![Application Caching
Cache an entire page
Memcache is your friend – RAM, autoexpire,
overload intelligent expire
Share between servers
Nice API in all languages
e.g. PHP
public mixed Memcached::get ( string $key [, callable
$cache_cb [, float &$cas_token ]] )](https://image.slidesharecdn.com/clug-webserveroptimisation-120322215727-phpapp01/85/Clug-2011-March-web-server-optimisation-23-320.jpg)
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Clug 2011 March web server optimisation
- 1. Website Optimisation CLUG March 2012
- 3. contents Client Network Compression HTTP Caching Structuring Measurement Application Caching Database tuning Monitoring Server
- 4. Network mtr c 10 r www.openquery.com HOST: spaceman.localhost Loss% Snt Last Avg Best Wrst StDev 1.| 192.168.1.1 0.0% 10 0.8 2.6 0.7 19.3 5.8 2.| 192.168.3.254 0.0% 10 1.1 1.2 1.1 1.5 0.1
- 5. Network (DNS) Check whois is showing the right nameserver whois openquery.com NS1.LINODE.COM NS2.LINODE.COM NS3.LINODE.COM NS4.LINODE.COM NS1.CREATIVECONTINGENCIES.COM NS2.CREATIVECONTINGENCIES.COM NS3.CREATIVECONTINGENCIES.COM Ensure correct record is returned by querying each nameserver dig www.openquery.com @ns1.creativecontingencies.com
- 7. Network (SSL/TLS) Session Tickets - 8 packets 3 roundtrips before application data EDH crypto – computational expensive by has perfect forwards secrecy
- 8. Network (HTTP keep-alive) Request / Response header Connection:keep-alive On by default. Can't handle variable length pages
- 10. Compression Apache's HTTPd Enable mod_deflate <IfModule mod_deflate.c> SetOutputFilter DEFLATE </IfModule> Lighty Enable “mod_compress” in server.modules Nginx gzip on;
- 11. Compression PHP Php.ini zlib.output_compression On
- 12. HTTP Caching RFC 2616 Hypertext Transfer Protocol – HTTP/1.1
- 13. HTTP Caching Etag Unique string – usual some form of digest Browsers request with HTTP header: If-None-Match: “uniquestring....” Server response: 304 not modified if nothing changes
- 14. HTTP Caching (Etag) HTTPd FileETag Mtime
- 15. HTTP Caching (Expires) HTTP Response header Expires: Thu, 01 Dec 2012 16:00:00 GMT Date:Thu, 22 Mar 2012 01:00:17 GMT Last-Modified:Sun, 11 Mar 2012 20:55:16 GMT HTTP Request If-Modified-Since: Sat, 29 Oct 1994 19:43:31 GMT
- 16. HTTP Caching (Cache-Control) Cache-Control = "Cache-Control" ":" 1#cache-directive cache-directive = cache-request-directive | cache-response-directive cache-request-directive = "no-cache" ; Section 14.9.1
- 17. Gzip + Caching Savings On initial response: 104.2K (vs 255.6K) / 44 trunk/roundcubemail/.htaccess ¶ requests) <IfModule mod_deflate.c>next page: 6.2K 2 requests (vs 204.7K / 44 On requests) SetOutputFilter DEFLATE </IfModule> <IfModule mod_headers.c> # replace 'append' with 'merge' for Apache version 2.2.9 and later Header append Cache-Control public env=!
- 18. Use Yslow / Firebug Structuring
- 19. Measurement
- 20. Measurement (Application) create table `timings` ( `id` int(4) NOT NULL AUTO_INCREMENT, 'host' varchar(20),'page' varchar(120), int t1,int t2, int t3.....) And in the index.php $sample = rand(0,100) < 5; # 5% sample rate if ($sample) $t0 = microtime(TRUE);
- 21. Application Caching Be strategic – cost / benefit Hard to generate – graphs, database queries, complex maths Frequent pages: front pages, rss, ajax
- 22. Application Caching (duplicate) if (!$db->count('name', $name, DB_CACHE)) { // if no cache entry exists, fetch the appropriate html and insert ... } else { // row exists - determine if it is still valid
- 23. Application Caching Cache an entire page Memcache is your friend – RAM, autoexpire, overload intelligent expire Share between servers Nice API in all languages e.g. PHP public mixed Memcached::get ( string $key [, callable $cache_cb [, float &$cas_token ]] )
- 24. Application scaling If the application scales by adding webservers you will save on hosting on high power servers Ensure application is stateless Reverse proxy state-full bits to central server if needed CDNs or separated servers for static content saves lots of cpu (latency, keep alives)
- 25. Application APC Graph from apc.php as part of the php_apc package
- 26. Database Know what indexes are and which queries aren't using them. EXPLAIN {sql expression} (Postgresql and Mysql) EXPLAIN ANALYSE {sql expression} Slow query log – enable Know differences between MySQL engines Tune your server Defaults well out of proportion with your sever.
- 27. Database (continued) Searching text in SQL – Use Sphinxsearch instead Same sql interfaces, pulls off database – much quicker at full text search
- 28. Databases (application) Eventually one DB will be too little Plan to buy big hardware (Oracle) or plan to use a replicated database (for reads) Some reads will need to occur on the master. The ones where the data was likely just changed very recently
- 29. Monitoring
- 30. Monitoring Include resource usage Cpu / RAM / processes / forking / swap / IO / Bandwidth... Web server – pages/second, threads Database – query cache hits/misses, connections, replication delay Business value: page load time. Alert if boundaries exceeded