Discovery failure in multi-process localhost scenario

[alsora]

Hi,
I have a setup with two ROS 2 applications running on the same machine.

One is the main application and it is always active, while the second one gets restarted from time to time.
The main application has a ROS 2 client and will wait for a corresponding server on the second application to come up.
We are currently using a discovery timeout of 10 seconds.
We know that the second application is already up and the server has already been created when we start the discovery timeout.

This usually works, with the server being discovered almost immediately, but we are noticing sporadic situations where the server doesn't get discovered and we time out.
This is happening with ROS 2 Humble and Fast-DDS 2.6.4

Do you have suggestions on how to make this setup more robust, besides increasing the timeout?

As already mentioned, both processes are in the same machine.
We are using the same XML profile for both applications, which allows discovery only on localhost

<?xml version="1.0" encoding="UTF-8" ?>
<profiles xmlns="http://www.eprosima.com/XMLSchemas/fastRTPS_Profiles">
    <transport_descriptors>
        <transport_descriptor>
            <transport_id>udp_transport</transport_id>
            <type>UDPv4</type>
            <maxMessageSize>65000</maxMessageSize>
            <non_blocking_send>true</non_blocking_send>
        </transport_descriptor>
    </transport_descriptors>

    <participant profile_name="disable_multicast" is_default_profile="true">
        <rtps>
            <userTransports>
                <transport_id>udp_transport</transport_id>
            </userTransports>
            <useBuiltinTransports>false</useBuiltinTransports>
            <builtin>
                <metatrafficUnicastLocatorList>
                    <locator/>
                </metatrafficUnicastLocatorList>
                <initialPeersList>
                    <locator>
                        <udpv4>
                            <address>127.0.0.1</address>
                        </udpv4>
                    </locator>
                </initialPeersList>
            </builtin>
        </rtps>
    </participant>
</profiles>

Thank you