Developing cacheable backend applications - Appdevcon 2019
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This document discusses developing cacheable backend applications. It covers topics like identifying slow parts of an application to optimize, using caching to improve performance once optimization limits are reached, different HTTP caching mechanisms, conditional requests to only fetch changed data, edge caching with reverse proxies, content composition with placeholders, cache variations based on request headers, purging cached content, and strategies when caching HTTP responses is not possible. The target is to design software with caching in mind from the start for improved control and consistent caching behavior.
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Developing cacheable backend applications - Appdevcon 2019
- 3. WEB PERFORMANCE IS AN ESSENTIAL PART OF THE USER EXPERIENCE
- 4. SLOW~DOWN
- 9. MO' MONEY MO' SERVERS MO' PROBLEMS
- 11. OPTIMIZE
- 12. AFTER A WHILE YOU HIT THE LIMITS
- 13. CACHE
- 14. HI, I'M THIJS
- 18. I'M @THIJSFERYN
- 20. DON’T RECOMPUTE IF THE DATA HASN’T CHANGED
- 25. WITH REVERSE CACHING PROXY USER PROXY SERVER
- 29. HTTP CACHING MECHANISMS Expires: Sat, 09 Sep 2017 14:30:00 GMT Cache-control: public, max-age=3600, s-maxage=86400 Cache-control: private, no-cache, no-store
- 30. IN AN IDEAL WORLD
- 31. ✓STATELESS ✓WELL-DEFINED TTL ✓CACHE / NO-CACHE PER RESOURCE ✓CACHE VARIATIONS ✓CONDITIONAL REQUESTS ✓PLACEHOLDERS FOR NON-CACHEABLE CONTENT IN AN IDEAL WORLD
- 32. REALITY SUCKS
- 35. TIME TO LIVE
- 36. CACHE VARIATIONS
- 37. LEGACY
- 38. WHAT IF WE COULD DESIGN OUR SOFTWARE WITH HTTP CACHING IN MIND?
- 39. CACHING STATE OF MIND ✓ PORTABILITY ✓ DEVELOPER EMPOWERMENT ✓ CONTROL ✓ CONSISTENT CACHING BEHAVIOR
- 41. CACHE-CONTROL
- 43. <?php namespace AppController; use SymfonyComponentHttpFoundationRequest; use SensioBundleFrameworkExtraBundleConfigurationRoute; use SymfonyBundleFrameworkBundleControllerController; class DefaultController extends Controller { /** * @Route("/", name="home") */ public function index() { return $this ->render('index.twig') ->setSharedMaxAge(500) ->setPublic(); } }
- 45. /** * @Route("/private", name="private") */ public function private() { $response = $this ->render('private.twig') ->setPrivate(); $response->headers->addCacheControlDirective('no-store'); return $response; }
- 47. ONLY FETCH PAYLOAD THAT HAS CHANGED
- 48. HTTP/1.1 200 OK
- 49. OTHERWISE: HTTP/1.1 304 NOT MODIFIED
- 50. CONDITIONAL REQUESTS HTTP/1.1 200 OK Host: localhost Etag: 7c9d70604c6061da9bb9377d3f00eb27 Content-type: text/html; charset=UTF-8 Hello world output GET / HTTP/1.1 Host: localhost
- 51. CONDITIONAL REQUESTS HTTP/1.1 304 Not Modified Host: localhost Etag: 7c9d70604c6061da9bb9377d3f00eb27 GET / HTTP/1.1 Host: localhost If-None-Match: 7c9d70604c6061da9bb9377d3f00eb27
- 52. CONDITIONAL REQUESTS HTTP/1.1 200 OK Host: localhost Last-Modified: Fri, 22 Jul 2016 10:11:16 GMT Content-type: text/html; charset=UTF-8 Hello world output GET / HTTP/1.1 Host: localhost
- 53. CONDITIONAL REQUESTS HTTP/1.1 304 Not Modified Host: localhost Last-Modified: Fri, 22 Jul 2016 10:11:16 GMT GET / HTTP/1.1 Host: localhost If-Last-Modified: Fri, 22 Jul 2016 10:11:16 GMT
- 54. Cache-Control: public, max-age=100, s-maxage=500, stale-while-revalidate=20
- 55. QUICKLY
- 56. EARLY
- 58. <?php namespace AppEventListener; use SymfonyComponentHttpFoundationResponse; use SymfonyComponentHttpFoundationRequest; use SymfonyComponentHttpKernelEventGetResponseEvent; use SymfonyComponentHttpKernelEventFilterResponseEvent; use SymfonyBundlesRedisBundleRedisClient as RedisClient; class ConditionalRequestListener { protected $redis; public function __construct(RedisClient $redis) { $this->redis = $redis; } protected function isModified(Request $request, $etag) { if ($etags = $request->getETags()) { return in_array($etag, $etags) || in_array('*', $etags); } return true; } ... src/EventListener/ConditionalRequestListener.php
