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

Subject: Re: alarm hook
From: Geoff Savage <[email protected]>
To: Matthias Clausen <[email protected]>
Cc: Geoff Savage <[email protected]>, Andrew Johnson <[email protected]>, EPICS core-talk <[email protected]>, Fritz Bartlett <[email protected]>, "Liyu, Andrei" <[email protected]>
Date: Thu, 22 Jun 2006 00:36:04 -0500

I am willing to accept the hook as proposed by Andrew. This is not the exact interface that I am currently using but it does provide the information that I require. I will modify the FNAL interface to match the proposed interface once the hook is in base.
It is not clear to me how an alarm hook function is registered in a
startup script. Can someone please provide an example that is
operating system independent?
From our (Matthias Clausen, Fritz Bartlett, Vladimir Sirotenko,
Geoff Savage) discussions on Tuesday we developed a "generic" (but
not matching Andrei's interface) interface. I'll address Andrei's
email next. We propose to include the following "tools" for pushing
alarms from the server in a package separate from base. Here is a
simple chain showing all the pieces.
hook -> logAlarm -> queue -> sendToNetwork -> createMessage -> send
to A -> send to B (if send to A fails)
Here is a summary of our discussions on each piece with some of my
experiences included (and indicated).
1. We start with the generic hook as proposed by Andrew.

2. The hook function which a user will register is logAlarm(struct dbCommon *prec, unsigned short sevr, unsigned short stat). Once this function has determined that an alarm needs to be sent it gathers the volatile data and inserts it into the alarm data queue. It should also do something reasonable if the data can't be inserted in the queue. It might simply keep track of the number of insertion failures and report this number in a message once the queue has space. Geoff - It should send messages on bad and good transitions. Care should be taken when a record is successfully processed for the first time as it transitions from an undefined (bad) state to a good state.
3. Users should be able to adjust the size of this queue to
accommodate different numbers of records in the IOCs.
Geoff - There are more alarms during maintenance periods than during
run times.
4. The sendToNetwork function is running as a separate thread
(vxworks task) at a priority lower than the scan tasks but higher
than channel access. It waits for data to arrive in the alarm data
queue. When data arrives it passes the data to the createMessage
5. The createMessage routine constructs a string message to be sent
across the network. To be more generic users should be able to
define their own createMessage routine. This allows users to use a
different message protocol within the push out framework.
Geoff - Using a string for messages removes byte ordering issues.

6. Send the message to server A. If sending the message to server A fails then send the message to server B.
All the requirements are not included here. Hopefully DESY will
provide more details as the project progresses.
Some other issues to consider -
a. From Jeff Hill - can we detect on a record by record basis when an alarm is not pushed out. I think this requires some study of the common fields available to all records. This is on my to do list. b. What will be in the data inserted into the alarm data queue? This should be all the volatile data needed in the network message to decrease the time spent collecting the data.
c. What are the contents of the network message?
d. A generic server also needs to be provided.

P.S.  I need to sleep and will reply to Andrei's email in the morning.

On Jun 19, 2006, at 10:02 PM, Matthias Clausen wrote:

Hi Andrew,

I had a meeting today with Geoff, Fritz and Vladimir at Fermilab.
We discussed the implementation based on the proposed function call and agreed on an implementation which should be as generic as possible. After Geoff's and Bernd Schoeneburg's vacation (next two weeks) we will work on an implementation. If Geoff does not see any unforeseen problems I would like to give you a 'go' for the change in base.
Thanks for your help!
And - by the way - thanks for your clarification regarding Andrei's mail.

