hydra-queue-runner.cc

#include <iostream>
#include <thread>

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include "state.hh"
#include "build-result.hh"
#include "store-api.hh"
#include "remote-store.hh"

#include "globals.hh"
#include "hydra-config.hh"
#include "json.hh"
#include "s3-binary-cache-store.hh"
#include "shared.hh"

using namespace nix;


namespace nix {

template<> void toJSON<std::atomic<long>>(std::ostream & str, const std::atomic<long> & n) { str << n; }
template<> void toJSON<std::atomic<unsigned long>>(std::ostream & str, const std::atomic<unsigned long> & n) { str << n; }
template<> void toJSON<std::atomic<unsigned long long>>(std::ostream & str, const std::atomic<unsigned long long> & n) { str << n; }
template<> void toJSON<double>(std::ostream & str, const double & n) { str << n; }

}


static uint64_t getMemSize()
{
    auto pages = sysconf(_SC_PHYS_PAGES);
    return pages >= 0 ? pages * sysconf(_SC_PAGESIZE) : 4ULL << 30;
}


std::string getEnvOrDie(const std::string & key)
{
    auto value = getEnv(key);
    if (!value) throw Error("environment variable '%s' is not set", key);
    return *value;
}


State::State()
    : config(std::make_unique<::Config>())
    , maxUnsupportedTime(config->getIntOption("max_unsupported_time", 0))
    , dbPool(config->getIntOption("max_db_connections", 128))
    , memoryTokens(config->getIntOption("nar_buffer_size", getMemSize() / 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))
    , rootsDir(config->getStrOption("gc_roots_dir", fmt("%s/gcroots/per-user/%s/hydra-roots", settings.nixStateDir, getEnvOrDie("LOGNAME"))))
{
    debug("using %d bytes for the NAR buffer", memoryTokens.capacity());

    hydraData = getEnvOrDie("HYDRA_DATA");

    logDir = canonPath(hydraData + "/build-logs");

    /* handle deprecated store specification */
    if (config->getStrOption("store_mode") != "")
        throw Error("store_mode in hydra.conf is deprecated, please use store_uri");
    if (config->getStrOption("binary_cache_dir") != "")
        printMsg(lvlError, "hydra.conf: binary_cache_dir is deprecated and ignored. use store_uri=file:// instead");
    if (config->getStrOption("binary_cache_s3_bucket") != "")
        printMsg(lvlError, "hydra.conf: binary_cache_s3_bucket is deprecated and ignored. use store_uri=s3:// instead");
    if (config->getStrOption("binary_cache_secret_key_file") != "")
        printMsg(lvlError, "hydra.conf: binary_cache_secret_key_file is deprecated and ignored. use store_uri=...?secret-key= instead");

    createDirs(rootsDir);
}


nix::MaintainCount<counter> State::startDbUpdate()
{
    if (nrActiveDbUpdates > 6)
        printError("warning: %d concurrent database updates; PostgreSQL may be stalled", nrActiveDbUpdates.load());
    return MaintainCount<counter>(nrActiveDbUpdates);
}


ref<Store> State::getDestStore()
{
    return ref<Store>(_destStore);
}


void State::parseMachines(const std::string & contents)
{
    Machines newMachines, oldMachines;
    {
        auto machines_(machines.lock());
        oldMachines = *machines_;
    }

    for (auto line : tokenizeString<Strings>(contents, "\n")) {
        line = trim(string(line, 0, line.find('#')));
        auto tokens = tokenizeString<std::vector<std::string>>(line);
        if (tokens.size() < 3) continue;
        tokens.resize(8);

        auto machine = std::make_shared<Machine>();
        machine->sshName = tokens[0];
        machine->systemTypes = tokenizeString<StringSet>(tokens[1], ",");
        machine->sshKey = tokens[2] == "-" ? string("") : tokens[2];
        if (tokens[3] != "")
            string2Int(tokens[3], machine->maxJobs);
        else
            machine->maxJobs = 1;
        machine->speedFactor = atof(tokens[4].c_str());
        if (tokens[5] == "-") tokens[5] = "";
        machine->supportedFeatures = tokenizeString<StringSet>(tokens[5], ",");
        if (tokens[6] == "-") tokens[6] = "";
        machine->mandatoryFeatures = tokenizeString<StringSet>(tokens[6], ",");
        for (auto & f : machine->mandatoryFeatures)
            machine->supportedFeatures.insert(f);
        if (tokens[7] != "" && tokens[7] != "-")
            machine->sshPublicHostKey = base64Decode(tokens[7]);

