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Gateway (Redux) PSI - GFA Controls IT Alain Bertrand

Renata Krempaska, Hubert Lutz, Matteo Provenzano, Dirk ZimochMay, 2013

EPICS Gateway redux

Content

-Basic introduction to the CA protocol through (our) gateway

-Why a rewrite

-Concept

-Configuration

-Current status

-Roadmap

-Live demo / Conclusion

Base introduction CA Protocol

EPICS Gateway redux

caget Gateway IOC

Search Request

Search Request

Search Response

Search Response

Create TCP Socket

Create channel

Create TCP socket

Create channel

Access Rights

Access Rights

Create channel answer

Create channel answer

Read Notify (GET)

Read Notify

Read Notify Resp.

Read Notify Resp.

TCP Disconnect

Wait 30 sec before Disc.

How it works with the new gateway

In green => Usually UDP broadcastmessages

In black => TCP messages (using asingle TCP connection per IOC)

Why a rewrite

EPICS Gateway redux

Current official CA Gateway:Written in C++ using CAS and the usual CA library(features limited by the underlining CAS and CA library)

- Hard to debug

- No real maintainer (bug report may or may not be fixed)

- Waits for a complete CA message to be sent before starting to passing it

- Requires more memory as each channel need to allocate the maxpossible memory pro channel (an issue while dealing large arrays)

- Severe performance problem (down to frozen channels) when dealing with arrays.

- Currently not stable with known and reported bugs

- Usually requires 2 process (imp / exp) pro network

Gateway process

EPICS Client

CASC++ code

Like a soft IOC

CA clientC code

Glue code

CA client(MEDM, Python,

etc..)IOC

Concept of the new gateway

EPICS Gateway redux

EPICS Client

CA client(MEDM, Python,

etc..)IOC

Gateway process

Packet Packet PacketPacket

What we need:- More stability.- A code easier to debug.- A lower latency while transferring large arrays.- A single process for the imp / exp (re-use same ports, simpler config).

Our solution:- A “pass through” (as defined by Cosylab) design which doesn’t waita full message before handling it. Act like a firewall more than a proxy.- A cleaner code (which doesn’t use 3rd parties libraries)- More debug information (activity logs)- .NET 4 / C# implementation

Configuration

EPICS Gateway redux

Currently: configured via special files, each gateway have its own set (up to 4 files)stored in CVS and then copied locally.

New gateway:

Configuration handled byour inventory database

XML file locally stored(for security in case of DBissues or manualconfiguration)

Generates an XML file.(gateway is not dependent of the inventory)

Current status

EPICS Gateway redux

- All CA messages implemented (search, get, put, monitor, …)

- Optional log on console, file, XML (with different levels of debug info)

- Fully implemented as standalone and service

- Integrated with our inventory database (the database generates the config).

- 1 in production, a couple of gateways in test

-Tested and running stable with standard EPICS tools, MEDM,QTDisplays, Archiver, capv-view (Java), setpoint.tcl (TCL/TK)

Roadmap

EPICS Gateway redux

Slowly replace old gateways with the new one, while keeping theold VM for quick failover in case of issues.

Planned full replacement: End 2014

Conclusion

EPICS Gateway redux

- The gateway concept works, and works well.

- React differently than the old gateway, as there is no caching,and whatever the IOC sends the clients will get it.