sticky-cookie.vcl

vcl 4.0;

import std;
import directors;
import cookie;
import header;

backend a1 { .host = "192.0.2.11"; }
backend a2 { .host = "192.0.2.12"; }
backend a3 { .host = "192.0.2.13"; }
backend a4 { .host = "192.0.2.14"; }

sub vcl_init {
    new hdir = directors.hash();
    hdir.add_backend(a1, 1); hdir.add_backend(a2, 1);
    hdir.add_backend(a3, 1); hdir.add_backend(a4, 1);
}

sub vcl_recv {
    cookie.parse(req.http.cookie);
    if (!cookie.isset("bucket")) {
        set req.http.placement = std.random(1, 4);
        cookie.set("bucket", req.http.placement);
    }
    set req.backend_hint = hdir.backend(cookie.get("bucket"));
}

sub vcl_deliver {
    if (req.http.placement) {
        header.append(resp.http.Set-Cookie,
            "bucket=" + req.http.placement + "; Expires=" +
            cookie.format_rfc1123(now, 5m) + ";");
    }
}