Re: pyepics not updating pv.enum_strs after connection

[Dirk Zimoch <dirk.zimoch@psi.ch>]

On 25.03.2015 17:21, Andrew Johnson wrote:
> On 03/25/2015 10:55 AM, Dirk Zimoch wrote:
> > On 25.03.2015 04:46, Matt Newville wrote:
> > > Yes, I think this idea of getting the ctrl variables in the connection
> > > callback is a good idea, and will allow more straightforward code  As it
> > > is, a pyepics.PV is already expected to be a "rich" object, even if
> > > sacrificing ultimate performance, and is normally expected to have the
> > > ctrl variables.   So, I think it's reasonable to have this getting of
> > > ctrl variables as the default.    I'll add that.
> >
> > This is generally a good idea for every ca client. After a reboot,
> > anything may have changed: Enum strings, limits, units, precision, array
> > size, even record type (and thus data type).
>
> Recent versions of Base (3.14.11 on) have a CA monitor event type
> DBE_PROPERTY which was intended for monitoring changes to metadata like
> the ctrl variables. 3.14 IOCs don't send out many property events (and
> the PV Gateway doesn't support property subscriptions yet either), but
> as 3.15 and later IOCs come in they make the case for using this quite a
> bit more compelling. I would encourage CA client developers to read the
> tech-talk threads discussing DBE_PROPERTY first though, there are a few
> gotchas.
>
> - Andrew

This is a different issue. The problem here was not that IOCs changed 
their properties on the fly but after a reboot! Even EPICS 3.13 should 
have been able to handle that. But many ca clients are too lazy. That 
means the client programmer had not thought about the possibility that 
IOCs may actually change during a reboot.

Dirk