In general, if it is necessary need to wait on an (externally) asynchronous event then the plugin should spawn a thread to do the waiting. That is what I did for the "SSL bump" work where the plugin has to wait on an external connection to provide data.
On the wait thread, when the wait completes, an event is scheduled on an ET_NET thread to forward the completion to the plugin. In your case, if you have an AsyncProvider, you would want to give it a Continuation and an event and have it send that event to the continuation when it completes. On Tue, Jan 21, 2020 at 12:29 PM Walt Karas <wka...@verizonmedia.com.invalid> wrote: > Using async seems roughly equivalent to scheduling a Continuation. Calling > it will likely create a thread or a thread pool, on top of the ones in the > ATS core. atscppapi also has a C++ wrapper for TSCont (in > Continuation.h). I tried to get in some improvements to this ( > https://github.com/apache/trafficserver/pull/4848 ). But the PR got such > a > cold shoulder, it died of hypothermia. I guess using async is a bypass for > our brute-force thing of requiring Continuations to be scheduled with a > mutex. > > On Tue, Jan 21, 2020 at 11:38 AM David Calavera <david.calav...@gmail.com> > wrote: > > > Hi all, > > > > I was exprimenting with a new plugin over the weekend with and arrived > to a > > blocking point, probably because my lack of experience with the async > story > > in C++. This is the challenge. > > > > I'm integrating a C++ client that invokes calls asynchronously and > returns > > objects that implement std::future. I was thinking about creating an > > AsyncProvider where the invocation happens in the `run()` method. When I > > started to think about the AsyncReceiver I started to question this > > approach. These are a few questions that came to my mind: > > > > - When do I send the dispatch to the AsyncProvider? > > - Where do I call `std::future::get` or any other blocking call to wait > for > > the future response? > > - Are these calls going to block the TrafficServer threads completely? > > - Should I be using a different TrafficServer API? > > > > I did not find any examples of using std::futures anywhere, so I thought > to > > ask the list. I'd really appreciate your feedback. > > > > Cheers, > > David > > >
