1 files changed, 59 insertions, 85 deletions

diff --git a/src/libstore/build/worker.hh b/src/libstore/build/worker.hh
index 6735ea0b9..925d289bf 100644
--- a/src/libstore/build/worker.hh
+++ b/src/libstore/build/worker.hh
@@ -1,6 +1,7 @@
 #pragma once
 ///@file
 
+#include "async-semaphore.hh"
 #include "notifying-counter.hh"
 #include "types.hh"
 #include "lock.hh"
@@ -21,34 +22,16 @@ class DrvOutputSubstitutionGoal;
 
 typedef std::chrono::time_point<std::chrono::steady_clock> steady_time_point;
 
-/**
- * A mapping used to remember for each child process to what goal it
- * belongs, and file descriptors for receiving log data and output
- * path creation commands.
- */
-struct Child
-{
-    WeakGoalPtr goal;
-    Goal * goal2; // ugly hackery
-    std::set<int> fds;
-    bool inBuildSlot;
-    /**
-     * Time we last got output on stdout/stderr
-     */
-    steady_time_point lastOutput;
-    steady_time_point timeStarted;
-};
-
 /* Forward definition. */
 struct HookInstance;
 
 class GoalFactory
 {
 public:
-    virtual std::shared_ptr<DerivationGoal> makeDerivationGoal(
+    virtual std::pair<std::shared_ptr<DerivationGoal>, kj::Promise<void>> makeDerivationGoal(
         const StorePath & drvPath, const OutputsSpec & wantedOutputs, BuildMode buildMode = bmNormal
     ) = 0;
-    virtual std::shared_ptr<DerivationGoal> makeBasicDerivationGoal(
+    virtual std::pair<std::shared_ptr<DerivationGoal>, kj::Promise<void>> makeBasicDerivationGoal(
         const StorePath & drvPath,
         const BasicDerivation & drv,
         const OutputsSpec & wantedOutputs,
@@ -58,12 +41,14 @@ public:
     /**
      * @ref SubstitutionGoal "substitution goal"
      */
-    virtual std::shared_ptr<PathSubstitutionGoal> makePathSubstitutionGoal(
+    virtual std::pair<std::shared_ptr<PathSubstitutionGoal>, kj::Promise<void>>
+    makePathSubstitutionGoal(
         const StorePath & storePath,
         RepairFlag repair = NoRepair,
         std::optional<ContentAddress> ca = std::nullopt
     ) = 0;
-    virtual std::shared_ptr<DrvOutputSubstitutionGoal> makeDrvOutputSubstitutionGoal(
+    virtual std::pair<std::shared_ptr<DrvOutputSubstitutionGoal>, kj::Promise<void>>
+    makeDrvOutputSubstitutionGoal(
         const DrvOutput & id,
         RepairFlag repair = NoRepair,
         std::optional<ContentAddress> ca = std::nullopt
@@ -75,7 +60,8 @@ public:
      * It will be a `DerivationGoal` for a `DerivedPath::Built` or
      * a `SubstitutionGoal` for a `DerivedPath::Opaque`.
      */
-    virtual GoalPtr makeGoal(const DerivedPath & req, BuildMode buildMode = bmNormal) = 0;
+    virtual std::pair<GoalPtr, kj::Promise<void>>
+    makeGoal(const DerivedPath & req, BuildMode buildMode = bmNormal) = 0;
 };
 
 // elaborate hoax to let goals access factory methods while hiding them from the public
@@ -111,44 +97,27 @@ private:
      */
     WeakGoals awake;
 
-    /**
-     * Goals waiting for a build slot.
-     */
-    WeakGoals wantingToBuild;
-
-    /**
-     * Child processes currently running.
-     */
-    std::list<Child> children;
-
-    /**
-     * Number of build slots occupied.  This includes local builds but does not
-     * include substitutions or remote builds via the build hook.
-     */
-    unsigned int nrLocalBuilds;
-
-    /**
-     * Number of substitution slots occupied.
-     */
-    unsigned int nrSubstitutions;
-
+    template<typename G>
+    struct CachedGoal
+    {
+        std::weak_ptr<G> goal;
+        kj::Own<kj::ForkedPromise<void>> promise;
+        kj::Own<kj::PromiseFulfiller<void>> fulfiller;
+
+        CachedGoal()
+        {
+            auto pf = kj::newPromiseAndFulfiller<void>();
+            promise = kj::heap(pf.promise.fork());
+            fulfiller = std::move(pf.fulfiller);
+        }
+    };
     /**
      * Maps used to prevent multiple instantiations of a goal for the
      * same derivation / path.
      */
-    std::map<StorePath, std::weak_ptr<DerivationGoal>> derivationGoals;
-    std::map<StorePath, std::weak_ptr<PathSubstitutionGoal>> substitutionGoals;
-    std::map<DrvOutput, std::weak_ptr<DrvOutputSubstitutionGoal>> drvOutputSubstitutionGoals;
-
-    /**
-     * Goals sleeping for a few seconds (polling a lock).
-     */
-    WeakGoals waitingForAWhile;
-
-    /**
-     * Last time the goals in `waitingForAWhile` where woken up.
-     */
-    steady_time_point lastWokenUp;
+    std::map<StorePath, CachedGoal<DerivationGoal>> derivationGoals;
+    std::map<StorePath, CachedGoal<PathSubstitutionGoal>> substitutionGoals;
+    std::map<DrvOutput, CachedGoal<DrvOutputSubstitutionGoal>> drvOutputSubstitutionGoals;
 
