Install Varnish on Vesta CP

apache.conf

<IfModule mpm_prefork_module>    
    StartServers          1
    MinSpareServers       1
    MaxSpareServers       3
    MaxClients            6
    MaxRequestsPerChild   0
</IfModule>

<IfModule mpm_worker_module>
    StartServers          1
    MinSpareThreads       5
    MaxSpareThreads      15
    ThreadLimit          25
    ThreadsPerChild       5
    MaxClients           25
    MaxRequestsPerChild   0
</IfModule>

<IfModule mpm_event_module>
    StartServers          1
    MinSpareThreads       5
    MaxSpareThreads      15
    ThreadLimit          25
    ThreadsPerChild       5
    MaxClients           25
    MaxRequestsPerChild   0
</IfModule>

my.cnf

thread_cache_size = 2

varnish

// usefull links
// http://ryanfrankel.com/run-wordpress-digital-ocean-512mb-vps/
// http://ryanfrankel.com/using-varnish-with-wordpress/

// start
apt-get update
apt-get upgrade

// set different ssh port
mcedit /etc/ssh/sshd_config

// change vesta firewall rules
mcedit /usr/local/vesta/data/firewall/rules.conf

// update vesta
v-update-firewall

// check if ssh is working on a new port
service ssh restart
netstat -taupen

// install varnish
// https://www.vultr.com/docs/installing-varnish-4-with-apache2-on-ubuntu-14-04
sudo apt-get install apt-transport-https
sudo curl https://repo.varnish-cache.org/ubuntu/GPG-key.txt | apt-key add -
echo "deb https://repo.varnish-cache.org/ubuntu/ trusty varnish-4.0" >> /etc/apt/sources.list.d/varnish-cache.list
sudo apt-get update
sudo apt-get install varnish

// edit varnish config - change port to 80
mcedit /etc/default/varnish

// edit varnish config - change ip and port to 8082
mcedit /etc/varnish/default.vcl

// disable default nginx config
mcedit /etc/nginx/conf.d/defaultIP.conf

// change nginx port to 8082
mcedit /etc/nginx/conf.d/yourIP.conf

// change proxy port to 8082
mcedit /usr/local/vesta/conf/vesta.conf

// change web port to 8082
mcedit /home/admin/conf/web/nginx.conf

// restart varnish
service varnish reload
service varnish restart

varnish.vcl

# VCL version 4
vcl 4.0;

/* SET THE HOST AND PORT OF WORDPRESS
* *********************************************************/
backend default {
    .host = "127.0.0.1";
    .port = "8082";
}

# SET THE ALLOWED IP OF PURGE REQUESTS
# ##########################################################
acl purge {
    "localhost";
    "162.243.20.190";
}

# THE RECV FUNCTION
# ##########################################################
sub vcl_recv {
    # For Testing: If you want to test with Varnish passing (not caching) uncomment
    # return( pass );
    
    # FORWARD THE IP OF THE REQUEST
    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;
        }
    }
    
    # CLEAN UP THE ENCODING HEADER.  
    # SET TO GZIP, DEFLATE, OR REMOVE ENTIRELY.  WITH VARY ACCEPT-ENCODING
    # VARNISH WILL CREATE SEPARATE CACHES FOR EACH
    # DO NOT ACCEPT-ENCODING IMAGES, ZIPPED FILES, AUDIO, ETC.
    # ##########################################################
    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 {
            # unknown algorithm
            unset req.http.Accept-Encoding;
        }
    }
    
    # IF THIS IS A PURGE REQUEST, THEN CHECK THE IPS SET ABOVE
    # BLOCK IF NOT ONE OF THOSE IPS
    # ##########################################################
    if (req.method == "PURGE") {
        if ( !client.ip ~ purge ) {
            return (synth(405, "Not allowed."));
        }
        return (purge);
    }
    
    # PIPE ALL NON-STANDARD REQUESTS
    # ##########################################################
    if (req.method != "GET" &&
    req.method != "HEAD" &&
    req.method != "PUT" && 
    req.method != "POST" &&
    req.method != "TRACE" &&
    req.method != "OPTIONS" &&
    req.method != "DELETE") {
        return (pipe);
    }
    
