queue runner: fix nullptr deref on build exception after releasing a machine reservation

(cherry picked from commit f23ec71227911891807706b6b978836e4d80edde)

package.nix

@@ -90,6 +90,7 @@ let
         DateTime
         DBDPg
         DBDSQLite
+        DBIxClassHelpers
         DigestSHA1
         EmailMIME
         EmailSender

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

@@ -412,8 +412,19 @@ void RemoteResult::updateWithBuildResult(const nix::BuildResult & buildResult)
 
 }
 
+/* Utility guard object to auto-release a semaphore on destruction. */
+template <typename T>
+class SemaphoreReleaser {
+public:
+    SemaphoreReleaser(T* s) : sem(s) {}
+    ~SemaphoreReleaser() { sem->release(); }
+
+private:
+    T* sem;
+};
 
 void State::buildRemote(ref<Store> destStore,
+    MachineReservation::ptr & reservation,
     ::Machine::ptr machine, Step::ptr step,
     const ServeProto::BuildOptions & buildOptions,
     RemoteResult & result, std::shared_ptr<ActiveStep> activeStep,
@@ -551,6 +562,24 @@ void State::buildRemote(ref<Store> destStore,
             result.logFile = "";
         }
 
+        /* Throttle CPU-bound work. Opportunistically skip updating the current
+         * step, since this requires a DB roundtrip. */
+        if (!localWorkThrottler.try_acquire()) {
+            MaintainCount<counter> mc(nrStepsWaitingForDownloadSlot);
+            updateStep(ssWaitingForLocalSlot);
+            localWorkThrottler.acquire();
+        }
+        SemaphoreReleaser releaser(&localWorkThrottler);
+
+        /* Once we've started copying outputs, release the machine reservation
+         * so further builds can happen. We do not release the machine earlier
+         * to avoid situations where the queue runner is bottlenecked on
+         * copying outputs and we end up building too many things that we
+         * haven't been able to allow copy slots for. */
+        assert(reservation.unique());
+        reservation = 0;
+        wakeDispatcher();
+
         StorePathSet outputs;
         for (auto & [_, realisation] : buildResult.builtOutputs)
             outputs.insert(realisation.outPath);

src/hydra-queue-runner/builder.cc

@@ -37,19 +37,22 @@ void State::builder(MachineReservation::ptr reservation)
 
         try {
             auto destStore = getDestStore();
+            // Might release the reservation.
             res = doBuildStep(destStore, reservation, activeStep);
         } catch (std::exception & e) {
             printMsg(lvlError, "uncaught exception building ‘%s’ on ‘%s’: %s",
-                localStore->printStorePath(reservation->step->drvPath),
-                reservation->machine->sshName,
+                localStore->printStorePath(activeStep->step->drvPath),
+                reservation ? reservation->machine->sshName : std::string("(no machine)"),
                 e.what());
         }
     }
 
-    /* Release the machine and wake up the dispatcher. */
-    assert(reservation.unique());
-    reservation = 0;
-    wakeDispatcher();
+    /* If the machine hasn't been released yet, release and wake up the dispatcher. */
+    if (reservation) {
+        assert(reservation.unique());
+        reservation = 0;
+        wakeDispatcher();
+    }
 
     /* If there was a temporary failure, retry the step after an
        exponentially increasing interval. */
@@ -72,11 +75,11 @@ void State::builder(MachineReservation::ptr reservation)
 
 
 State::StepResult State::doBuildStep(nix::ref<Store> destStore,
-    MachineReservation::ptr reservation,
+    MachineReservation::ptr & reservation,
     std::shared_ptr<ActiveStep> activeStep)
 {
-    auto & step(reservation->step);
-    auto & machine(reservation->machine);
+    auto step(reservation->step);
+    auto machine(reservation->machine);
 
     {
         auto step_(step->state.lock());
@@ -211,7 +214,7 @@ State::StepResult State::doBuildStep(nix::ref<Store> destStore,
 
         try {
             /* FIXME: referring builds may have conflicting timeouts. */
-            buildRemote(destStore, machine, step, buildOptions, result, activeStep, updateStep, narMembers);
+            buildRemote(destStore, reservation, machine, step, buildOptions, result, activeStep, updateStep, narMembers);
         } catch (Error & e) {
             if (activeStep->state_.lock()->cancelled) {
                 printInfo("marking step %d of build %d as cancelled", stepNr, buildId);

src/hydra-queue-runner/dispatcher.cc

@@ -40,13 +40,15 @@ void State::dispatcher()
             printMsg(lvlDebug, "dispatcher woken up");
             nrDispatcherWakeups++;
 
-            auto now1 = std::chrono::steady_clock::now();
+            auto t_before_work = std::chrono::steady_clock::now();
 
             auto sleepUntil = doDispatch();
 
-            auto now2 = std::chrono::steady_clock::now();
+            auto t_after_work = std::chrono::steady_clock::now();
 
-            dispatchTimeMs += std::chrono::duration_cast<std::chrono::milliseconds>(now2 - now1).count();
+            prom.dispatcher_time_spent_running.Increment(
+                std::chrono::duration_cast<std::chrono::microseconds>(t_after_work - t_before_work).count());
+            dispatchTimeMs += std::chrono::duration_cast<std::chrono::milliseconds>(t_after_work - t_before_work).count();
 
             /* Sleep until we're woken up (either because a runnable build
                is added, or because a build finishes). */
@@ -60,6 +62,10 @@ void State::dispatcher()
                 *dispatcherWakeup_ = false;
             }
 
+            auto t_after_sleep = std::chrono::steady_clock::now();
+            prom.dispatcher_time_spent_waiting.Increment(
+                std::chrono::duration_cast<std::chrono::microseconds>(t_after_sleep - t_after_work).count());
+
         } catch (std::exception & e) {
             printError("dispatcher: %s", e.what());
             sleep(1);

