[Question]How to detect pipe(obtained from ctx->connect()) is writable?

[Rhett-Ying]

Hi,

when I get a pipe via ctx->context(address), how do I know the pipe is ready for write or read? A return from ctx->connect() does not mean the connection has been built, right? If I call pipe->write() immediately, such write could fail as the underlying connection has not built yet.

[lw]

A pipe is always immediately writable, and the pipe might "hold onto" your write requests for a bit until the connections are ready, but this is invisible to you.

[Rhett-Ying]

oh, I do hit error when write immediately. something wrong in my code? could you help take a look?

My scenario is CLIENT triggers connection before SERVER starts to listen. In the write callback, sometimes error is evaluated as true.

CLIENT:
std::shared_ptr<Pipe> pipe; pipe = context->connect(addr); auto done = std::make_shared<std::promise<bool>>(); tensorpipe::Message tpmsg; tpmsg.metadata = "connect"; pipe->write(tpmsg, [done](const tensorpipe::Error &error) { if (error) { LOG(WARNING) << "Error occurred when write to pipe: " << error.what(); done->set_value(false); } else { done->set_value(true);

LOG:
Error occurred when write to pipe: ECONNREFUSED: connection refused (this error originated at tensorpipe/transport/uv/connection_impl.cc:62)

[Rhett-Ying]

Additional info for my scenario: I used same TensorPipe::Context instance to connect to multiple servers, namely I have called context->connect() multiple times and obtained multiple pipes. I think it's a normal use case, right? Alternatively, we could create TP::Context for each connection.

[lw]

A "connection refused" means that the server isn't listening on that address/port, you should check how you're obtaining that address, it should come from the server's Listener instance.

[Rhett-Ying]

If I keep calling auto pipe = context->connect();pipe->write() until write successfully in client side, will I hit any potential resource leak or run out issue? Just assume the server starts listen a quite long time later.

[eedalong]

If I keep calling auto pipe = context->connect();pipe->write() until write successfully in client side, will I hit any potential resource leak or run out issue? Just assume the server starts listen a quite long time later.

@Rhett-Ying I guess there will be no harm cuz message sending requires both client and server come into play. Write operation will not finish if receiver doesnt issue a read operation. So if server is not ready to issue read opreation and you call pipe->write, this operation will be stucked