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, 3 insertions, 22 deletions

diff --git a/src/libstore/build/goal.hh b/src/libstore/build/goal.hh
index 189505308..3f6e8396e 100644
--- a/src/libstore/build/goal.hh
+++ b/src/libstore/build/goal.hh
@@ -114,6 +114,8 @@ struct Goal
 
 public:
 
+    struct Finished;
+
     struct [[nodiscard]] StillAlive {};
     struct [[nodiscard]] WaitForSlot {};
     struct [[nodiscard]] WaitForAWhile {};
@@ -122,7 +124,7 @@ public:
         Goals goals;
     };
     struct [[nodiscard]] WaitForWorld {
-        std::set<int> fds;
+        kj::Promise<Outcome<void, Finished>> promise;
         bool inBuildSlot;
     };
     struct [[nodiscard]] Finished {
@@ -167,20 +169,6 @@ public:
 
     virtual void waiteeDone(GoalPtr waitee) { }
 
-    virtual WorkResult handleChildOutput(int fd, std::string_view data)
-    {
-        abort();
-    }
-
-    virtual void handleEOF(int fd)
-    {
-    }
-
-    virtual bool respectsTimeouts()
-    {
-        return false;
-    }
-
     void trace(std::string_view s);
 
     std::string getName() const
@@ -188,13 +176,6 @@ public:
         return name;
     }
 
-    /**
-     * Callback in case of a timeout.  It should wake up its waiters,
-     * get rid of any running child processes that are being monitored
-     * by the worker (important!), etc.
-     */
-    virtual Finished timedOut(Error && ex) = 0;
-
     virtual std::string key() = 0;
 
     virtual void cleanup() { }