johnscancella/default.vcl

## default.vcl
# new 4.0 format.
vcl 4.0;

import directors;

backend app1 {
    .host = "ndnpappvlp01.loc.gov";
    .probe = {
        .url = "/";
        .interval = 60s;
        .timeout = 10s;
        .window = 5;
        .threshold = 3;
    }
}

backend app2 {
    .host = "ndnpappvlp02.loc.gov";
    .probe = {
        .url = "/";
        .interval = 60s;
        .timeout = 10s;
        .window = 5;
        .threshold = 3;
    }
}

#create a virtual group for use when we do the load balancing
sub vcl_init {
    new app = directors.hash();
    app.add_backend(app1, 1);
    app.add_backend(app2, 1);
}

#stream all files, otherwise you have to wait for e.g. an entire PDF or JP2, etc. to be saved into the cache before Varnish will send the first byte to the client
sub vcl_backend_response {
    set beresp.do_stream = true;
    set beresp.grace = 1h;
    if (beresp.http.content-type ~ "(text|application)") {
        set beresp.do_gzip = true;
    }
}

sub vcl_recv {
    #load balance by the user's ip address
    set req.backend_hint = app.backend(client.identity);

    # unset cookies since we don't want to bypass caching normally
    if (req.http.cookie) {
        unset req.http.cookie;
    }

    #don't cache or modify /data or any pdf files
    if (req.url ~ "^/data/") {
        return (pass);
    }
    if (req.url ~ "\.pdf$") {
        return (pass);
    }
}

#prefer a fresh object, but when one cannot be found Varnish will look for stale one. This replaces req.grace in vcl_recv()
sub vcl_hit {
    if (obj.ttl >= 0s) {
       return (deliver);
    }
    if (obj.ttl + obj.grace > 0s) {
        return (deliver);
    }
    return (fetch);
}

#vcl_deliver’s support for Vary headers needs to be preserved – at the very least we need the “Vary: Accept-Encoding” for anything which has gzip-compression enabled
sub vcl_deliver {
    if (!resp.http.Vary) {
        set resp.http.Vary = "Accept-Encoding";
    } else if (resp.http.Vary !~ "(?i)Accept-Encoding") {
        set resp.http.Vary = resp.http.Vary + ",Accept-Encoding";
    }
}

#TODO but we should probably use a standard LC error page or confirm that CloudFlare will substitute the nice P1 error page for a backend 5xx error
sub vcl_backend_error {
    set beresp.http.Content-Type = "text/html; charset=utf-8";
    set beresp.http.Retry-After = "5";
    synthetic ({"
    <?xml version="1.0" encoding="utf-8"?>
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
     <html>
     <head>
       <title>The page is temporarily unavailable</title>
       </head>
       <body>
         <h1>Chronicling America is currently unavailable</h1>
           <p>The Chronicling America website is currently offline, undergoing maintenance.  We regret the inconvenience, and invite you to visit other collections available on the Library of Congress website at <a href="http://www.loc.gov">www.loc.gov</a> while we are working to restore service.</p>
            </body>
            </html>
            "});

    return (deliver);
}
	# new 4.0 format.
	vcl 4.0;

	import directors;

	backend app1 {
	.host = "ndnpappvlp01.loc.gov";
	.probe = {
	.url = "/";
	.interval = 60s;
	.timeout = 10s;
	.window = 5;
	.threshold = 3;
	}
	}

	backend app2 {
	.host = "ndnpappvlp02.loc.gov";
	.probe = {
	.url = "/";
	.interval = 60s;
	.timeout = 10s;
	.window = 5;
	.threshold = 3;
	}
	}

	#create a virtual group for use when we do the load balancing
	sub vcl_init {
	new app = directors.hash();
	app.add_backend(app1, 1);
	app.add_backend(app2, 1);
	}

	#stream all files, otherwise you have to wait for e.g. an entire PDF or JP2, etc. to be saved into the cache before Varnish will send the first byte to the client
	sub vcl_backend_response {
	set beresp.do_stream = true;
	set beresp.grace = 1h;
	if (beresp.http.content-type ~ "(text\|application)") {
	set beresp.do_gzip = true;
	}
	}

	sub vcl_recv {
	#load balance by the user's ip address
	set req.backend_hint = app.backend(client.identity);

	# unset cookies since we don't want to bypass caching normally
	if (req.http.cookie) {
	unset req.http.cookie;
	}

	#don't cache or modify /data or any pdf files
	if (req.url ~ "^/data/") {
	return (pass);
	}
	if (req.url ~ "\.pdf$") {
	return (pass);
	}
	}

	#prefer a fresh object, but when one cannot be found Varnish will look for stale one. This replaces req.grace in vcl_recv()
	sub vcl_hit {
	if (obj.ttl >= 0s) {
	return (deliver);
	}
	if (obj.ttl + obj.grace > 0s) {
	return (deliver);
	}
	return (fetch);
	}

	#vcl_deliver’s support for Vary headers needs to be preserved – at the very least we need the “Vary: Accept-Encoding” for anything which has gzip-compression enabled
	sub vcl_deliver {
	if (!resp.http.Vary) {
	set resp.http.Vary = "Accept-Encoding";
	} else if (resp.http.Vary !~ "(?i)Accept-Encoding") {
	set resp.http.Vary = resp.http.Vary + ",Accept-Encoding";
	}
	}

	#TODO but we should probably use a standard LC error page or confirm that CloudFlare will substitute the nice P1 error page for a backend 5xx error
	sub vcl_backend_error {
	set beresp.http.Content-Type = "text/html; charset=utf-8";
	set beresp.http.Retry-After = "5";
	synthetic ({"
	<?xml version="1.0" encoding="utf-8"?>
	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
	"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
	<html>
	<head>
	<title>The page is temporarily unavailable</title>
	</head>
	<body>
	<h1>Chronicling America is currently unavailable</h1>
	<p>The Chronicling America website is currently offline, undergoing maintenance. We regret the inconvenience, and invite you to visit other collections available on the Library of Congress website at <a href="http://www.loc.gov">www.loc.gov</a> while we are working to restore service.</p>
	</body>
	</html>
	"});

	return (deliver);
	}