     /**
      * Cache for pathContentsGood().
@@ -179,19 +148,7 @@ private:
     void goalFinished(GoalPtr goal, Goal::Finished & f);
     void handleWorkResult(GoalPtr goal, Goal::WorkResult how);
 
-    /**
-     * Put `goal` to sleep until a build slot becomes available (which
-     * might be right away).
-     */
-    void waitForBuildSlot(GoalPtr goal);
-
-    /**
-     * Wait for a few seconds and then retry this goal.  Used when
-     * waiting for a lock held by another process.  This kind of
-     * polling is inefficient, but POSIX doesn't really provide a way
-     * to wait for multiple locks in the main select() loop.
-     */
-    void waitForAWhile(GoalPtr goal);
+    kj::Own<kj::PromiseFulfiller<void>> childFinished;
 
     /**
      * Wake up a goal (i.e., there is something for it to do).
@@ -209,11 +166,14 @@ private:
     void removeGoal(GoalPtr goal);
 
     /**
-     * Registers a running child process.  `inBuildSlot` means that
-     * the process counts towards the jobs limit.
+     * Registers a running child process.
+     */
+    void childStarted(GoalPtr goal, kj::Promise<Result<Goal::WorkResult>> promise);
+
+    /**
+     * Unregisters a running child process.
      */
-    void childStarted(GoalPtr goal, const std::set<int> & fds,
-        bool inBuildSlot);
+    void childTerminated(GoalPtr goal);
 
     /**
       * Pass current stats counters to the logger for progress bar updates.
@@ -239,7 +199,13 @@ public:
     Store & store;
     Store & evalStore;
     kj::AsyncIoContext & aio;
+    AsyncSemaphore substitutions, localBuilds;
 
+private:
+    kj::TaskSet children;
+    std::exception_ptr childException;
+
+public:
     struct HookState {
         std::unique_ptr<HookInstance> instance;
 
@@ -277,21 +243,31 @@ public:
      * @ref DerivationGoal "derivation goal"
      */
 private:
-    std::shared_ptr<DerivationGoal> makeDerivationGoalCommon(
+    std::pair<std::shared_ptr<DerivationGoal>, kj::Promise<void>> makeDerivationGoalCommon(
         const StorePath & drvPath, const OutputsSpec & wantedOutputs,
         std::function<std::shared_ptr<DerivationGoal>()> mkDrvGoal);
-    std::shared_ptr<DerivationGoal> makeDerivationGoal(
+    std::pair<std::shared_ptr<DerivationGoal>, kj::Promise<void>> makeDerivationGoal(
         const StorePath & drvPath,
         const OutputsSpec & wantedOutputs, BuildMode buildMode = bmNormal) override;
-    std::shared_ptr<DerivationGoal> makeBasicDerivationGoal(
+    std::pair<std::shared_ptr<DerivationGoal>, kj::Promise<void>> makeBasicDerivationGoal(
         const StorePath & drvPath, const BasicDerivation & drv,
         const OutputsSpec & wantedOutputs, BuildMode buildMode = bmNormal) override;
 
     /**
      * @ref SubstitutionGoal "substitution goal"
      */
-    std::shared_ptr<PathSubstitutionGoal> makePathSubstitutionGoal(const StorePath & storePath, RepairFlag repair = NoRepair, std::optional<ContentAddress> ca = std::nullopt) override;
-    std::shared_ptr<DrvOutputSubstitutionGoal> makeDrvOutputSubstitutionGoal(const DrvOutput & id, RepairFlag repair = NoRepair, std::optional<ContentAddress> ca = std::nullopt) override;
+    std::pair<std::shared_ptr<PathSubstitutionGoal>, kj::Promise<void>>
+    makePathSubstitutionGoal(
+        const StorePath & storePath,
+        RepairFlag repair = NoRepair,
+        std::optional<ContentAddress> ca = std::nullopt
+    ) override;
+    std::pair<std::shared_ptr<DrvOutputSubstitutionGoal>, kj::Promise<void>>
+    makeDrvOutputSubstitutionGoal(
+        const DrvOutput & id,
+        RepairFlag repair = NoRepair,
+        std::optional<ContentAddress> ca = std::nullopt
+    ) override;
 
     /**
      * Make a goal corresponding to the `DerivedPath`.
@@ -299,18 +275,16 @@ private:
      * It will be a `DerivationGoal` for a `DerivedPath::Built` or
      * a `SubstitutionGoal` for a `DerivedPath::Opaque`.
      */
-    GoalPtr makeGoal(const DerivedPath & req, BuildMode buildMode = bmNormal) override;
+    std::pair<GoalPtr, kj::Promise<void>>
+    makeGoal(const DerivedPath & req, BuildMode buildMode = bmNormal) override;
 
 public:
-    /**
-     * Unregisters a running child process.
-     */
-    void childTerminated(Goal * goal);
+    using Targets = std::map<GoalPtr, kj::Promise<void>>;
 
     /**
      * Loop until the specified top-level goals have finished.
      */
-    Goals run(std::function<Goals (GoalFactory &)> req);
+    std::vector<GoalPtr> run(std::function<Targets (GoalFactory &)> req);
 
     /***
      * The exit status in case of failure.