public CuratorDiscoverySpecBuilder instanceId(String instanceId) {
        checkState(converter == null, "converter() and instanceId() are mutually exclusive.");
        this.instanceId = requireNonNull(instanceId, "instanceId");
        return this;
    }
Sets the specified instance ID. If this is set, the {@link ZooKeeperEndpointGroup} will only connect to
the instance.
zookeeper3/src/main/java/com/linecorp/armeria/client/zookeeper/CuratorDiscoverySpecBuilder.java