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nix/src/build-remote/build-remote.cc
John Ericson d972f9e2e2 Split out store-open.hh and store-registration.hh 
The existing header is a bit too big. Now the following use-cases are
separated, and get their own headers:

- Using or implementing an arbitrary store: remaining `store-api.hh`

  This is closer to just being about the `Store` (and `StoreConfig`)
  classes, as one would expect.

- Opening a store from a textual description: `store-open.hh`

  Opening an aribtrary store implementation like this requires some sort
  of store registration mechanism to exists, but the caller doesn't need
  to know how it works. This just exposes the functions which use such a
  mechanism, without exposing the mechanism itself

- Registering a store implementation: `store-registration.hh`

  This requires understanding how the mechanism actually works, and the
  mechanism in question involves templated machinery in headers we
  rather not expose to things that don't need it, as it would slow down
  compilation for no reason.
2025-05-14 16:07:57 -04:00

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#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <set>
#include <memory>
#include <tuple>
#include <iomanip>
#ifdef __APPLE__
#include <sys/time.h>
#endif
#include "nix/store/machines.hh"
#include "nix/main/shared.hh"
#include "nix/main/plugin.hh"
#include "nix/store/pathlocks.hh"
#include "nix/store/globals.hh"
#include "nix/util/serialise.hh"
#include "nix/store/build-result.hh"
#include "nix/store/store-open.hh"
#include "nix/util/strings.hh"
#include "nix/store/derivations.hh"
#include "nix/store/local-store.hh"
#include "nix/cmd/legacy.hh"
#include "nix/util/experimental-features.hh"
using namespace nix;
using std::cin;
static void handleAlarm(int sig) {
}
std::string escapeUri(std::string uri)
{
std::replace(uri.begin(), uri.end(), '/', '_');
return uri;
}
static std::string currentLoad;
static AutoCloseFD openSlotLock(const Machine & m, uint64_t slot)
{
return openLockFile(fmt("%s/%s-%d", currentLoad, escapeUri(m.storeUri.render()), slot), true);
}
static bool allSupportedLocally(Store & store, const StringSet& requiredFeatures) {
for (auto & feature : requiredFeatures)
if (!store.config.systemFeatures.get().count(feature)) return false;
return true;
}
static int main_build_remote(int argc, char * * argv)
{
{
logger = makeJSONLogger(getStandardError());
/* Ensure we don't get any SSH passphrase or host key popups. */
unsetenv("DISPLAY");
unsetenv("SSH_ASKPASS");
/* If we ever use the common args framework, make sure to
remove initPlugins below and initialize settings first.
*/
if (argc != 2)
throw UsageError("called without required arguments");
verbosity = (Verbosity) std::stoll(argv[1]);
FdSource source(STDIN_FILENO);
/* Read the parent's settings. */
while (readInt(source)) {
auto name = readString(source);
auto value = readString(source);
settings.set(name, value);
}
auto maxBuildJobs = settings.maxBuildJobs;
settings.maxBuildJobs.set("1"); // hack to make tests with local?root= work
initPlugins();
auto store = openStore();
/* It would be more appropriate to use $XDG_RUNTIME_DIR, since
that gets cleared on reboot, but it wouldn't work on macOS. */
auto currentLoadName = "/current-load";
if (auto localStore = store.dynamic_pointer_cast<LocalFSStore>())
currentLoad = std::string { localStore->config.stateDir } + currentLoadName;
else
currentLoad = settings.nixStateDir + currentLoadName;
std::shared_ptr<Store> sshStore;
AutoCloseFD bestSlotLock;
auto machines = getMachines();
debug("got %d remote builders", machines.size());
if (machines.empty()) {
std::cerr << "# decline-permanently\n";
return 0;
}
std::optional<StorePath> drvPath;
std::string storeUri;
while (true) {
try {
auto s = readString(source);
if (s != "try") return 0;
} catch (EndOfFile &) { return 0; }
auto amWilling = readInt(source);
auto neededSystem = readString(source);
drvPath = store->parseStorePath(readString(source));
