nix/src/libstore/build/worker.cc

#include "build.hh"

#include <poll.h>

namespace nix {

Worker::Worker(LocalStore & store)
    : act(*logger, actRealise)
    , actDerivations(*logger, actBuilds)
    , actSubstitutions(*logger, actCopyPaths)
    , store(store)
{
    /* Debugging: prevent recursive workers. */
    nrLocalBuilds = 0;
    lastWokenUp = steady_time_point::min();
    permanentFailure = false;
    timedOut = false;
    hashMismatch = false;
    checkMismatch = false;
}


Worker::~Worker()
{
    /* Explicitly get rid of all strong pointers now.  After this all
       goals that refer to this worker should be gone.  (Otherwise we
       are in trouble, since goals may call childTerminated() etc. in
       their destructors). */
    topGoals.clear();

    assert(expectedSubstitutions == 0);
    assert(expectedDownloadSize == 0);
    assert(expectedNarSize == 0);
}


std::shared_ptr<DerivationGoal> Worker::makeDerivationGoalCommon(
    const StorePath & drvPath,
    const StringSet & wantedOutputs,
    std::function<std::shared_ptr<DerivationGoal>()> mkDrvGoal)
{
    WeakGoalPtr & abstract_goal_weak = derivationGoals[drvPath];
    GoalPtr abstract_goal = abstract_goal_weak.lock(); // FIXME
    std::shared_ptr<DerivationGoal> goal;
    if (!abstract_goal) {
        goal = mkDrvGoal();
        abstract_goal_weak = goal;
        wakeUp(goal);
    } else {
        goal = std::dynamic_pointer_cast<DerivationGoal>(abstract_goal);
        assert(goal);
        goal->addWantedOutputs(wantedOutputs);
    }
    return goal;
}


std::shared_ptr<DerivationGoal> Worker::makeDerivationGoal(const StorePath & drvPath,
    const StringSet & wantedOutputs, BuildMode buildMode)
{
    return makeDerivationGoalCommon(drvPath, wantedOutputs, [&]() {
        return std::make_shared<DerivationGoal>(drvPath, wantedOutputs, *this, buildMode);
    });
}


std::shared_ptr<DerivationGoal> Worker::makeBasicDerivationGoal(const StorePath & drvPath,
    const BasicDerivation & drv, const StringSet & wantedOutputs, BuildMode buildMode)
{
    return makeDerivationGoalCommon(drvPath, wantedOutputs, [&]() {
        return std::make_shared<DerivationGoal>(drvPath, drv, wantedOutputs, *this, buildMode);
    });
}


GoalPtr Worker::makeSubstitutionGoal(const StorePath & path, RepairFlag repair, std::optional<ContentAddress> ca)
{
    WeakGoalPtr & goal_weak = substitutionGoals[path];
    GoalPtr goal = goal_weak.lock(); // FIXME
    if (!goal) {
        goal = std::make_shared<SubstitutionGoal>(path, *this, repair, ca);
        goal_weak = goal;
        wakeUp(goal);
    }
    return goal;
}


static void removeGoal(GoalPtr goal, WeakGoalMap & goalMap)
{
    /* !!! inefficient */
    for (WeakGoalMap::iterator i = goalMap.begin();
         i != goalMap.end(); )
        if (i->second.lock() == goal) {
            WeakGoalMap::iterator j = i; ++j;
            goalMap.erase(i);
            i = j;
        }
        else ++i;
}


void Worker::removeGoal(GoalPtr goal)
{
    nix::removeGoal(goal, derivationGoals);
    nix::removeGoal(goal, substitutionGoals);
    if (topGoals.find(goal) != topGoals.end()) {
        topGoals.erase(goal);
        /* If a top-level goal failed, then kill all other goals
           (unless keepGoing was set). */
        if (goal->exitCode == Goal::ecFailed && !settings.keepGoing)
            topGoals.clear();
    }

    /* Wake up goals waiting for any goal to finish. */
    for (auto & i : waitingForAnyGoal) {
        GoalPtr goal = i.lock();
        if (goal) wakeUp(goal);
    }

    waitingForAnyGoal.clear();
}


void Worker::wakeUp(GoalPtr goal)
{
    goal->trace("woken up");
    addToWeakGoals(awake, goal);
}


unsigned Worker::getNrLocalBuilds()
{
    return nrLocalBuilds;
}


void Worker::childStarted(GoalPtr goal, const set<int> & fds,
    bool inBuildSlot, bool respectTimeouts)
{
    Child child;
    child.goal = goal;
    child.goal2 = goal.get();
    child.fds = fds;
    child.timeStarted = child.lastOutput = steady_time_point::clock::now();
    child.inBuildSlot = inBuildSlot;
    child.respectTimeouts = respectTimeouts;
    children.emplace_back(child);
    if (inBuildSlot) nrLocalBuilds++;
}