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

@@ -70,10 +70,31 @@ State::PromMetrics::PromMetrics()
             .Register(*registry)
             .Add({})
     )
-    , queue_max_id(
-        prometheus::BuildGauge()
-            .Name("hydraqueuerunner_queue_max_build_id_info")
-            .Help("Maximum build record ID in the queue")
+    , dispatcher_time_spent_running(
+        prometheus::BuildCounter()
+            .Name("hydraqueuerunner_dispatcher_time_spent_running")
+            .Help("Time (in micros) spent running the dispatcher")
+            .Register(*registry)
+            .Add({})
+    )
+    , dispatcher_time_spent_waiting(
+        prometheus::BuildCounter()
+            .Name("hydraqueuerunner_dispatcher_time_spent_waiting")
+            .Help("Time (in micros) spent waiting for the dispatcher to obtain work")
+            .Register(*registry)
+            .Add({})
+    )
+    , queue_monitor_time_spent_running(
+        prometheus::BuildCounter()
+            .Name("hydraqueuerunner_queue_monitor_time_spent_running")
+            .Help("Time (in micros) spent running the queue monitor")
+            .Register(*registry)
+            .Add({})
+    )
+    , queue_monitor_time_spent_waiting(
+        prometheus::BuildCounter()
+            .Name("hydraqueuerunner_queue_monitor_time_spent_waiting")
+            .Help("Time (in micros) spent waiting for the queue monitor to obtain work")
             .Register(*registry)
             .Add({})
     )
@@ -85,6 +106,7 @@ State::State(std::optional<std::string> metricsAddrOpt)
     : config(std::make_unique<HydraConfig>())
     , maxUnsupportedTime(config->getIntOption("max_unsupported_time", 0))
     , dbPool(config->getIntOption("max_db_connections", 128))
+    , localWorkThrottler(config->getIntOption("max_local_worker_threads", std::min(maxSupportedLocalWorkers, std::max(4u, std::thread::hardware_concurrency()) - 2)))
     , maxOutputSize(config->getIntOption("max_output_size", 2ULL << 30))
     , maxLogSize(config->getIntOption("max_log_size", 64ULL << 20))
     , uploadLogsToBinaryCache(config->getBoolOption("upload_logs_to_binary_cache", false))
@@ -590,6 +612,7 @@ void State::dumpStatus(Connection & conn)
         {"nrActiveSteps", activeSteps_.lock()->size()},
         {"nrStepsBuilding", nrStepsBuilding.load()},
         {"nrStepsCopyingTo", nrStepsCopyingTo.load()},
+        {"nrStepsWaitingForDownloadSlot", nrStepsWaitingForDownloadSlot.load()},
         {"nrStepsCopyingFrom", nrStepsCopyingFrom.load()},
         {"nrStepsWaiting", nrStepsWaiting.load()},
         {"nrUnsupportedSteps", nrUnsupportedSteps.load()},

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

@@ -1,6 +1,7 @@
 #include "state.hh"
 #include "hydra-build-result.hh"
 #include "globals.hh"
+#include "thread-pool.hh"
 
 #include <cstring>
 
@@ -37,16 +38,21 @@ void State::queueMonitorLoop(Connection & conn)
 
     auto destStore = getDestStore();
 
-    unsigned int lastBuildId = 0;
-
     bool quit = false;
     while (!quit) {
+        auto t_before_work = std::chrono::steady_clock::now();
+
         localStore->clearPathInfoCache();
 
-        bool done = getQueuedBuilds(conn, destStore, lastBuildId);
+        bool done = getQueuedBuilds(conn, destStore);
 
         if (buildOne && buildOneDone) quit = true;
 
+        auto t_after_work = std::chrono::steady_clock::now();
+
+        prom.queue_monitor_time_spent_running.Increment(
+            std::chrono::duration_cast<std::chrono::microseconds>(t_after_work - t_before_work).count());
+
         /* Sleep until we get notification from the database about an
            event. */
         if (done && !quit) {
@@ -56,12 +62,10 @@ void State::queueMonitorLoop(Connection & conn)
             conn.get_notifs();
 
         if (auto lowestId = buildsAdded.get()) {
-            lastBuildId = std::min(lastBuildId, static_cast<unsigned>(std::stoul(*lowestId) - 1));
             printMsg(lvlTalkative, "got notification: new builds added to the queue");
         }
         if (buildsRestarted.get()) {
             printMsg(lvlTalkative, "got notification: builds restarted");
-            lastBuildId = 0; // check all builds
         }
         if (buildsCancelled.get() || buildsDeleted.get() || buildsBumped.get()) {
             printMsg(lvlTalkative, "got notification: builds cancelled or bumped");
@@ -71,6 +75,10 @@ void State::queueMonitorLoop(Connection & conn)
             printMsg(lvlTalkative, "got notification: jobset shares changed");
             processJobsetSharesChange(conn);
         }
+
+        auto t_after_sleep = std::chrono::steady_clock::now();
+        prom.queue_monitor_time_spent_waiting.Increment(
+            std::chrono::duration_cast<std::chrono::microseconds>(t_after_sleep - t_after_work).count());
     }
 
     exit(0);
@@ -84,20 +92,18 @@ struct PreviousFailure : public std::exception {
 
 
 bool State::getQueuedBuilds(Connection & conn,
-    ref<Store> destStore, unsigned int & lastBuildId)
+    ref<Store> destStore)
 {
     prom.queue_checks_started.Increment();
 
-    printInfo("checking the queue for builds > %d...", lastBuildId);
+    printInfo("checking the queue for builds...");
 
     /* Grab the queued builds from the database, but don't process
        them yet (since we don't want a long-running transaction). */
     std::vector<BuildID> newIDs;
-    std::map<BuildID, Build::ptr> newBuildsByID;
+    std::unordered_map<BuildID, Build::ptr> newBuildsByID;
     std::multimap<StorePath, BuildID> newBuildsByPath;
 
