Integrating cppwamp into a multithreaded app

[yupuquiz]

Hello,

Just a question about integrating cppwap library into a multithreaded app.
publish an event is a thread safe? how could be the library use when it is integrated in a multi-thread app?

Thanks

[ecorm]

No, publishing an event is currently not thread-safe. Nor are any of Session's (and CoroSession's) public member functions. You need to serialize these calls coming from multiple threads by queuing them in the boost::io_service using boost::io_service::post:

Event event("myapp.foo").withArgs(42, otherStuff);
iosvc.post( [event]() {session->publish(event);} );

where iosvc is the same io_service used by the Session or CoroSession.

You might also be able use mutexes to serialize the publish calls, but I find the io_service approach to be less error-prone. Furthermore, mutex contention might degrade the performance of your worker threads.

Please note that if you have several Session / CoroSession instances, then they can be safely used in separate threads (I've never tested this, though).

I have an open issue #89 to consider making Session thread-safe, but I don't know when I'll have the time to look into this.

[yupuquiz]

ok, thanks for your explanation.

I guess to call a remote procedure is not thread-safe as well.

[ecorm]

Like I said, none of the public Session methods are thread-safe, including calling an RPC.

[ecorm]

You may find this question, and this Google Groups discussion to be informative.

[ecorm]

v0.10.0 now has thread-safe method overloads for Session taking the ThreadSafe tag type. These thread-safe overloads take care of serializing the operation via Session::strand().

It's also now possible to pass the boost::asio::thread_pool context to Session::create. User handlers would then be posted to that thread pool automatically.

It's also now possible to use boost::asio::bind_executor in a more fine-grained manner to make Session post a handler via a thread pool's executor.