Scalable Architectures 101 ConFoo Mar 10, 2011 Mike Willbanks Blog: http://blog.digitalstruct.com Twitter: mwillbanks IRC: lubs on freenode
Who am I? ● Software Development Manager ● Organizer of MNPHP / MNMySQL ● Zend Certified Engineer (PHP/ZF)
Scalability? Your application is growing, your systems are slowing and growth is inevitable... ● Where do we go from here? ● Load Balancing ● Job Servers ● Web Servers ● DNS Servers ● CDN Servers ● Database Servers ● Cache Servers ● FrontEnd Performance
The Beginning Single Server Syndrome ● One Server Many Functions ● Web Server, Database Server, Cache Server, Job Server, DNS Server, Mail Server.... ● How we know its time ● iostat, cpu load, overall degradation ● OR.....
Load Balancing Options ● DNS Rotation (Little to No Cost) ● Not reliable, but it can work on a small scale. ● Software Based (Commodity Server Cost) ● HAProxy, Pound, Varnish, Squid, Wackamole, Perlbal, Web Server Proxy (Nginx, Apache, etc)... ● Hardware Based (High Cost Appliance) ● Several vendors ranging based on need. – A10, F5, etc.
Load Balancing Routing Types ● Round Robin ● URI ● Static ● URI Parameter ● Least Connections ● Header ● Source ● Cookie ● IP ● Regular Expression ● Basic Authentication
Targeting Open Source Software Packages ● Out of the many options we will focus in on 3 ● HAProxy – By and large one of the most popular. ● Pound – Said to be great for medium traffic sites. ● Varnish – A caching solution that also does load balancing
HAProxy ● Pros ● Extremely full featured ● Very well known ● Handles just about every type of routing ● Several examples online ● Has a webbased GUI ● Cons ● No native SSL support (use Stunnel) ● Setup can be complex and take a lot of time
HAProxy: Sample Configuration global listen localhost 0.0.0.0:80 log 127.0.0.1 local0 option httpchk GET / log 127.0.0.1 local1 notice balance roundrobin maxconn 4096 cookie SERVERID user haproxy server serv1 0.0.0.0:8080 check group haproxy inter 2000 rise 2 fall 5 daemon server serv2 0.0.0.0:8080 check inter 2000 rise 2 fall 5 defaults option httpclose log global stats enable mode http stats uri /lb?stats option httplog stats realm haproxy option dontlognull stats auth test:test retries 3 option redispatch maxconn 2000 contimeout 5000 clitimeout 50000 srvtimeout 50000
Pound ● Pros ● chroot support ● Native SSL support ● Insanely simple setup ● Supports virtually all types of routing ● Many online tutorials ● Cons ● No webbased statistics (use poundctl) ● HAProxy can scale more...
Pound: Sample Configuration User "www-data" Group "www-data" LogLevel 1 Alive 30 Control "/var/run/pound/poundctl.socket" ListenHTTP Address 127.0.0.1 Port 80 xHTTP 0 Service BackEnd Address 127.0.0.1 Port 8080 End BackEnd Address 127.0.0.1 Port 8080 End End End
Varnish ● Pros ● Supports frontend caching ● Farily simple setup ● Extremely well known ● Many online tutorials ● Large suite of tools (varnishstat, varnishtop, varnishlog, varnishreplay, varnishncsa) ● Cons ● No native SSL support (use Pound or Stunnel) ● If you want a WebGUI you must PAY
Load Balancing: Keep in Mind ● Web Servers ● One always needs to be available ● Dont use SSL on the web server level! ● Headers ● Pass headers if SSL is on or not ● Client IP is likely on Xforwardedfor ● If using Virtual Hosts pass the Host ● Sessions ● Need a solution if not using sticky routing
Many Web Servers ● Apache ● IIS ● Nginx ● Lighttpd ● etc.
Web Server Configuration ● Sever name should be the same on all servers ● Make a server alias so you can reach individual servers w/o load balancing ● Each configuration SHOULD or MUST be the same. ● Client IP generally is in Xforwardedfor. ● SSL will not be in $_SERVER[HTTPS] and HTTP_ header instead.
Web Servers: Keep in Mind ● Files ● All web servers need our files. ● Static content could be tagged in version control. ● Static content may need a file server / CDN / etc. ● User Generated content on NFS mount or served from the cloud or a CDN. ● Sessions ● All web servers need access to our sessions. ● Remember disk is slow and the database will be a bottleneck. How about distributed caching?
Web Servers: Other Information ● Running PHP on your web server may be a resource hog, you may want to offload static content requests to varnish, nginx, lighttpd or some other lightweight web server. ● Running a proxy to your main web servers works great for hardworking processes. While serving static content from the lightweight server.
Single Database Server Single Database Server ● Lots of options and steps as we move forward.
Database Replication Single Master, Single Slave ● Write code that can write to the master and read from the slave. ● Exception: Be smart, dont write to the master and read from the slave on the table you just wrote to.
