"Catchall" Throttling

"Catchall" throttling is the term used to describe throttling on a VxWorks IOC that pertains to all messages sent through that IOC. This is done by creating a throttle on the IOC that will match every message sent through the CMLOG API on that IOC. The idea is to have some sort of master limit that will take effect if a process spews out a large number of messages in a short period, and is not caught by the existing throttles, if any.

At SLAC, we use the following throttle for "catch-all" functionality:

  cml_string("facility", 100, 10, "EPICS")

On a particular IOC, this throttle would only allow 100 messages per 10 seconds, assuming that all messages coming through that IOC would have the value "EPICS" in the "facility" tag. Since this is the case, we know that this throttle will come into effect if the message volume gets exceedingly high.

"Catchall" throttling can be administrated and maintained through a special VxWorks-only API, which can be found here.