Memcached Distributed Setup on Debian 12

Memcached itself has no cluster mode — distribution is handled by the client using consistent hashing.

Run multiple instances

memcached -d -l 192.168.1.10 -p 11211 -m 512 -t 4 -u memcache
memcached -d -l 192.168.1.11 -p 11211 -m 512 -t 4 -u memcache

systemd template unit (/etc/systemd/system/[email protected])

[Unit]
Description=Memcached instance %i
[Service]
Type=forking
ExecStart=/usr/bin/memcached -d -l 127.0.0.1 -p %i -m 256 -t 4 -u memcache
PIDFile=/run/memcached/memcached-%i.pid
[Install]
WantedBy=multi-user.target

systemctl enable --now memcached@11211 memcached@11212

PHP consistent hashing

$mc = new Memcached();
$mc->setOption(Memcached::OPT_DISTRIBUTION, Memcached::DISTRIBUTION_CONSISTENT);
$mc->setOption(Memcached::OPT_LIBKETAMA_COMPATIBLE, true);
$mc->addServers([
    ['192.168.1.10', 11211],
    ['192.168.1.11', 11211],
    ['192.168.1.12', 11211],
]);

Monitor all nodes

for h in 192.168.1.10 192.168.1.11 192.168.1.12; do
    echo -n "$h: "; echo "stats" | nc $h 11211 | grep -E 'curr_items|bytes '
done