Experimental Physics and
Industrial Control System

<[email protected]> · Mon, 17 Dec 2012 11:38:10 +0000

From: [email protected] [mailto:tech-talk-
> If possible I would like to avoid such requirement of manually creating
> the database.
> 
> By looking at the CA docs, I see that the IOCs emit periodic beacons,
> so by listening for at least EPICS_CA_BEACON_PERIOD seconds I should be able
> to gather a list of active IOCs. Is that right?

At Diamond I have created a tool which gathers a list of all PVs, but it relies on monitoring for CA_PROTO_SEARCH discovery messages, and so will only ever gather PVs which have at some time been requested.  Having run this tool for a couple of months our database of PVs has grown to 350,000 entries!

The purpose of this tool is simply to answer the following question: "when a PV goes dead, which IOC was serving it?"  This is intended to be used to locate the appropriate IOC to restart when screens in the control room start to go dead.

This monitoring tool sits between the machine network carrying PV traffic and our internal database, which itself provides a web interface.  Each time a CA_PROTO_SEARCH message is seen for a new PV I add it to an internal table and create my own discovery message to locate the serving IOC; once found, an update is sent to our database and the PV is periodically refreshed.  Updates and retries are carefully throttled to avoid generating significant network load.

> And if so, is there a way of interrogating a given IOC for its PVs?

In principle such a mechanism could be created, but I don't believe it exists at present.  To be honest, however, I suspect your requirement is back to front -- I don't see that there is a real need for a complete list of PVs on a network!

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System