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Varnish, The Good, The Awesome, and the Downright Crazy Varnish, The Good, The Awesome, and the Downright Crazy Presentation Transcript

  • MinneBar April 7, 2012Varnish, The Good, The Awesome, and the Downright Crazy By Mike Willbanks Software Engineering Manager CaringBridge
  • Housekeeping… • Talk  Slides will be online later! • Me  Software Engineering Manager at CaringBridge  MNPHP Organizer  Open Source Contributor (Zend Framework and various others)  Where you can find me: • Twitter: mwillbanks G+: Mike Willbanks • IRC (freenode): mwillbanks Blog: http://blog.digitalstruct.com • GitHub: https://github.com/mwillbanks2
  • Agenda • What the … is Varnish? • The Good  “I don’t want to listen to you but only want to play on my laptop.”  The quick, easy and uninformed way... You listening over there? • The Awesome  VCL’s, Directors and more… now we’re going places. • The Crazy  ESI, Purging, VCL C, and VMOD… my head hurts, stop! • Varnish Command Line Apps  varnishtop, varnishstat, etc. • Questions  Although you can bring them up at anytime!3
  • What the… is Varnish?Official StatementWhat the hell it meansGraphs, oh my!
  • Official Statement “Varnish is a web application accelerator. You install it in front of your web application and it will speed it up significantly.”5
  • What The Hell? Tell me! • Varnish allow you to accelerate your website  By using memory and keeping in mind cookies, request headers and more… • It caches pages so that your web server can RELAX!  What about my apache, tomcat, uhhh… (mongrel|thin|goliath….)  Generally caching by TTL + HTTP Headers (cookies too!) • A load banancer, proxy and more…  What? …. Yes, it can do that! #winning6
  • A General Use Case • CaringBridge Status Server  We need to get a message to our mobile users!  The system is down, or we want to be able to communicate a message to them about some subject… maybe a campaign.  The apps and mobile site rely on an API • Trouble in paradise? Few and far in between. • We want to talk to our users? Of course!  Let an API talk to a server…  A story on crashing and burning  A story on a bad thing making a huge success!7
  • The Graph - AWS Req/s Peak Load700 14600 12500 10400 8300 Req/s Peak Load 6200 4100 2 0 0 Small X-Large Small Varnish Small X-Large Small Varnish Time Requests500 80000450 70000400 60000350300 50000250 40000 Time Requests200 30000150 2000010050 10000 0 0 8 Small X-Large Small Varnish Small X-Large Small Varnish
  • The Raw Data Small X-Large Small Varnish Concurrency 10 150 150 Requests 5000 55558 75000 Time 438 347 36 Req/s 11.42 58 585 Peak Load 11.91 8.44 0.35 19,442 Comments failed reqs9
  • The Good – Listen Up!InstallmentDocumentationFinding Existing VCL’s
  • Installment • RTM : http://goo.gl/hl4Tt  Debian: sudo apt-get install varnish  EPEL: yum install varnish • only 6.x otherwise you’ll be out of date!  WOOT Compiling #winning #git • git clone git://git.varnish-cache.org/varnish-cache • cd varnish-cache • sh autogen.sh • ./configure • Make && make install11
  • Documentation • Reference Manual  https://www.varnish-cache.org/docs/3.0/reference/index.html • Tutorial – more like a book version of the reference manual  https://www.varnish-cache.org/docs/3.0/tutorial/index.html • Knock yourselves out! There is a ton of documentation • Yes, this makes happy developers.  Documentation is very accurate, read carefully.  Focus heavily on VCL’s, that is generally what you need.  I’m attempting to show you some of how this works but you will require the documentation to assist you.12
  • Existing VCL’s – The truly lazy… • VCL’s are available for common open source projects  Hi wordpress and drupal! • https://www.varnish-cache.org/trac/wiki/VarnishAndWordpress • https://www.varnish-cache.org/trac/wiki/VarnishAndDrupal  Examples of all sorts of crazy • https://www.varnish-cache.org/trac/wiki/VCLExamples13
