For completeness, re-implement meta.schedulingPriority

src/hydra-queue-runner/dispatcher.cc

@@ -118,9 +118,29 @@ system_time State::doDispatch()
                     a.currentJobs > b.currentJobs;
             });
 
-        /* Sort the runnable steps by priority. FIXME: O(n lg n);
-           obviously, it would be better to keep a runnable queue sorted
-           by priority. */
+        /* Sort the runnable steps by priority. Priority is establised
+           as follows (in order of precedence):
+
+           - The global priority of the builds that depend on the
+             step. This allows admins to bump a build to the front of
+             the queue.
+
+           - The lowest used scheduling share of the jobsets depending
+             on the step.
+
+           - The local priority of the build, as set via the build's
+             meta.schedulingPriority field. Note that this is not
+             quite correct: the local priority should only be used to
+             establish priority between builds in the same jobset, but
+             here it's used between steps in different jobsets if they
+             happen to have the same lowest used scheduling share. But
+             that's not every likely.
+
+           - The lowest ID of the builds depending on the step;
+             i.e. older builds take priority over new ones.
+
+           FIXME: O(n lg n); obviously, it would be better to keep a
+           runnable queue sorted by priority. */
         std::vector<Step::ptr> runnableSorted;
         {
             auto runnable_(runnable.lock());
@@ -166,6 +186,7 @@ system_time State::doDispatch()
                 return
                     a_->highestGlobalPriority != b_->highestGlobalPriority ? a_->highestGlobalPriority > b_->highestGlobalPriority :
                     a_->lowestShareUsed != b_->lowestShareUsed ? a_->lowestShareUsed < b_->lowestShareUsed :
+                    a_->highestLocalPriority != b_->highestLocalPriority ? a_->highestLocalPriority > b_->highestLocalPriority :
                     a_->lowestBuildID < b_->lowestBuildID;
             });
 

src/hydra-queue-runner/queue-monitor.cc

@@ -67,7 +67,7 @@ void State::getQueuedBuilds(Connection & conn, std::shared_ptr<StoreAPI> store,
         pqxx::work txn(conn);
 
         auto res = txn.parameterized
-            ("select id, project, jobset, job, drvPath, maxsilent, timeout, timestamp, globalPriority from Builds "
+            ("select id, project, jobset, job, drvPath, maxsilent, timeout, timestamp, globalPriority, priority from Builds "
              "where id > $1 and finished = 0 order by globalPriority desc, id")
             (lastBuildId).exec();
 
@@ -88,6 +88,7 @@ void State::getQueuedBuilds(Connection & conn, std::shared_ptr<StoreAPI> store,
             build->buildTimeout = row["timeout"].as<int>();
             build->timestamp = row["timestamp"].as<time_t>();
             build->globalPriority = row["globalPriority"].as<int>();
+            build->localPriority = row["priority"].as<int>();
             build->jobset = createJobset(txn, build->projectName, build->jobsetName);
 
             newIDs.push_back(id);
@@ -259,6 +260,7 @@ void Build::propagatePriorities()
     visitDependencies([&](const Step::ptr & step) {
         auto step_(step->state.lock());
         step_->highestGlobalPriority = std::max(step_->highestGlobalPriority, globalPriority);
+        step_->highestLocalPriority = std::max(step_->highestLocalPriority, localPriority);
         step_->lowestBuildID = std::min(step_->lowestBuildID, id);
         step_->jobsets.insert(jobset);
     }, toplevel);

src/hydra-queue-runner/state.hh

@@ -105,7 +105,7 @@ struct Build
     std::string projectName, jobsetName, jobName;
     time_t timestamp;
     unsigned int maxSilentTime, buildTimeout;
-    int globalPriority;
+    int localPriority, globalPriority;
 
     std::shared_ptr<Step> toplevel;
 
@@ -164,6 +164,10 @@ struct Step
            step. */
         double lowestShareUsed;
 
+        /* The highest local priority of any build depending on this
+           step. */
+        int highestLocalPriority{0};
+
         /* The lowest ID of any build depending on this step. */
         BuildID lowestBuildID{std::numeric_limits<BuildID>::max()};
     };