-    unsigned int newLastBuildId = lastBuildId;
-
     {
         pqxx::work txn(conn);
 
@@ -106,17 +112,12 @@ bool State::getQueuedBuilds(Connection & conn,
              "jobsets.name as jobset, job, drvPath, maxsilent, timeout, timestamp, "
              "globalPriority, priority from Builds "
              "inner join jobsets on builds.jobset_id = jobsets.id "
-             "where builds.id > $1 and finished = 0 order by globalPriority desc, builds.id",
-            lastBuildId);
+             "where finished = 0 order by globalPriority desc, random()");
 
         for (auto const & row : res) {
             auto builds_(builds.lock());
             BuildID id = row["id"].as<BuildID>();
             if (buildOne && id != buildOne) continue;
-            if (id > newLastBuildId) {
-                newLastBuildId = id;
-                prom.queue_max_id.Set(id);
-            }
             if (builds_->count(id)) continue;
 
             auto build = std::make_shared<Build>(
@@ -318,15 +319,13 @@ bool State::getQueuedBuilds(Connection & conn,
 
         /* Stop after a certain time to allow priority bumps to be
            processed. */
-        if (std::chrono::system_clock::now() > start + std::chrono::seconds(600)) {
+        if (std::chrono::system_clock::now() > start + std::chrono::seconds(60)) {
             prom.queue_checks_early_exits.Increment();
             break;
         }
     }
 
     prom.queue_checks_finished.Increment();
-
-    lastBuildId = newBuildsByID.empty() ? newLastBuildId : newBuildsByID.begin()->first - 1;
     return newBuildsByID.empty();
 }
 
@@ -405,6 +404,34 @@ void State::processQueueChange(Connection & conn)
 }
 
 
+std::map<DrvOutput, std::optional<StorePath>> State::getMissingRemotePaths(
+    ref<Store> destStore,
+    const std::map<DrvOutput, std::optional<StorePath>> & paths)
+{
+    Sync<std::map<DrvOutput, std::optional<StorePath>>> missing_;
+    ThreadPool tp;
+
+    for (auto & [output, maybeOutputPath] : paths) {
+        if (!maybeOutputPath) {
+            auto missing(missing_.lock());
+            missing->insert({output, maybeOutputPath});
+        } else {
+            tp.enqueue([&] {
+                if (!destStore->isValidPath(*maybeOutputPath)) {
+                    auto missing(missing_.lock());
+                    missing->insert({output, maybeOutputPath});
+                }
+            });
+        }
+    }
+
+    tp.process();
+
+    auto missing(missing_.lock());
+    return *missing;
+}
+
+
 Step::ptr State::createStep(ref<Store> destStore,
     Connection & conn, Build::ptr build, const StorePath & drvPath,
     Build::ptr referringBuild, Step::ptr referringStep, std::set<StorePath> & finishedDrvs,
@@ -485,16 +512,15 @@ Step::ptr State::createStep(ref<Store> destStore,
 
     /* Are all outputs valid? */
     auto outputHashes = staticOutputHashes(*localStore, *(step->drv));
-    bool valid = true;
-    std::map<DrvOutput, std::optional<StorePath>> missing;
+    std::map<DrvOutput, std::optional<StorePath>> paths;
     for (auto & [outputName, maybeOutputPath] : destStore->queryPartialDerivationOutputMap(drvPath, &*localStore)) {
         auto outputHash = outputHashes.at(outputName);
-        if (maybeOutputPath && destStore->isValidPath(*maybeOutputPath))
-            continue;
-        valid = false;
-        missing.insert({{outputHash, outputName}, maybeOutputPath});
+        paths.insert({{outputHash, outputName}, maybeOutputPath});
     }
 
+    auto missing = getMissingRemotePaths(destStore, paths);
+    bool valid = missing.empty();
+
     /* Try to copy the missing paths from the local store or from
        substitutes. */
     if (!missing.empty()) {

src/hydra-queue-runner/state.hh

@@ -7,6 +7,7 @@
 #include <memory>
 #include <queue>
 #include <regex>
+#include <semaphore>
 
 #include <prometheus/counter.h>
 #include <prometheus/gauge.h>
@@ -58,6 +59,7 @@ typedef enum {
     ssConnecting = 10,
     ssSendingInputs = 20,
     ssBuilding = 30,
+    ssWaitingForLocalSlot = 35,
     ssReceivingOutputs = 40,
     ssPostProcessing = 50,
 } StepState;
@@ -361,6 +363,10 @@ private:
     typedef std::map<std::string, Machine::ptr> Machines;
     nix::Sync<Machines> machines; // FIXME: use atomic_shared_ptr
 
+    /* Throttler for CPU-bound local work. */
+    static constexpr unsigned int maxSupportedLocalWorkers = 1024;
+    std::counting_semaphore<maxSupportedLocalWorkers> localWorkThrottler;
+
     /* Various stats. */
     time_t startedAt;
     counter nrBuildsRead{0};
@@ -370,6 +376,7 @@ private:
     counter nrStepsDone{0};
     counter nrStepsBuilding{0};
     counter nrStepsCopyingTo{0};
+    counter nrStepsWaitingForDownloadSlot{0};
     counter nrStepsCopyingFrom{0};
     counter nrStepsWaiting{0};
     counter nrUnsupportedSteps{0};
@@ -458,7 +465,12 @@ private:
         prometheus::Counter& queue_steps_created;
         prometheus::Counter& queue_checks_early_exits;
         prometheus::Counter& queue_checks_finished;
-        prometheus::Gauge& queue_max_id;
+
+        prometheus::Counter& dispatcher_time_spent_running;
+        prometheus::Counter& dispatcher_time_spent_waiting;
+
+        prometheus::Counter& queue_monitor_time_spent_running;
+        prometheus::Counter& queue_monitor_time_spent_waiting;
 