    # ONLY CACHE GET AND HEAD REQUESTS
    # ##########################################################
    if (req.method != "GET" && req.method != "HEAD") {
        return (pass);
    }
    
    # OPTIONAL: DO NOT CACHE LOGGED IN USERS (THIS OCCURS IN FETCH TO, EITHER
    # COMMENT OR UNCOMMENT BOTH
    # ##########################################################
    if ( req.http.cookie ~ "wordpress_logged_in" ) {
        return( pass );
    }
    
    # IF THE REQUEST IS NOT FOR A PREVIEW, WP-ADMIN OR WP-LOGIN
    # THEN UNSET THE COOKIES
    # ##########################################################
    if (
        !(req.url ~ "wp-(login|admin)") 
        && !(req.url ~ "&preview=true" ) 
    ){
        unset req.http.cookie;
    }
    
    
    # DISABLE CACHE FOR PHPMYADMIN
    if (
        req.url ~ "phpmyadmin")
    {
        return (pass);
    }

    
    # IF BASIC AUTH IS ON THEN DO NOT CACHE
    # ##########################################################
    if (req.http.Authorization || req.http.Cookie) {
        return (pass);
    }
    
    # LIST URLS NOT TO BE CACHED
    # USUALLY THIS INCLUDES THE PREVIEW QUERY STRING, A NOCACHE
    # QUERY STRING, AND FILES THAT WILL BE SERVED BY THE CDN
    # SUCH AS IMAGES, CSS, AND JS.  IF YOU ARE NOT USING A CDN 
    # YOU CAN CACHE YOUR STATIC RESOURCES TOO
    # ##########################################################
    if ( 
        req.url ~ "preview" 
        || req.url ~ "nocache"
        || req.url ~ "\.css$"
        || req.url ~ "\.js$"
        || req.url ~ "\.jpg$"
        || req.url ~ "\.jpeg$"
        || req.url ~ "\.gif$"
        || req.url ~ "\.png$" 
    ) {
        return (pass);
    }
    
    # IF YOU GET HERE THEN THIS REQUEST SHOULD BE CACHED
    # ##########################################################
    return (pass);
}

# HIT FUNCTION
# ##########################################################
sub vcl_hit {
    # IF THIS IS A PURGE REQUEST THEN DO THE PURGE
    # ##########################################################
    if (req.method == "PURGE") {
        return (synth(200, "Purged."));
    }
    return (deliver);
}

# MISS FUNCTION
# ##########################################################
sub vcl_miss {
    if (req.method == "PURGE") {
        return (synth(200, "Purged."));
    }
    return (fetch);
}

# FETCH FUNCTION
# ##########################################################
sub vcl_backend_response {
    # I SET THE VARY TO ACCEPT-ENCODING, THIS OVERRIDES W3TC 
    # TENDANCY TO SET VARY USER-AGENT.  YOU MAY OR MAY NOT WANT
    # TO DO THIS
    # ##########################################################
    set beresp.http.Vary = "Accept-Encoding";
    
    # IF NOT WP-ADMIN THEN UNSET COOKIES AND SET THE AMOUNT OF 
    # TIME THIS PAGE WILL STAY CACHED (TTL)
    # ##########################################################
    if (!(bereq.url ~ "wp-(login|admin)") && !bereq.http.cookie ~ "wordpress_logged_in" ) {
        unset beresp.http.set-cookie;
        set beresp.ttl = 96h;
    }
    
    if (beresp.ttl <= 0s ||
        beresp.http.Set-Cookie ||
        beresp.http.Vary == "*") {
        set beresp.uncacheable = true;
        set beresp.ttl = 120s;
        return (deliver);
    }
    
    return (deliver);
}
    
# DELIVER FUNCTION
# ##########################################################
sub vcl_deliver {
    # IF THIS PAGE IS ALREADY CACHED THEN RETURN A 'HIT' TEXT 
    # IN THE HEADER (GREAT FOR DEBUGGING)
    # ##########################################################
    if (obj.hits > 0) {
        set resp.http.X-Cache = "HIT";
        # IF THIS IS A MISS RETURN THAT IN THE HEADER
        # ##########################################################
    } else {
        set resp.http.X-Cache = "MISS";
    }
}