- 59. { $this->redis = $redis; } protected function isModified(Request $request, $etag) { if ($etags = $request->getETags()) { return in_array($etag, $etags) || in_array('*', $etags); } return true; } public function onKernelRequest(GetResponseEvent $event) { $request = $event->getRequest(); $etag = $this->redis->get('etag:'.md5($request->getUri())); if(!$this->isModified($request,$etag)) { $event->setResponse(Response::create('Not Modified',Response::HTTP_NOT_MODIFIED)); } } public function onKernelResponse(FilterResponseEvent $event) { $response = $event->getResponse(); $request = $event->getRequest(); $etag = md5($response->getContent()); $response->setEtag($etag); if($this->isModified($request,$etag)) { $this->redis->set('etag:'.md5($request->getUri()),$etag); } } } src/EventListener/ConditionalRequestListener.php
- 66. PLACEHOLDERS
- 67. AJAX
- 70. EDGE SIDE INCLUDES ✓ PLACEHOLDER ✓ W3C STANDARD ✓ PROCESSED "ON THE EDGE" (E.G. VARNISH) ✓ OUTPUT IS A COMPOSITION OF BLOCKS ✓ STATE PER BLOCK ✓ TTL PER BLOCK <esi:include src="/header" />
- 71. VARNISH Surrogate-Capability: key="ESI/1.0" Surrogate-Control: content="ESI/1.0" <esi:include src="/header" /> BACKEND Parse ESI placeholdersVARNISH
- 73. ESI VS AJAX
- 74. EDGE SIDE INCLUDES ✓ SERVER-SIDE ✓ STANDARDIZED ✓ PROCESSED ON THE “EDGE”, NOT IN THE BROWSER ✓ GENERALLY FASTER - SEQUENTIAL (ONLY PARALLEL IN ENTERPRISE VERSION) - ONE FAILS, ALL FAIL - LIMITED IMPLEMENTATION IN VARNISH
- 75. AJAX ✓ CLIENT-SIDE ✓ COMMON KNOWLEDGE ✓ PARALLEL PROCESSING ✓ GRACEFUL DEGRADATION - PROCESSED BY THE BROWSER - EXTRA ROUNDTRIPS - SOMEWHAT SLOWER
- 76. COMPOSITION AT THE VIEW LAYER
- 77. /** * @Route("/", name="home") */ public function index() { return $this ->render('index.twig') ->setPublic() ->setSharedMaxAge(500); } /** * @Route("/header", name="header") */ public function header() { $response = $this ->render('header.twig') ->setPrivate(); $response->headers->addCacheControlDirective('no-store'); return $response; } /** * @Route("/footer", name="footer") */ public function footer() { $response = $this->render('footer.twig'); $response ->setSharedMaxAge(500) ->setPublic(); return $response; } /** * @Route("/nav", name="nav") */ public function nav() { $response = $this->render('nav.twig'); $response ->setVary('X-Login',false) ->setSharedMaxAge(500) ->setPublic(); return $response; } Controller action per fragment
- 78. <div class="container-fluid"> {{ include('header.twig') }} <div class="row"> <div class="col-sm-3 col-lg-2"> {{ include('nav.twig') }} </div> <div class="col-sm-9 col-lg-10"> {% block content %}{% endblock %} </div> </div> {{ include('footer.twig') }} </div> <div class="container-fluid"> {{ render_esi(url('header')) }} <div class="row"> <div class="col-sm-3 col-lg-2"> {{ render_esi(url('nav')) }} </div> <div class="col-sm-9 col-lg-10"> {% block content %}{% endblock %} </div> </div> {{ render_esi(url('footer')) }} </div>
- 79. <div class="container-fluid"> <esi:include src="/header" /> <div class="row"> <div class="col-sm-3 col-lg-2"> <esi:include src="/nav" /> </div> <div class="col-sm-9 col-lg-10"> <div class="page-header"> <h1>An example page <small>Rendered at 2017-05-17 16:57:14</small></h1> </div> <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris consequat orci eget libero sollicitudin,…</p> </div> </div> <esi:include src="/footer" /> </div>
- 80. CACHE VARIATIONS
- 81. HOW DO YOU IDENTIFY AN OBJECT IN CACHE?
