Running Element

One Element’s core feature, the render helper, is used to generated sub request processes by a dedicated controller. The internal implementation of this feature rely on an ESI tag or SSI tag. So Element requires to be behind a reverse proxy like Nginx or Varnish.

To run an element instance, you need a process manager like supervisord:

[program:rabaix.net]
command=/home/rabaix/site/bin/python start.py tornado:start -np 8 -p 5001 --bind thomas.rabaix.net
autostart=true
autorestart=true
startsecs=3
user=rabaix
directory=/home/rabaix/site/src

This will spawn 8 independents processes to process http requests.

The Nginx configuration can be:

server {
    listen   80;
    server_name thomas.rabaix.net;

    location / {
        ssi on;

        proxy_pass http://127.0.0.1:5001;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

or the Varnish configuration (from the Symfony2 documentation):

sub vcl_fetch {
    /*
    Check for ESI acknowledgement
    and remove Surrogate-Control header
    */
    if (beresp.http.Surrogate-Control ~ "ESI/1.0") {
        unset beresp.http.Surrogate-Control;

        // For Varnish >= 3.0
        set beresp.do_esi = true;
        // For Varnish < 3.0
        // esi;
    }
    /* By default Varnish ignores Cache-Control: nocache
    (https://www.varnish-cache.org/docs/3.0/tutorial/increasing_your_hitrate.html#cache-control),
    so in order avoid caching it has to be done explicitly */
    if (beresp.http.Pragma ~ "no-cache" ||
         beresp.http.Cache-Control ~ "no-cache" ||
         beresp.http.Cache-Control ~ "private") {
        return (hit_for_pass);
    }
}

Note

Depends on the use case, you can use varnish or nginx with specific caching rules, Nginx runs SSI in in parallel while Varnish runs ESI sequentially.

If you don’t have a local reverse proxy (ie, varnish) you can use the proxy.py script which able to render esi:include tag:

[program:rabaix.net]
command=/home/rabaix/site/bin/python proxy.py --bind thomas.rabaix.net -p 5000 -sp 5001
autostart=true
autorestart=true
startsecs=3
user=rabaix
directory=/home/rabaix/site/src

Note

This proxy is not save for production usage. And should only be used to your development environment.