         PromMetrics();
     };
@@ -502,8 +514,7 @@ private:
     void queueMonitorLoop(Connection & conn);
 
     /* Check the queue for new builds. */
-    bool getQueuedBuilds(Connection & conn,
-        nix::ref<nix::Store> destStore, unsigned int & lastBuildId);
+    bool getQueuedBuilds(Connection & conn, nix::ref<nix::Store> destStore);
 
     /* Handle cancellation, deletion and priority bumps. */
     void processQueueChange(Connection & conn);
@@ -511,6 +522,12 @@ private:
     BuildOutput getBuildOutputCached(Connection & conn, nix::ref<nix::Store> destStore,
         const nix::StorePath & drvPath);
 
+    /* Returns paths missing from the remote store. Paths are processed in
+     * parallel to work around the possible latency of remote stores. */
+    std::map<nix::DrvOutput, std::optional<nix::StorePath>> getMissingRemotePaths(
+        nix::ref<nix::Store> destStore,
+        const std::map<nix::DrvOutput, std::optional<nix::StorePath>> & paths);
+
     Step::ptr createStep(nix::ref<nix::Store> store,
         Connection & conn, Build::ptr build, const nix::StorePath & drvPath,
         Build::ptr referringBuild, Step::ptr referringStep, std::set<nix::StorePath> & finishedDrvs,
@@ -546,10 +563,11 @@ private:
        retried. */
     enum StepResult { sDone, sRetry, sMaybeCancelled };
     StepResult doBuildStep(nix::ref<nix::Store> destStore,
-        MachineReservation::ptr reservation,
+        MachineReservation::ptr & reservation,
         std::shared_ptr<ActiveStep> activeStep);
 
     void buildRemote(nix::ref<nix::Store> destStore,
+        MachineReservation::ptr & reservation,
         Machine::ptr machine, Step::ptr step,
         const nix::ServeProto::BuildOptions & buildOptions,
         RemoteResult & result, std::shared_ptr<ActiveStep> activeStep,

src/lib/Hydra/Controller/Build.pm

@@ -238,7 +238,7 @@ sub serveFile {
         # XSS hole.
         $c->response->header('Content-Security-Policy' => 'sandbox allow-scripts');
 
-        $c->stash->{'plain'} = { data => grab(cmd => ["nix", "--experimental-features", "nix-command",
+        $c->stash->{'plain'} = { data => readIntoSocket(cmd => ["nix", "--experimental-features", "nix-command",
                                                       "store", "cat", "--store", getStoreUri(), "$path"]) };
 
         # Detect MIME type.

src/lib/Hydra/Controller/Jobset.pm

@@ -364,6 +364,21 @@ sub evals_GET {
     );
 }
 
+sub errors :Chained('jobsetChain') :PathPart('errors') :Args(0) :ActionClass('REST') { }
+
+sub errors_GET {
+    my ($self, $c) = @_;
+
+    $c->stash->{template} = 'eval-error.tt';
+
+    my $jobsetName = $c->stash->{params}->{name};
+    $c->stash->{jobset} = $c->stash->{project}->jobsets->find(
+        { name => $jobsetName },
+        { '+columns' => { 'errormsg' => 'errormsg' } }
+    );
+
+    $self->status_ok($c, entity => $c->stash->{jobset});
+}
 
 # Redirect to the latest finished evaluation of this jobset.
 sub latest_eval : Chained('jobsetChain') PathPart('latest-eval') {

src/lib/Hydra/Controller/JobsetEval.pm

@@ -86,6 +86,17 @@ sub view_GET {
     );
 }
 
+sub errors :Chained('evalChain') :PathPart('errors') :Args(0) :ActionClass('REST') { }
+
+sub errors_GET {
+    my ($self, $c) = @_;
+
+    $c->stash->{template} = 'eval-error.tt';
+
+    $c->stash->{eval} = $c->model('DB::JobsetEvals')->find($c->stash->{eval}->id, { prefetch => 'evaluationerror' });
+
+    $self->status_ok($c, entity => $c->stash->{eval});
+}
 
 sub create_jobset : Chained('evalChain') PathPart('create-jobset') Args(0) {
     my ($self, $c) = @_;

src/lib/Hydra/Controller/Root.pm

@@ -162,7 +162,7 @@ sub status_GET {
             { "buildsteps.busy" => { '!=', 0 } },
             { order_by => ["globalpriority DESC", "id"],
               join => "buildsteps",
-              columns => [@buildListColumns]
+              columns => [@buildListColumns, 'buildsteps.drvpath', 'buildsteps.type']
             })]
     );
 }

src/lib/Hydra/Helper/BuildDiff.pm

@@ -37,7 +37,16 @@ sub buildDiff {
 
     my $n = 0;
     foreach my $build (@{$builds}) {
-        my $aborted = $build->finished != 0 && ($build->buildstatus == 3 || $build->buildstatus == 4);
+        my $aborted = $build->finished != 0 && (
+            # aborted
+            $build->buildstatus == 3
+            # cancelled
+            || $build->buildstatus == 4
+            # timeout
+            || $build->buildstatus == 7
+            # log limit exceeded
+            || $build->buildstatus == 10
+        );
         my $d;
         my $found = 0;
         while ($n < scalar(@{$builds2})) {

src/lib/Hydra/Helper/Nix.pm

@@ -36,6 +36,7 @@ our @EXPORT = qw(
     jobsetOverview
     jobsetOverview_
     pathIsInsidePrefix
+    readIntoSocket
     readNixFile
     registerRoot
     restartBuilds
@@ -296,8 +297,7 @@ sub getEvals {
 
     my @evals = $evals_result_set->search(
         { hasnewbuilds => 1 },
-        { order_by => "$me.id DESC", rows => $rows, offset => $offset
-        , prefetch => { evaluationerror => [ ] } });
+        { order_by => "$me.id DESC", rows => $rows, offset => $offset });
     my @res = ();
     my $cache = {};
 