  • Wordpress = Bad Slashdot Bad!!! backend default { .host = "127.0.0.1“; .port = "8080"; } sub vcl_recv { if (!(req.url ~ "wp-(login|admin)")) { unset req.http.cookie; } } sub vcl_fetch { if (!(req.url ~ "wp-(login|admin)")) { unset beresp.http.set-cookie; } }14
  • The Awesome – Going PlacesVCLDirectorsA Few Examples
  • Mind ****16
  • VCL – Varnish Configuration Language • VCL State Engine  Each Request is Processed Separately & Independently  States are Isolated but are Related  Return statements exit one state and start another  VCL defaults are ALWAYS appended below your own VCL • VCL can be complex, but…  Two main subroutines; vcl_recv and vcl_fetch  Common actions: pass, hit_for_pass, lookup, pipe, deliver  Common variables: req, beresp and obj  More subroutines, functions and complexity can arise dependent on condition.17
  • VCL - Subroutines • vcl_init – VCL is loaded, no request yet; VMOD initialization • vcl_recv – Beginning of request, req is in scope • vcl_pipe – Client & backend data passed unaltered • vcl_pass – Request goes to backend and not cached • vcl_hash – call hash_data to add to the hash • vcl_hit – called on request found in the cache • vcl_miss – called on request not found in the cache • vcl_fetch – called on document retrieved from backend • vcl_deliver – called prior to delivery of cached object • vcl_error – called on errors18 • vcl_fini – all requests have exited VCL, cleanup of VMOD’s
  • VCL - Variables • Always Available • Backend Req Prepartion  now – epoch time  bereq – backend request • Backend Declarations • Retrieved Backend Request  .host – hostname / IP  beresp – backend response  .port – port number • Cached Object • Request Processing  obj – Cached object, can only  client – ip & identity change .ttl  server – ip & port • Response Preparation  req – request information  resp – http stuff19
  • VCL - Functions • hash_data(string) – adds a string to the hash input.  Request host and URL is default from the default vcl. • regsub(string, regex, sub) – substitution on first occurance  sub can contain numbers 0-n to inject matches from the regex. • regsuball(string, regex, sub) – substitution on all occurances • ban(expression) – Ban all objects in cache that match • ban(regex) – Ban all objects in cache that have a URL match20
  • Directors • Directors allow you to talk to the backend servers • Directors are a glorified reverse proxy  Allows for certain types of load balancing  Allows for talking to a cluster “A director is a logical group of backend servers clustered together for redundancy. The basic role of the director is to let Varnish choose a backend server amongst several so if one is down another can be used.”21
  • Directors – The Types • Random Director – picks a backend by random number • Client Director – picks a backend by client identity • Hash Director – picks a backend by URL hash value • Round-Robin Director – picks a backend in order • DNS Director – picks a backend by means of DNS  Random OR Round-Robin • Fallback – picks the first “healthy” backend22
  • Director - Probing • To ensure healthy backends, you need to use probing.  It really sounds like a colonoscopy for servers. • Variables  .url  .request  .window  .threshold  .intial  .expected_response  .interval  .timeout23
  • Example VCL Configuration24
  • The CrazyESI – Edge-Side IncludesPurgingVMOD
  • ESI – Edge Side Includes • ESI is a small markup language much like SSI (server side includes) to include fragments (or dynamic content for that matter). • If don’t think you can use varnish because you have say, user information displayed on every page; think again! • Think of it as replacing regions inside of a page as if you were using XHR (AJAX). • Three Statements are Implemented  esi:include – Include a page  esi:remove – Remove content  <!-- esi --> - ESI disabled, execute normally26
  • ESI – By Diagram27
