Re: External: Re: problems with running EPICS Gateway on virtual machines?

[Ralph Lange via Tech-talk <tech-talk at aps.anl.gov>]

On Wed, 14 Apr 2021 at 09:04, Ru Igarashi via Tech-talk <tech-talk at aps.anl.gov> wrote:

Thanks for the -no_cache suggestion.  It did stop the problem but is not
a long term solution because I'm relying on caching so that the
gateway can act as a proxy or channel access concentrator (to
reduce traffic).

The '-no_cache' option stops the Gateway from answering CA get() requests directly from its internal data cache. Instead, the Gateway will forward all get() requests to the IOC and relay the IOC answer back to the client.

This option does not change the Gateway behavior regarding subscriptions, i.e., it will still "concentrate" many identical subscriptions by its clients into a single subscription to the IOC and do the fanning out of updates.

Original motivation for the '-no_cache' option was the chance of visible inconsistencies introduced by the cache, where - assuming an analog value with a deadband for monitor updates - a client would get a different value directly from the IOC (the actual current value) than from the Gateway (the last monitor update from the IOC that may differ by the deadband width).

Again: For subscriptions, '-no_cache' or not should not make any difference.

Cheers,
~Ralph