        /* Re-use the State object of the previous machine with the
           same name. */
        auto i = oldMachines.find(machine->sshName);
        if (i == oldMachines.end())
            printMsg(lvlChatty, format("adding new machine ‘%1%’") % machine->sshName);
        else
            printMsg(lvlChatty, format("updating machine ‘%1%’") % machine->sshName);
        machine->state = i == oldMachines.end()
            ? std::make_shared<Machine::State>()
            : i->second->state;
        newMachines[machine->sshName] = machine;
    }

    for (auto & m : oldMachines)
        if (newMachines.find(m.first) == newMachines.end()) {
            if (m.second->enabled)
                printMsg(lvlInfo, format("removing machine ‘%1%’") % m.first);
            /* Add a disabled Machine object to make sure stats are
               maintained. */
            auto machine = std::make_shared<Machine>(*(m.second));
            machine->enabled = false;
            newMachines[m.first] = machine;
        }

    static bool warned = false;
    if (newMachines.empty() && !warned) {
        printError("warning: no build machines are defined");
        warned = true;
    }

    auto machines_(machines.lock());
    *machines_ = newMachines;

    wakeDispatcher();
}


void State::monitorMachinesFile()
{
    string defaultMachinesFile = "/etc/nix/machines";
    auto machinesFiles = tokenizeString<std::vector<Path>>(
        getEnv("NIX_REMOTE_SYSTEMS").value_or(pathExists(defaultMachinesFile) ? defaultMachinesFile : ""), ":");

    if (machinesFiles.empty()) {
        parseMachines("localhost " +
            (settings.thisSystem == "x86_64-linux" ? "x86_64-linux,i686-linux" : settings.thisSystem.get())
            + " - " + std::to_string(settings.maxBuildJobs) + " 1");
        return;
    }

    std::vector<struct stat> fileStats;
    fileStats.resize(machinesFiles.size());
    for (unsigned int n = 0; n < machinesFiles.size(); ++n) {
        auto & st(fileStats[n]);
        st.st_ino = st.st_mtime = 0;
    }

    auto readMachinesFiles = [&]() {

        /* Check if any of the machines files changed. */
        bool anyChanged = false;
        for (unsigned int n = 0; n < machinesFiles.size(); ++n) {
            Path machinesFile = machinesFiles[n];
            struct stat st;
            if (stat(machinesFile.c_str(), &st) != 0) {
                if (errno != ENOENT)
                    throw SysError(format("getting stats about ‘%1%’") % machinesFile);
                st.st_ino = st.st_mtime = 0;
            }
            auto & old(fileStats[n]);
            if (old.st_ino != st.st_ino || old.st_mtime != st.st_mtime)
                anyChanged = true;
            old = st;
        }

        if (!anyChanged) return;

        debug("reloading machines files");

        string contents;
        for (auto & machinesFile : machinesFiles) {
            try {
                contents += readFile(machinesFile);
                contents += '\n';
            } catch (SysError & e) {
                if (e.errNo != ENOENT) throw;
            }
        }

        parseMachines(contents);
    };

    while (true) {
        try {
            readMachinesFiles();
            // FIXME: use inotify.
            sleep(30);
        } catch (std::exception & e) {
            printMsg(lvlError, format("reloading machines file: %1%") % e.what());
        }
    }
}


void State::clearBusy(Connection & conn, time_t stopTime)
{
    pqxx::work txn(conn);
    txn.parameterized
        ("update BuildSteps set busy = 0, status = $1, stopTime = $2 where busy != 0")
        ((int) bsAborted)
        (stopTime, stopTime != 0).exec();
    txn.commit();
}


