elePHPants

Cache stampeding

Memcache code ? DB

Run it before starting Webserver !

-> lots of new connections

-> memory spike

What if the process that created the lock fails ?

Exception to the rule : things that have an end date (calendar items)

Reverse proxy

Lightweight, fast

7.5% of all Websites

Uses epoll / kqueue

Low memory footprint

10000 active connections = normal

mod_dav*

Some 3 rd party modules (needs recompilation !)

Win32 binaries

Build from source (./configure; make; make install)

Nginx - Configuration server { listen 80; server_name www.domain.ext *.domain.ext; index index.html; root /home/domain.ext/www; } server { listen 80; server_name photo.domain.ext; index index.html; root /home/domain.ext/photo; }

Put Nginx at port 80

Nginx serves all statics (images, css, js, …)

Forward dynamic requests to Apache

Nginx for static files only server { listen 80; server_name www.domain.ext; location ~* ^.*(jpg|jpeg|gif|png|ico|css|zip|tgz|gz|rar|bz2|doc|xls|pdf|ppt|txt|tar|rtf|js)$ { expires 30d; root /home/www.domain.ext; } location / { proxy_pass http://www.domain.ext:8080; proxy_pass_header Set-Cookie; proxy_set_header X-Real-IP $remote_addr; proxy_set_header Host $host; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; } }

Nginx - let's give that a go !

Now : PHP-FPM (in PHP 5.3.3 !)

Runs on port 9000

Nginx connects using fastcgi method location / { fastcgi_pass 127.0.0.1:9000; fastcgi_index index.php; include fastcgi_params; fastcgi_param SCRIPT_NAME $fastcgi_script_name; fastcgi_param SCRIPT_FILENAME /home/www.phpbenelux.eu/$fastcgi_script_name; fastcgi_param SERVER_NAME $host; fastcgi_intercept_errors on; }

Spawn new processes under high load

Chroot

Slow request log !

Spawn new processed under high load

Chroot

Slow request log !

fastcgi_finish_request() -> offline processing

Nginx + PHP-FPM - performance ?

LAMP

Reverse proxy cache / http accelerator / …

Caches (parts of) pages in memory

Nginx is faster (but doesn't have VCL)

/etc/varnish/*.vcl

Varnish - backends + load balancing backend server1 { .host = &quot;192.168.0.10&quot;; } backend server2{ .host = &quot;192.168.0.11&quot;; } director example_director round-robin { { .backend = server1; } { .backend = server2; } }

Varnish - backends + load balancing backend server1 { .host = &quot;192.168.0.10&quot;; .probe = { .url = &quot;/&quot;; .interval = 5s; .timeout = 1 s; .window = 5; .threshold = 3; } }

ACLs

ESI

Varnish with ESI - hold on tight !

Images, js, css

Requests with Set-Cookie

Very large files (it's not a file server !)

User-specific content

Set AllowOverride to None

Don't mod_proxy -> use Nginx or Varnish !

High load on an SSL-site ? -> put SSL on a reverse proxy

Use an opcode cache

Caching storage - Opcode caching

Use an opcode cache

Let's see what difference opcode caching and profilers make...

KCachegrind is your friend

Select the right storage engine

Don't use persistent connect

Caching & Tuning @ frontend http://www.websiteoptimization.com/speed/tweak/average-web-page/

Expires/Cache-Control header

HTTP 304 First request Next requests

HTTP 304 with ETag First request Next requests

Seconds to expiry

Date to expire on

Used by old proxies

Requires clock to be accurate !

HTTP/1.1 : &quot;Cache-Control: no-store&quot;

Test frontend

Check what requests frontend sends to backend

Use inline images in CSS/XHTML (not supported on all browsers yet)

Frontend tuning - inline CSS/XHTML images #navbar span { width: 31px; height: 31px; display: inline; float: left; margin-right: 4px; } .home { background-image: url(data:image/gif;base64,R0lGODlhHwAfAPcAAAAAAIxKAKVjCLW1tb29tcbGvc7OxtZ7ANbWztbW1tbe1t7e1uelMefn1ufn3ufn5+fv3u+MAO/v5+/v7/fGCPf35/f37//nY////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////........MEl0nGVUC6tObNnPceSFBaQVMJAxC4lo3gNOrUaFnTHoAxNm3XVxPfRq139e8BEGAjWD5bgIALw287T8AcAXLly2kjOACdc17higXSIKDO/Lpv7Qq4bw7APgBq8eOzX69InrZ6xe3dbxZffyTGkb8tdx8F+b0Xn2sFsCSBAgTM5lp63RHYnoHUudZgRgkGOGCB+43nGk4OGcQTabKx5dyJKJ7ImoUNCaRRAZYN1ppsrT3Y2gIwyjSQBAtUpABml/0IJGYd6VjQUDH9uBFkGxGm5I8dPQaRUAQUMBdhhBV25ZYUJZBcSAtSJBddWZZ5UAGPOTXlgkNVOSZdBxEwIkYu7VhYnAol5GaadRqF0Uaz0TgXnX2umVFyGakJUUAAADs=); margin-left: 4px; } <img border=0 src=&quot;data:image/gif;base64,R0lGODlhHwAfAPcAAAAAAIxKAKVjCLW1tb29tcbGvc7OxtZ7ANbWztbW1tbe1t7e1uelMefn1ufn3ufn5+fv3u+MAO/v5+/v7/fGCPf35/f37//nY/......Uaz0TgXnX2umVFyGakJUUAAADs=&quot;>

Use inline images in CSS (not supported on all browsers yet)

Use CSS Sprites

CSS Sprites

Tuning content - CSS sprites

Tuning content - CSS sprites 11 images 11 HTTP requests 24KByte 1 images 1 HTTP requests 14KByte

Use inline images in CSS (not supported on all browsers yet)

Have a favicon.ico (don't 404 it !)

Split requests across subdomains

Put statics on a separate subdomain (without cookies !) www.phpbenelux.eu www.phpbenelux.eu images.phpbenelux.eu

HttpGzipModule in Nginx (HttpGzipStaticModule for pre-zipped statics !)

No native support in Varnish

Try to avoid redirects anyway

Watch the logging process ->

Logging = disk I/O -> can kill your site !

Slashdot effect

Use a cache abstraction layer (disk -> Memcache)

Don't install for the worst -> prepare for the worst

Have a test-setup

Slides http://www.slideshare.net/wimg

Twitter @wimgtr

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