On Mon, Jun 17, 2019 at 3:33 AM Schaik, Jacco van <jacco.van.sch...@nlr.nl> wrote:
> Hi, > > I'm building an application using the Qpid Proton C API, version 0.28.0. > I'm using a Connection Driver because my application has its own event > loop.? > > Everything seems to be working, but the application on the other side of > the connection has an idle timeout, so if nothing comes over the line for > (in my case) 30 seconds it times out and drops the connection. I know AMQP > has heartbeat messages that can be used to keep the connection open, but > obviously Proton doesn't get a chance to send them when I'm waiting in my > own event loop. > > Now I can have my event loop wake up every now and then, and call a Proton > function to send a heartbeat. But I haven't been able to find a function > that does that?. I've tried calling pn_transport_tick() but that doesn't > seem to work. Is there some other function that will send a heartbeat for > me? > pn_transport_tick() takes a timestamp and checks if a heartbeat is needed. If it is, it adds that to the "to-do" list for the next outgoing write and marks the transport as writable. The heartbeat actually will be sent on the next write. Note that heart beats are *only* sent if the connection is idle for longer than the idle-timeout, as if there is normal traffic then no heart beats are needed. It is safe and recommended to call pn_transport_tick() every time you wake for IO. It will queue up a heartbeat frame for writing if needed, and return the next time at which it should be called. You should set a timer on your event loop in case there is no IO before then. You can reset the timer on each call to pn_transport_tick to avoid un-necessary wakeups, but it's always safe to make extra calls to tick(). The timestamp you use doesn't have to represent any particular time, it should be a monotonically increasing count of milliseconds, for exmaple libuv's uv_time() or the POSIX CLOCK_MONOTONIC. You can see examples in the proton proactor event-loop code, for example: https://github.com/apache/qpid-proton/blob/master/c/src/proactor/epoll.c#L1425 I don't think we have any surviving examples of transport-based integration but there are 3 proactors (epoll, iocp and libuv) that should provide pretty good examples. > > > Any info greatly appreciated. > > > Regards, Jacco >