unsigned int State::allocBuildStep(pqxx::work & txn, BuildID buildId)
{
    auto res = txn.parameterized("select max(stepnr) from BuildSteps where build = $1")(buildId).exec();
    return res[0][0].is_null() ? 1 : res[0][0].as<int>() + 1;
}


unsigned int State::createBuildStep(pqxx::work & txn, time_t startTime, BuildID buildId, Step::ptr step,
    const std::string & machine, BuildStatus status, const std::string & errorMsg, BuildID propagatedFrom)
{
 restart:
    auto stepNr = allocBuildStep(txn, buildId);

    auto r = txn.parameterized
        ("insert into BuildSteps (build, stepnr, type, drvPath, busy, startTime, system, status, propagatedFrom, errorMsg, stopTime, machine) values ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12) on conflict do nothing")
        (buildId)
        (stepNr)
        (0) // == build
        (localStore->printStorePath(step->drvPath))
        (status == bsBusy ? 1 : 0)
        (startTime, startTime != 0)
        (step->drv->platform)
        ((int) status, status != bsBusy)
        (propagatedFrom, propagatedFrom != 0)
        (errorMsg, errorMsg != "")
        (startTime, startTime != 0 && status != bsBusy)
        (machine).exec();

    if (r.affected_rows() == 0) goto restart;

    for (auto & output : step->drv->outputs)
        txn.parameterized
            ("insert into BuildStepOutputs (build, stepnr, name, path) values ($1, $2, $3, $4)")
            (buildId)(stepNr)(output.first)(localStore->printStorePath(output.second.path)).exec();

    if (status == bsBusy)
        txn.exec(fmt("notify step_started, '%d\t%d'", buildId, stepNr));

    return stepNr;
}


void State::updateBuildStep(pqxx::work & txn, BuildID buildId, unsigned int stepNr, StepState stepState)
{
    if (txn.parameterized
        ("update BuildSteps set busy = $1 where build = $2 and stepnr = $3 and busy != 0 and status is null")
        ((int) stepState)
        (buildId)
        (stepNr)
        .exec().affected_rows() != 1)
        throw Error("step %d of build %d is in an unexpected state", stepNr, buildId);
}


void State::finishBuildStep(pqxx::work & txn, const RemoteResult & result,
    BuildID buildId, unsigned int stepNr, const std::string & machine)
{
    assert(result.startTime);
    assert(result.stopTime);
    txn.parameterized
        ("update BuildSteps set busy = 0, status = $1, errorMsg = $4, startTime = $5, stopTime = $6, machine = $7, overhead = $8, timesBuilt = $9, isNonDeterministic = $10 where build = $2 and stepnr = $3")
        ((int) result.stepStatus)(buildId)(stepNr)
        (result.errorMsg, result.errorMsg != "")
        (result.startTime)(result.stopTime)
        (machine, machine != "")
        (result.overhead, result.overhead != 0)
        (result.timesBuilt, result.timesBuilt > 0)
        (result.isNonDeterministic, result.timesBuilt > 1)
        .exec();
    assert(result.logFile.find('\t') == std::string::npos);
    txn.exec(fmt("notify step_finished, '%d\t%d\t%s'",
            buildId, stepNr, result.logFile));
}


int State::createSubstitutionStep(pqxx::work & txn, time_t startTime, time_t stopTime,
    Build::ptr build, const StorePath & drvPath, const string & outputName, const StorePath & storePath)
{
 restart:
    auto stepNr = allocBuildStep(txn, build->id);

    auto r = txn.parameterized
        ("insert into BuildSteps (build, stepnr, type, drvPath, busy, status, startTime, stopTime) values ($1, $2, $3, $4, $5, $6, $7, $8) on conflict do nothing")
        (build->id)
        (stepNr)
        (1) // == substitution
        (localStore->printStorePath(drvPath))
        (0)
        (0)
        (startTime)
        (stopTime).exec();