@@ -417,6 +417,16 @@ sub pathIsInsidePrefix {
     return $cur;
 }
 
+sub readIntoSocket{
+    my (%args) = @_;
+    my $sock;
+
+    eval {
+        open($sock, "-|", @{$args{cmd}}) or die q(failed to open socket from command:\n $x);
+    };
+
+    return $sock;
+}
 
 
 

src/lib/Hydra/Schema/Result/EvaluationErrors.pm

@@ -105,4 +105,6 @@ __PACKAGE__->add_column(
     "+id" => { retrieve_on_insert => 1 }
 );
 
+__PACKAGE__->mk_group_accessors('column' => 'has_error');
+
 1;

src/lib/Hydra/Schema/Result/Jobsets.pm

@@ -386,6 +386,8 @@ __PACKAGE__->add_column(
     "+id" => { retrieve_on_insert => 1 }
 );
 
+__PACKAGE__->mk_group_accessors('column' => 'has_error');
+
 sub supportsDynamicRunCommand {
   my ($self) = @_;
 

src/lib/Hydra/Schema/ResultSet/EvaluationErrors.pm

@@ -0,0 +1,30 @@
+package Hydra::Schema::ResultSet::EvaluationErrors;
+
+use strict;
+use utf8;
+use warnings;
+
+use parent 'DBIx::Class::ResultSet';
+
+use Storable qw(dclone);
+
+__PACKAGE__->load_components('Helper::ResultSet::RemoveColumns');
+
+# Exclude expensive error message values unless explicitly requested, and
+# replace them with a summary field describing their presence/absence.
+sub search_rs {
+  my ( $class, $query, $attrs ) = @_;
+
+  if ($attrs) {
+    $attrs = dclone($attrs);
+  }
+
+  unless (exists $attrs->{'select'} || exists $attrs->{'columns'}) {
+    $attrs->{'+columns'}->{'has_error'} = "errormsg != ''";
+  }
+  unless (exists $attrs->{'+columns'}->{'errormsg'}) {
+    push @{ $attrs->{'remove_columns'} }, 'errormsg';
+  }
+
+  return $class->next::method($query, $attrs);
+}

src/lib/Hydra/Schema/ResultSet/Jobsets.pm

@@ -0,0 +1,30 @@
+package Hydra::Schema::ResultSet::Jobsets;
+
+use strict;
+use utf8;
+use warnings;
+
+use parent 'DBIx::Class::ResultSet';
+
+use Storable qw(dclone);
+
+__PACKAGE__->load_components('Helper::ResultSet::RemoveColumns');
+
+# Exclude expensive error message values unless explicitly requested, and
+# replace them with a summary field describing their presence/absence.
+sub search_rs {
+  my ( $class, $query, $attrs ) = @_;
+
+  if ($attrs) {
+    $attrs = dclone($attrs);
+  }
+
+  unless (exists $attrs->{'select'} || exists $attrs->{'columns'}) {
+    $attrs->{'+columns'}->{'has_error'} = "errormsg != ''";
+  }
+  unless (exists $attrs->{'+columns'}->{'errormsg'}) {
+    push @{ $attrs->{'remove_columns'} }, 'errormsg';
+  }
+
+  return $class->next::method($query, $attrs);
+}

src/root/build.tt

@@ -61,21 +61,7 @@ END;
             <td>[% IF step.busy != 0 || ((step.machine || step.starttime) && (step.status == 0 || step.status == 1 || step.status == 3 || step.status == 4 || step.status == 7)); INCLUDE renderMachineName machine=step.machine; ELSE; "<em>n/a</em>"; END %]</td>
             <td class="step-status">
               [% IF step.busy != 0 %]
-                [% IF step.busy == 1 %]
-                  <strong>Preparing</strong>
-                [% ELSIF step.busy == 10 %]
-                  <strong>Connecting</strong>
-                [% ELSIF step.busy == 20 %]
-                  <strong>Sending inputs</strong>
-                [% ELSIF step.busy == 30 %]
-                  <strong>Building</strong>
-                [% ELSIF step.busy == 40 %]
-                  <strong>Receiving outputs</strong>
-                [% ELSIF step.busy == 50 %]
-                  <strong>Post-processing</strong>
-                [% ELSE %]
-                  <strong>Unknown state</strong>
-                [% END %]
+                [% INCLUDE renderBusyStatus %]
               [% ELSIF step.status == 0 %]
                 [% IF step.isnondeterministic %]
                   <span class="warn">Succeeded with non-determistic result</span>

src/root/common.tt

@@ -91,6 +91,17 @@ BLOCK renderDuration;
   duration % 60 %]s[%
 END;
 
+BLOCK renderDrvInfo;
+  drvname = step.drvpath
+    .substr(11) # strip `/nix/store/`
+    .split('-').slice(1).join("-") # strip hash part
+    .substr(0, -4); # strip `.drv`
+  IF drvname != releasename;
+    IF step.type == 0; action = "Build"; ELSE; action = "Substitution"; END;
+    IF drvname; %]<em> ([% action %] of [% drvname %])</em>[% END;
+  END;
+END;
+
 
