Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Fri, 21 Jun 2013 10:58:28 +0200

On Thursday, June 20, 2013 16:19:39 Andrew Johnson wrote:
> On 2013-06-20 J. Lewis Muir wrote:
> > Why would I want to use this wrapper instead of just using the EPICS
> > errlog facility directly?
>
> See these tech-talk messages for context:
>
> http://www.aps.anl.gov/epics/tech-talk/2013/msg01107.php
> http://www.aps.anl.gov/epics/tech-talk/2013/msg01115.php
> http://www.aps.anl.gov/epics/tech-talk/2013/msg01126.php
> http://www.aps.anl.gov/epics/tech-talk/2013/msg01256.php

Hi Andrew,

thanks for providing the context, I should have done that in the original
announcement.

> > I didn't think the EPICS errlog facility provided a way to log to a
> > file;
>
> It does if you connect it to an iocLogServer, see section 10.7 in the
> AppDevGuide.

Yes, but this is not the intended usage with feller. If you use an
iocLogServer you get one file per server, and you have to filter messages
offline. You can do that of course, but it depends on such a server running
and my personal experience is that exactly when you desparately need the log
of a specific subsystem you always find that the server was down (Murphy's
Law).

So I took the simpler way and write to the file directly in the
errlogListener. Additionally you can use different feller instances per
subsystem, so you need not apply any filtering, feller does that automatically
for you.

> > how does Feller log to a file using the EPICS errlog facility?
>
> I assume it registers an errlogListener routine on the IOC by calling
> errlogAddListener() (section 10.3 of the AppDevGuide) and writes the
> messages it gets to the file.

Yes. In this it behaves just like seqLog in the old 2.0 version of the
sequencer. Only the writing to the file is done by the low-priority errlog
task, not the one that calls seqLog.

Cheers
--
Ben Franksen
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System