libstore: turn builder output processing into event loop

this removes the rather janky did-you-mean-async poll loop we had so
far. sadly kj does not play well with pty file descriptors, so we do
have to add our own async input stream that does not eat pty EIO and
turns it into an exception. that's still a *lot* better than the old
code, and using a real even loop makes everything else easier later.

Change-Id: Idd7e0428c59758602cc530bcad224cd2fed4c15e

1 files changed, 6 insertions, 6 deletions

diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index f14d09652..040fa7461 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -121,8 +121,6 @@ LocalStore & LocalDerivationGoal::getLocalStore()
 void LocalDerivationGoal::killChild()
 {
     if (pid) {
-        worker.childTerminated(this);
-
         /* If we're using a build user, then there is a tricky race
            condition: if we kill the build user before the child has
            done its setuid() to the build user uid, then it won't be
@@ -243,14 +241,14 @@ try {
     try {
 
         /* Okay, we have to build. */
-        auto fds = startBuilder();
+        auto promise = startBuilder();
 
         /* This state will be reached when we get EOF on the child's
            log pipe. */
         state = &DerivationGoal::buildDone;
 
         started();
-        return {WaitForWorld{std::move(fds), true}};
+        return {WaitForWorld{std::move(promise), true}};
 
     } catch (BuildError & e) {
         outputLocks.unlock();
@@ -390,7 +388,9 @@ void LocalDerivationGoal::cleanupPostOutputsRegisteredModeNonCheck()
     cleanupPostOutputsRegisteredModeCheck();
 }
 
-std::set<int> LocalDerivationGoal::startBuilder()
+// NOTE this one isn't noexcept because it's called from places that expect
+// exceptions to signal failure to launch. we should change this some time.
+kj::Promise<Outcome<void, Goal::Finished>> LocalDerivationGoal::startBuilder()
 {
     if ((buildUser && buildUser->getUIDCount() != 1)
         #if __linux__
@@ -779,7 +779,7 @@ std::set<int> LocalDerivationGoal::startBuilder()
         msgs.push_back(std::move(msg));
     }
 
-    return {builderOutPTY.get()};
+    return handleChildOutput();
 }