Caching the Uncacheable

Or how to make visitor specific
content super fast.
Caching the
uncachable

I'm Daniel Rotter
@danrot90 | https://github.com/danrot
core developer and
support guru.
Passionate traveler and
soccer player.

HTTP Caching Basics
A short recap

Browser
Reverse
Proxy
Symfony
Application
GET / GET /
200 OK 200 OK
Browser
GET /
200 OK

GET /
HTTP/1.1 200 OK
Cache-Control: public, max-age=3600, s-maxage=86400
<!DOCTYPE html>
<html>
<body>
Interesting content
</body>
</html>

GET /
HTTP/1.1 200 OK
Last-Modified: Sun, 4, Feb 2018 20:18:00 GMT
<!DOCTYPE html>
<html>
<body>
Quite recent Content
</body>
</html>
GET /
If-Modified-Since: Sun, 4 Feb 2018 20:18:00 GMT
HTTP/1.1 304 Not Modified

Apply more logic in the reverse proxy layer
Custom HTTP Header

200 OK
Cache-Control: max-age=240
Browser
Reverse
Proxy
Symfony
Application
GET / GET /
200 OK
200 OK
X-Reverse-Proxy-TTL: 2400
Browser
GET /

200 OK
200 OK
200 OK
Browser
Reverse
Proxy
Symfony
Application
GET / GET /
Browser
GET /
PURGE /
GET /
200 OK

Caching
Implementations
Symfony Cache or Varnish?

Symfony Cache
– Easy to setup
– Implemented in PHP
– Not feature complete

// src/CacheKernel.php
<?php
namespace App;
use SymfonyBundleFrameworkBundleHttpCacheHttpCache;
class CacheKernel extends HttpCache {}
// public/index.php
<?php
use AppKernel;
use AppCacheKernel;
// ...
$kernel = new Kernel($env, $debug);
$kernel = new CacheKernel($kernel);
// ...

// src/Controller/NameController.php
<?php
namespace AppController;
use SymfonyComponentHttpFoundationResponse;
use SymfonyComponentRoutingAnnotationRoute;
class NameController {
/**
* @Route("/name/{name}")
*/
public function index(string $name) {
$response = new Response('Your name is ' . $name);
$response->setSharedMaxAge(3600);
return $response;
}
}

– Harder to setup
– Implemented in C
– Super performant
– Many more features
– Configured using VCL
Varnish

Varnish Installation
1. Actually install varnish
2. Start varnish on port 80
3. Start your application on a different port
4. Tell varnish on which port your application is running
5. Add varnish as a trusted proxy in Symfony
6. Add cache headers to your responses
7. Configure the cache with VCL in more detail

# default.vcl
vcl 4.0;
# Default backend definition. Set this to point to your content server.
backend default {
.host = "127.0.0.1";
.port = "8080";
}
4

// public/index.php
// ...
Request::setTrustedProxies(['127.0.0.1'], Request::HEADER_X_FORWARDED_ALL);
// ...
5

// src/Controller/NameController.php
<?php
namespace AppController;
use SymfonyComponentHttpFoundationResponse;
use SymfonyComponentRoutingAnnotationRoute;
class NameController {
/**
* @Route("/name/{name}")
*/
public function index(string $name) {
$response = new Response('Your name is ' . $name);
$response->setSharedMaxAge(3600);
return $response;
}
} 6

# default.vcl
sub vcl_recv {
# Happens before we check if we have this in cache already.
#
# Typically you clean up the request here, removing cookies you don't need,
# rewriting the request, etc.
}
sub vcl_deliver {
# Happens when we have all the pieces we need, and are about to send the
# response to the client.
#
# You can do accounting or modifying the final object here.
}
7

Audience Targeting
Show (and cache!) different content for different target
groups on the same URL

Audience Targeting
Goals
– Differentiate between different visitor target groups
– Target groups are evaluated by a ruleset
– first visit
– each browser session
– each hit
– Do not start a session on the server
– Cache the response per target group

