Experimental Physics and
Industrial Control System

"Schoeneburg, Bernd" <[email protected]> · Thu, 04 Sep 2008 13:37:25 +0200

Hello Artem,

it is just as you have already assumed. We are preparing a module which

includes a redundancy-start routine. This function is called from the

shell during startup. The function registers a function into the task

watchdog to maintain a list of epics tasks and registers to the rmt as

only one PRR "base". An other function is registered in the task

watchdog for each of these epics tasks to be called when such a task

becomes suspended. This function sets the status, read by the rmt, to "bad".

The module provides the functions for the rmt-api: stop, start,

getStatus. stop calls iocPause(), start calls iocRun() and getStatus

sends the status which is set by the callback function mentioned above.

getInfo can send detailed information about the health of individual

epics tasks.

In this way, no additional task is necessary.

This is the simple way to solve the redundancy control. As you mentioned

already, we normally stop or start all epics tasks together. So if

iocRun does already manage to start the individual components in the

right order, we don't have to care about this any more.

Concerning the field attribute red_update: Different proposals exists to

replace it. Up to now we didn't use it at all, because databases have

not been so big and the processors have enough power to update all

fields in the slave ioc. If it appears to become necessary the global

field attribute would be the best solution in my opinion. Benjamin

Franksen has proposed to have an expendable attribute list.

Gongfa is our main redundancy expert. Please ask him for details.

- Bernd

Artem Kazakov schrieb:

From memory, the last message I got from Bernd implied that he didn't think
the redundancy monitor needed control over the individual tasks, so I took
out that detail and provided the iocRun and iocPause commands instead (in
src/misc/iocInit.c), which start and stop the whole IOC at once.  If you want
a little more control over the subsystems you can use these functions which
are called by the above routines, but I don't have APIs giving control down
to the individual thread level:

   scanRun();
   dbCaRun();
   rsrv_run();
   rsrv_pause();
   dbCaPause();
   scanPause();

If this is not sufficient, please let me know ASAP as I'm trying to put out
the R3.14.10-pre1 pre-release version later this week or early next week.

For me it seems to be sufficient enough. As far as I understand for
the redundancy purposes if stop something then we have to stop
everything else, and when we start  we want everything to start.

Again the last message from Bernd I thought said that you weren't actually
using this field yet.  If I have misunderstood that please let me know ASAP.

Indeed it is not really used. The code which uses it is present but it
is permanently cut off by several  if(FALSE) statements. I'm just
commenting it out now (otherwise compiler is complaining about missing
red_update field)

At a first glance now everything seems to be OK for redundancy. At
least I can compile, link and run the redundant IOC with new base on
my PC. Still need to check two PC to see if it really works. I'll let
you know if something is missing.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System