[Fastly VCL Boilerplate for handling mutliple subdomains]

Tags: #fastly #vcl #boilerplate
Fastly VCL Boilerplate for handling mutliple subdomains.vcl

######################################################################################
#
# detailed blog post on fastly's implementation details:
# http://www.integralist.co.uk/posts/fastly-varnish/
#
# fastly custom vcl boilerplate:
# https://docs.fastly.com/vcl/custom-vcl/creating-custom-vcl/#fastlys-vcl-boilerplate
#
# vcl_recv
# vcl_error
# vcl_hash
# vcl_pass
# vcl_miss
# vcl_hit
# vcl_fetch
# vcl_deliver
#
######################################################################################

table deny_list {
  "/bad-thing-1": "true",
  "/bad-thing-2": "true",
}

sub set_backend {
  set req.backend = F_httpbin;

  if (req.http.Host == "example-stage.acme.com/") {
   set req.backend = F_httpbin_stage;
  }
}

sub vcl_recv {
  #FASTLY recv

  call set_backend;

  # configure purges to require api authentication:
  # https://docs.fastly.com/en/guides/authenticating-api-purge-requests
  #
  if (req.method == "FASTLYPURGE") {
      set req.http.Fastly-Purge-Requires-Auth = "1";
  }

  # force HTTP to HTTPS
  #
  # related: req.http.Fastly-SSL
  # https://docs.fastly.com/en/guides/tls-termination
  #
  if (req.protocol != "https") {
    error 601 "Force SSL";
  }

  # fastly 'tables' are different to 'edge dictionaries':
  # https://docs.fastly.com/en/guides/about-edge-dictionaries
  #
  if (table.lookup(deny_list, req.url.path)) {
    error 600 "Not found";
  }

  # don't bother doing a cache lookup for a request type that isn't cacheable
  if (req.method !~ "(GET|HEAD|FASTLYPURGE)") {
    return(pass);
  }

  if (req.restarts == 0) {
    # nagios/monitoring cache bypass
    #
    if (req.url ~ "123") {
      set req.http.X-Monitoring = "true";
      return(pass);
    }
  }

  return(lookup);
}

sub vcl_error {
  #FASTLY error

  # fastly synthetic error responses:
  # https://docs.fastly.com/en/guides/creating-error-pages-with-custom-responses
  #
  if (obj.status == 600) {
    set obj.status = 404;

    synthetic {"
      <!doctype html>
      <html>
        <head>
          <meta charset="utf-8">
          <title>Error</title>
        </head>
        <body>
          <h1>404 Not Found (varnish)</h1>
        </body>
      </html>
      "};

    return(deliver);
  }

  # fastly HTTP to HTTPS 301 redirect:
  # https://docs.fastly.com/en/guides/generating-http-redirects-at-the-edge
  #
  # example:
  # curl -sD - http://example.acme.com/
  # curl -H Fastly-Debug:1 -sLD - -o /dev/null http://example.acme.com/?cachebust=$(uuidgen)
  #
  if (obj.status == 601 && obj.response == "Force SSL") {
    set obj.status = 301;
    set obj.response = "Moved Permanently";
    set obj.http.Location = "https://" req.http.host req.url;
    synthetic {""};
    return (deliver);
  }
}

sub vcl_hash {
  #FASTLY hash

  set req.hash += req.url;
  set req.hash += req.http.host;

  # call debug_info_hash;

  return(hash);
}

sub vcl_pass {
  #FASTLY pass
}

sub vcl_miss {
  #FASTLY miss

  return(fetch);
}

sub vcl_hit {
  #FASTLY hit
}

sub vcl_fetch {
  #FASTLY fetch

  # fastly caching directive:
  # https://docs.fastly.com/en/guides/cache-control-tutorial
  #
  # example:
  # define stale behaviour if none provided by origin
  #
  if (beresp.http.Surrogate-Control !~ "(stale-while-revalidate|stale-if-error)") {
    set beresp.stale_if_error = 31536000s; // 1 year
    set beresp.stale_while_revalidate = 60s; // 1 minute
  }

  # fastly stale-if-error:
  # https://docs.fastly.com/en/guides/serving-stale-content
  #
  if (beresp.status >= 500 && beresp.status < 600) {
    if (stale.exists) {
      return(deliver_stale);
    }
  }

  # hit-for-pass:
  # https://www.integralist.co.uk/posts/fastly-varnish/#hit-for-pass
  #
  if (beresp.http.Cache-Control ~ "private") {
    return(pass);
  }
  
  # ensure we set our own default cache TTL if no caching directives found
  if (beresp.cacheable && !beresp.http.Surrogate-Control:max-age && !beresp.http.Cache-Control:max-age) {
    set beresp.ttl = 1h; # 1 hour
  }

  return(deliver);
}

sub vcl_deliver {
  #FASTLY deliver

  # fastly internal state information:
  # https://docs.fastly.com/en/guides/useful-variables-to-log
  #
  set resp.http.Fastly-State = fastly_info.state;

  if (req.http.X-Monitoring == "true") {
    set resp.http.X-Monitoring = req.http.X-Monitoring;
  }

  return(deliver);
}