Varnish 4.0 file for our Craft CMS projects

craftcms_varnish.vcl

# Varnish 4.0 file for our Craft CMS projects
# Based on https://github.com/mattiasgeniar/varnish-4.0-configuration-templates/blob/master/default.vcl
# 
# This is still work in progress, comments appreciated.

vcl 4.0;

import std; 
import directors;

# Default backend definition. Set this to point to your content server.
backend server1 {
    .host = "xxx.xxx.xxx.xxx";
    .port = "80";
    .max_connections = 300; # That's it
    .probe = {
	      #.url = "/"; # short easy way (GET /)
	      # We prefer to only do a HEAD /
            .request = 
                "HEAD / HTTP/1.1"
                "Host: localhost"
                "Connection: close";      	
            .interval = 5s; # check the health of each backend every 5 seconds
            .timeout = 1s; # timing out after 1 second.
            
            # If 3 out of the last 5 polls succeeded the backend is considered healthy, otherwise it will be marked as sick
            .window = 5;
            .threshold = 3;
         }
    .first_byte_timeout     = 300s;   # How long to wait before we receive a first byte from our backend?
    .connect_timeout        = 5s;     # How long to wait for a backend connection?
    .between_bytes_timeout  = 2s;     # How long to wait between bytes received from our backend?
}

acl purge {
    # For now, I'll only allow purges coming from localhost
    "127.0.0.1";
    "localhost";
}

sub vcl_init {
    # Called when VCL is loaded, before any requests pass through it. Typically used to initialize VMODs.

    new vdir = directors.round_robin();
    vdir.add_backend(server1);
    # vdir.add_backend(server...);
    # vdir.add_backend(servern);
}

# Handle the HTTP request received by the client
sub vcl_recv {

    # Kept as an example of a 404 redirect
    # shortcut for DFind requests
    #if (req.url ~ "^/w00tw00t") {
    #    return (synth(404, "Not Found"));
    #}

    if (req.restarts == 0) {
        if (req.http.X-Forwarded-For) {
            set req.http.X-Forwarded-For = req.http.X-Forwarded-For + ", " + client.ip;
        } else {
            set req.http.X-Forwarded-For = client.ip;
        }
    }

    # Normalize the header, remove the port (in case you're testing this on various TCP ports)
    set req.http.Host = regsub(req.http.Host, ":[0-9]+", "");

    # Normalize the query arguments
    set req.url = std.querysort(req.url);

    # Exclude the following
    if (req.url ~ "(\/admin|p=admin)(.*)" ||
      req.url ~ "^/search(.*)"
    ) {
        return(pass);
    }

    # Allow purging
    if (req.method == "PURGE") {
        if (!client.ip ~ purge) {
            # Not from an allowed IP? Then die with an error.
            return (synth(405, "This IP is not allowed to send PURGE requests."));
        }

        # If you got this stage (and didn't error out above), purge the cached result
        return (purge);
    }

    # Only cache GET or HEAD requests. This makes sure the POST requests are always passed.
    if (req.method != "GET" && req.method != "HEAD") {
        return (pass);
    }

    # Only deal with "normal" types
    if (req.method != "GET" &&
            req.method != "HEAD" &&
            req.method != "PUT" &&
            req.method != "POST" &&
            req.method != "TRACE" &&
            req.method != "OPTIONS" &&
            req.method != "PATCH" &&
            req.method != "DELETE") {
        /* Non-RFC2616 or CONNECT which is weird. */
        return (pipe);
    }

    # Only cache GET or HEAD requests. This makes sure the POST requests are always passed.
    if (req.method != "GET" && req.method != "HEAD") {
        return (pass);
    }

    # Configure grace period, in case the backend goes down. This allows otherwise "outdated"
    # cache entries to still be served to the user, because the backend is unavailable to refresh them.
    # This may not be desireable for you, but showing a Varnish Guru Meditation error probably isn't either.
    #set req.grace = 15s;
    #if (std.healthy(req.backend)) {
    #    set req.grace = 30s;
    #} else {
    #    unset req.http.Cookie;
    #    set req.grace = 6h;
    #}

    # Some generic URL manipulation, useful for all templates that follow
    # First remove the Google Analytics added parameters, useless for our backend
    if (req.url ~ "(\?|&)(utm_source|utm_medium|utm_campaign|gclid|cx|ie|cof|siteurl)=") {
        set req.url = regsuball(req.url, "&(utm_source|utm_medium|utm_campaign|gclid|cx|ie|cof|siteurl)=([A-z0-9_\-\.%25]+)", "");
        set req.url = regsuball(req.url, "\?(utm_source|utm_medium|utm_campaign|gclid|cx|ie|cof|siteurl)=([A-z0-9_\-\.%25]+)", "?");
        set req.url = regsub(req.url, "\?&", "?");
        set req.url = regsub(req.url, "\?$", "");
    }