 BLOCK renderBuildListHeader %]
   <table class="table table-striped table-condensed clickable-rows">
@@ -131,7 +142,12 @@ BLOCK renderBuildListBody;
       [% END %]
       <td><a class="row-link" href="[% link %]">[% build.id %]</a></td>
       [% IF !hideJobName %]
-        <td><a href="[%link%]">[% IF !hideJobsetName %][%build.jobset.get_column("project")%]:[%build.jobset.get_column("name")%]:[% END %][%build.get_column("job")%]</td>
+        <td>
+          <a href="[%link%]">[% IF !hideJobsetName %][%build.jobset.get_column("project")%]:[%build.jobset.get_column("name")%]:[% END %][%build.get_column("job")%]</a>
+          [% IF showStepName %]
+            [% INCLUDE renderDrvInfo step=build.buildsteps releasename=build.nixname %]
+          [% END %]
+        </td>
       [% END %]
       <td class="nowrap">[% t = showSchedulingInfo ? build.timestamp : build.stoptime; IF t; INCLUDE renderRelativeDate timestamp=(showSchedulingInfo ? build.timestamp : build.stoptime); ELSE; "-"; END %]</td>
       <td>[% !showSchedulingInfo and build.get_column('releasename') ? build.get_column('releasename') : build.nixname %]</td>
@@ -245,6 +261,27 @@ BLOCK renderBuildStatusIcon;
 END;
 
 
+BLOCK renderBusyStatus;
+  IF step.busy == 1 %]
+    <strong>Preparing</strong>
+  [% ELSIF step.busy == 10 %]
+    <strong>Connecting</strong>
+  [% ELSIF step.busy == 20 %]
+    <strong>Sending inputs</strong>
+  [% ELSIF step.busy == 30 %]
+    <strong>Building</strong>
+  [% ELSIF step.busy == 35 %]
+    <strong>Waiting to receive outputs</strong>
+  [% ELSIF step.busy == 40 %]
+    <strong>Receiving outputs</strong>
+  [% ELSIF step.busy == 50 %]
+    <strong>Post-processing</strong>
+  [% ELSE %]
+    <strong>Unknown state</strong>
+  [% END;
+END;
+
+
 BLOCK renderStatus;
   IF build.finished;
     buildstatus = build.buildstatus;
@@ -476,7 +513,7 @@ BLOCK renderEvals %]
             ELSE %]
              -
             [% END %]
-            [% IF eval.evaluationerror.errormsg %]
+            [% IF eval.evaluationerror.has_error %]
               <span class="badge badge-warning">Eval Errors</span>
             [% END %]
           </td>
@@ -602,7 +639,7 @@ BLOCK renderJobsetOverview %]
         <td>[% HTML.escape(j.description) %]</td>
         <td>[% IF j.lastcheckedtime;
                  INCLUDE renderDateTime timestamp = j.lastcheckedtime;
-                 IF j.errormsg || j.fetcherrormsg; %]&nbsp;<span class = 'badge badge-warning'>Error</span>[% END;
+                 IF j.has_error || j.fetcherrormsg; %]&nbsp;<span class = 'badge badge-warning'>Error</span>[% END;
                  ELSE; "-";
                END %]</td>
         [% IF j.get_column('nrtotal') > 0 %]

src/root/eval-error.tt

@@ -0,0 +1,26 @@
+[% PROCESS common.tt %]
+<!DOCTYPE html>
+
+<html lang="en">
+
+  <head>
+    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+    <meta http-equiv="X-UA-Compatible" content="IE=Edge" />
+    [% INCLUDE style.tt %]
+  </head>
+
+  <body>
+
+    <div class="tab-content tab-pane">
+        <div id="tabs-errors" class="">
+          [% IF jobset %]
+              <p>Errors occurred at [% INCLUDE renderDateTime timestamp=(jobset.errortime || jobset.lastcheckedtime) %].</p>
+              <div class="card bg-light"><div class="card-body"><pre>[% HTML.escape(jobset.fetcherrormsg || jobset.errormsg) %]</pre></div></div>
+          [% ELSIF eval %]
+              <p>Errors occurred at [% INCLUDE renderDateTime timestamp=(eval.evaluationerror.errortime || eval.timestamp) %].</p>
+              <div class="card bg-light"><div class="card-body"><pre>[% HTML.escape(eval.evaluationerror.errormsg) %]</pre></div></div>
+          [% END %]
+        </div>
+    </div>
+  </body>
+</html>

src/root/jobset-eval.tt

@@ -65,7 +65,7 @@ c.uri_for(c.controller('JobsetEval').action_for('view'),
   [% END %]
 
   [% IF aborted.size > 0 %]
-    <li class="nav-item"><a class="nav-link" href="#tabs-aborted" data-toggle="tab"><span class="text-warning">Aborted Jobs ([% aborted.size %])</span></a></li>
+    <li class="nav-item"><a class="nav-link" href="#tabs-aborted" data-toggle="tab"><span class="text-warning">Aborted / Timed out Jobs ([% aborted.size %])</span></a></li>
   [% END %]
   [% IF nowFail.size > 0 %]
     <li class="nav-item"><a class="nav-link" href="#tabs-now-fail" data-toggle="tab"><span class="text-warning">Newly Failing Jobs ([% nowFail.size %])</span></a></li>
@@ -90,7 +90,7 @@ c.uri_for(c.controller('JobsetEval').action_for('view'),
   [% END %]
   <li class="nav-item"><a class="nav-link" href="#tabs-inputs" data-toggle="tab">Inputs</a></li>
 
-  [% IF eval.evaluationerror.errormsg %]
+  [% IF eval.evaluationerror.has_error %]
     <li class="nav-item"><a class="nav-link" href="#tabs-errors" data-toggle="tab"><span class="text-warning">Evaluation Errors</span></a></li>
   [% END %]
 </ul>
@@ -108,13 +108,6 @@ c.uri_for(c.controller('JobsetEval').action_for('view'),
 