Andrew Johnson wrote:
Hi Matthias,

Matthias Clausen wrote:
in preparation for my meeting with Geoff at Fermilab I wand to
send you the proposed hook into base which Bernd Schoeneburg and
Bob already 'somehow' agreed on:
Here's Berns mail to Bob:

recGblResetAlarms is called in monitor() which is called in the
end of record processing just before recGblFwdLink and after
recGblGetTimeStamp. After calling recGblResetAlarms in monitor()
the value changes are checked (not interesting for us).
recGblResetAlarms checks for alarm changes and returns the fist
approach of the monitor mask, which is later used for
postEvents. postEvents can be called from anywhere like device
support, snl, subroutines, 'homebrew' records etc. I think
recGblResetAlarms is called in the monitor function of records
only. So I think it is the perfect place. Please check it and
correct me if I am wrong.
The code could look like this (the end of recGblResetAlarms):

    if(sevr!=nsev || stat!=nsta) {

++:    logAlarm (pdbc, sevr, stat);
++:    /* nsev and nsta are in pdbc->sevr and pdbc->stat */

        ackt = pdbc->ackt; acks = pdbc->acks;
        if(!ackt || nsev>=acks){
My question:
Do you also agree with approach?
I agree with the location and arguments of the call, which I
believe are the same as Fermilab have been using.
And - what would be implemented in base for logAlarm ()?
This could be an empty function which just returns - or it could be the 'real' thing where you'll have to check whether alarm logging should be used at all. The empty function could be replaced/ overloaded by the 'real' function if you want to use putAlarm.
I think we just need a global pointer for the routine which will
be called if it's not NULL, so your code just sets it to hook in.
Here's my proposed patch:

Index: recGbl.h
RCS file: /net/phoebus/epicsmgr/cvsroot/epics/base/src/db/recGbl.h,v
retrieving revision 1.9
diff -u -b -r1.9 recGbl.h
--- recGbl.h    12 Feb 2003 21:22:23 -0000      1.9
+++ recGbl.h    19 Jun 2006 15:25:16 -0000
@@ -30,13 +30,23 @@
      : FALSE\

+/* Structures needed for args */

-/* Global Record Support Routines*/
 struct link;
 struct dbAddr;
 struct dbr_alDouble;
 struct dbr_ctrlDouble;
 struct dbr_grDouble;
+struct dbCommon;
+/* Hook Routine */
+typedef void (*RECGBL_ALARM_HOOK_ROUTINE)(struct dbCommon *prec,
+    unsigned short sevr, unsigned short stat);
+extern RECGBL_ALARM_HOOK_ROUTINE recGblAlarmHook;
+/* Global Record Support Routines */
 epicsShareFunc void epicsShareAPI recGblDbaddrError(
     long status, struct dbAddr *paddr, char *pcaller_name);
 epicsShareFunc void epicsShareAPI recGblRecordError(
Index: recGbl.c
RCS file: /net/phoebus/epicsmgr/cvsroot/epics/base/src/db/recGbl.c,v
retrieving revision
diff -u -b -r1.60.2.2 recGbl.c
--- recGbl.c    4 Nov 2004 19:21:08 -0000
+++ recGbl.c    19 Jun 2006 15:25:16 -0000
@@ -42,6 +42,10 @@
 #include "recGbl.h"

+/* Hook Routines */
 /* local routines */
 static void getMaxRangeValues();

@@ -239,6 +243,7 @@
     if(sevr!=nsev || stat!=nsta) {
+       if (recGblAlarmHook) (*recGblAlarmHook)(pdbc, sevr, stat);
        ackt = pdbc->ackt; acks = pdbc->acks;
        if(!ackt || nsev>=acks){

If there is general agreement between DESY and FNAL about this, I'll commit the change which will then appear in R3-14-9.
- Andrew

---------------------------------------------------------------------- -- Matthias Clausen Cryogenic Controls Group (MKS-2) phone: +49-40-8998-3256 Deutsches Elektronen Synchrotron fax: +49-40-8994-3256 Notkestr. 85 e-mail: [email protected] 22607 Hamburg WWW-MKS2.desy.de Germany ---------------------------------------------------------------------- --

RE: alarm hook Dalesio, Leo `Bob`
Re: alarm hook Andrew Johnson
Re: alarm hook Matthias Clausen

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