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WHAT WE'LL COVER ✅ HTTP Caching Basics ✅ Expiration And Validation ✅ Caching With Symfony ✅ Edge side includes

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OUT OF SCOPE ❌ Varnish, Squid etc. ❌ Application Caching ❌ Specific Techniques (eg Russian Doll Caching)

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WHO DIS? ! Marco Petersen " Software Developer @ SensioLabs # @ocrampete16

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ONCE UPON A CACHE

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HOW TO MAKE A WEB APPLICATION FASTER > Optimize database queries > Use more efficient algorithms > Rewrite Your Backend in a faster language > . . .

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SYMFONY — HTTP* * the HTTP/1.1 specification (RFC2616)

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TYPES OF CACHES > Browser Caches > Chrome, Firefox > Proxy Caches > Squid > Gateway Caches > Varnish, Nginx, Squid, Cloudflare

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Without Caching

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Browser Caches cache the sites you surf

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Proxy Caches cache incoming traffic

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Gateway Caches cache outgoing traffic

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LET'S GET CACHING

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CACHING MODELS > Expiration > Expires > Cache-Control > Validation > ETag / If-None-Match > Last-Modified / If-Modified-Since

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EXPIRATION

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THE GAME PLAN 1. Client requests a resource and receives a response. 2. Cache intercepts and stores resouce with expiration date. 3. Client requests same resource. 4. Cached resource is returned if it is still fresh. > The server is not hit.

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EXPIRES SPECIFIES A SPECIFIC DATE AND TIME AFTER WHICH THE RESOURCE BECOMES STALE.

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/** * @Cache(expires="+600 seconds") */ public function bar() { return $response; } // or public function foo() { $response->setExpires(new \DateTime('+600 seconds')); return $response; }

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HTTP/1.1 200 OK Expires: Wed, 21 Oct 2015 07:28:00 GMT Lorem ipsum dolor sit amet

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CACHE-CONTROL THE MULTI-TALENT! > defines several caching directives > for now, we're only interested in max-age and s-maxage

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MAX-AGE AND S-MAXAGE ARE LIKE EXPIRES, BUT THEY SPECIFY THE NUMBER OF SECONDS UNTIL A RESOURCE BECOMES STALE

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/** * @Cache(smaxage=600) */ public function bar() { return $response; } // or public function foo() { $response->setSharedMaxAge(600); return $response; }

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HTTP/1.1 200 OK Cache-Control: s-maxage=600 Lorem ipsum dolor sit amet

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MAX-AGE AND S-MAXAGE > Browser caches only look for max-age. > Shared caches look for s-maxage if it exists, otherwise it follows max-age.

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VALIDATION

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THE GAME PLAN 1. Client requests a resource. 2. Server returns a response with validation information. 3. Client requests same resource with the validation information. 4. 304 (Not Modified) is returned if the resource is still valid. > The server is hit, but the response is much smaller.

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ETAG?

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AN ETAG IS A STRING THAT REPRESENTS A SPECIFIC VERSION OF A RESOURCE.

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/** * @Cache(Etag="post.getId() ~ post.getUpdatedAt().getTimestamp()") */ public function bar(Post $post) { return $response; } // or public function foo(Request $request) { $reponse = new Response(); // Compute the ETag $response->setEtag($etag) if ($response->isNotModified($request)) { return $response; } return $this->render('foo.html.twig', [], $response); }

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// server responds HTTP/1.1 200 OK ETag: "qwerasdfyxcv" Lorem ipsum dolor sit amet // client requests same resource again GET /foo HTTP/1.1 If-None-Match: "qwerasdfyxcv" // server responds HTTP/1.1 304 NOT MODIFIED

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LAST-MODIFIED SPECIFIES WHEN A RESOURCE WAS LAST MODIFIED

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/** * @Cache(lastModified="post.getUpdatedAt()") */ public function bar(Post $post) { return $response; } // or public function foo(Request $request, Post $post) { $reponse = new Response(); $response->setLastModified($post->getUpdatedAt()) if ($response->isNotModified($request)) { return $response; } return $this->render('foo.html.twig', [], $response); }

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// server responds HTTP/1.1 200 OK Last-Modified: Wed, 21 Oct 2015 07:28:00 GMT Lorem ipsum dolor sit amet // client requests same resource again GET /foo HTTP/1.1 If-Modified-Since: Wed, 21 Oct 2015 07:28:00 GMT // server responds HTTP/1.1 304 NOT MODIFIED

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CAN'T DECIDE WHICH MODEL TO PICK?

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BOTH WORK WELL TOGETHER, ALTHOUGH EXPIRATION TRUMPS VALIDATION. // max_age > etag $response->setCache([ 'max_age' => 20, 'etag' => $etag, ]);

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NEED A GATEWAY CACHE FOR DEVELOPMENT? NO PROBLEM!

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// public/index.php use App\Kernel; use Symfony\Bundle\FrameworkBundle\HttpCache\HttpCache; // ... $kernel = new Kernel($env, $debug); if ('prod' === $env) { $kernel = new HttpCache($kernel); }

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// public/index.php use App\Kernel; use Symfony\Bundle\FrameworkBundle\HttpCache\HttpCache; // ... $kernel = new Kernel($env, $debug); if ('prod' === $env) { $kernel = new HttpCache($kernel); }

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// src/CacheKernel.php namespace App; use Symfony\Bundle\FrameworkBundle\HttpCache\HttpCache; final class CacheKernel extends HttpCache { protected function getOptions(): array { return [ 'default_ttl' => 0, ]; } }

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// src/CacheKernel.php namespace App; use Symfony\Bundle\FrameworkBundle\HttpCache\HttpCache; final class CacheKernel extends HttpCache { protected function getOptions(): array { return [ 'default_ttl' => 0, ]; } }

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DEMO TIME

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RECAP

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RECAP > Expiration asks "When does it become stale?" > Expires specifies a future point in time > Cache-Control is like Expires, but relative > Validation asks "Is it still fresh?" > Etag specifies an identifier to compare > Last-Modified specifies a point in time in the past > All work well with Symfony!

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EDGE SIDE INCLUDES

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DEMO TIME

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FINAL RECAP

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FINAL RECAP > Cache to bypass your application. > Expiration - "When does this expire?" > Validation - "Is this still valid?" > ESI caches fragments of pages separately.

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WHERE TO GO FROM HERE > Set up your own gateway cache > Read the HTTP/1.1 spec (RFC-2616) > Check out HTTP/2's new features (RFC-7540) > Server Push > Multiplexing

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$kernel->terminate($request, $response);

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