- 82. THE URL IDENTIFIES THE OBJECT IN CACHE
- 83. WHAT IF THE CONTENT OF A URL VARIES BASED ON THE VALUE OF A REQUEST HEADER?
- 84. CACHE VARIATIONS HTTP/1.1 200 OK Host: localhost Content-Language: en Content-type: text/html; charset=UTF-8 Hello world output GET / HTTP/1.1 Host: localhost Accept-Language: en, nl, de
- 87. THERE'S ONLY ONE THING WORSE THAN NOT CACHING ENOUGH
- 88. IT'S CACHING TOO MUCH OR TOO LONG
- 89. PURGING
- 90. sub vcl_recv { if (req.method == "PURGE") { if (!client.ip ~ purge) { return (synth(405, "This IP is not allowed to send PURGE.")); } if (req.http.X-Purge-Pattern) { ban("obj.http.X-Req-URL ~ " + req.url + " && obj.http.X-Req-Host == " + req.http.host); return (synth(200, "Purged")); } else { ban("obj.http.x-url == " + req.url + " && obj.http.x-host == " + req.http.host); return (synth(200, "Purged")); } } } sub vcl_backend_response { set beresp.http.x-url = bereq.url; set beresp.http.x-host = bereq.http.host; }
- 91. curl -XPURGE -H"X-Purge-Pattern:/products/(.*)" http://localhost
- 92. vcl 4.0; import xkey; backend default { .host = "192.0.2.11"; .port = "8080"; } acl purgers { "203.0.113.0"/24; } sub vcl_recv { if (req.method == "PURGE") { if (client.ip !~ purgers) { return (synth(403, "Forbidden")); } set req.http.n-gone = xkey.purge(req.http.xkey-purge); return (synth(200, "Invalidated "+req.http.n-gone+" objects")); } }
- 93. HTTP/1.1 OK xkey: 8155054 xkey: 166412 xkey: 234323 BACKEND RESPONSE PURGE / HTTP/1.1 Host: www.example.com xkey-purge: 166412 INVALIDATION REQUEST
- 94. HIGH TTL + PURGING
- 96. WHAT IF YOU CAN'T LEVERAGE HTTP?
- 97. WRITE VCL CODE
- 98. sub vcl_recv { if (req.url ~ "^/status.php$" || req.url ~ "^/update.php$" || req.url ~ "^/admin$" || req.url ~ "^/admin/.*$" || req.url ~ "^/flag/.*$" || req.url ~ "^.*/ajax/.*$" || req.url ~ "^.*/ahah/.*$") { return (pass); } } URL blacklist example
- 99. vcl 4.0; sub vcl_recv { if (req.http.Cookie) { set req.http.Cookie = ";" + req.http.Cookie; set req.http.Cookie = regsuball(req.http.Cookie, "; +", ";"); set req.http.Cookie = regsuball(req.http.Cookie, ";(SESS[a-z0-9]+|SSESS[a-z0-9]+|NO_CACHE)=", "; 1="); set req.http.Cookie = regsuball(req.http.Cookie, ";[^ ][^;]*", ""); set req.http.Cookie = regsuball(req.http.Cookie, "^[; ]+|[; ]+$", ""); if (req.http.Cookie == "") { unset req.http.Cookie; } else { return (pass); } } } Cookie example
- 101. AUTHENTICATION VALIDATED AND TERMINATED AT THE PROXY LEVEL CLIENT VARNISH BACKEND
- 103. BASIC AUTH
- 105. WHAT ABOUT STATIC RESOURCES?
- 106. WHAT ABOUT VIDEO?
- 108. VARNISH ENTERPRISE ✓ CLIENT SSL TERMINATION ✓ BACKEND SSL CONNECTIONS ✓ PARALLEL ESI ✓ MASSIVE STORAGE ENGINE ✓ ENCRYPTION ✓ THROTTLING ✓ RATE LIMITING ✓ PREFETCHING ✓ GEOLOCATION ✓ AUTHENTICATION ✓ EDGESTASH ✓ CUSTOM STATISTICS ✓ ADMIN MODULE ✓ SUPPORT ✓ HIGH AVAILABILITY