    if (r.affected_rows() == 0) goto restart;

    txn.parameterized
        ("insert into BuildStepOutputs (build, stepnr, name, path) values ($1, $2, $3, $4)")
        (build->id)
        (stepNr)
        (outputName)
        (localStore->printStorePath(storePath)).exec();

    return stepNr;
}


/* Get the steps and unfinished builds that depend on the given step. */
void getDependents(Step::ptr step, std::set<Build::ptr> & builds, std::set<Step::ptr> & steps)
{
    std::function<void(Step::ptr)> visit;

    visit = [&](Step::ptr step) {
        if (steps.count(step)) return;
        steps.insert(step);

        std::vector<Step::wptr> rdeps;

        {
            auto step_(step->state.lock());

            for (auto & build : step_->builds) {
                auto build_ = build.lock();
                if (build_ && !build_->finishedInDB) builds.insert(build_);
            }

            /* Make a copy of rdeps so that we don't hold the lock for
               very long. */
            rdeps = step_->rdeps;
        }

        for (auto & rdep : rdeps) {
            auto rdep_ = rdep.lock();
            if (rdep_) visit(rdep_);
        }
    };

    visit(step);
}


void visitDependencies(std::function<void(Step::ptr)> visitor, Step::ptr start)
{
    std::set<Step::ptr> queued;
    std::queue<Step::ptr> todo;
    todo.push(start);

    while (!todo.empty()) {
        auto step = todo.front();
        todo.pop();

        visitor(step);

        auto state(step->state.lock());
        for (auto & dep : state->deps)
            if (queued.find(dep) == queued.end()) {
                queued.insert(dep);
                todo.push(dep);
            }
    }
}


void State::markSucceededBuild(pqxx::work & txn, Build::ptr build,
    const BuildOutput & res, bool isCachedBuild, time_t startTime, time_t stopTime)
{
    if (build->finishedInDB) return;

    if (txn.parameterized("select 1 from Builds where id = $1 and finished = 0")(build->id).exec().empty()) return;

    txn.parameterized
        ("update Builds set finished = 1, buildStatus = $2, startTime = $3, stopTime = $4, size = $5, closureSize = $6, releaseName = $7, isCachedBuild = $8, notificationPendingSince = $4 where id = $1")
        (build->id)
        ((int) (res.failed ? bsFailedWithOutput : bsSuccess))
        (startTime)
        (stopTime)
        (res.size)
        (res.closureSize)
        (res.releaseName, res.releaseName != "")
        (isCachedBuild ? 1 : 0).exec();

    txn.parameterized("delete from BuildProducts where build = $1")(build->id).exec();

    unsigned int productNr = 1;
    for (auto & product : res.products) {
        txn.parameterized
            ("insert into BuildProducts (build, productnr, type, subtype, fileSize, sha1hash, sha256hash, path, name, defaultPath) values ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)")
            (build->id)
            (productNr++)
            (product.type)
            (product.subtype)
            (product.fileSize, product.isRegular)
            (product.sha1hash.to_string(Base16, false), product.isRegular)
            (product.sha256hash.to_string(Base16, false), product.isRegular)
            (product.path)
            (product.name)
            (product.defaultPath).exec();
    }

    txn.parameterized("delete from BuildMetrics where build = $1")(build->id).exec();

    for (auto & metric : res.metrics) {
        txn.parameterized
            ("insert into BuildMetrics (build, name, unit, value, project, jobset, job, timestamp) values ($1, $2, $3, $4, $5, $6, $7, $8)")
            (build->id)
            (metric.second.name)
            (metric.second.unit, metric.second.unit != "")
            (metric.second.value)
            (build->projectName)
            (build->jobsetName)
            (build->jobName)
            (build->timestamp).exec();
    }

    nrBuildsDone++;
}


bool State::checkCachedFailure(Step::ptr step, Connection & conn)
{
    pqxx::work txn(conn);
    for (auto & path : step->drv->outputPaths())
        if (!txn.parameterized("select 1 from FailedPaths where path = $1")(localStore->printStorePath(path)).exec().empty())
            return true;
    return false;
}


