libstore: use notifications for stats counters

updating statistics *immediately* when any counter changes declutters
things somewhat and makes useful status reports less dependent on the
current worker main loop. using callbacks will make it easier to move
the worker loop into kj entirely, using only promises for scheduling.

Change-Id: I695dfa83111b1ec09b1a54cff268f3c1d7743ed6

1 files changed, 24 insertions, 12 deletions

diff --git a/src/libstore/build/worker.cc b/src/libstore/build/worker.cc
index 7336ad50f..24c700396 100644
--- a/src/libstore/build/worker.cc
+++ b/src/libstore/build/worker.cc
@@ -320,6 +320,27 @@ void Worker::waitForAWhile(GoalPtr goal)
 }
 
 
+void Worker::updateStatistics()
+{
+    // only update progress info while running. this notably excludes updating
+    // progress info while destroying, which causes the progress bar to assert
+    if (running && statisticsOutdated) {
+        actDerivations.progress(
+            doneBuilds, expectedBuilds + doneBuilds, runningBuilds, failedBuilds
+        );
+        actSubstitutions.progress(
+            doneSubstitutions,
+            expectedSubstitutions + doneSubstitutions,
+            runningSubstitutions,
+            failedSubstitutions
+        );
+        act.setExpected(actFileTransfer, expectedDownloadSize + doneDownloadSize);
+        act.setExpected(actCopyPath, expectedNarSize + doneNarSize);
+
+        statisticsOutdated = false;
+    }
+}
+
 Goals Worker::run(std::function<Goals (GoalFactory &)> req)
 {
     auto _topGoals = req(goalFactory());
@@ -329,6 +350,8 @@ Goals Worker::run(std::function<Goals (GoalFactory &)> req)
     running = true;
     Finally const _stop([&] { running = false; });
 
+    updateStatistics();
+
     for (auto & i : _topGoals) {
         topGoals.insert(i);
         if (auto goal = dynamic_cast<DerivationGoal *>(i.get())) {
@@ -373,18 +396,7 @@ Goals Worker::run(std::function<Goals (GoalFactory &)> req)
                     ? nrSubstitutions < std::max(1U, (unsigned int) settings.maxSubstitutionJobs)
                     : nrLocalBuilds < settings.maxBuildJobs;
                 handleWorkResult(goal, goal->work(inSlot));
-
-                actDerivations.progress(
-                    doneBuilds, expectedBuilds + doneBuilds, runningBuilds, failedBuilds
-                );
-                actSubstitutions.progress(
-                    doneSubstitutions,
-                    expectedSubstitutions + doneSubstitutions,
-                    runningSubstitutions,
-                    failedSubstitutions
-                );
-                act.setExpected(actFileTransfer, expectedDownloadSize + doneDownloadSize);
-                act.setExpected(actCopyPath, expectedNarSize + doneNarSize);
+                updateStatistics();
 
                 if (topGoals.empty()) break; // stuff may have been cancelled
             }