 <div class="tab-content">
 
-  [% IF eval.evaluationerror.errormsg %]
-    <div id="tabs-errors" class="tab-pane">
-      <p>Errors occurred at [% INCLUDE renderDateTime timestamp=(eval.evaluationerror.errortime || eval.timestamp) %].</p>
-      <div class="card bg-light"><div class="card-body"><pre>[% HTML.escape(eval.evaluationerror.errormsg) %]</pre></div></div>
-    </div>
-  [% END %]
-
   <div id="tabs-aborted" class="tab-pane">
     [% INCLUDE renderSome builds=aborted tabname="#tabs-aborted" %]
   </div>
@@ -172,10 +165,9 @@ c.uri_for(c.controller('JobsetEval').action_for('view'),
     [% END %]
   </div>
 
-  [% IF eval.evaluationerror.errormsg %]
+  [% IF eval.evaluationerror.has_error %]
     <div id="tabs-errors" class="tab-pane">
-      <p>Errors occurred at [% INCLUDE renderDateTime timestamp=(eval.evaluationerror.errortime || eval.timestamp) %].</p>
-      <div class="card bg-light"><div class="card-body"><pre>[% HTML.escape(eval.evaluationerror.errormsg) %]</pre></div></div>
+      <iframe src="[% c.uri_for(c.controller('JobsetEval').action_for('errors'), [eval.id], params) %]" loading="lazy" frameBorder="0" width="100%"></iframe>
     </div>
   [% END %]
 </div>

src/root/jobset.tt

@@ -61,7 +61,7 @@
   [% END %]
 
   <li class="nav-item"><a class="nav-link active" href="#tabs-evaluations" data-toggle="tab">Evaluations</a></li>
-  [% IF jobset.errormsg || jobset.fetcherrormsg %]
+  [% IF jobset.has_error || jobset.fetcherrormsg %]
     <li class="nav-item"><a class="nav-link" href="#tabs-errors" data-toggle="tab"><span class="text-warning">Evaluation Errors</span></a></li>
   [% END %]
   <li class="nav-item"><a class="nav-link" href="#tabs-jobs" data-toggle="tab">Jobs</a></li>
@@ -79,7 +79,7 @@
         <th>Last checked:</th>
         <td>
           [% IF jobset.lastcheckedtime %]
-            [% INCLUDE renderDateTime timestamp = jobset.lastcheckedtime %], [% IF jobset.errormsg || jobset.fetcherrormsg %]<em class="text-warning">with errors!</em>[% ELSE %]<em>no errors</em>[% END %]
+            [% INCLUDE renderDateTime timestamp = jobset.lastcheckedtime %], [% IF jobset.has_error || jobset.fetcherrormsg %]<em class="text-warning">with errors!</em>[% ELSE %]<em>no errors</em>[% END %]
           [% ELSE %]
             <em>never</em>
           [% END %]
@@ -117,10 +117,9 @@
 
   </div>
 
-  [% IF jobset.errormsg || jobset.fetcherrormsg %]
+  [% IF jobset.has_error || jobset.fetcherrormsg %]
     <div id="tabs-errors" class="tab-pane">
-      <p>Errors occurred at [% INCLUDE renderDateTime timestamp=(jobset.errortime || jobset.lastcheckedtime) %].</p>
-      <div class="card bg-light"><div class="card-body"><pre>[% HTML.escape(jobset.fetcherrormsg || jobset.errormsg) %]</pre></div></div>
+      <iframe src="[% c.uri_for('/jobset' project.name jobset.name "errors") %]" loading="lazy" frameBorder="0" width="100%"></iframe>
     </div>
   [% END %]
 

src/root/layout.tt

@@ -10,31 +10,7 @@
 
     <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
     <meta http-equiv="X-UA-Compatible" content="IE=Edge" />
-
-    <script type="text/javascript" src="[% c.uri_for("/static/js/jquery/jquery-3.4.1.min.js") %]"></script>
-    <script type="text/javascript" src="[% c.uri_for("/static/js/jquery/jquery-ui-1.10.4.min.js") %]"></script>
-    <script type="text/javascript" src="[% c.uri_for("/static/js/moment/moment-2.24.0.min.js") %]"></script>
-
-    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-
-    <link href="[% c.uri_for("/static/fontawesome/css/all.css") %]" rel="stylesheet" />
-    <script type="text/javascript" src="[% c.uri_for("/static/js/popper.min.js") %]"></script>
-    <script type="text/javascript" src="[% c.uri_for("/static/bootstrap/js/bootstrap.min.js") %]"></script>
-    <link href="[% c.uri_for("/static/bootstrap/css/bootstrap.min.css") %]" rel="stylesheet" />
-
-    <!-- hydra.css may need to be moved to before boostrap to make the @media rule work. -->
-    <link rel="stylesheet" href="[% c.uri_for("/static/css/hydra.css") %]" type="text/css" />
-    <link rel="stylesheet" href="[% c.uri_for("/static/css/rotated-th.css") %]" type="text/css" />
-
-    <style>
-      .popover { max-width: 40%; }
-    </style>
-
-    <script type="text/javascript" src="[% c.uri_for("/static/js/bootbox.min.js") %]"></script>
-
-    <link rel="stylesheet" href="[% c.uri_for("/static/css/tree.css") %]" type="text/css" />
-
-    <script type="text/javascript" src="[% c.uri_for("/static/js/common.js") %]"></script>
+    [% INCLUDE style.tt %]
 
