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

Subject: Re: alarm hook
From: Andrew Johnson <[email protected]>
To: Matthias Clausen <[email protected]>
Cc: "Dalesio, Leo `Bob`" <[email protected]>, Jeff Hill <[email protected]>, Ralph Lange <[email protected]>, Geoff Savage <[email protected]>, EPICS core-talk <[email protected]>, Fritz Bartlett <[email protected]>, "Liyu, Andrei" <[email protected]>, Bernd Schoeneburg <[email protected]>
Date: Fri, 23 Jun 2006 12:01:26 -0500
Matthias Clausen wrote:
Sending all alarms _on change_ - no always all alarms permanently.
To make this reliable we need a queue between the hook and the network task.
If the queue is full we - for now - send the number of lost messages.
To make this even more reliable - as Jeff points out - we could set a 'did not send alarm' flag to the record like:
Channel Access does not have a flag in each record, it keeps a structure
for each channel/client combination that holds the 'changes pending'
flag. I don't like the idea of adding another field to dbCommon for the
alarm logger, I see your reimplementing this as just one of the costs of
replacing CA as your alarm transport mechanism if you want to use a hook
in recGblResetAlarms().
It occurs to me that another model you could consider would be to run a
local CA client on each IOC that subscribes to alarm events for all
local records, and forwards them to the log server; this would then make
use of CA's queue/ cache mechanism, and would mean this CA client
doesn't need to keep its own queue of messages going to the log server,
all that queueing would be done for you by CA. This would avoid having
to add the hook at all...
- Andrew
--
Not everything that can be counted counts,
and not everything that counts can be counted.
  -- Albert Einstein

Replies:
RE: alarm hook Dalesio, Leo `Bob`
References:
RE: alarm hook Dalesio, Leo `Bob`
Re: alarm hook Matthias Clausen

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