Merge pull request #9240 from edolstra/libgit2

Introduce libgit2

Makefile.config.in

@@ -8,15 +8,19 @@ CXX = @CXX@
 CXXFLAGS = @CXXFLAGS@
 CXXLTO = @CXXLTO@
 EDITLINE_LIBS = @EDITLINE_LIBS@
+ENABLE_BUILD = @ENABLE_BUILD@
 ENABLE_S3 = @ENABLE_S3@
+ENABLE_TESTS = @ENABLE_TESTS@
 GTEST_LIBS = @GTEST_LIBS@
 HAVE_LIBCPUID = @HAVE_LIBCPUID@
 HAVE_SECCOMP = @HAVE_SECCOMP@
 HOST_OS = @host_os@
+INSTALL_UNIT_TESTS = @INSTALL_UNIT_TESTS@
 LDFLAGS = @LDFLAGS@
 LIBARCHIVE_LIBS = @LIBARCHIVE_LIBS@
 LIBBROTLI_LIBS = @LIBBROTLI_LIBS@
 LIBCURL_LIBS = @LIBCURL_LIBS@
+LIBGIT2_LIBS = @LIBGIT2_LIBS@
 LIBSECCOMP_LIBS = @LIBSECCOMP_LIBS@
 LOWDOWN_LIBS = @LOWDOWN_LIBS@
 OPENSSL_LIBS = @OPENSSL_LIBS@
@@ -37,6 +41,7 @@ docdir = @docdir@
 embedded_sandbox_shell = @embedded_sandbox_shell@
 exec_prefix = @exec_prefix@
 includedir = @includedir@
+internal_api_docs = @internal_api_docs@
 libdir = @libdir@
 libexecdir = @libexecdir@
 localstatedir = @localstatedir@
@@ -48,7 +53,3 @@ sandbox_shell = @sandbox_shell@
 storedir = @storedir@
 sysconfdir = @sysconfdir@
 system = @system@
-ENABLE_BUILD = @ENABLE_BUILD@
-ENABLE_TESTS = @ENABLE_TESTS@
-INSTALL_UNIT_TESTS = @INSTALL_UNIT_TESTS@
-internal_api_docs = @internal_api_docs@

configure.ac

@@ -347,9 +347,15 @@ AC_ARG_ENABLE(doc-gen, AS_HELP_STRING([--disable-doc-gen],[disable documentation
   doc_generate=$enableval, doc_generate=yes)
 AC_SUBST(doc_generate)
 
+
 # Look for lowdown library.
 PKG_CHECK_MODULES([LOWDOWN], [lowdown >= 0.9.0], [CXXFLAGS="$LOWDOWN_CFLAGS $CXXFLAGS"])
 
+
+# Look for libgit2.
+PKG_CHECK_MODULES([LIBGIT2], [libgit2])
+
+
 # Setuid installations.
 AC_CHECK_FUNCS([setresuid setreuid lchown])
 

flake.nix

@@ -7,8 +7,9 @@
   inputs.nixpkgs-regression.url = "github:NixOS/nixpkgs/215d4d0fd80ca5163643b03a33fde804a29cc1e2";
   inputs.lowdown-src = { url = "github:kristapsdz/lowdown"; flake = false; };
   inputs.flake-compat = { url = "github:edolstra/flake-compat"; flake = false; };
+  inputs.libgit2 = { url = "github:libgit2/libgit2"; flake = false; };
 
-  outputs = { self, nixpkgs, nixpkgs-regression, lowdown-src, flake-compat }:
+  outputs = { self, nixpkgs, nixpkgs-regression, lowdown-src, flake-compat, libgit2 }:
 
     let
       inherit (nixpkgs) lib;
@@ -198,6 +199,11 @@
             bzip2 xz brotli editline
             openssl sqlite
             libarchive
+            (pkgs.libgit2.overrideAttrs (attrs: {
+              src = libgit2;
+              version = libgit2.lastModifiedDate;
+              cmakeFlags = (attrs.cmakeFlags or []) ++ ["-DUSE_SSH=exec"];
+            }))
             boost
             lowdown-nix
             libsodium

src/libfetchers/cache.cc

@@ -20,6 +20,9 @@ create table if not exists Cache (
 );
 )sql";
 
+// FIXME: we should periodically purge/nuke this cache to prevent it
+// from growing too big.
+
 struct CacheImpl : Cache
 {
     struct State
@@ -48,6 +51,60 @@ struct CacheImpl : Cache
             "select info, path, immutable, timestamp from Cache where input = ?");
     }
 
