libstore: check for interrupts in parallel promise

this simplifies the worker loop, and lets us remove it entirely later.
note that ideally only one promise waiting for interrupts should exist
in the entire system. not one per event loop, one per *process*. extra
interrupt waiters make interrupt response nondeterministic and as such
aren't great for user experience. if anything wants to react to aborts
caused by explicit interruptions, or anything else, those things would
be much better served using RAII guards such as Finally (or KJ_DEFER).

Change-Id: I41d035ff40172d536e098153c7375b0972110d51

1 files changed, 7 insertions, 4 deletions

diff --git a/src/libstore/build/worker.cc b/src/libstore/build/worker.cc
index 0ca805b4d..0e8694a6d 100644
--- a/src/libstore/build/worker.cc
+++ b/src/libstore/build/worker.cc
@@ -294,7 +294,13 @@ std::vector<GoalPtr> Worker::run(std::function<Targets (GoalFactory &)> req)
         topGoals.insert(goal);
     }
 
-    auto promise = runImpl().exclusiveJoin(updateStatistics());
+    auto onInterrupt = kj::newPromiseAndCrossThreadFulfiller<Result<void>>();
+    auto interruptCallback = createInterruptCallback([&] {
+        return result::failure(std::make_exception_ptr(makeInterrupted()));
+    });
+
+    auto promise =
+        runImpl().exclusiveJoin(updateStatistics()).exclusiveJoin(std::move(onInterrupt.promise));
 
     // TODO GC interface?
     if (auto localStore = dynamic_cast<LocalStore *>(&store); localStore && settings.minFree != 0) {
@@ -316,9 +322,6 @@ try {
     debug("entered goal loop");
 
     while (1) {
-
-        checkInterrupt();
-
         if (topGoals.empty()) break;
 
         /* Wait for input. */