void State::notifyBuildStarted(pqxx::work & txn, BuildID buildId)
{
    txn.exec(fmt("notify build_started, '%s'", buildId));
}


void State::notifyBuildFinished(pqxx::work & txn, BuildID buildId,
    const std::vector<BuildID> & dependentIds)
{
    auto payload = fmt("%d ", buildId);
    for (auto & d : dependentIds)
        payload += fmt("%d ", d);
    // FIXME: apparently parameterized() doesn't support NOTIFY.
    txn.exec(fmt("notify build_finished, '%s'", payload));
}


std::shared_ptr<PathLocks> State::acquireGlobalLock()
{
    Path lockPath = hydraData + "/queue-runner/lock";

    createDirs(dirOf(lockPath));

    auto lock = std::make_shared<PathLocks>();
    if (!lock->lockPaths(PathSet({lockPath}), "", false)) return 0;

    return lock;
}


void State::dumpStatus(Connection & conn, bool log)
{
    std::ostringstream out;

    {
        JSONObject root(out);
        time_t now = time(0);
        root.attr("status", "up");
        root.attr("time", time(0));
        root.attr("uptime", now - startedAt);
        root.attr("pid", getpid());
        {
            auto builds_(builds.lock());
            root.attr("nrQueuedBuilds", builds_->size());
        }
        {
            auto steps_(steps.lock());
            for (auto i = steps_->begin(); i != steps_->end(); )
                if (i->second.lock()) ++i; else i = steps_->erase(i);
            root.attr("nrUnfinishedSteps", steps_->size());
        }
        {
            auto runnable_(runnable.lock());
            for (auto i = runnable_->begin(); i != runnable_->end(); )
                if (i->lock()) ++i; else i = runnable_->erase(i);
            root.attr("nrRunnableSteps", runnable_->size());
        }
        root.attr("nrActiveSteps", activeSteps_.lock()->size());
        root.attr("nrStepsBuilding", nrStepsBuilding);
        root.attr("nrStepsCopyingTo", nrStepsCopyingTo);
        root.attr("nrStepsCopyingFrom", nrStepsCopyingFrom);
        root.attr("nrStepsWaiting", nrStepsWaiting);
        root.attr("bytesSent", bytesSent);
        root.attr("bytesReceived", bytesReceived);
        root.attr("nrBuildsRead", nrBuildsRead);
        root.attr("buildReadTimeMs", buildReadTimeMs);
        root.attr("buildReadTimeAvgMs", nrBuildsRead == 0 ? 0.0 : (float) buildReadTimeMs / nrBuildsRead);
        root.attr("nrBuildsDone", nrBuildsDone);
        root.attr("nrStepsStarted", nrStepsStarted);
        root.attr("nrStepsDone", nrStepsDone);
        root.attr("nrRetries", nrRetries);
        root.attr("maxNrRetries", maxNrRetries);
        if (nrStepsDone) {
            root.attr("totalStepTime", totalStepTime);
            root.attr("totalStepBuildTime", totalStepBuildTime);
            root.attr("avgStepTime", (float) totalStepTime / nrStepsDone);
            root.attr("avgStepBuildTime", (float) totalStepBuildTime / nrStepsDone);
        }
        root.attr("nrQueueWakeups", nrQueueWakeups);
        root.attr("nrDispatcherWakeups", nrDispatcherWakeups);
        root.attr("dispatchTimeMs", dispatchTimeMs);
        root.attr("dispatchTimeAvgMs", nrDispatcherWakeups == 0 ? 0.0 : (float) dispatchTimeMs / nrDispatcherWakeups);
        root.attr("nrDbConnections", dbPool.count());
        root.attr("nrActiveDbUpdates", nrActiveDbUpdates);
        root.attr("memoryTokensInUse", memoryTokens.currentUse());

        {
            auto nested = root.object("machines");
            auto machines_(machines.lock());
            for (auto & i : *machines_) {
                auto & m(i.second);
                auto & s(m->state);
                auto nested2 = nested.object(m->sshName);
                nested2.attr("enabled", m->enabled);

