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<== Date ==> <== Thread ==>

Subject: Re: Archiver: Problems with disconnected PVs
From: Andrew Johnson <anj@aps.anl.gov>
To: <tech-talk@aps.anl.gov>
Date: Mon, 25 Sep 2017 14:19:35 -0500
Hi Ben, Dirk,

On 09/25/2017 10:32 AM, Benjamin Franksen wrote:
> On 09/01/2017 04:07 PM, Dirk Zimoch wrote:
>> We have already started thinking about a different CA connection model.
>> Since the archiver is a well known client, it should be possible to
>> initiate the CA connection from the IOC to the archiver instead of the
>> other way round. This would not require any broadcasts and remove the
>> need for an archiver configuration file with an up-to-date record list.
>> But it would need some programming effort.
> 
> Interesting idea. Does pvAccess support such a model?

Not directly, but there is nothing stopping you from running a local
archiver client in your IOC and pushing the data it collects to an
archive server over something like a pvAccess ChannelRPC or even just
doing puts to an "archive-me" channel. The local archiver client could
connect to the IOC over any protocol so the IOC doesn't have to run a
pvAccess server for this to work.

Making changes to CA (i.e. to all of libCa, rsrv, pcas and jca/caj) to
enable push subscriptions doesn't sound like it would be particularly
easy to do. The current core developers would generally prefer to
concentrate on continuing to develop pvAccess, which is already a lot
more flexible without having to modify it.

- Andrew

-- 
Arguing for surveillance because you have nothing to hide is no
different than making the claim, "I don't care about freedom of
speech because I have nothing to say." -- Edward Snowdon

References:
Archiver: Problems with disconnected PVs Gabriel de Souza Fedel
Re: Archiver: Problems with disconnected PVs Dirk Zimoch
Re: Archiver: Problems with disconnected PVs Benjamin Franksen

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