Varnish and Drupal- Accelerating Website Performance and Flexibility with Varnish Cache

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Introduction
Matt Ackley
Marketing Team
@mbackley

Varnish + Drupal Accelerating Drupal Performance and Flexibility with Varnish Cache Kurt Gray Hosting Engineer Acquia Inc. @kurt Kristian Lyngstøl Software Engineer Varnish Software @kristian Matt Ackley Marketing Acquia Inc. @mbackley

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International support 408-435-7088
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Introduction
Kristian Lyngstol
Varnish Software
@ kristian

What is Varnish? © 2010 Acquia, Inc.
Reverse proxy cache server
... and more (load balancer, filter, director, ...)
Open Source (BSD), commercially supported
Typically in front of a LAMP stack:

Example Benchmarks: pages/second © 2010 Acquia, Inc.
Typical HA Drupal stack: 200 Drupal pages/ minute
... with Varnish: 2500 Drupal pages/ second
... using smaller backend hardware!

Example Benchmarks: Page latency © 2010 Acquia, Inc.
Varnish also improves response times:

Use cases for Varnish © 2010 Acquia, Inc.
Typical: Reverse proxy cache in front LAMP stack
As a web request load balancer
... or behind a load balancer
Behind a CDN
Next to a CDN
As a CDN
With other proxy caches
...and more!

What does Varnish do? © 2010 Acquia, Inc.
Caches backend responses, delivers from cache

How does it work? © 2010 Acquia, Inc.
Varnish stores a cache entry for each Host + URL

What can be cached in Varnish? © 2010 Acquia, Inc.
Drupal pages for anonymous users
Static content: images, js, css
Other types of static or generated content
What should NOT be cached in Varnish?
Responses to POST requests
Responses with a Set-Cookie : header
User-specific content (logged-in page requests)
Very large media files (> 100MB)
Has a Cache-Control: no-cache header

All cache policies can be tuned using VCL

How long will it be cached in Varnish? © 2010 Acquia, Inc.
Response header: Cache-Control: max-age= 300
If no Cache-Control specified then Varnish uses the Expires date, if specified
If no Cache-Control or Expires header then uses Varnish's default TTL, 2 minutes (adjustable)
All cache policies can be tuned using VCL ...

VCL: Varnish Configuration Language © 2010 Acquia, Inc.
Extend and modify Varnish cache policies
Add behaviors during each phase of delivery: recv, hash, fetch, hit, miss, deliver, ...
sub vcl_recv { # direct image requests to image servers if (req.url ~ "(jpg|gif|png)") { set req.backend = image_servers; } }

VCL: Varnish Configuration Language © 2010 Acquia, Inc.
Add/remove/change request or response headers
sub vcl_deliver { # Add a HIT/MISS header to the response if (obj.hits > 0) { set resp.http.X-Cache = "HIT"; set resp.http.X-Cache-Hits = obj.hits; } else { set resp.http.X-Cache = "MISS"; } }

Other VCL capabilities © 2010 Acquia, Inc.
Add/remove/change HTTP headers
Redirects based on request parameters
Rewrite requests
Retry failed requests
Synthesize direct responses
Saint and Grace: Deliver cached content when backend is unresponsive
ACLs: Network-address filtering
Request filtering
ESI: Separate cache entries and separate cache policies for each part of a document
Inline C code (eg. redirects based on GeoIP)

Varnish realtime tools © 2010 Acquia, Inc.
varnishstat: realtime status and performance metrics

varnishhist: live frequency plot of response times

Varnish CLI: live admin capabilities

varnishtop: live list of hottest files

varnishtop: analyze incoming HTTP headers

Introduction
Kurt Gray
Hosting Engineer
@kurt

Varnish and Drupal: Cache variances © 2010 Acquia, Inc.
Drupal emits Vary: Cookie,Accept-Encoding
Cookie : Avoids cache collisions between users
Accept-Encoding : maintain separate cache entries for compressed content (gzip, deflate) vs. uncompressed content

Varnish and Drupal: VCL snippets © 2010 Acquia, Inc. sub vcl_recv { # Normalize the Accept-Encoding header if (req.http.Accept-Encoding) { if (req.http.Accept-Encoding ~ "gzip") { set req.http.Accept-Encoding = "gzip"; } elsif (req.http.Accept-Encoding ~ "deflate") { set req.http.Accept-Encoding = "deflate"; } else { # unkown algorithm remove req.http.Accept-Encoding; } } }

Varnish and Drupal: VCL snippets © 2010 Acquia, Inc. sub vcl_recv { # Don't check cache for logged-in users if(req.http.cookie ~ "SESS") { return(pass); } # Cookie Bypass module: Don't check cache for anon # user who POSTed content less than 10 minutes ago. if(req.http.cookie ~ "NO_CACHE") { return(pass); } }

Varnish and Drupal: VCL snippets © 2010 Acquia, Inc. sub vcl_fetch { # Don't cache if response has explicit no-cache headers if (beresp.http.Pragma ~ "no-cache" || beresp.http.Cache-Control ~ "no-cache" || beresp.http.Cache-Control ~ "private") { return(pass); } }

Varnish and Pressflow Drupal, D7 © 2010 Acquia, Inc.
Pressflow = Drupal w/ many performance tweaks
Allows Varnish to cache and deliver Drupal page requests for anonymous visitors
...because Pressflow doesn't emit "lazy sessions"
No SESS cookies for anonymous visitors
Drupal 7 has same key features

Controlling cache expiration times © 2010 Acquia, Inc.
Drupal Admin > Performance page
Agressive or External caching
Minimum Page Lifetime = max-age
Active purging: use Drupal Varnish module
Static content: See the mod_expires directives in Drupal's .htaccess file
If no Cache-Control or Expires headers: Uses Varnish's default TTL (2 minutes)

Varnish and Acquia Hosting © 2010 Acquia, Inc.
All Acquia-hosted sites benefit from Varnish
Pressflow sites on Acquia-hosting get most benefit
Fully managed HA environment: No setup, no fuss
Reduces backend server size requirments
Excellent load test results

Do you love working with Drupal?
If so, Acquia is hiring in North America & Europe :
Engineering & design
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Varnish and Drupal- Accelerating Website Performance and Flexibility with Varnish Cache

by Acquia on Nov 12, 2010

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Varnish and Drupal- Accelerating Website Performance and Flexibility with Varnish Cache — Presentation Transcript