void Worker::childTerminated(Goal * goal, bool wakeSleepers)
{
    auto i = std::find_if(children.begin(), children.end(),
        [&](const Child & child) { return child.goal2 == goal; });
    if (i == children.end()) return;

    if (i->inBuildSlot) {
        assert(nrLocalBuilds > 0);
        nrLocalBuilds--;
    }

    children.erase(i);

    if (wakeSleepers) {

        /* Wake up goals waiting for a build slot. */
        for (auto & j : wantingToBuild) {
            GoalPtr goal = j.lock();
            if (goal) wakeUp(goal);
        }

        wantingToBuild.clear();
    }
}


void Worker::waitForBuildSlot(GoalPtr goal)
{
    debug("wait for build slot");
    if (getNrLocalBuilds() < settings.maxBuildJobs)
        wakeUp(goal); /* we can do it right away */
    else
        addToWeakGoals(wantingToBuild, goal);
}


void Worker::waitForAnyGoal(GoalPtr goal)
{
    debug("wait for any goal");
    addToWeakGoals(waitingForAnyGoal, goal);
}


void Worker::waitForAWhile(GoalPtr goal)
{
    debug("wait for a while");
    addToWeakGoals(waitingForAWhile, goal);
}


void Worker::run(const Goals & _topGoals)
{
    for (auto & i : _topGoals) topGoals.insert(i);

    debug("entered goal loop");

    while (1) {

        checkInterrupt();

        store.autoGC(false);

        /* Call every wake goal (in the ordering established by
           CompareGoalPtrs). */
        while (!awake.empty() && !topGoals.empty()) {
            Goals awake2;
            for (auto & i : awake) {
                GoalPtr goal = i.lock();
                if (goal) awake2.insert(goal);
            }
            awake.clear();
            for (auto & goal : awake2) {
                checkInterrupt();
                goal->work();
                if (topGoals.empty()) break; // stuff may have been cancelled
            }
        }

        if (topGoals.empty()) break;

        /* Wait for input. */
        if (!children.empty() || !waitingForAWhile.empty())
            waitForInput();
        else {
            if (awake.empty() && 0 == settings.maxBuildJobs)
            {
                if (getMachines().empty())
                   throw Error("unable to start any build; either increase '--max-jobs' "
                            "or enable remote builds."
                            "\nhttps://nixos.org/nix/manual/#chap-distributed-builds");
                else
                   throw Error("unable to start any build; remote machines may not have "
                            "all required system features."
                            "\nhttps://nixos.org/nix/manual/#chap-distributed-builds");

            }
            assert(!awake.empty());
        }
    }

    /* If --keep-going is not set, it's possible that the main goal
       exited while some of its subgoals were still active.  But if
       --keep-going *is* set, then they must all be finished now. */
    assert(!settings.keepGoing || awake.empty());
    assert(!settings.keepGoing || wantingToBuild.empty());
    assert(!settings.keepGoing || children.empty());
}

void Worker::waitForInput()
{
    printMsg(lvlVomit, "waiting for children");

    /* Process output from the file descriptors attached to the
       children, namely log output and output path creation commands.
       We also use this to detect child termination: if we get EOF on
       the logger pipe of a build, we assume that the builder has
       terminated. */

    bool useTimeout = false;
    long timeout = 0;
    auto before = steady_time_point::clock::now();

    /* If we're monitoring for silence on stdout/stderr, or if there
       is a build timeout, then wait for input until the first
       deadline for any child. */
    auto nearest = steady_time_point::max(); // nearest deadline
    if (settings.minFree.get() != 0)
        // Periodicallty wake up to see if we need to run the garbage collector.
        nearest = before + std::chrono::seconds(10);
    for (auto & i : children) {
        if (!i.respectTimeouts) continue;
        if (0 != settings.maxSilentTime)
            nearest = std::min(nearest, i.lastOutput + std::chrono::seconds(settings.maxSilentTime));
        if (0 != settings.buildTimeout)
            nearest = std::min(nearest, i.timeStarted + std::chrono::seconds(settings.buildTimeout));
    }
    if (nearest != steady_time_point::max()) {
        timeout = std::max(1L, (long) std::chrono::duration_cast<std::chrono::seconds>(nearest - before).count());
        useTimeout = true;
    }

    /* If we are polling goals that are waiting for a lock, then wake
       up after a few seconds at most. */
    if (!waitingForAWhile.empty()) {
        useTimeout = true;
        if (lastWokenUp == steady_time_point::min() || lastWokenUp > before) lastWokenUp = before;
        timeout = std::max(1L,
            (long) std::chrono::duration_cast<std::chrono::seconds>(
                lastWokenUp + std::chrono::seconds(settings.pollInterval) - before).count());
    } else lastWokenUp = steady_time_point::min();

    if (useTimeout)
        vomit("sleeping %d seconds", timeout);

