EPICS Directory Service

In EPICS, a client finds a channel to connect to by issuing a broadcast message on a subnet. IOC’s hosting the channel then respond to this message. Though this approach is very reliable and fast, it does have some drawbacks.

In EPICS , a client finds a channel to connect to by issuing a broadcast message on a subnet. IOC’s hosting the channel then respond to this message. Though this approach is very reliable and fast, it does have some drawbacks.

• large CPU and network load on IOCs, especially if many clients are connecting concurrently
• large amounts of network traffic
• inability to distinguish between the case when a channel does not exist or the case when it is just temporarily unavailable
• no central directory of available channels and their associated meta information
• in case of multiple subnets, channel search broadcast addresses must be properly configured on each client separately, which may be difficult to maintain

EPICS Directory Service is a service through which EPICS clients can efficiently find channels. Thus, every EPICS client directs channel search requests to the directory service. If the directory service does not know of a channel, it tries to look it up using the traditional broadcast method, caching the result for subsequent queries. EPICS Directory Service is replicated using advanced active replication techniques. A client can direct a request towards any (or all) of the replicas. If the state on one replica changes, the change is propagated to the other replicas. The state remains consistent even in scenarios where the replicas crash or end up in disjoint networks (e.g., due to router failures).

Features

 * information about all IOCs available in one place

 * reduction of network traffic and IOC server load

 * no administration and easy installation

 * high-reliability

 * advanced features such as redundant channels and channel load balancing are foreseen


Requirements


* Windows:
   - Microsoft Windows XP SP 2
   - Microsoft .NET Framework 2.0
   - Spread Toolkit 3.17.3

* Linux:
   - Mono 1.1.14
   - Spread Toolkit 3.17.3

Download

You may download the released binaries v1.1.0 from http://users.cosylab.com/~kzagar/dedisys-continuous/epicsds-1.1.0-bin.tar.gz

More Information

If you would like more information about this product, please contact . As we are very interested in extending the product to meet any additional needs you might have, do not hesitate to send us your feature requests as well.

The model for improving this product is the same as is already in use for VisualDCT: users jointly sponsor development, Cosylab performs development, and the resulting product is freely available to everybody.

Acknowledgements

So far, the development of this product has been supported by:

 * Dependable Distributed Systems DeDiSys
project, funded by European Community within the Framework Programme 6 under Contract number 004152.

 * Microsoft through 'Empower for ISV' programme.


For more details, contact :