auto requiredFeatures = readStrings<StringSet>(source);
/* It would be possible to build locally after some builds clear out,
so don't show the warning now: */
bool couldBuildLocally = maxBuildJobs > 0
&& ( neededSystem == settings.thisSystem
|| settings.extraPlatforms.get().count(neededSystem) > 0)
&& allSupportedLocally(*store, requiredFeatures);
/* It's possible to build this locally right now: */
bool canBuildLocally = amWilling && couldBuildLocally;
/* Error ignored here, will be caught later */
mkdir(currentLoad.c_str(), 0777);
while (true) {
bestSlotLock = -1;
AutoCloseFD lock = openLockFile(currentLoad + "/main-lock", true);
lockFile(lock.get(), ltWrite, true);
bool rightType = false;
Machine * bestMachine = nullptr;
uint64_t bestLoad = 0;
for (auto & m : machines) {
debug("considering building on remote machine '%s'", m.storeUri.render());
if (m.enabled &&
m.systemSupported(neededSystem) &&
m.allSupported(requiredFeatures) &&
m.mandatoryMet(requiredFeatures))
{
rightType = true;
AutoCloseFD free;
uint64_t load = 0;
for (uint64_t slot = 0; slot < m.maxJobs; ++slot) {
auto slotLock = openSlotLock(m, slot);
if (lockFile(slotLock.get(), ltWrite, false)) {
if (!free) {
free = std::move(slotLock);
}
} else {
++load;
}
}
if (!free) {
continue;
}
bool best = false;
if (!bestSlotLock) {
best = true;
} else if (load / m.speedFactor < bestLoad / bestMachine->speedFactor) {
best = true;
} else if (load / m.speedFactor == bestLoad / bestMachine->speedFactor) {
if (m.speedFactor > bestMachine->speedFactor) {
best = true;
} else if (m.speedFactor == bestMachine->speedFactor) {
if (load < bestLoad) {
best = true;
}
}
}
if (best) {
bestLoad = load;
bestSlotLock = std::move(free);
bestMachine = &m;
}
}
}
if (!bestSlotLock) {
if (rightType && !canBuildLocally)
std::cerr << "# postpone\n";
else
{
// build the hint template.
std::string errorText =
"Failed to find a machine for remote build!\n"
"derivation: %s\nrequired (system, features): (%s, [%s])";
errorText += "\n%s available machines:";
errorText += "\n(systems, maxjobs, supportedFeatures, mandatoryFeatures)";
for (unsigned int i = 0; i < machines.size(); ++i)
errorText += "\n([%s], %s, [%s], [%s])";
// add the template values.
std::string drvstr;
if (drvPath.has_value())
drvstr = drvPath->to_string();
else
drvstr = "<unknown>";
auto error = HintFmt::fromFormatString(errorText);
error
% drvstr
% neededSystem
% concatStringsSep<StringSet>(", ", requiredFeatures)
% machines.size();
for (auto & m : machines)
error
% concatStringsSep<StringSet>(", ", m.systemTypes)
% m.maxJobs
% concatStringsSep<StringSet>(", ", m.supportedFeatures)
% concatStringsSep<StringSet>(", ", m.mandatoryFeatures);
printMsg(couldBuildLocally ? lvlChatty : lvlWarn, error.str());
std::cerr << "# decline\n";
}
break;
}
#ifdef __APPLE__
futimes(bestSlotLock.get(), NULL);
#else
futimens(bestSlotLock.get(), NULL);
#endif
lock = -1;
try {
storeUri = bestMachine->storeUri.render();
Activity act(*logger, lvlTalkative, actUnknown, fmt("connecting to '%s'", storeUri));
sshStore = bestMachine->openStore();
sshStore->connect();
} catch (std::exception & e) {
auto msg = chomp(drainFD(5, false));
printError("cannot build on '%s': %s%s",
storeUri, e.what(),
msg.empty() ? "" : ": " + msg);
bestMachine->enabled = false;
continue;
}
goto connected;
}
}
connected:
close(5);
assert(sshStore);
std::cerr << "# accept\n" << storeUri << "\n";
auto inputs = readStrings<PathSet>(source);
auto wantedOutputs = readStrings<StringSet>(source);
AutoCloseFD uploadLock;
{
auto setUpdateLock = [&](auto && fileName){
uploadLock = openLockFile(currentLoad + "/" + escapeUri(fileName) + ".upload-lock", true);
};
try {
setUpdateLock(storeUri);
} catch (SysError & e) {
if (e.errNo != ENAMETOOLONG) throw;
// Try again hashing the store URL so we have a shorter path
auto h = hashString(HashAlgorithm::MD5, storeUri);
setUpdateLock(h.to_string(HashFormat::Base64, false));
}
}
{
Activity act(*logger, lvlTalkative, actUnknown, fmt("waiting for the upload lock to '%s'", storeUri));