    # Strip hash, server doesn't need it.
    if (req.url ~ "\#") {
        set req.url = regsub(req.url, "\#.*$", "");
    }

    # Strip a trailing ? if it exists
    if (req.url ~ "\?$") {
        set req.url = regsub(req.url, "\?$", "");
    }

    # Remove ALL cookies
    # A bit heavy handed, but I don’t need ‘em.
    unset req.http.Cookie;

    # Normalize Accept-Encoding header
    # straight from the manual: https://www.varnish-cache.org/docs/3.0/tutorial/vary.html
    if (req.http.Accept-Encoding) {
        if (req.url ~ "\.(jpg|png|gif|gz|tgz|bz2|tbz|mp3|ogg)$") {
            # No point in compressing these
            unset req.http.Accept-Encoding;
        } elsif (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
            unset req.http.Accept-Encoding;
        }
    }
    
    # Normalize Accept-Language
    if (req.http.Accept-Language) {
        unset req.http.Accept-Language;
    }

    # Large static files are delivered directly to the end-user without
    # waiting for Varnish to fully read the file first.
    # Varnish 4 fully supports Streaming, so set do_stream in vcl_backend_response()
    if (req.url ~ "^[^?]*\.(mp[34]|rar|tar|tgz|gz|wav|zip|bz2|xz|7z|avi|mov|ogm|mpe?g|mk[av])(\?.*)?$") {
        unset req.http.Cookie;
        return (hash);
    }

    # Remove all cookies for static files
    # A valid discussion could be held on this line: do you really need to cache static files that don't cause load? Only if you have memory left.
    # Sure, there's disk I/O, but chances are your OS will already have these files in their buffers (thus memory).
    # Before you blindly enable this, have a read here: http://mattiasgeniar.be/2012/11/28/stop-caching-static-files/
    if (req.url ~ "^[^?]*\.(bmp|bz2|css|doc|eot|flv|gif|gz|ico|jpeg|jpg|js|less|pdf|png|rtf|swf|txt|woff|xml)(\?.*)?$") {
        unset req.http.Cookie;
        return (hash);
    }

    # Send Surrogate-Capability headers to announce ESI support to backend
    set req.http.Surrogate-Capability = "key=ESI/1.0";

    if (req.http.Authorization) {
        # Not cacheable by default
        return (pass);
    }

    return (hash);
}

sub vcl_pipe {
# Called upon entering pipe mode. In this mode, the request is passed on to the backend, and any further data from both the client and backend is passed on unaltered until either end closes the connection. Basically, Varnish will degrade into a simple TCP proxy, shuffling bytes back and forth. For a connection in pipe mode, no other VCL subroutine will ever get called after vcl_pipe.

	# Note that only the first request to the backend will have
	# X-Forwarded-For set.  If you use X-Forwarded-For and want to
	# have it set for all requests, make sure to have:
	# set bereq.http.connection = "close";
	# here.  It is not set by default as it might break some broken web
	# applications, like IIS with NTLM authentication.

	#set bereq.http.Connection = "Close";

	# Implementing websocket support (https://www.varnish-cache.org/docs/4.0/users-guide/vcl-example-websockets.html)
     	if (req.http.upgrade) {
        	set bereq.http.upgrade = req.http.upgrade;
     	}

	return (pipe);
}


sub vcl_pass {
#    return (pass);
}

# The data on which the hashing will take place
sub vcl_hash {
    hash_data(req.url);

    if (req.http.host) {
        hash_data(req.http.host);
    } else {
        hash_data(server.ip);
    }

    # hash cookies for requests that have them
    if (req.http.Cookie) {
        hash_data(req.http.Cookie);
    }
}

sub vcl_hit {
	# Called when a cache lookup is successful.

	if (obj.ttl >= 0s) {
		# A pure unadultered hit, deliver it
		return (deliver);
	}

	# https://www.varnish-cache.org/docs/trunk/users-guide/vcl-grace.html
	# When several clients are requesting the same page Varnish will send one request to the backend and place the others on hold while fetching one copy from the backend. In some products this is called request coalescing and Varnish does this automatically.
	# If you are serving thousands of hits per second the queue of waiting requests can get huge. There are two potential problems - one is a thundering herd problem - suddenly releasing a thousand threads to serve content might send the load sky high. Secondly - nobody likes to wait. To deal with this we can instruct Varnish to keep the objects in cache beyond their TTL and to serve the waiting requests somewhat stale content.

