Logic Error in Qcodes Session Creator?

[samantha-ho]

I believe I've found a logic error in the ZISession class which is used to create toolkit sessions for the Qcodes instrument instances.

The error is in the following code block:

        if not new_session:
            for instance in Session.instances():
                if instance.server_host == server_host and (
                    instance.is_hf2_server == hf2
                    or server_port is None
                    or instance.server_port == server_port
                ):
                    return instance

If I attempt to instantiate two MFLIs on different ziDataServer ports, and I do not use the new_session keyword argument, the instance.is_hf2_server == hf2 flag causes the 2nd MFLI to end up on the same session and port as the first instance, even though I explicitly set different ports.

If I do use the new_session keyword, then I cannot have more than one MFLI on the second ziDataServer port on the same session.

[mehdialem]

Thank you, @samantha-ho, for reporting this issue. We are on it and we'll provide the fix as soon as our tests confirm it.

To better understand your use case, I assume you have multiple MFLIs and you'd like to synchronize them in multiple MDS clusters where each group of MFLIs are synchronized independently from the other groups.

[samantha-ho]

That's correct. I have 4-6 MFLIs, and I'd like to sync them in pairs. I received some guidance from a ZI engineer on how to accomplish this, and in implementing their suggestion, ran into this issue.

[samantha-ho]

With a little more thought, I think it should be:

if instance.server_host == server_host and (
    instance.is_hf2_server == hf2) and (
    server_port is None
   or instance.server_port == server_port
):

But I don't have any experience with HF2 servers

[samantha-ho]

Also, here is a minimal code fragment that reproduces the problem

from zhinst.qcodes import MFLI

mfli1 = MFLI(serial="DEV6890", host="localhost", interface="1GbE", port=8004)
mfli2 = MFLI(serial="DEV6504", host="localhost", interface="1GBE", port=8008)

assert mfli1.session.server_port == 8004
assert mfli2.session.server_port == 8008