libstore: clear derivation build activities when done

without this derivations do not show as completely processed in the
internal-json logs (or the newer multiline output). the former also
breaks external tools like nix-output-monitor which, like multiline
output, grow vertically until at least some goals are finally freed

Change-Id: I55758daf526ba29ae15fb82e0d88da8afb45bf5c

1 files changed, 5 insertions, 1 deletions

diff --git a/src/libstore/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc
index 96140e10b..5de159b2d 100644
--- a/src/libstore/build/derivation-goal.cc
+++ b/src/libstore/build/derivation-goal.cc
@@ -127,7 +127,11 @@ Goal::WorkResult DerivationGoal::timedOut(Error && ex)
 
 kj::Promise<Result<Goal::WorkResult>> DerivationGoal::workImpl() noexcept
 {
-    return useDerivation ? getDerivation() : haveDerivation();
+    return (useDerivation ? getDerivation() : haveDerivation()).attach(kj::defer([this] {
+        act.reset();
+        actLock.reset();
+        builderActivities.clear();
+    }));
 }
 
 bool DerivationGoal::addWantedOutputs(const OutputsSpec & outputs)