getQueuedBuilds(): Handle dependent builds first

If a build A depends on a derivation that is the top-level derivation
of some build B, then we should process B before A (meaning we
shouldn't make the derivation runnable before B has been
added). Otherwise, the derivation will be "accounted" to A rather than
B (so the build step will show up in the wrong build).

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

@@ -479,7 +479,7 @@ void State::getQueuedBuilds(Connection & conn, std::shared_ptr<StoreAPI> store,
 
     /* Grab the queued builds from the database, but don't process
        them yet (since we don't want a long-running transaction). */
-    std::list<Build::ptr> newBuilds; // FIXME: use queue
+    std::multimap<Path, Build::ptr> newBuilds;
 
     {
         pqxx::work txn(conn);
@@ -498,20 +498,18 @@ void State::getQueuedBuilds(Connection & conn, std::shared_ptr<StoreAPI> store,
             build->fullJobName = row["project"].as<string>() + ":" + row["jobset"].as<string>() + ":" + row["job"].as<string>();
             build->maxSilentTime = row["maxsilent"].as<int>();
             build->buildTimeout = row["timeout"].as<int>();
-            std::cerr << build->id << " " << build->buildTimeout  << std::endl;
 
-            newBuilds.push_back(build);
+            newBuilds.emplace(std::make_pair(build->drvPath, build));
         }
     }
 
-    /* Now instantiate build steps for each new build. The builder
+    std::set<Step::ptr> newRunnable;
-       threads can start building the runnable build steps right away,
+    unsigned int nrAdded;
-       even while we're still processing other new builds. */
+    std::function<void(Build::ptr)> createBuild;
-    for (auto & build : newBuilds) {
-        // FIXME: remove build from newBuilds to ensure quick destruction
-        // FIXME: exception handling
 
+    createBuild = [&](Build::ptr build) {
         printMsg(lvlTalkative, format("loading build %1% (%2%)") % build->id % build->fullJobName);
+        nrAdded++;
 
         if (!store->isValidPath(build->drvPath)) {
             /* Derivation has been GC'ed prematurely. */
@@ -524,12 +522,26 @@ void State::getQueuedBuilds(Connection & conn, std::shared_ptr<StoreAPI> store,
                 (time(0))
                 ("derivation was garbage-collected prior to build").exec();
             txn.commit();
-            continue;
+            return;
         }
 
-        std::set<Step::ptr> newSteps, newRunnable;
+        std::set<Step::ptr> newSteps;
         Step::ptr step = createStep(store, build->drvPath, newSteps, newRunnable);
 
+        /* Some of the new steps may be the top level of builds that
+           we haven't processed yet. So do them now. This ensures that
+           if build A depends on build B with top-level step X, then X
+           will be "accounted" to B in doBuildStep(). */
+        for (auto & r : newSteps) {
+            while (true) {
+                auto i = newBuilds.find(r->drvPath);
+                if (i == newBuilds.end()) break;
+                Build::ptr b = i->second;
+                newBuilds.erase(i);
+                createBuild(b);
+            }
+        }
+
         /* If we didn't get a step, it means the step's outputs are
            all valid. So we mark this as a finished, cached build. */
         if (!step) {
@@ -543,7 +555,7 @@ void State::getQueuedBuilds(Connection & conn, std::shared_ptr<StoreAPI> store,
             markSucceededBuild(txn, build, res, true, now, now);
             txn.commit();
 
-            continue;
+            return;
         }
 
         /* If any step has an unsupported system type or has a
@@ -591,7 +603,7 @@ void State::getQueuedBuilds(Connection & conn, std::shared_ptr<StoreAPI> store,
             }
         }
 
-        if (badStep) continue;
+        if (badStep) return;
 
         /* Note: if we exit this scope prior to this, the build and
            all newly created steps are destroyed. */
@@ -604,16 +616,30 @@ void State::getQueuedBuilds(Connection & conn, std::shared_ptr<StoreAPI> store,
             build->toplevel = step;
         }
 
-        printMsg(lvlChatty, format("added build %1% (top-level step %2%, %3% new steps, %4% new runnable steps)")
+        printMsg(lvlChatty, format("added build %1% (top-level step %2%, %3% new steps)")
-            % build->id % step->drvPath % newSteps.size() % newRunnable.size());
+            % build->id % step->drvPath % newSteps.size());
 
         /* Prior to this, the build is not visible to
            getDependentBuilds().  Now it is, so the build can be
            failed if a dependency fails. (It can't succeed right away
            because its top-level is not runnable yet). */
 
+    };
+
+    /* Now instantiate build steps for each new build. The builder
+       threads can start building the runnable build steps right away,
+       even while we're still processing other new builds. */
+    while (!newBuilds.empty()) {
+        auto build = newBuilds.begin()->second;
+        newBuilds.erase(newBuilds.begin());
+
+        newRunnable.clear();
+        nrAdded = 0;
+        createBuild(build);
+
         /* Add the new runnable build steps to ‘runnable’ and wake up
            the builder threads. */
+        printMsg(lvlChatty, format("got %1% new runnable steps from %2% new builds") % newRunnable.size() % nrAdded);
         for (auto & r : newRunnable)
             makeRunnable(r);
     }
@@ -1235,8 +1261,6 @@ void State::run()
 
     auto queueMonitorThread = std::thread(&State::queueMonitor, this);
 
-    sleep(5);
-
     std::thread(&State::dispatcher, this).detach();
 
     queueMonitorThread.join();