+    void upsert(
+        const Attrs & inAttrs,
+        const Attrs & infoAttrs) override
+    {
+        _state.lock()->add.use()
+            (attrsToJSON(inAttrs).dump())
+            (attrsToJSON(infoAttrs).dump())
+            ("") // no path
+            (false)
+            (time(0)).exec();
+    }
+
+    std::optional<Attrs> lookup(const Attrs & inAttrs) override
+    {
+        if (auto res = lookupExpired(inAttrs))
+            return std::move(res->infoAttrs);
+        return {};
+    }
+
+    std::optional<Attrs> lookupWithTTL(const Attrs & inAttrs) override
+    {
+        if (auto res = lookupExpired(inAttrs)) {
+            if (!res->expired)
+                return std::move(res->infoAttrs);
+            debug("ignoring expired cache entry '%s'",
+                attrsToJSON(inAttrs).dump());
+        }
+        return {};
+    }
+
+    std::optional<Result2> lookupExpired(const Attrs & inAttrs) override
+    {
+        auto state(_state.lock());
+
+        auto inAttrsJSON = attrsToJSON(inAttrs).dump();
+
+        auto stmt(state->lookup.use()(inAttrsJSON));
+        if (!stmt.next()) {
+            debug("did not find cache entry for '%s'", inAttrsJSON);
+            return {};
+        }
+
+        auto infoJSON = stmt.getStr(0);
+        auto locked = stmt.getInt(2) != 0;
+        auto timestamp = stmt.getInt(3);
+
+        debug("using cache entry '%s' -> '%s'", inAttrsJSON, infoJSON);
+
+        return Result2 {
+            .expired = !locked && (settings.tarballTtl.get() == 0 || timestamp + settings.tarballTtl < time(0)),
+            .infoAttrs = jsonToAttrs(nlohmann::json::parse(infoJSON)),
+        };
+    }
+
     void add(
         ref<Store> store,
         const Attrs & inAttrs,

src/libfetchers/cache.hh

@@ -6,10 +6,49 @@
 
 namespace nix::fetchers {
 
+/**
+ * A cache for arbitrary `Attrs` -> `Attrs` mappings with a timestamp
+ * for expiration.
+ */
 struct Cache
 {
     virtual ~Cache() { }
 
+    /**
+     * Add a value to the cache. The cache is an arbitrary mapping of
+     * Attrs to Attrs.
+     */
+    virtual void upsert(
+        const Attrs & inAttrs,
+        const Attrs & infoAttrs) = 0;
+
+    /**
+     * Look up a key with infinite TTL.
+     */
+    virtual std::optional<Attrs> lookup(
+        const Attrs & inAttrs) = 0;
+
+    /**
+     * Look up a key. Return nothing if its TTL has exceeded
+     * `settings.tarballTTL`.
+     */
+    virtual std::optional<Attrs> lookupWithTTL(
+        const Attrs & inAttrs) = 0;
+
+    struct Result2
+    {
+        bool expired = false;
+        Attrs infoAttrs;
+    };
+
+    /**
+     * Look up a key. Return a bool denoting whether its TTL has
+     * exceeded `settings.tarballTTL`.
+     */
+    virtual std::optional<Result2> lookupExpired(
+        const Attrs & inAttrs) = 0;
+
+    /* Old cache for things that have a store path. */
     virtual void add(
         ref<Store> store,
         const Attrs & inAttrs,

src/libfetchers/fetchers.cc

@@ -1,5 +1,6 @@
 #include "fetchers.hh"
 #include "store-api.hh"
+#include "input-accessor.hh"
 
 #include <nlohmann/json.hpp>
 
@@ -219,6 +220,16 @@ std::pair<StorePath, Input> Input::fetch(ref<Store> store) const
     return {std::move(storePath), input};
 }
 
+std::pair<ref<InputAccessor>, Input> Input::getAccessor(ref<Store> store) const
+{
+    try {
+        return scheme->getAccessor(store, *this);
+    } catch (Error & e) {
+        e.addTrace({}, "while fetching the input '%s'", to_string());
+        throw;
+    }
+}
+
 Input Input::applyOverrides(
     std::optional<std::string> ref,
     std::optional<Hash> rev) const
@@ -355,6 +366,18 @@ void InputScheme::clone(const Input & input, const Path & destDir) const
     throw Error("do not know how to clone input '%s'", input.to_string());
 }
 
+std::pair<StorePath, Input> InputScheme::fetch(ref<Store> store, const Input & input)
+{
+    auto [accessor, input2] = getAccessor(store, input);
+    auto storePath = accessor->root().fetchToStore(store, input2.getName());
+    return {storePath, input2};
+}
+
+std::pair<ref<InputAccessor>, Input> InputScheme::getAccessor(ref<Store> store, const Input & input) const
+{
+    throw UnimplementedError("InputScheme must implement fetch() or getAccessor()");
+}
+
 std::optional<ExperimentalFeature> InputScheme::experimentalFeature() const
 {
     return {};

src/libfetchers/fetchers.hh

@@ -10,7 +10,7 @@
 #include <memory>
 #include <nlohmann/json_fwd.hpp>
 
-namespace nix { class Store; class StorePath; }
+namespace nix { class Store; class StorePath; struct InputAccessor; }
 
 namespace nix::fetchers {
 
@@ -83,6 +83,8 @@ public:
      */
     std::pair<StorePath, Input> fetch(ref<Store> store) const;
 
+    std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store) const;
+
     Input applyOverrides(
         std::optional<std::string> ref,
         std::optional<Hash> rev) const;
@@ -167,7 +169,9 @@ struct InputScheme
         std::string_view contents,
         std::optional<std::string> commitMsg) const;
 
-    virtual std::pair<StorePath, Input> fetch(ref<Store> store, const Input & input) = 0;
+    virtual std::pair<StorePath, Input> fetch(ref<Store> store, const Input & input);
+
+    virtual std::pair<ref<InputAccessor>, Input> getAccessor(ref<Store> store, const Input & input) const;
 
     /**
      * Is this `InputScheme` part of an experimental feature?