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

I'm Thomas Schedler @chirimoya | https://github.com/chirimoya ... head of development and technical consultant. Young father trying to master Heston Blumenthal recipes.

Why?

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Who knows about HTTP Caching?

HTTP Caching Basics A short recap.

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

HTTP/1.1 200 OK Cache-Control: public, max-age=3600, s-maxage=86400 Interesting content GET /

HTTP/1.1 200 OK Expires: Sat, 27 Oct 2015 16:00:00 GMT More Content GET /

HTTP/1.1 200 OK Last-Modified: Wed, 24 Oct 2018 07:28:00 GMT Quite recent Content GET / GET / If-Modified-Since: Wed, 24 Oct 2018 07:28:00 GMT HTTP/1.1 304 Not Modified

HTTP/1.1 200 OK ETag: "33a64df551425fcc55e4d42a148795d9f25f89d4" Still more Content GET / GET / If-None-Match: "33a64df551425fcc55e4d42a148795d9f25f89d4" HTTP/1.1 304 Not Modified

Custom HTTP Header Pass additional information with the request or the response.

Browser Reverse Proxy Symfony Application GET / GET / Browser 200 OK Cache-Control: max-age=240 200 OK X-Reverse-Proxy-TTL: 3600 GET / GET / 200 OK X-Reverse-Proxy-TTL: 3600 200 OK Cache-Control: max-age=240 PURGE /

Browser Reverse Proxy Symfony Application GET / GET / Browser 200 OK Cache-Control: max-age=240 200 OK X-Reverse-Proxy-TTL: 3600 X-Cache-Tags: p1,p2,p3 GET / GET / 200 OK X-Reverse-Proxy-TTL: 3600 X-Cache-Tags: p1,p2 200 OK Cache-Control: max-age=240 BAN X-Cache-Tags: p3

“ Caching entire responses isn't always possible for highly dynamic sites, or is it?

Partly caching with ESI HTTP Standards FTW!

ESI - Edge Side Includes – The ESI specification describes tags to communicate with the gateway cache – In Symfony the is implemented – If the response contains ESI tags, the cache either requests the page fragment from the backend or embeds the fresh cache entry

// app/config/config.yml framework:
 ... esi: { enabled: true } // app/Resources/views/Default/index.html.twig
 
 {# you can use a controller reference #}
 {{ render_esi(controller('AppBundle:News:latest', { 'limit': 5 })) }}
 
 {# ... or a URL #}
 {{ render_esi(url('latest_news', { 'limit': 5 })) }}

https://www.kuechengoetter.de

Caching Implementations Symfony HttpCache or Varnish?

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

// src/CacheKernel.php

// src/Controller/NameController.php setSharedMaxAge(3600); return $response; } }

Varnish – Super performant – Feature complete – Configured using VCL – Implemented in C – Harder to setup

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

// public/index.php

// src/Controller/NameController.php setSharedMaxAge(3600); return $response; } }

# 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"; }

# 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. }

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FOSHttpCacheBundle Simplifies cache handling and invalidation in Symfony applications.

FOSHttpCacheBundle Features – Use rules to set cache headers – CacheManager / Annotations for comfortable Invalidation – Tagged Cache Invalidation – User Context based caching using session

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

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Who knows the Vary header?

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

Reverse Proxy Symfony Application GET /en Browser 200 OK X-Sulu-Target-Group: 1 GET /_sulu_target_group X-Sulu-Original-Url: /en 200 OK Cache-Control: max-age=0 Set-Cookie: _svtg=1; Set-Cookie: _svs=…; GET /en Cookie: _svtg=1; _svs=… 200 OK Cache-Control: max-age=0 200 OK Vary: X-Sulu-Target-Group X-Reverse-Proxy-TTL: 3600 GET /en X-Sulu-Target-Group: 1

Reverse Proxy Symfony Application Browser GET /about-us X-Sulu-Target-Group: 1 200 OK X-Reverse-Proxy-TTL: 3600 GET /about-us Cookie: _svtg=1; _svs=… Browser 200 OK Cache-Control: max-age=0 GET /about-us Cookie: _svtg=1; _svs=… 200 OK Cache-Control: max-age=0

Symfony HttpCache Use extended version of the Symfony HttpCache from Sulu to support Audience Targeting.

hasAudienceTargeting = $hasAudienceTargeting; } // ...

// app/WebsiteCache.php

// web/website.php

Varnish VCL to the rescue!

“ I really love the Varnish Configuration Language! Said no one, ever.

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# default.vcl 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_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_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=/;"); } }

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=/;"); } }

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=/;"); } }

Sulu Docs

How to reevaluate target groups on cache hit? Good old Javascript.

Thanks for watching! sulu.io