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, 3 insertions, 3 deletions

diff --git a/src/libstore/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc
index 1dda1b1b4..c288003b4 100644
--- a/src/libstore/build/derivation-goal.cc
+++ b/src/libstore/build/derivation-goal.cc
@@ -71,7 +71,7 @@ DerivationGoal::DerivationGoal(const StorePath & drvPath,
         DerivedPath::Built { makeConstantStorePathRef(drvPath), wantedOutputs }.to_string(worker.store));
     trace("created");
 
-    mcExpectedBuilds = std::make_unique<MaintainCount<uint64_t>>(worker.expectedBuilds);
+    mcExpectedBuilds = worker.expectedBuilds.addTemporarily(1);
 }
 
 
@@ -91,7 +91,7 @@ DerivationGoal::DerivationGoal(const StorePath & drvPath, const BasicDerivation
         DerivedPath::Built { makeConstantStorePathRef(drvPath), drv.outputNames() }.to_string(worker.store));
     trace("created");
 
-    mcExpectedBuilds = std::make_unique<MaintainCount<uint64_t>>(worker.expectedBuilds);
+    mcExpectedBuilds = worker.expectedBuilds.addTemporarily(1);
 
     /* Prevent the .chroot directory from being
        garbage-collected. (See isActiveTempFile() in gc.cc.) */
@@ -662,7 +662,7 @@ void DerivationGoal::started()
     if (hook) msg += fmt(" on '%s'", machineName);
     act = std::make_unique<Activity>(*logger, lvlInfo, actBuild, msg,
         Logger::Fields{worker.store.printStorePath(drvPath), hook ? machineName : "", 1, 1});
-    mcRunningBuilds = std::make_unique<MaintainCount<uint64_t>>(worker.runningBuilds);
+    mcRunningBuilds = worker.runningBuilds.addTemporarily(1);
 }
 
 Goal::WorkResult DerivationGoal::tryToBuild(bool inBuildSlot)