                {
                    auto list = nested2.list("systemTypes");
                    for (auto & s : m->systemTypes)
                        list.elem(s);
                }

                {
                    auto list = nested2.list("supportedFeatures");
                    for (auto & s : m->supportedFeatures)
                        list.elem(s);
                }

                {
                    auto list = nested2.list("mandatoryFeatures");
                    for (auto & s : m->mandatoryFeatures)
                        list.elem(s);
                }

                nested2.attr("currentJobs", s->currentJobs);
                if (s->currentJobs == 0)
                    nested2.attr("idleSince", s->idleSince);
                nested2.attr("nrStepsDone", s->nrStepsDone);
                if (m->state->nrStepsDone) {
                    nested2.attr("totalStepTime", s->totalStepTime);
                    nested2.attr("totalStepBuildTime", s->totalStepBuildTime);
                    nested2.attr("avgStepTime", (float) s->totalStepTime / s->nrStepsDone);
                    nested2.attr("avgStepBuildTime", (float) s->totalStepBuildTime / s->nrStepsDone);
                }

                auto info(m->state->connectInfo.lock());
                nested2.attr("disabledUntil", std::chrono::system_clock::to_time_t(info->disabledUntil));
                nested2.attr("lastFailure", std::chrono::system_clock::to_time_t(info->lastFailure));
                nested2.attr("consecutiveFailures", info->consecutiveFailures);

            }
        }

        {
            auto nested = root.object("jobsets");
            auto jobsets_(jobsets.lock());
            for (auto & jobset : *jobsets_) {
                auto nested2 = nested.object(jobset.first.first + ":" + jobset.first.second);
                nested2.attr("shareUsed", jobset.second->shareUsed());
                nested2.attr("seconds", jobset.second->getSeconds());
            }
        }

        {
            auto nested = root.object("machineTypes");
            auto machineTypes_(machineTypes.lock());
            for (auto & i : *machineTypes_) {
                auto nested2 = nested.object(i.first);
                nested2.attr("runnable", i.second.runnable);
                nested2.attr("running", i.second.running);
                if (i.second.runnable > 0)
                    nested2.attr("waitTime", i.second.waitTime.count() +
                        i.second.runnable * (time(0) - lastDispatcherCheck));
                if (i.second.running == 0)
                    nested2.attr("lastActive", std::chrono::system_clock::to_time_t(i.second.lastActive));
            }
        }

        auto store = getDestStore();

        auto nested = root.object("store");

        auto & stats = store->getStats();
        nested.attr("narInfoRead", stats.narInfoRead);
        nested.attr("narInfoReadAverted", stats.narInfoReadAverted);
        nested.attr("narInfoMissing", stats.narInfoMissing);
        nested.attr("narInfoWrite", stats.narInfoWrite);
        nested.attr("narInfoCacheSize", stats.pathInfoCacheSize);
        nested.attr("narRead", stats.narRead);
        nested.attr("narReadBytes", stats.narReadBytes);
        nested.attr("narReadCompressedBytes", stats.narReadCompressedBytes);
        nested.attr("narWrite", stats.narWrite);
        nested.attr("narWriteAverted", stats.narWriteAverted);
        nested.attr("narWriteBytes", stats.narWriteBytes);
        nested.attr("narWriteCompressedBytes", stats.narWriteCompressedBytes);
        nested.attr("narWriteCompressionTimeMs", stats.narWriteCompressionTimeMs);
        nested.attr("narCompressionSavings",
            stats.narWriteBytes
            ? 1.0 - (double) stats.narWriteCompressedBytes / stats.narWriteBytes
            : 0.0);
        nested.attr("narCompressionSpeed", // MiB/s
            stats.narWriteCompressionTimeMs
            ? (double) stats.narWriteBytes / stats.narWriteCompressionTimeMs * 1000.0 / (1024.0 * 1024.0)
            : 0.0);