auto old = signal(SIGALRM, handleAlarm);
alarm(15 * 60);
if (!lockFile(uploadLock.get(), ltWrite, true))
printError("somebody is hogging the upload lock for '%s', continuing...");
alarm(0);
signal(SIGALRM, old);
}
auto substitute = settings.buildersUseSubstitutes ? Substitute : NoSubstitute;
{
Activity act(*logger, lvlTalkative, actUnknown, fmt("copying dependencies to '%s'", storeUri));
copyPaths(*store, *sshStore, store->parseStorePathSet(inputs), NoRepair, NoCheckSigs, substitute);
}
uploadLock = -1;
auto drv = store->readDerivation(*drvPath);
std::optional<BuildResult> optResult;
// If we don't know whether we are trusted (e.g. `ssh://`
// stores), we assume we are. This is necessary for backwards
// compat.
bool trustedOrLegacy = ({
std::optional trusted = sshStore->isTrustedClient();
!trusted || *trusted;
});
// See the very large comment in `case WorkerProto::Op::BuildDerivation:` in
// `src/libstore/daemon.cc` that explains the trust model here.
//
// This condition mirrors that: that code enforces the "rules" outlined there;
// we do the best we can given those "rules".
if (trustedOrLegacy || drv.type().isCA()) {
// Hijack the inputs paths of the derivation to include all
// the paths that come from the `inputDrvs` set. We don’t do
// that for the derivations whose `inputDrvs` is empty
// because:
//
// 1. It’s not needed
//
// 2. Changing the `inputSrcs` set changes the associated
// output ids, which break CA derivations
if (!drv.inputDrvs.map.empty())
drv.inputSrcs = store->parseStorePathSet(inputs);
optResult = sshStore->buildDerivation(*drvPath, (const BasicDerivation &) drv);
auto & result = *optResult;
if (!result.success())
throw Error("build of '%s' on '%s' failed: %s", store->printStorePath(*drvPath), storeUri, result.errorMsg);
} else {
copyClosure(*store, *sshStore, StorePathSet {*drvPath}, NoRepair, NoCheckSigs, substitute);
auto res = sshStore->buildPathsWithResults({
DerivedPath::Built {
.drvPath = makeConstantStorePathRef(*drvPath),
.outputs = OutputsSpec::All {},
}
});
// One path to build should produce exactly one build result
assert(res.size() == 1);
optResult = std::move(res[0]);
}
auto outputHashes = staticOutputHashes(*store, drv);
std::set<Realisation> missingRealisations;
StorePathSet missingPaths;
if (experimentalFeatureSettings.isEnabled(Xp::CaDerivations) && !drv.type().hasKnownOutputPaths()) {
for (auto & outputName : wantedOutputs) {
auto thisOutputHash = outputHashes.at(outputName);
auto thisOutputId = DrvOutput{ thisOutputHash, outputName };
if (!store->queryRealisation(thisOutputId)) {
debug("missing output %s", outputName);
assert(optResult);
auto & result = *optResult;
auto i = result.builtOutputs.find(outputName);
assert(i != result.builtOutputs.end());
auto & newRealisation = i->second;
missingRealisations.insert(newRealisation);
missingPaths.insert(newRealisation.outPath);
}
}
} else {
auto outputPaths = drv.outputsAndOptPaths(*store);
for (auto & [outputName, hopefullyOutputPath] : outputPaths) {
assert(hopefullyOutputPath.second);
if (!store->isValidPath(*hopefullyOutputPath.second))
missingPaths.insert(*hopefullyOutputPath.second);
}
}
if (!missingPaths.empty()) {
Activity act(*logger, lvlTalkative, actUnknown, fmt("copying outputs from '%s'", storeUri));
if (auto localStore = store.dynamic_pointer_cast<LocalStore>())
for (auto & path : missingPaths)
localStore->locksHeld.insert(store->printStorePath(path)); /* FIXME: ugly */
copyPaths(*sshStore, *store, missingPaths, NoRepair, NoCheckSigs, NoSubstitute);
}
// XXX: Should be done as part of `copyPaths`
for (auto & realisation : missingRealisations) {
// Should hold, because if the feature isn't enabled the set
// of missing realisations should be empty
experimentalFeatureSettings.require(Xp::CaDerivations);
store->registerDrvOutput(realisation);
}
return 0;
}
}
static RegisterLegacyCommand r_build_remote("build-remote", main_build_remote);
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