  • Using ESI • In vcl_fetch, you must set ESI to be on  set beresp.do_esi = true;  By default, ESI will still cache, so add an exclusion if you need it • if (req.url == “/show_username.php”) { return (pass); }  Varnish refuses to parse content for ESI if it does not look like XML • This is by default; so check varnishstat and varnishlog28
  • ESI – By Example <html> <head><title>Rock it with ESI</title></head> <body> <header> <esi:include src="/user_header.php" /> <!-- Dont do this as youd lose the advantage of varnish --> <!--esi <?php include user_header.php; ?> --> </header> <section id="main"></section <footer></footer> </body> </html>29
  • Purging – Beer anyone? • Sometimes, you just need to purge.  Don’t drink too much tonight, ok? • If you do… find a DD or a cab. • The various ways of purging  varnishadm – command line utility • It’s the ole finger in the back of the throat  Sockets (port 6082) – everyone likes a good socket wrench • Sure, Ipecac is likely overkill.  HTTP – now that is the sexiness • See, now we’re not forcing the point!30
  • Purging Examples varnishadm -T 127.0.0.1:6082 purge req.url == "/foo/bar“ telnet localhost 6082 purge req.url == "/foo/bar telnet localhost 80 Response: Trying 127.0.0.1... Connected to localhost. Escape character is ^]. PURGE /foo/bar HTTP/1.0 Host: bacon.org31
  • Sexy Purging • Distributed Purging… now that’s a punch line!  Use a message queue (or gearman job server)  Have a worker that knows about the varnish servers  Submit the request to clear the cache in the asynchronously or synchronously depending on your use case. • Have enough workers to make this effective at purging the cache quickly.32
  • Embedding C in VCL – you must be crazy • Before getting into VMOD; did you know you can embed C into the VCL for varnish? • Want to do something crazy fast or leverage a C library for pre or post processing? • I know… you’re thinking that’s useless..  On to the example; and a good one from the Varnish WIKI!33
  • VCL - Embedded C for syslog – uber sexy C{ #include <syslog.h> }C sub vcl_something { C{ syslog(LOG_INFO, "Something happened at VCL line XX."); }C } # Example with using varnish variables C{ syslog(LOG_ERR, "Spurious response from backend: xid %s request %s %s "%s" %d "%s" "%s"", VRT_r_req_xid(sp), VRT_r_req_request(sp), VRT_GetHdr(sp, HDR_REQ, "005host:"), VRT_r_req_url(sp), VRT_r_obj_status(sp), VRT_r_obj_response(sp), VRT_GetHdr(sp, HDR_OBJ, "011Location:")); }C34
  • VMOD – Varnish Modules / Extensions • Taking VCL embedded C to the next level • Allows you to extend varnish and create new functions • Now, if you are writing modules for varnish you have a specialty use case!  Go read up on it!  https://www.varnish-cache.org/docs/trunk/reference/vmod.html35
  • VMOD - std • The VMOD std is shipped with varnish; it provides some useful commands  toupper  syslog  tolower  fileread  set_up_tos  duration  Random  integer  Log  collect36
  • Varnish Command Line Appsvarnish varnishadm varnishhistvarnishlog varnishncsa varnishreplayvarnishsizes varnishstat varnishtest varnishtop
  • What is Varnish doing… • What is varnish doing right now? • How do I debug what is happening?  varnishtop38
  • Logging • Many times people want to log the requests to a file  By default Varnish only stores these in shared memory.  Apache Style Logs • varnishncsa –D –a –w log.txt39
  • Cache Warmup • Need to warm up your cache before putting a sever in the queue or load test an environment?  varnishreplay –r log.txt • Replaying logs can allow you to do this. This is great for when you are going to be deploying code to check for performance issues.40
  • Cache Hit Ratios? No Problem • How to see your cache hit ratios…  varnishstat • Want to parse them from XML?  varnishstat –x41
  • Questions?These slides will be posted to SlideShare & SpeakerDeck. Slideshare: http://www.slideshare.net/mwillbanks SpeakerDeck: http://speakerdeck.com/u/mwillbanks Twitter: mwillbanks G+: Mike Willbanks IRC (freenode): mwillbanks Blog: http://blog.digitalstruct.com GitHub: https://github.com/mwillbanks