Database Replication Multiple Slaves Single Master, Multiple Slaves ● It is a great time to start to implement connection pooling.
Database Replication Multiple Everything Multiple Master, Multiple Slaves ● Do NOT write to both masters at once with MySQL! ● Be warned, autoincrementing now should change so you do not conflict.
Database Table Partitioning Segmenting your Data ● Vertical Partitioning ● Move less accessed columns, large data columns and columns not likely in the where to other tables. ● Horizontal Partitioning ● Done by moving rows into different tables. – Based on Range, Date, User or Interlaced – May require duplicate lookup tables for different indexes.
Database Servers: Keep in Mind ● Replication ● There may be a lag! ● All reports / read queries should go here ● Dont read here directly after a write – Transactions / Lag / etc. ● Sessions ● Never store sessions in the DB – Large binlogs, garbage collection causes slow queries, queue may fill up and cause a crash or max connections.
Cache Servers: What Type? “Caching is imperative in scaling and performance” ● Single Server – Shared Memory: APC / Xcache / etc – File Based: Files / Sqlite / etc – Not highly scalable, great for configuration files. ● Distributed – Memcached, Redis, etc. – Setup consistent hashing. ● Do not cache what cannot be recreated.
Caching: Single Server In The Beginning ● Single Caching Server ● Start to cache fetches, invalidate cache on write and write new cache, always reading from the cache.
Caching: Going Distributed Distributed Mania ● Write based on consistent hashing (hash of a key that you are writing) ● Server depends on the hash. ● Hint – use the memcached pecl extension.
Caching: Read / Write with a Database In the most simple form...
Caching: Keep in Mind ● Replicated or not... ● Elasticity ● Consistent hashing – cannot add or remove w/o losing data ● Sessions ● Store me here... please please please! ● Memory Caches ● Durability If it fails, its gone! ● Ensure dedicated memory! ● If you run out of memory, does it remove an old and add the new or not allow anything to come in?
“Message queues and mailboxes are softwareengineering components used for interprocess communication, or for interthread communication within the same process. They use a queue for messaging – the passing of control or of content.” http://en.wikipedia.org/wiki/Message_queue
Message Queues: What are They? ● A FIFO buffer ● Asynchronous push / pull ● An application framework for sending and receiving messages. ● A way to communicate between applications / systems. ● A way to decouple components. ● A way to offload work.
Message Queues: The Basic Concept Single Job Server Producer Message Queue Consumer Queue Receive Server ● Lots of options and steps as we move forward.
Message Queue: Going Distributed Distributed Mania Producer Producer Producer Queue Queue Queue Server Server Server Consumer Consumer Consumer Consumer Consumer ● Load balance a message queue for scale ● Can continue to create more workers
Message Queues: Useful for? ● Asynchronous Processing ● Communication between Applications / Systems ● Image Resizing ● Video Processing ● Sending out Emails ● AutoScaling Virtual Instances ● Log Analysis ● The list goes on...
Message Queues: Keep in Mind ● Replication or not? ● You need to keep your workers running ● Supervisord or monit or some other monitoring... ● Dont offload things just to offload ● If it needs to be realtime and not near realtime this is not a good place for things – however, your boss does not need to know :)
DNS Servers: Are you running your own? ● Just about every domain registrar runs DNS ● If you dont need to, do not run your own. ● Anycast DNS ● Anycast is a network addressing and routing scheme whereby data is routed to the "nearest" or "best" destination as viewed by the routing topology. ● Its sexy, its sweet and it is FAST!
DNS Servers: Identifying a Good Service ● Wildcard support ● Failover / Distributed ● CNAME support ● TXT support ● Name Server support
CDN: What is a CDN? ● A content delivery network or content distribution network (CDN) is a system of computers containing copies of data, placed at various points in a network so as to maximize bandwidth for access to the data from clients throughout the network. A client accesses a copy of the data near to the client, as opposed to all clients accessing the same central server, so as to avoid bottlenecks near that server. ● Content types include web objects, downloadable objects (media files, software, documents), applications, real time media streams, and other components of internet delivery (DNS, routes, and database queries). http://en.wikipedia.org/wiki/Content_delivery_network
CDN: Why Use One? ● Extremely fast at serving files ● Increased serving capacity ● Distributed nodes ● Frees up your server for the difficult stuff
CDN: The Types ● Origin Pull ● Utilizes your own web server and pulls the content and stores it in their nodes. ● PoP Pull ● You upload the content to something like S3 and it has a CDN on the top of it like CloudFront.
CDN: What Should I Use? ● Depends on your need... ● Origin Pull is great if you want to maintain all of the content in your web server. ● PoP Push is great for storing things like user generated content.
FrontEnd Performance: Tools ● Tools for Identifying Areas ● Yslow ● Firebug ● Google Page Speed ● Google Webmaster Tools ● Pingdom
Questions? Mike Willbanks Blog : http://blog.digitalstruct.com Twitter : mwillbanks IRC : lubs on freenode Joind.in : http://joind.in/2838
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