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tango_zmq

Experiment ZMQ to replace CORBA in Tango CS

Prerequisites:

There are only few files in this project:

  • clnt.c which simulates a client
  • svr.c which simulates a server
  • Makefile which has to be adapted to your setup

To run the example, start three server processes

  • One with 9000 (port number) as argument
  • Another one with 9001 as argument
  • The last one with 9002 as argument

Then start the client which does the following:

  • Connect the client router ZMQ socket used for synchronous communication to the three servers
  • Connect the client router ZMQ socket used for asynchronous communication to the three servers
  • Send two messages to server 9001 asynchronously. Each request sent to server 9001 needs 1 second to be executed
  • Send one synchronous message to server 9000 with a timeout of 3 seconds. Each request sent to server 9000 or 9002 needs 4 seconds to be executed. Therefore, this request timed out
  • Send one synchronous message to server 9002 with a timeout of 5 seconds.
  • Read the asynchronous requests answers

Work to be done or points to be analyzed (some are big tasks, some are small tasks)

  • Define a Tango protocol (in ABNF) with at least: request id obj id (uniq in DS, in CS?) method name request type protocol release data

  • Implement all Tango::DevVarXXXArray type Similar interface - Similar memory management

  • Implement a CORBA::string_dup/string_free/string_alloc methods

  • Implement a dummy (?) CORBA::Any object (used in Pogo generated code for commands) in order to provide compatibility

  • omnithread library compatibility (C++11 ?) thread class (detached and undetached) oomni_mutex, omni_mutex_lock, omni_condition variable

  • Manage TANGO_HOST definition like "orion:10000,orion:11000"

  • Implement something like ORBtraceLevel, ORBtraceFile, ORBtraceTime, ORBtraceThreadId Is Tango logging adequate?

  • Select a serialiation lib: No lib Google protbuf capnproto Messagepack

  • Implement a kind of "is_a" method for all devices in order to manage interface changes with time

  • Define a TOR (Tango Object Reference) stored in DB in order to build object connection How are we going to manage DS on host with several NIC boards?

  • Select which kind of container used in DS in which we will store the device object pointer (vector, map,...) Choose the object_id coherent with choice

  • Try to implement things in a way we could easily replace ZMQ by something else (nanomsg...)

  • Can we write it using C++11 features?

  • Is it possible to remove event heartbeat by using XPUB in server (instead of PUB) and monitor socket API in client?

  • Possible to replace DevString (char *) with C++ string?

  • Collocated calls?

  • Device server with user event loop

  • DS command line option to start DS on a specific port (like ORBendPoint)

  • DS command line option to listen on a specific NIC