     [% IF c.config.enable_google_login %]
       <meta name="google-signin-client_id" content="[% c.config.google_client_id %]">

src/root/machine-status.tt

@@ -6,10 +6,10 @@
   <thead>
     <tr>
       <th>Job</th>
-      <th>System</th>
       <th>Build</th>
       <th>Step</th>
       <th>What</th>
+      <th>Status</th>
       <th>Since</th>
     </tr>
   </thead>
@@ -40,10 +40,10 @@
           [% idle = 0 %]
           <tr>
             <td><tt>[% INCLUDE renderFullJobName project=step.project jobset=step.jobset job=step.job %]</tt></td>
-            <td><tt>[% step.system %]</tt></td>
             <td><a href="[% c.uri_for('/build' step.build) %]">[% step.build %]</a></td>
             <td>[% IF step.busy >= 30 %]<a class="row-link" href="[% c.uri_for('/build' step.build 'nixlog' step.stepnr 'tail') %]">[% step.stepnr %]</a>[% ELSE; step.stepnr; END %]</td>
             <td><tt>[% step.drvpath.match('-(.*)').0 %]</tt></td>
+            <td>[% INCLUDE renderBusyStatus %]</td>
             <td style="width: 10em">[% INCLUDE renderDuration duration = curTime - step.starttime %] </td>
           </tr>
         [% END %]

src/root/static/js/common.js

@@ -129,6 +129,12 @@ $(document).ready(function() {
             el.addClass("is-local");
         }
     });
+
+    [...document.getElementsByTagName("iframe")].forEach((element) => {
+        element.contentWindow.addEventListener("DOMContentLoaded", (_) => {
+            element.style.height = element.contentWindow.document.body.scrollHeight + 'px';
+        })
+    })
 });
 
 var tabsLoaded = {};

src/root/status.tt

@@ -7,7 +7,7 @@
 
 [% ELSE %]
 
-  [% INCLUDE renderBuildList builds=resource showSchedulingInfo=1 hideResultInfo=1 busy=1 %]
+  [% INCLUDE renderBuildList builds=resource showSchedulingInfo=1 hideResultInfo=1 busy=1 showStepName=1 %]
 
 [% END %]
 

src/root/style.tt

@@ -0,0 +1,24 @@
+<script type="text/javascript" src="[% c.uri_for("/static/js/jquery/jquery-3.4.1.min.js") %]"></script>
+<script type="text/javascript" src="[% c.uri_for("/static/js/jquery/jquery-ui-1.10.4.min.js") %]"></script>
+<script type="text/javascript" src="[% c.uri_for("/static/js/moment/moment-2.24.0.min.js") %]"></script>
+
+<meta name="viewport" content="width=device-width, initial-scale=1.0" />
+
+<link href="[% c.uri_for("/static/fontawesome/css/all.css") %]" rel="stylesheet" />
+<script type="text/javascript" src="[% c.uri_for("/static/js/popper.min.js") %]"></script>
+<script type="text/javascript" src="[% c.uri_for("/static/bootstrap/js/bootstrap.min.js") %]"></script>
+<link href="[% c.uri_for("/static/bootstrap/css/bootstrap.min.css") %]" rel="stylesheet" />
+
+<!-- hydra.css may need to be moved to before boostrap to make the @media rule work. -->
+<link rel="stylesheet" href="[% c.uri_for("/static/css/hydra.css") %]" type="text/css" />
+<link rel="stylesheet" href="[% c.uri_for("/static/css/rotated-th.css") %]" type="text/css" />
+
+<style>
+  .popover { max-width: 40%; }
+</style>
+
+<script type="text/javascript" src="[% c.uri_for("/static/js/bootbox.min.js") %]"></script>
+
+<link rel="stylesheet" href="[% c.uri_for("/static/css/tree.css") %]" type="text/css" />
+
+<script type="text/javascript" src="[% c.uri_for("/static/js/common.js") %]"></script>

t/Hydra/Controller/Jobset/evals.t

@@ -32,4 +32,9 @@ subtest "/jobset/PROJECT/JOBSET/evals" => sub {
     ok($jobsetevals->is_success, "The page showing the jobset evals returns 200.");
 };
 
+subtest "/jobset/PROJECT/JOBSET/errors" => sub {
+    my $jobsetevals = request(GET '/jobset/' . $project->name . '/' . $jobset->name . '/errors');
+    ok($jobsetevals->is_success, "The page showing the jobset eval errors returns 200.");
+};
+
 done_testing;

t/Hydra/Controller/JobsetEval/fetch.t

@@ -35,6 +35,10 @@ subtest "Fetching the eval's overview" => sub {
     is($fetch->code, 200, "channel page is 200");
 };
 
+subtest "Fetching the eval's overview" => sub {
+    my $fetch = request(GET '/eval/' . $eval->id, '/errors');
+    is($fetch->code, 200, "errors page is 200");
+};
 
 
 done_testing;

t/lib/CliRunners.pm

@@ -14,7 +14,7 @@ our @EXPORT = qw(
 sub evalSucceeds {
     my ($jobset) = @_;
     my ($res, $stdout, $stderr) = captureStdoutStderr(60, ("hydra-eval-jobset", $jobset->project->name, $jobset->name));
-    $jobset->discard_changes;  # refresh from DB
+    $jobset->discard_changes({ '+columns' => {'errormsg' => 'errormsg'} });  # refresh from DB
     if ($res) {
         chomp $stdout; chomp $stderr;
         utf8::decode($stdout) or die "Invalid unicode in stdout.";
@@ -29,7 +29,7 @@ sub evalSucceeds {
 sub evalFails {
     my ($jobset) = @_;
     my ($res, $stdout, $stderr) = captureStdoutStderr(60, ("hydra-eval-jobset", $jobset->project->name, $jobset->name));
-    $jobset->discard_changes;  # refresh from DB
+    $jobset->discard_changes({ '+columns' => {'errormsg' => 'errormsg'} });  # refresh from DB
     if (!$res) {
         chomp $stdout; chomp $stderr;
         utf8::decode($stdout) or die "Invalid unicode in stdout.";

t/queue-runner/direct-indirect-constituents.t

@@ -13,7 +13,7 @@ my $constituentBuildA = $builds->{"constituentA"};
 my $constituentBuildB = $builds->{"constituentB"};
 
 my $eval = $constituentBuildA->jobsetevals->first();
-is($eval->evaluationerror->errormsg, "");
+is($eval->evaluationerror->has_error, 0);
 
 subtest "Verifying the direct aggregate" => sub {
     my $aggBuild = $builds->{"direct_aggregate"};