Parallel RPC Streaming Operations Block Until All Sessions Complete

[yaseiva]

Hello,

I'm experiencing unexpected behavior with parallel RPC streaming operations in FastDDS. When I create multiple streaming operations (e.g., sum_all) in parallel, I cannot retrieve results from completed operations until ALL started operations are finished.

auto writer1 = std::shared_ptr<RpcClientWriter<int32_t>>();
auto future1 = client->sum_all(writer1);

auto writer2 = std::shared_ptr<RpcClientWriter<int32_t>>();
auto future2 = client->sum_all(writer2);

// Complete only the second operation
writer2->write(3);
writer2->finish();

// Try to get result from completed operation
auto result2 = future2.get();  // This blocks/times out!

Expected Behavior:
Each streaming operation should be independent. Calling get() on future2 should return the result (3) immediately after writer2->finish() is called, regardless of the state of writer1.
Actual Behavior:
future2.get() blocks indefinitely (or times out) until writer1 is also finished. The operation only succeeds if I finish both streams:

writer1->finish();  // Must finish this too
auto result2 = future2.get();  // Now this works

[MiguelCompany]

The example server creates a thread pool for processing requests.
The number of threads in the pool is passed in the call to create_CalculatorServer.
In the example, a value of 0 is used, which is equivalent to passing 1.
Passing a bigger number will make the server process requests in parallel.

Also, as explained in this section of the documentation, you can pass a custom scheduler when creating the server, instead of using the default (thread pool) one.

[yaseiva]

Thanks