EPICS V4 Telecon, June 10, 2014

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Agenda

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One item: V4 Gateway Requirements 1st Review

Minutes

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PRESENT: GW, MK, MS, DH, GC, RL, TK, AJ

CHAIR: GW

SCRIBE: GC

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TOPIC: V4 Gateway Requirements 1st Review

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http://epics-pvdata.sourceforge.net/doc/pvGateway/requirements.html

RL: Put together a document. Some requirements are contradictory. What does the v4 group want? [Reading the design document]

RL Q: Should gw be able to do both CA and PVA?

Matthias Clausen’s group developed, but never released, a v of gw that included redundancy

AJ: Add requirement to bind pvs to different interfaces

AJ: Does pva support negative responses (channel does not exist?)

MS: Yes (not clear for broadcast)

MK: How many CA gateways are there?

RL: One gateway that most sites are using from APS. Caches data (no streaming). PSI Have a completely new GW which works at a lower level, written in C# so Windows-only.

Current support of gateway is “community”. Murali from SLAC is projected to do some work.

GW: Should we concentrate on the new gateway to cover missing functionality of current CA gateway?

AJ, RL: No

GW: we want a gateway for access to dbpv and dbgroup

AJ: no, it has nothing to do with it

[Discussion: AJ and RL saying dbPv and dbGroup had nothing to do with gateway, GW saying they assuredly do. GW pointing out that they are key because, particularly dbGroup offers key new functionality to the IOC which is offered though PVA, so an absolutely key motivation for the gateway is to enable those functions now offered for ca channels to IOCs, also to PVA channels.]

GW: As a first step, you should get the whole structure, and rebroadcast only the piece requested (even if it is wasteful)

AJ: Agree, but may not be usable for production

[GW notes: can ans why;

ask tt about req? when?

must,should,could;

add examples of v3 gateway non-transparent behaviour, that can be fixed in this v;

so which of RL’s req are important - or better, which are not so important?

logging - eg with statistics?

]

AJ: Does pva support streaming, re req 111?

MS: yes, supports chunking, so supports streaming.

GW: How much this gateway effort should cover the shortcoming of the CA current gateway?

Consensus: Can’t do much fix the existing gateway, since the protocol doesn’t support more.