NLP balancer Varnish configuration

# systemd service (with multiple ports for testing)

[Unit]
Description=Varnish HTTP accelerator
Documentation=https://www.varnish-cache.org/docs/6.1/ man:varnishd

[Service]
Type=simple
Restart=always
LimitNOFILE=131072
LimitMEMLOCK=82000
ExecStart=/usr/sbin/varnishd -j unix,user=vcache -F -a :80 -a :8000 -a :8001 -a :8002 -a :8003 -a :8004 -a :8005 -T localhost:6082 -f /etc/varnish/default.vcl -S /etc/varnish/secret -s malloc,14g
ExecReload=/usr/share/varnish/varnishreload
ProtectSystem=full
ProtectHome=true
PrivateTmp=true
PrivateDevices=true

[Install]
WantedBy=multi-user.target




# Varnish VCL configuration

vcl 4.0;

import directors;    # load the directors

# Default backend definition. Set this to point to your content server.
backend nlp1 {
    .host = "nlp1";
    .host_header = "nlp1";
    .probe = {
        .url = "/status";
        .timeout = 1s;
        .interval = 5s;
        .window = 5;
        .threshold = 3;
    }
}

backend nlp2 {
    .host = "nlp2";
    .host_header = "nlp2";
    .probe = {
        .url = "/status";
        .timeout = 1s;
        .interval = 5s;
        .window = 5;
        .threshold = 3;
    }
}

backend nlp3 {
    .host = "nlp3";
    .host_header = "nlp3";
    .probe = {
        .url = "/status";
        .timeout = 1s;
        .interval = 5s;
        .window = 5;
        .threshold = 3;
    }
}

backend nlp4 {
    .host = "nlp4";
    .host_header = "nlp4";
    .probe = {
        .url = "/status";
        .timeout = 1s;
        .interval = 5s;
        .window = 5;
        .threshold = 3;
    }
}

backend nlp5 {
    .host = "nlp5";
    .host_header = "nlp5";
    .probe = {
        .url = "/status";
        .timeout = 1s;
        .interval = 5s;
        .window = 5;
        .threshold = 3;
    }
}

backend nlp6 {
    .host = "nlp6";
    .host_header = "nlp6";
    .probe = {
        .url = "/status";
        .timeout = 1s;
        .interval = 5s;
        .window = 5;
        .threshold = 3;
    }
}

sub vcl_init {
    new nlp_vdir = directors.round_robin();
    nlp_vdir.add_backend(nlp1);
    nlp_vdir.add_backend(nlp2);
    nlp_vdir.add_backend(nlp3);
    nlp_vdir.add_backend(nlp4);
    nlp_vdir.add_backend(nlp5);
    nlp_vdir.add_backend(nlp6);
}

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.

    # Set backend
    set req.backend_hint = nlp_vdir.backend();

    # Pass if X-No-Cache is set
    if (req.http.X-No-Cache){
        return(pass);
    }

    # Unset cookies
    unset req.http.Cookie;
}

sub vcl_backend_fetch {
    # Use host defined in backend
    unset bereq.http.host;

    return(fetch);
}

sub vcl_backend_response {
    # Happens after we have read the response headers from the backend.
    #
    # Here you clean the response headers, removing silly Set-Cookie headers
    # and other mistakes your backend does.

    unset beresp.http.Set-Cookie;

    // Set TTL if request that should be cached and status code is 2xx, 3xx or 4xx
    if (
        beresp.status >= 200 && beresp.status < 500
        && beresp.http.Cache-Control !~ "no-cache"
    ){
        set beresp.ttl = 1w;
    }
    else {
        set beresp.ttl = 0s;
    }
}

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.

    if (obj.hits > 0){
        set resp.http.X-Cache = "HIT";
    }
    else {
        set resp.http.X-Cache = "MISS";
    }
}