Merge pull request #5367 from cloudflare/gv/exclusivejoin

containers: Keep doing exclusive join just in case the service request does not exit

Author: gabivlj

src/workerd/api/container.c++

@@ -162,18 +162,27 @@ class Container::TcpPortWorkerInterface final: public WorkerInterface {
     // ... and then adapt that to an HttpService ...
     auto service = kj::newHttpService(*client);
 
-    // ... and now we can just forward our call to that.
+    // ... fork connection promises so we can keep the original exception around ...
+    auto connectionPromiseForked = connectionPromise.fork();
+    auto connectionPromiseBranch = connectionPromiseForked.addBranch();
+    auto connectionPromiseToKeepException = connectionPromiseForked.addBranch();
+
+    // ... and now we can just forward our call to that ...
     try {
-      co_await service->request(method, noHostUrl, newHeaders, requestBody, response);
+      co_await service->request(method, noHostUrl, newHeaders, requestBody, response)
+          .exclusiveJoin(
+              // never done as we do not want a Connection RPC exiting successfully
+              // affecting the request
+              connectionPromiseBranch.then([]() -> kj::Promise<void> { return kj::NEVER_DONE; }));
     } catch (...) {
       auto exception = kj::getCaughtExceptionAsKj();
       connectionException = kj::some(kj::mv(exception));
     }
 
-    // we prefer an exception from the container service that might've caused
-    // the error in the first place, that's why we await for the connectionPromise
+    // ... and last but not least, if the connect() call succeeded but the connection
+    // was broken, we throw that exception.
     KJ_IF_SOME(exception, connectionException) {
-      co_await connectionPromise;
+      co_await connectionPromiseToKeepException;
       kj::throwFatalException(kj::mv(exception));
     }
   }