        auto s3Store = dynamic_cast<S3BinaryCacheStore *>(&*store);
        if (s3Store) {
            auto nested2 = nested.object("s3");
            auto & s3Stats = s3Store->getS3Stats();
            nested2.attr("put", s3Stats.put);
            nested2.attr("putBytes", s3Stats.putBytes);
            nested2.attr("putTimeMs", s3Stats.putTimeMs);
            nested2.attr("putSpeed",
                s3Stats.putTimeMs
                ? (double) s3Stats.putBytes / s3Stats.putTimeMs * 1000.0 / (1024.0 * 1024.0)
                : 0.0);
            nested2.attr("get", s3Stats.get);
            nested2.attr("getBytes", s3Stats.getBytes);
            nested2.attr("getTimeMs", s3Stats.getTimeMs);
            nested2.attr("getSpeed",
                s3Stats.getTimeMs
                ? (double) s3Stats.getBytes / s3Stats.getTimeMs * 1000.0 / (1024.0 * 1024.0)
                : 0.0);
            nested2.attr("head", s3Stats.head);
            nested2.attr("costDollarApprox",
                (s3Stats.get + s3Stats.head) / 10000.0 * 0.004
                + s3Stats.put / 1000.0 * 0.005 +
                + s3Stats.getBytes / (1024.0 * 1024.0 * 1024.0) * 0.09);
        }
    }

    if (log && time(0) >= lastStatusLogged + statusLogInterval) {
        printMsg(lvlInfo, format("status: %1%") % out.str());
        lastStatusLogged = time(0);
    }

    {
        auto mc = startDbUpdate();
        pqxx::work txn(conn);
        // FIXME: use PostgreSQL 9.5 upsert.
        txn.exec("delete from SystemStatus where what = 'queue-runner'");
        txn.parameterized("insert into SystemStatus values ('queue-runner', $1)")(out.str()).exec();
        txn.exec("notify status_dumped");
        txn.commit();
    }
}


void State::showStatus()
{
    auto conn(dbPool.get());
    receiver statusDumped(*conn, "status_dumped");

    string status;
    bool barf = false;

    /* Get the last JSON status dump from the database. */
    {
        pqxx::work txn(*conn);
        auto res = txn.exec("select status from SystemStatus where what = 'queue-runner'");
        if (res.size()) status = res[0][0].as<string>();
    }

    if (status != "") {

        /* If the status is not empty, then the queue runner is
           running. Ask it to update the status dump. */
        {
            pqxx::work txn(*conn);
            txn.exec("notify dump_status");
            txn.commit();
        }

        /* Wait until it has done so. */
        barf = conn->await_notification(5, 0) == 0;

        /* Get the new status. */
        {
            pqxx::work txn(*conn);
            auto res = txn.exec("select status from SystemStatus where what = 'queue-runner'");
            if (res.size()) status = res[0][0].as<string>();
        }

    }

    if (status == "") status = R"({"status":"down"})";

    std::cout << status << "\n";

    if (barf)
        throw Error("queue runner did not respond; status information may be wrong");
}


void State::unlock()
{
    auto lock = acquireGlobalLock();
    if (!lock)
        throw Error("hydra-queue-runner is currently running");

    auto conn(dbPool.get());

    clearBusy(*conn, 0);

    {
        pqxx::work txn(*conn);
        txn.exec("delete from SystemStatus where what = 'queue-runner'");
        txn.commit();
    }
}


void State::run(BuildID buildOne)
{
    /* Can't be bothered to shut down cleanly. Goodbye! */
    auto callback = createInterruptCallback([&]() { std::_Exit(0); });

    startedAt = time(0);
    this->buildOne = buildOne;

    auto lock = acquireGlobalLock();
    if (!lock)
        throw Error("hydra-queue-runner is already running");

    Store::Params localParams;
    localParams["max-connections"] = "16";
    localParams["max-connection-age"] = "600";
    localStore = openStore(getEnv("NIX_REMOTE").value_or(""), localParams);

    auto storeUri = config->getStrOption("store_uri");
    _destStore = storeUri == "" ? localStore : openStore(storeUri);

    useSubstitutes = config->getBoolOption("use-substitutes", false);

