Expose a bunch of things in the Legacy SSH Store for Hydra

(cherry picked from commit 5eade48252)

src/libstore/legacy-ssh-store.hh

@@ -6,6 +6,7 @@
 #include "ssh.hh"
 #include "callback.hh"
 #include "pool.hh"
+#include "serve-protocol.hh"
 
 namespace nix {
 
@@ -24,6 +25,11 @@ struct LegacySSHStoreConfig : virtual CommonSSHStoreConfig
     const Setting<int> maxConnections{this, 1, "max-connections",
         "Maximum number of concurrent SSH connections."};
 
+    /**
+     * Hack for hydra
+     */
+    Strings extraSshArgs = {};
+
     const std::string name() override { return "SSH Store"; }
 
     static std::set<std::string> uriSchemes() { return {"ssh"}; }
@@ -60,11 +66,24 @@ struct LegacySSHStore : public virtual LegacySSHStoreConfig, public virtual Stor
     void queryPathInfoUncached(const StorePath & path,
         Callback<std::shared_ptr<const ValidPathInfo>> callback) noexcept override;
 
+    std::map<StorePath, UnkeyedValidPathInfo> queryPathInfosUncached(
+        const StorePathSet & paths);
+
     void addToStore(const ValidPathInfo & info, Source & source,
         RepairFlag repair, CheckSigsFlag checkSigs) override;
 
     void narFromPath(const StorePath & path, Sink & sink) override;
 
+    /**
+     * Hands over the connection temporarily as source to the given
+     * function. The function must not consume beyond the NAR; it can
+     * not just blindly try to always read more bytes until it is
+     * cut-off.
+     *
+     * This is exposed for sake of Hydra.
+     */
+    void narFromPath(const StorePath & path, std::function<void(Source &)> fun);
+
     std::optional<StorePath> queryPathFromHashPart(const std::string & hashPart) override
     { unsupported("queryPathFromHashPart"); }
 
@@ -93,6 +112,16 @@ public:
     BuildResult buildDerivation(const StorePath & drvPath, const BasicDerivation & drv,
         BuildMode buildMode) override;
 
+    /**
+     * Note, the returned function must only be called once, or we'll
+     * try to read from the connection twice.
+     *
+     * @todo Use C++23 `std::move_only_function`.
+     */
+    std::function<BuildResult()> buildDerivationAsync(
+        const StorePath & drvPath, const BasicDerivation & drv,
+        const ServeProto::BuildOptions & options);
+
     void buildPaths(const std::vector<DerivedPath> & drvPaths, BuildMode buildMode, std::shared_ptr<Store> evalStore) override;
 
     void ensurePath(const StorePath & path) override
@@ -119,10 +148,36 @@ public:
     StorePathSet queryValidPaths(const StorePathSet & paths,
         SubstituteFlag maybeSubstitute = NoSubstitute) override;
 
+    /**
+     * Custom variation that atomically creates temp locks on the remote
+     * side.
+     *
+     * This exists to prevent a race where the remote host
+     * garbage-collects paths that are already there. Optionally, ask
+     * the remote host to substitute missing paths.
+     */
+    StorePathSet queryValidPaths(const StorePathSet & paths,
+        bool lock,
+        SubstituteFlag maybeSubstitute = NoSubstitute);
+
+    /**
+     * Just exists because this is exactly what Hydra was doing, and we
+     * don't yet want an algorithmic change.
+     */
+    void addMultipleToStoreLegacy(Store & srcStore, const StorePathSet & paths);
+
     void connect() override;
 
     unsigned int getProtocol() override;
 
+    struct ConnectionStats {
+        size_t bytesReceived, bytesSent;
+    };
+
+    ConnectionStats getConnectionStats();
+
+    pid_t getConnectionPid();
+
     /**
      * The legacy ssh protocol doesn't support checking for trusted-user.
      * Try using ssh-ng:// instead if you want to know.