Experimental Physics and
Industrial Control System

"Shankar, Murali" <[email protected]> · Mon, 17 Apr 2017 17:19:45 +0000

Some more followup:

>> (Mike) Murali also mentioned that there was a configuration option to control this (defaults to 10)
>> (Andrew) ..but from the evidence you have posted it probably uses a configurable (default 10)
number of agent processes which connect to the IOCs.

This is correct; you can configure this in the archappl.properties using the key org.epics.archiverappliance.engine.epics.commandThreadCount=10. 

>> or maybe it does try, but it can't always honour that).
All connections to the same channel and its metafields are indeed sent to the same CAJContext. 

>> As Michael explained, the SLAC installation solves the problem of overloading their IOCs with archiver
connections by making the archiver connect through a CA Gateway
This is correct and something we "borrowed" from Bessy. We have a nice naming scheme and we use multiple gateways that leverage this naming scheme to consolidate the connections from the archiver. The gateway(s) take the hit; the notion being that we can always add more gateways when needed.

Regards,
Murali

________________________________________
From: Shankar, Murali
Sent: Saturday, April 15, 2017 9:43 AM
To: Michael Davidsaver; Wang, Lin
Cc: [email protected]
Subject: Re: Archiver Appliance established multiple CA connections for one channel

Apologies for the delay; I just got back from a break.

As Michael said, if you use the default policies file, the appliance will open multiple camonitors for each PV. This is determined in the policies.py and depends on the RTYP of the PV. For example, for "ao" fields, we'd establish all of these

elif pvRTYP=="ao":
    archiveFields=['HIHI','HIGH','LOW','LOLO','LOPR','HOPR','DRVH','DRVL']
...
pvPolicyDict["archiveFields"]=archiveFields

In addition, we'll also establish a connection for the DESC field on behalf of the viewer.

You can control all of these from using a custom policies.py file (use the environment variable ARCHAPPL_POLICIES to point to your new policy file). If you want to eliminate the DESC camonitor as well, you can do so in the archappl.properties file.

There is support for using DBE_PROPERTIES; this has been tested but you'd be the first to use in a production environment. Please let me know if you are willing to do this; I can help you thru the process. For this, I think you'd need all your IOC's to be on 3.15 or later. This will reduce your connections to 3 (one for the .VAL, one for the all the fields in a DBR_CTRL and the third for the DESC).

Hope that helps. Please let me know if you run into any issues.

Regards,
Murali

________________________________________
From: Michael Davidsaver <[email protected]>
Sent: Friday, April 14, 2017 9:33 AM
To: Wang, Lin
Cc: [email protected]; Shankar, Murali
Subject: Re: Archiver Appliance established multiple CA connections for one channel

On 04/13/2017 09:17 PM, Wang, Lin wrote:
> accessed ~1692 channels in total, which I cannot understand.

For each user provided PV name, Archive Appliance can (and by default
does) subscribe to several related PVs.  This is determined in the
policy hook script.

By default it will try to subscribe to additional PVs by appending .EGU
.HIGH and others to the user provided PV name.

This is where your addition channels come in.

I'm not sure what the state of DBE_PROPERTY support is in AA.  This
would help to reduce, but not eliminate, the number of extra channels
needed to also archive this meta-data.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System