    // FIXME: hacky mechanism for configuring determinism checks.
    for (auto & s : tokenizeString<Strings>(config->getStrOption("xxx-jobset-repeats"))) {
        auto s2 = tokenizeString<std::vector<std::string>>(s, ":");
        if (s2.size() != 3) throw Error("bad value in xxx-jobset-repeats");
        jobsetRepeats.emplace(std::make_pair(s2[0], s2[1]), std::stoi(s2[2]));
    }

    {
        auto conn(dbPool.get());
        clearBusy(*conn, 0);
        dumpStatus(*conn, false);
    }

    std::thread(&State::monitorMachinesFile, this).detach();

    std::thread(&State::queueMonitor, this).detach();

    std::thread(&State::dispatcher, this).detach();

    /* Periodically clean up orphaned busy steps in the database. */
    std::thread([&]() {
        while (true) {
            sleep(180);

            std::set<std::pair<BuildID, int>> steps;
            {
                auto orphanedSteps_(orphanedSteps.lock());
                if (orphanedSteps_->empty()) continue;
                steps = *orphanedSteps_;
                orphanedSteps_->clear();
            }

            try {
                auto conn(dbPool.get());
                pqxx::work txn(*conn);
                for (auto & step : steps) {
                    printMsg(lvlError, format("cleaning orphaned step %d of build %d") % step.second % step.first);
                    txn.parameterized
                        ("update BuildSteps set busy = 0, status = $1 where build = $2 and stepnr = $3 and busy != 0")
                        ((int) bsAborted)
                        (step.first)
                        (step.second).exec();
                }
                txn.commit();
            } catch (std::exception & e) {
                printMsg(lvlError, format("cleanup thread: %1%") % e.what());
                auto orphanedSteps_(orphanedSteps.lock());
                orphanedSteps_->insert(steps.begin(), steps.end());
            }
        }
    }).detach();

    /* Make sure that old daemon connections are closed even when
       we're not doing much. */
    std::thread([&]() {
        while (true) {
            sleep(10);
            try {
                if (auto remoteStore = getDestStore().dynamic_pointer_cast<RemoteStore>())
                    remoteStore->flushBadConnections();
            } catch (std::exception & e) {
                printMsg(lvlError, format("connection flush thread: %1%") % e.what());
            }
        }
    }).detach();

    /* Monitor the database for status dump requests (e.g. from
       ‘hydra-queue-runner --status’). */
    while (true) {
        try {
            auto conn(dbPool.get());
            receiver dumpStatus_(*conn, "dump_status");
            while (true) {
                conn->await_notification(statusLogInterval / 2 + 1, 0);
                dumpStatus(*conn, true);
            }
        } catch (std::exception & e) {
            printMsg(lvlError, format("main thread: %1%") % e.what());
            sleep(10); // probably a DB problem, so don't retry right away
        }
    }
}


int main(int argc, char * * argv)
{
    return handleExceptions(argv[0], [&]() {
        initNix();

        signal(SIGINT, SIG_DFL);
        signal(SIGTERM, SIG_DFL);
        signal(SIGHUP, SIG_DFL);

        // FIXME: do this in the child environment in openConnection().
        unsetenv("IN_SYSTEMD");

        bool unlock = false;
        bool status = false;
        BuildID buildOne = 0;

        parseCmdLine(argc, argv, [&](Strings::iterator & arg, const Strings::iterator & end) {
            if (*arg == "--unlock")
                unlock = true;
            else if (*arg == "--status")
                status = true;
            else if (*arg == "--build-one") {
                if (!string2Int<BuildID>(getArg(*arg, arg, end), buildOne))
                    throw Error("‘--build-one’ requires a build ID");
            } else
                return false;
            return true;
        });

        settings.verboseBuild = true;
        settings.lockCPU = false;

        State state;
        if (status)
            state.showStatus();
        else if (unlock)
            state.unlock();
        else
            state.run(buildOne);
    });
}