Re: Receiving duplicate monitor values using CA PV Gateway

["Johnson, Andrew N. via Tech-talk" <tech-talk at aps.anl.gov>]

Hi Ralph,

On Aug 27, 2020, at 9:45 AM, Ralph Lange via Tech-talk <tech-talk at aps.anl.gov> wrote:

Now, in that -no_cache mode, when a monitor connection to the PV exists and an additional external client connects - what should the Gateway do?

It doesn't have the cached value, so it must do another get() on the inside to the IOC. When the answer to that get() arrives, it can't be distinguished from a monitor update. So with a list of clients for that PV, which ones should get the update, which shouldn’t?

Why can’t that ca_get_callback() be distinguished, couldn’t it use a different pFunc and/or pArg than the monitors use? That would allow the gets to trigger different behavior (i.e. not update the cached value or forward this event to the monitoring clients).

- Andrew

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