Browser
Reverse
Proxy
Symfony
Application
GET /en
Accept-Encoding: gzip
200 OK
Vary: Accept-Encoding
GET /en
Accept-Encoding: identity
200 OK
GET /en
200 OK
GET /en
200 OK
Browser
200 OK
GET /en
Accept-Encoding: identity

Browser
Reverse
Proxy
Symfony
Application
GET /en
GET /_sulu_target_group
X-Sulu-Original-Url: /en
GET /en
X-Sulu-Target-Group: 1
200 OK
200 OK
Vary: X-Sulu-Target-Group
200 OK
Set-Cookie: _svtg=1;
Set-Cookie: _svs=...;
GET /en
Cookie: _svtg=1; _svs=..
200 OK

Reverse
Proxy
Symfony
Application
GET /about-us
GET /about-us
200 OK
X-Reverse-Proxy-TTL: 2400200 OK
Browser
Browser
GET /about-us
200 OK

Symfony Cache
Use extended version of the SymfonyCache from Sulu to support
Audience Targeting

<?php
namespace SuluComponentHttpCache;
use SymfonyBundleFrameworkBundleHttpCacheHttpCache as AbstractHttpCache;
use SymfonyComponentHttpKernelHttpKernelInterface;
class HttpCache extends AbstractHttpCache
{
public function __construct(HttpKernelInterface $kernel, $hasAudienceTargeting =
false, $cacheDir = null)
{
parent::__construct($kernel, $cacheDir);
$this->hasAudienceTargeting = $hasAudienceTargeting;
}
}

// app/WebsiteCache.php
<?php
use SuluComponentHttpCacheHttpCache;
class WebsiteCache extends HttpCache
{
}

// web/website.php
<?php
// ...
$kernel = new WebsiteKernel(SYMFONY_ENV, SYMFONY_DEBUG);
$kernel->loadClassCache();
if (SYMFONY_ENV != 'dev') {
$kernel = new WebsiteCache($kernel, true);
Request::enableHttpMethodParameterOverride();
}
// ...

“I really love VCL!
Said no one,
ever.

vcl 4.0;
import header;
backend default {
.host = "127.0.0.1";
.port = "8000";
}
sub vcl_recv {
if (req.http.Cookie ~ "_svtg" && req.http.Cookie ~ "_svs") {
set req.http.X-Sulu-Target-Group = regsub(req.http.Cookie, ".*_svtg=([^;]+).*", "1");
} elseif (req.restarts == 0) {
set req.http.X-Sulu-Original-Url = req.url;
set req.http.X-Sulu-Target-Group = regsub(req.http.Cookie, ".*_svtg=([^;]+).*", "1");
set req.url = "/_sulu_target_group";
} elseif (req.restarts > 0) {
set req.url = req.http.X-Sulu-Original-Url;
unset req.http.X-Sulu-Original-Url;
}
unset req.http.Cookie;
}
sub vcl_deliver {
if (resp.http.X-Sulu-Target-Group) {
set req.http.X-Sulu-Target-Group = resp.http.X-Sulu-Target-Group;
set req.http.Set-Cookie = "_svtg=" + resp.http.X-Sulu-Target-Group + "; expires=Tue, 19 Jan 2038
03:14:07 GMT; path=/;";
return (restart);
}
if (resp.http.Vary ~ "X-Sulu-Target-Group") {
set resp.http.Cache-Control = regsub(resp.http.Cache-Control, "max-age=(d+)", "max-age=0");
set resp.http.Cache-Control = regsub(resp.http.Cache-Control, "s-maxage=(d+)", "s-maxage=0");
}
if (req.http.Set-Cookie) {
set resp.http.Set-Cookie = req.http.Set-Cookie;
header.append(resp.http.Set-Cookie, "_svs=" + now + "; path=/;");
}
}
zz

Good ol’ Javascript
How to reevaluate
target groups on
cache hit?

Caching the Uncacheable

More Related Content

What's hot (20)

Similar to Caching the Uncacheable (20)

Recently uploaded (20)

Caching the Uncacheable