Memcached::set() returns false, and data delayed appearing in memcached when SASL in use

[rgagnon24]

When running memcached server with options:
memcached -l 127.0.0.1 -U 0 -p 11211 -vvvv -u memcached -S
And then connecting with PHP 7.4 using:

$mc = new \Memcached();
$mc->addServer('127.0.0.1', 11211);
$mc->setOption(\Memcached::OPT_BINARY_PROTOCOL, true);
$mc->setSaslAuthData($username, $password);

When you set data via:
$ok = $mc->set('abc', 'value', 1800);

The value of $ok will be returned false, but the data will appear on the server some time later.

In the meantime, an immediate call to $v = $mc->get('abc'); will fail, but eventually work and return the value.

When SASL is disabled on the server (IE: no -S option), and the setOption() and setSaslAuthData() methods are not used, the value of $ok when performing the set() operation returns true, and an immediate get() call returns the data.

Is there some asynchronous operation happening that is unexpected when using SASL authentication? Is this a php_memcached bug, or a configuration problem in memcached?

I should add that the memcached server is running on CentOS 7 with the cyrus-sasl SASL library using a config file in /etc/sasl2/memcached.conf that has content:

mech_list: plain
log_level: 7
sasldb_path: /etc/sasl2/memcached-sasldb2

[m6w6]

Works for me. What's your memcached's output?