The evergreen/antithesis_image_build_and_push.sh script runs a sanity check to verify a test run by resmoke against a Docker Compose spawned MongoDB cluster will succeed. For concurrency tests which use $config.passConnectionCache === true this involves using ReplSetTest to dynamically discover all of the shards and all of the replica set members within the shards.

ReplSetTest#getURL() returns a connection string based which relies on the ReplSetTest#host property. However the ReplSetTest#host property is arbitrarily assigned to be the hostname of the first node in the replica set configuration.

ReplSetTest.prototype.getURL = function() {
    var hosts = [];

    for (var i = 0; i < this.ports.length; i++) {
        hosts.push(this.host + ":" + this.ports[i]);
    }

    return this.name + "/" + hosts.join(",");
};

We should introduce a mechanism to enable FSMShardingTest to receive a connection string from a ReplSetTest object which preserves the hostnames of the individual cluster members.