Experimental Physics and
Industrial Control System

> Hello Simon,
>
>> Is it considered standard practice to start a caRepeater daemon
>> at machine boot time for any machine on which you might want to
>> run CA clients ?  (If there are many potential machines this might
>> be a bit of a burden to the system administrators).
>
>
> The CA reference manual provides no advice on which is the best approach
> partly because this is a system management issue

> Here is a summary of the two pitfalls I can see related to *not* starting
> the ca repeater when the workstation is booted:
>
> 1) The repeater must be in the path of the account that starts the first ca
> client. If not, this client will not have access to ca repeater
> functionality.
>
> 2) If the first ca client is an IOC then other ca clients might become
> dependent on the ca repeater embedded in the IOC. These clients might
> subsequently loose ca repeater functionality if the IOC exits.

I think it depends on what kind of machines you're talking about in the sense
of what they are used for.

Working in a somewhat similar environment as Simon, at UKIRT this works
as follows:

The machine the IOCs boot from (we have one of those at UKIRT, one at JCMT,
but I don't think we have one in Hilo, where our office is) should start
the caRepeater at boot time (it's a server, not a client, really).
Machines that are used to run clients on on a regular (nightly or daily)
basis may do this too, or rely on that the first client will start the
caRepeater. Machines on users' desks (we don't have "users' desks at
the telescopes, don't know how this is at LaPalma) usually don't start
caRepeater at boot time because they may or may not ever run an EPICS
client (most of the EPICS clients I run I run on one of the machines
at the telescope which is used for this on a regular basis).

At this time (in our case) caRepeater on the machine that the IOCs boot
from is owned by root (as it should be, starting at boot time), and has
been running since March, and on the machine that runs the instrument
system at night it is owned by me and running since mid April - which
was when it was last booted as well, but the caRepeater probably started
by me running up a dm screen.

References:

RE: caRepeater working practices Jeff Hill

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