nix/src/libstore/build/drv-output-substitution-goal.cc

#include "nix/store/build/drv-output-substitution-goal.hh"
#include "nix/util/finally.hh"
#include "nix/store/build/worker.hh"
#include "nix/store/build/substitution-goal.hh"
#include "nix/util/callback.hh"
#include "nix/store/store-open.hh"

namespace nix {

DrvOutputSubstitutionGoal::DrvOutputSubstitutionGoal(
    const DrvOutput & id,
    Worker & worker,
    RepairFlag repair,
    std::optional<ContentAddress> ca)
    : Goal(worker, init())
    , id(id)
{
    name = fmt("substitution of '%s'", id.to_string());
    trace("created");
}


Goal::Co DrvOutputSubstitutionGoal::init()
{
    trace("init");

    /* If the derivation already exists, we’re done */
    if (worker.store.queryRealisation(id)) {
        co_return amDone(ecSuccess);
    }

    auto subs = settings.useSubstitutes ? getDefaultSubstituters() : std::list<ref<Store>>();

    bool substituterFailed = false;

    for (const auto & sub : subs) {
        trace("trying next substituter");

        /* The callback of the curl download below can outlive `this` (if
           some other error occurs), so it must not touch `this`. So put
           the shared state in a separate refcounted object. */
        auto outPipe = std::make_shared<MuxablePipe>();
    #ifndef _WIN32
        outPipe->create();
    #else
        outPipe->createAsyncPipe(worker.ioport.get());
    #endif

        auto promise = std::make_shared<std::promise<std::shared_ptr<const Realisation>>>();

        sub->queryRealisation(
            id,
            { [outPipe(outPipe), promise(promise)](std::future<std::shared_ptr<const Realisation>> res) {
                try {
                    Finally updateStats([&]() { outPipe->writeSide.close(); });
                    promise->set_value(res.get());
                } catch (...) {
                    promise->set_exception(std::current_exception());
                }
            } });

        worker.childStarted(shared_from_this(), {
    #ifndef _WIN32
            outPipe->readSide.get()
    #else
            &*outPipe
    #endif
        }, true, false);

        co_await Suspend{};

        worker.childTerminated(this);

        /*
         * The realisation corresponding to the given output id.
         * Will be filled once we can get it.
         */
        std::shared_ptr<const Realisation> outputInfo;

        try {
            outputInfo = promise->get_future().get();
        } catch (std::exception & e) {
            printError(e.what());
            substituterFailed = true;
        }

        if (!outputInfo) continue;

        bool failed = false;

        Goals waitees;

        for (const auto & [depId, depPath] : outputInfo->dependentRealisations) {
            if (depId != id) {
                if (auto localOutputInfo = worker.store.queryRealisation(depId);
                    localOutputInfo && localOutputInfo->outPath != depPath) {
                    warn(
                        "substituter '%s' has an incompatible realisation for '%s', ignoring.\n"
                        "Local:  %s\n"
                        "Remote: %s",
                        sub->getUri(),
                        depId.to_string(),
                        worker.store.printStorePath(localOutputInfo->outPath),
                        worker.store.printStorePath(depPath)
                    );
                    failed = true;
                    break;
                }
                waitees.insert(worker.makeDrvOutputSubstitutionGoal(depId));
            }
        }

        if (failed) continue;

        co_return realisationFetched(std::move(waitees), outputInfo, sub);
    }

    /* None left.  Terminate this goal and let someone else deal
       with it. */
    debug("derivation output '%s' is required, but there is no substituter that can provide it", id.to_string());

    if (substituterFailed) {
        worker.failedSubstitutions++;
        worker.updateProgress();
    }

    /* Hack: don't indicate failure if there were no substituters.
       In that case the calling derivation should just do a
       build. */
    co_return amDone(substituterFailed ? ecFailed : ecNoSubstituters);
}

Goal::Co DrvOutputSubstitutionGoal::realisationFetched(Goals waitees, std::shared_ptr<const Realisation> outputInfo, nix::ref<nix::Store> sub) {
    waitees.insert(worker.makePathSubstitutionGoal(outputInfo->outPath));

    co_await await(std::move(waitees));

    trace("output path substituted");

    if (nrFailed > 0) {
        debug("The output path of the derivation output '%s' could not be substituted", id.to_string());
        co_return amDone(nrNoSubstituters > 0 ? ecNoSubstituters : ecFailed);
    }

    worker.store.registerDrvOutput(*outputInfo);

    trace("finished");
    co_return amDone(ecSuccess);
}

std::string DrvOutputSubstitutionGoal::key()
{
    /* "a$" ensures substitution goals happen before derivation
       goals. */
    return "a$" + std::string(id.to_string());
}

void DrvOutputSubstitutionGoal::handleEOF(Descriptor fd)
{
    worker.wakeUp(shared_from_this());
}


}