Dead lock in OmmConsumer ?

epfeuffer
epfeuffer Newcomer
in EMA

Hi i'm subscribing to symbols with the following type of code

consumer.registerClient(                                    
    ReqMsg()                                                  
      // default subscription domain is MMT_MARKET_PRICE      
      .serviceName( "ELEKTRON_AD" )                           
      .name( "IBM.N" ),                                       
    client );

at the same time i'm receiving data. Is the Ema C++ interface threadsafe? Can i subscribe

symbols while receiving data? Are there any precautions i should take to ensure there's no

deadlock condition? I"m receiving updates in the derived class


class AppClient : public thomsonreuters::ema::access::OmmConsumerClient

just like the example

Thanks

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Best Answer

  • zoya faberov
    zoya faberov ✭✭✭✭✭
    Answer ✓

    Hi @epfeuffer

    Suggest you print the value, before casting it into double. If it's not a double, for example, if it's a blank, you can not cast double out of it.

    Guessing here, but I think what is stopping you is blanks.

    Please see this previous discussion

    Let us know if this helps?

Answers

  • zoya faberov
    zoya faberov ✭✭✭✭✭

    Hello @epfeuffer,

    EMA API is thread-safe. Please see EMA C++ API Concepts Guide -> API Features section.

    Yes, one can add and remove subscriptions while subscribing to data.

    In terms of the best practices while achieving very high performance with EMA C++, it may be helpful to review Perf Consumer threaded example. It can be found in Elektron C++ SDK, in EMA\Examples\PerfTools\EmaCppConsPerf.

  • epfeuffer
    epfeuffer Newcomer

    Thank you for the fast reply. the call to reg hangs and never comes back. how should i interpret that?

  • zoya faberov
    zoya faberov ✭✭✭✭✭

    Hello @epfeuffer,

    I would start with a question, in order to understand exactly what you observe.

    Have you tested with our standard examples and tutorials for EMA C++, do they run for you?

    Quickstart guide, select for your infra connectivity

    EMA C++ Consumer Tutorials

    Is the issue limited to the newly written custom consumer?


  • epfeuffer
    epfeuffer Newcomer

    Hi i'm connected and receiving data, able to subscribe while receiving data, which is good, but i've determined the sticking point. using the function fe.getReal().getAsDouble() causes the code to halt, if i exclude this function, all works fine. Is this function using a static buffer or something that's not re-entrant?

  • epfeuffer
    epfeuffer Newcomer

    ok, i'll try that.. is there a class reference ? does the code throw and exception or just hang?

  • zoya faberov
    zoya faberov ✭✭✭✭✭

    Here is the link to EMA Reference Guide , click where is says "Click Here To Launch".

    You should be able to, if this is what is happening, check for blanks prior as in the discussion above, or catch the Exception. Usually, the first approach is preferred.

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