CA Gateway Update

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CA Gateway Update
Ralph Lange EPICS Collaboration Meeting March
2008 _at_ SSRF
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Credits Main Authors and Contributors

• Channel Access Development
• Jeff Hill (LANL)
• CA Gateway Development
• 1996 Jim Kowalkowski (APS)
• Janet Anderson (APS)
• 1999 Ken Evans (APS)
• 2000 Ralph Lange (BESSY)
• 2002 Ken Evans (APS)
• Jeff Hill (LANL)
• 2007 Gasper Jansa (cosylab)
• Dirk Zimoch (SLS)

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What is a CA Gateway?

• An application that forwards connections between
  CA clients and servers.

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It's a Gateway.

• Allows CA between networks configurable through
  regular expression filters and CA access security.

CA Clients
Gateway
CA Servers (IOCs)
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Its a Proxy.

• Clients point to one proxy that distributes the
  data with minimal impact on the IOCs.

CA Clients
Gateway
CA Servers (IOCs)
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Overview Key Features

• As well CA server as CA client
• Usually runs on workstation with multiple network
  interfaces
• Connects and separates networks in terms of CA
  connections
• May use channel aliases (e.g. add prefixes)
• May cache data (CA get is answered by the
  gateway)
• Keeps IOC-side connections alive
• Watchdog mode restarts on core dump
• Provides statistics channels to allow monitoring

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CA Gateway Configuration Symmetric

• Each network sees the channels of all other
  networks.Gateways may run on a single host with
  multiple (virtual) interfaces.

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CA Gateway Configuration Reverse Gateway

• All networks see channels in network Z.The
  reverse Gateway forwards Gateway statistics.

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CA Gateway Configuration Alias Gateway

• The Gateway provides aliases for channel names.

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Recent CA Gateway Changes

• Option to disable cache (forward each CA get to
  the IOC)
• Transparently works for Alarm Handler and
  Archiver connections
• Option to use Perl regexp instead of GNU regexp
  (allows easy negation of regexp)
• Numerous bugfixes (beacons missing, Gateway
  hangs)
• The CA Gateway is available from the EPICS
  extensions page.