	#	if (!std.healthy(req.backend_hint) && (obj.ttl + obj.grace > 0s)) {
	#		return (deliver);
	#	} else {
	#		return (fetch);
	#	}

	# We have no fresh fish. Lets look at the stale ones.
	if (std.healthy(req.backend_hint)) {
		# Backend is healthy. Limit age to 10s.
		if (obj.ttl + 10s > 0s) {
				#set req.http.grace = "normal(limited)";
				return (deliver);
		} else {
			# No candidate for grace. Fetch a fresh object.
			return(fetch);
		}
	} else {
		# backend is sick - use full grace
    if (obj.ttl + obj.grace > 0s) {
    	#set req.http.grace = "full";
			return (deliver);
		} else {
			# no graced object.
			return (fetch);
    }
  }

  # fetch & deliver once we get the result
  return (fetch);	# Dead code, keep as a safeguard
}

sub vcl_miss {
    return (fetch);
}

# Handle the HTTP request coming from our backend
sub vcl_backend_response {
  # Pause ESI request and remove Surrogate-Control header
  if (beresp.http.Surrogate-Control ~ "ESI/1.0") {
    unset beresp.http.Surrogate-Control;
    set beresp.do_esi = true;
  }

  # Enable cache for all static files
  # The same argument as the static caches from above: monitor your cache size, if you get data nuked out of it, consider giving up the static file cache.
  # Before you blindly enable this, have a read here: http://mattiasgeniar.be/2012/11/28/stop-caching-static-files/
  #if (bereq.url ~ "^[^?]*\.(bmp|bz2|css|doc|eot|flv|gif|gz|ico|jpeg|jpg|js|less|mp[34]|pdf|png|rar|rtf|swf|tar|tgz|txt|wav|woff|xml|zip)(\?.*)?$") {
  #    unset beresp.http.set-cookie;
  #}

  # Removes Crafts Set-Cookie on everything except admin and other selected url’s
  if (!(bereq.url ~ "(\/admin|p=admin)(.*)" ||
          bereq.url ~ "^/search(.*)"
       )) {
  	unset beresp.http.set-cookie;
  }
    
	# Large static files are delivered directly to the end-user without
	# waiting for Varnish to fully read the file first.
	# Varnish 4 fully supports Streaming, so use streaming here to avoid locking.
	if (bereq.url ~ "^[^?]*\.(mp[34]|rar|tar|tgz|gz|wav|zip|bz2|xz|7z|avi|mov|ogm|mpe?g|mk[av])(\?.*)?$") {
		unset beresp.http.set-cookie;		
		set beresp.do_stream = true; # Check memory usage it'll grow in fetch_chunksize blocks (128k by default) if the backend doesn't send a Content-Length header, so only enable it for big objects
		set beresp.do_gzip = false;	# Don't try to compress it for storage
	}    

  # Set 2min cache if unset for static files
  if (beresp.ttl <= 0s || beresp.http.Set-Cookie || beresp.http.Vary == "*") {
  	set beresp.ttl = 120s;
    set beresp.uncacheable = true;
    return (deliver);
  }

  # Allow stale content, in case the backend goes down.
  set beresp.grace = 1h;

  return (deliver);
}

# The routine when we deliver the HTTP request to the user
# Last chance to modify headers that are sent to the client
sub vcl_deliver {
    if (obj.hits > 0) {
        set resp.http.X-Cache = "HIT";
    } else {
        set resp.http.x-Cache = "MISS";
    }
    
		# Please note that obj.hits behaviour changed in 4.0, now it counts per objecthead, not per object
		# and obj.hits may not be reset in some cases where bans are in use. See bug 1492 for details.
		# So take hits with a grain of salt
		set resp.http.X-Cache-Hits = obj.hits;

    # Check if remove cache control was set by backend. 
    if (resp.http.X-Remove-Cache-Control) {
       # Remove the marker and set cache control headers 
       unset resp.http.X-Remove-Cache-Control;
       unset resp.http.Expires;
       set resp.http.Cache-Control =  "no-cache";
       set resp.http.Pragma = "no-cache";
       set resp.http.X-Varnish-Age = resp.http.age;
       
       # By definition we have a fresh object
       set resp.http.age = "0";
    }

    # Remove some headers: PHP version
    unset resp.http.X-Powered-By;

    # Remove some headers: Apache/nginx version & OS
    unset resp.http.Server;
    unset resp.http.X-Varnish;
    unset resp.http.Via;
    unset resp.http.Link;
     
    # Set some headers
    set resp.http.X-Domain-Juice-By = "vaersaagod.no";

    return (deliver);
}

sub vcl_purge {
    # restart request
    set req.http.X-Purge = "Yes";
    return(restart);
}

sub vcl_synth {
    if (resp.status == 720) {
        # We use this special error status 720 to force redirects with 301 (permanent) redirects
        # To use this, call the following from anywhere in vcl_recv: error 720 "http://host/new.html"
        set resp.status = 301;
        set resp.http.Location = resp.reason;
        return (deliver);
    } elseif (resp.status == 721) {
        # And we use error status 721 to force redirects with a 302 (temporary) redirect
        # To use this, call the following from anywhere in vcl_recv: error 720 "http://host/new.html"
        set resp.status = 302;
        set resp.http.Location = resp.reason;
        return (deliver);
    }

    return (deliver);
}

sub vcl_fini {
    return (ok);
}