Support arbitrary stores for building

flake.nix

@@ -85,6 +85,7 @@
             nix-util
             nix-store
             nix-main
+            nix-cmd
             nix-cli
             ;
           nix-perl-bindings = nix.hydraJobs.perlBindings.${system};

foreman/start-manual.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-mdbook serve \
+exec mdbook serve \
   --port 63332 \
   --dest-dir ./.hydra-data/manual \
   ./doc/manual/

package.nix

@@ -11,6 +11,7 @@
 , nix-util
 , nix-store
 , nix-main
+, nix-cmd
 , nix-cli
 , nix-perl-bindings
 , git
@@ -178,6 +179,7 @@ stdenv.mkDerivation (finalAttrs: {
     nix-util
     nix-store
     nix-main
+    nix-cmd
     perlDeps
     perl
     boost

src/hydra-build-step/hydra-build-step.cc

@@ -0,0 +1,213 @@
+/* This is a helper program that performs a build step, i.e. a single
+   derivation. In addition to a derivation path, it takes three store
+   URLs as arguments:
+
+   * --store: The store that will hold the resulting store paths
+       (typically a binary cache).
+
+   * --eval-store: The store that holds the .drv files, as produced by
+       hydra-evaluator.
+
+   * --build-store: The store that performs the build (often a
+       SSHStore for remote builds).
+
+   The build log is written to the path indicated by --log-file.
+*/
+
+#include "util.hh"
+#include "shared.hh"
+#include "common-eval-args.hh"
+#include "store-api.hh"
+#include "build-result.hh"
+#include "derivations.hh"
+#include "worker-protocol.hh"
+
+#include <chrono>
+
+using namespace nix;
+
+// FIXME: cut&paste
+static std::string_view getS(const std::vector<Logger::Field> & fields, size_t n)
+{
+    assert(n < fields.size());
+    assert(fields[n].type == Logger::Field::tString);
+    return fields[n].s;
+}
+
+void mainWrapped(std::list<std::string> args)
+{
+    verbosity = lvlError;
+
+    struct MyArgs : MixEvalArgs, MixCommonArgs, RootArgs
+    {
+        Path drvPath;
+        std::optional<std::string> buildStoreUrl;
+        std::optional<Path> logPath;
+        std::optional<uint64_t> maxOutputSize;
+
+        MyArgs() : MixCommonArgs("hydra-build-step")
+        {
+            expectArg("drv-path", &drvPath);
+
+            addFlag({
+                .longName = "build-store",
+                .description = "The Nix store to use for building the derivation.",
+                //.category = category,
+                .labels = {"store-url"},
+                .handler = {&buildStoreUrl},
+            });
+
+            addFlag({
+                .longName = "log-file",
+                .description = "The path to the build log.",
+                .labels = {"path"},
+                .handler = {&logPath},
+            });
+
+            addFlag({
+                .longName = "max-output-size",
+                .description = "Maximum size of the outputs.",
+                .labels = {"bytes"},
+                .handler = {&maxOutputSize},
+            });
+        }
+    };
+
+    /* A logger that intercepts all build log lines and writes them to
+       the log file. */
+    MyArgs myArgs;
+    myArgs.parseCmdline(args);
+
+    struct MyLogger : public Logger
+    {
+        Logger & prev;
+        AutoCloseFD logFile;
+
+        MyLogger(Logger & prev, Path logPath) : prev(prev)
+        {
+            logFile = open(logPath.c_str(), O_CREAT | O_TRUNC | O_WRONLY, 0666);
+            if (!logFile)
+                throw SysError("creating log file '%s'", logPath);
+        }
+
+        void log(Verbosity lvl, std::string_view s) override
+        { prev.log(lvl, s); }
+
+        void logEI(const ErrorInfo & ei) override
+        { prev.logEI(ei); }
+
+        void writeToStdout(std::string_view s) override
+        { prev.writeToStdout(s); }
+
+        void result(ActivityId act, ResultType type, const Fields & fields) override
+        {
+            if (type == resBuildLogLine)
+                writeLine(logFile.get(), std::string(getS(fields, 0)));
+            else