    /* Use select() to wait for the input side of any logger pipe to
       become `available'.  Note that `available' (i.e., non-blocking)
       includes EOF. */
    std::vector<struct pollfd> pollStatus;
    std::map <int, int> fdToPollStatus;
    for (auto & i : children) {
        for (auto & j : i.fds) {
            pollStatus.push_back((struct pollfd) { .fd = j, .events = POLLIN });
            fdToPollStatus[j] = pollStatus.size() - 1;
        }
    }

    if (poll(pollStatus.data(), pollStatus.size(),
            useTimeout ? timeout * 1000 : -1) == -1) {
        if (errno == EINTR) return;
        throw SysError("waiting for input");
    }

    auto after = steady_time_point::clock::now();

    /* Process all available file descriptors. FIXME: this is
       O(children * fds). */
    decltype(children)::iterator i;
    for (auto j = children.begin(); j != children.end(); j = i) {
        i = std::next(j);

        checkInterrupt();

        GoalPtr goal = j->goal.lock();
        assert(goal);

        set<int> fds2(j->fds);
        std::vector<unsigned char> buffer(4096);
        for (auto & k : fds2) {
            if (pollStatus.at(fdToPollStatus.at(k)).revents) {
                ssize_t rd = ::read(k, buffer.data(), buffer.size());
                // FIXME: is there a cleaner way to handle pt close
                // than EIO? Is this even standard?
                if (rd == 0 || (rd == -1 && errno == EIO)) {
                    debug("%1%: got EOF", goal->getName());
                    goal->handleEOF(k);
                    j->fds.erase(k);
                } else if (rd == -1) {
                    if (errno != EINTR)
                        throw SysError("%s: read failed", goal->getName());
                } else {
                    printMsg(lvlVomit, "%1%: read %2% bytes",
                        goal->getName(), rd);
                    string data((char *) buffer.data(), rd);
                    j->lastOutput = after;
                    goal->handleChildOutput(k, data);
                }
            }
        }

        if (goal->exitCode == Goal::ecBusy &&
            0 != settings.maxSilentTime &&
            j->respectTimeouts &&
            after - j->lastOutput >= std::chrono::seconds(settings.maxSilentTime))
        {
            goal->timedOut(Error(
                    "%1% timed out after %2% seconds of silence",
                    goal->getName(), settings.maxSilentTime));
        }

        else if (goal->exitCode == Goal::ecBusy &&
            0 != settings.buildTimeout &&
            j->respectTimeouts &&
            after - j->timeStarted >= std::chrono::seconds(settings.buildTimeout))
        {
            goal->timedOut(Error(
                    "%1% timed out after %2% seconds",
                    goal->getName(), settings.buildTimeout));
        }
    }

    if (!waitingForAWhile.empty() && lastWokenUp + std::chrono::seconds(settings.pollInterval) <= after) {
        lastWokenUp = after;
        for (auto & i : waitingForAWhile) {
            GoalPtr goal = i.lock();
            if (goal) wakeUp(goal);
        }
        waitingForAWhile.clear();
    }
}


unsigned int Worker::exitStatus()
{
    /*
     * 1100100
     *    ^^^^
     *    |||`- timeout
     *    ||`-- output hash mismatch
     *    |`--- build failure
     *    `---- not deterministic
     */
    unsigned int mask = 0;
    bool buildFailure = permanentFailure || timedOut || hashMismatch;
    if (buildFailure)
        mask |= 0x04;  // 100
    if (timedOut)
        mask |= 0x01;  // 101
    if (hashMismatch)
        mask |= 0x02;  // 102
    if (checkMismatch) {
        mask |= 0x08;  // 104
    }

    if (mask)
        mask |= 0x60;
    return mask ? mask : 1;
}


bool Worker::pathContentsGood(const StorePath & path)
{
    auto i = pathContentsGoodCache.find(path);
    if (i != pathContentsGoodCache.end()) return i->second;
    printInfo("checking path '%s'...", store.printStorePath(path));
    auto info = store.queryPathInfo(path);
    bool res;
    if (!pathExists(store.printStorePath(path)))
        res = false;
    else {
        HashResult current = hashPath(info->narHash.type, store.printStorePath(path));
        Hash nullHash(htSHA256);
        res = info->narHash == nullHash || info->narHash == current.first;
    }
    pathContentsGoodCache.insert_or_assign(path, res);
    if (!res)
        logError({
            .name = "Corrupted path",
            .hint = hintfmt("path '%s' is corrupted or missing!", store.printStorePath(path))
        });
    return res;
}


void Worker::markContentsGood(const StorePath & path)
{
    pathContentsGoodCache.insert_or_assign(path, true);
}

}