Re: IOC unusable if no ethernet interface at startup

[Markus Kristensson via Tech-talk <tech-talk at aps.anl.gov>]

Hi again,
I've investigated the problem further. It turns out that I was too quick 
in judging that the IOC was starting up more or less correctly even when 
the ethernet cable was not plugged in. The reason for that conclusion 
was two-fold: 1. I ran the RPi in headless mode without any monitor 
connected. 2. The RPi did respond to change in some hardware, namely me 
changing a physical switch between two states. The response of changing 
the switch was seen in the opening/closening of a relay. As already 
stated, the response was very slow (sometimes around 10 s). What bugged 
me was that the same relay card did not open when a number of other DI:s 
received signal.

With a monitor connected I now realise that the IOC is actually NOT 
starting correctly when the ethernet cable is unplugged. The error is a 
BaseException with "No (specified) network interface(s) available". 
Interestingly, the plc (I run the ecmc-module) which handels the logic 
starts up briefly before the IOC startup is terminated. This gives 
enough time to read the input from the switch and to open up the relay, 
but not enough time for the other inputs to respond because of the logic 
using hysteresis (this is a solution for dealing with 14 cooling rooms 
and 2 cooling machines etc...). The slow responding time of the switch 
(max around 10 s) should then basically be related to the restart time 
of the IOC which I've configured using systemd to 10 s.

So, some things better understood, but my basic problem still remains. 
Do you have any suggestions of how I can resolve the problem of starting 
an IOC without it being connected to any network? I suspect I need to 
modify the startup script of the IOC, e.g. specifying EPICS_CA_ADDR_LIST 
to localhost. So far I have not been successful with such modifications.

Cheers,
Markus


2021-05-26 20:31 skrev Markus Kristensson via Tech-talk:
> Hi,
> I have configured a Raspberry Pi 3 Model b+ to autostart and launch an
> IOC. The startup works fine if the RasPi is connected via ethernet to
> another computer. If the lan is not connected at startup, the IOC is
> basically unusable, responding to certain inputs, but extremely slow.
> If the ethernet cable is plugged back in, the responsiveness of the
> IOC is back to normal.
>
> The RasPi will normally be connected to the other computer, but it is
> not necessarily so. I only need to control and access the IOC on the
> RasPi locally (i.e. on the Raspberry Pi itself). Do you have any
> suggestions how to proceed?
>
> Cheers,
> Markus Kristensson