+                prev.result(act, type, fields);
+        }
+    };
+
+    auto destStore = openStore();
+    auto evalStore = myArgs.evalStoreUrl ? openStore(*myArgs.evalStoreUrl) : destStore;
+    auto buildStore = myArgs.buildStoreUrl ? openStore(*myArgs.buildStoreUrl) : destStore;
+
+    auto drvPath = evalStore->parseStorePath(myArgs.drvPath);
+
+    auto drv = evalStore->readDerivation(drvPath);
+    BasicDerivation basicDrv(drv);
+
+    uint64_t overhead = 0;
+
+    /* Gather the inputs. */
+    StorePathSet inputs;
+
+    for (auto & p : drv.inputSrcs)
+        inputs.insert(p);
+
+    for (auto & [drvPath, node] : drv.inputDrvs.map) {
+        auto drv2 = evalStore->readDerivation(drvPath);
+        for (auto & name : node.value) {
+            if (auto i = get(drv2.outputs, name)) {
+                auto outPath = i->path(*evalStore, drv2.name, name);
+                inputs.insert(*outPath);
+                basicDrv.inputSrcs.insert(*outPath);
+            }
+        }
+    }
+
+    /* Ensure that the inputs exist in the destination store (so that
+       the builder can substitute them from the destination
+       store). This is a no-op for regular stores, but for the binary
+       cache store, this will copy the inputs to the binary cache from
+       the local store. */
+    {
+        auto now1 = std::chrono::steady_clock::now();
+
+        debug("sending closure of '%s' to '%s'",
+            evalStore->printStorePath(drvPath), destStore->getUri());
+
+        if (evalStore != destStore)
+            copyClosure(*evalStore, *destStore, drv.inputSrcs, NoRepair, NoCheckSigs);
+
+        copyClosure(*destStore, *buildStore, inputs, NoRepair, NoCheckSigs, Substitute);
+
+        auto now2 = std::chrono::steady_clock::now();
+
+        overhead += std::chrono::duration_cast<std::chrono::milliseconds>(now2 - now1).count();
+    }
+
+    /* Perform the build. */
+    if (myArgs.logPath)
+        logger = new MyLogger(*logger, *myArgs.logPath);
+
+    auto buildResult = buildStore->buildDerivation(drvPath, basicDrv);
+
+    /* Copy the output paths from the build store to the destination
+       store. */
+    size_t totalNarSize = 0;
+
+    if (buildResult.success()) {
+
+        std::map<StorePath, ValidPathInfo> infos;
+        StorePathSet outputs;
+        for (auto & [output, realisation] : buildResult.builtOutputs) {
+            auto info = buildStore->queryPathInfo(realisation.outPath);
+            totalNarSize += info->narSize;
+            infos.insert_or_assign(info->path, *info);
+            outputs.insert(info->path);
+        }
+
+        if ((!myArgs.maxOutputSize || totalNarSize <= *myArgs.maxOutputSize)
+            && buildStore != destStore)
+        {
+            debug("copying outputs of '%s' from '%s' (%d bytes)",
+                buildStore->printStorePath(drvPath), buildStore->getUri(), totalNarSize);
+
+            auto now1 = std::chrono::steady_clock::now();
+
+            copyPaths(*buildStore, *destStore, outputs, NoRepair, NoCheckSigs);
+
+            auto now2 = std::chrono::steady_clock::now();
+
+            overhead += std::chrono::duration_cast<std::chrono::milliseconds>(now2 - now1).count();
+        }
+    }
+
+    FdSink to { STDOUT_FILENO };
+    WorkerProto::WriteConn wconn {
+        .to = to,
+        // Hardcode latest version because we are deploying hydra
+        // itself atomically
+        .version = PROTOCOL_VERSION,
+    };
+    WorkerProto::write(*evalStore, wconn, buildResult);
+}
+
+int main(int argc, char * * argv)
+{
+    return handleExceptions(argv[0], [&]() {
+        initNix();
+        mainWrapped(argvToStrings(argc, argv));
+    });
+}

src/hydra-build-step/meson.build

@@ -0,0 +1,14 @@
+srcs = files(
+  'hydra-build-step.cc',
+)
+
+hydra_build_step = executable('hydra-build-step',
+  'hydra-build-step.cc',
+  srcs,
+  dependencies: [
+    libhydra_dep,
+    nix_dep,
+    dependency('nix-cmd', required: true)
+  ],
+  install: true,
+)