Test how accurately a shard reconfiguration will remap

shard_test.vcl

# Shard reconfiguration accuracy
# Create two different shard configurations, s1 and s2
# See what percentage of URLs map the same (200) vs different (500)

vcl 4.0;

import crypto;
import directors;

backend b01 { .host = "0"; }
backend b02 { .host = "0"; }
backend b03 { .host = "0"; }
backend b04 { .host = "0"; }
backend b05 { .host = "0"; }
backend b06 { .host = "0"; }
#backend b07 { .host = "0"; }
#backend b08 { .host = "0"; }
#backend b09 { .host = "0"; }
#backend b10 { .host = "0"; }
#backend b11 { .host = "0"; }
#backend b12 { .host = "0"; }
#backend b13 { .host = "0"; }

sub vcl_init
{
    new s1 = directors.shard();
    s1.add_backend(b01);
    s1.add_backend(b02);
    s1.add_backend(b03);
    s1.add_backend(b04);
    #s1.add_backend(b05);
    #s1.add_backend(b06);
    #s1.add_backend(b07);
    #s1.add_backend(b08);
    #s1.add_backend(b09);
    #s1.add_backend(b10);
    #s1.add_backend(b11);
    #s1.add_backend(b12);
    s1.reconfigure();

    new s2 = directors.shard();
    s2.add_backend(b01);
    s2.add_backend(b02);
    s2.add_backend(b03);
    s2.add_backend(b04);
    s2.add_backend(b05);
    s2.add_backend(b06);
    #s2.add_backend(b07);
    #s2.add_backend(b08);
    #s2.add_backend(b09);
    #s2.add_backend(b10);
    #s2.add_backend(b11);
    #s2.add_backend(b12);
    #s2.add_backend(b13);
    s2.reconfigure();
}

sub vcl_recv
{
    set req.url = "/" + crypto.hex_encode(crypto.urandom(32));

    set req.backend_hint = s1.backend(URL);
    set req.http.s1 = req.backend_hint;

    set req.backend_hint = s2.backend(URL);
    set req.http.s2 = req.backend_hint;

    # Shard mapping matches
    if (req.http.s1 == req.http.s2) {
        return (synth(200));
    }

    return (synth(500));
}

sub vcl_synth {
    set resp.http.url = req.url;
    set resp.http.s1 = req.http.s1;
    set resp.http.s2 = req.http.s2;
    return (deliver);
}