Add new Git execution api that can interact with any remote

...irrespective of the used protocol.

This api is useful in enabling just-mr and the SourceTree service
of just serve to interact seamlessly with any remote-execution
endpoint.

3 files changed, 348 insertions, 0 deletions

diff --git a/src/buildtool/execution_api/serve/TARGETS b/src/buildtool/execution_api/serve/TARGETS
index 087c32a7..d54b01d9 100644
--- a/src/buildtool/execution_api/serve/TARGETS
+++ b/src/buildtool/execution_api/serve/TARGETS
@@ -16,4 +16,31 @@
     , ["src/buildtool/storage", "fs_utils"]
     ]
   }
+, "mr_git_api":
+  { "type": ["@", "rules", "CC", "library"]
+  , "name": ["mr_git_api"]
+  , "hdrs": ["mr_git_api.hpp"]
+  , "srcs": ["mr_git_api.cpp"]
+  , "deps":
+    [ ["@", "gsl", "", "gsl"]
+    , ["src/buildtool/common", "common"]
+    , ["src/buildtool/common", "config"]
+    , ["src/buildtool/crypto", "hash_function"]
+    , ["src/buildtool/execution_api/common", "artifact_blob_container"]
+    , ["src/buildtool/execution_api/common", "common"]
+    , ["src/buildtool/execution_engine/dag", "dag"]
+    , ["src/buildtool/storage", "config"]
+    , ["src/buildtool/storage", "storage"]
+    ]
+  , "stage": ["src", "buildtool", "execution_api", "serve"]
+  , "private-deps":
+    [ "utils"
+    , ["src/buildtool/execution_api/bazel_msg", "bazel_msg_factory"]
+    , ["src/buildtool/execution_api/git", "git"]
+    , ["src/buildtool/file_system", "object_type"]
+    , ["src/buildtool/logging", "log_level"]
+    , ["src/buildtool/logging", "logging"]
+    , ["src/utils/cpp", "expected"]
+    ]
+  }
 }
diff --git a/src/buildtool/execution_api/serve/mr_git_api.cpp b/src/buildtool/execution_api/serve/mr_git_api.cpp
new file mode 100644
index 00000000..1e433fff
--- /dev/null
+++ b/src/buildtool/execution_api/serve/mr_git_api.cpp
@@ -0,0 +1,178 @@
+// Copyright 2024 Huawei Cloud Computing Technology Co., Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "src/buildtool/execution_api/serve/mr_git_api.hpp"
+
+#include <utility>
+
+#include "src/buildtool/execution_api/bazel_msg/bazel_msg_factory.hpp"
+#include "src/buildtool/execution_api/git/git_api.hpp"
+#include "src/buildtool/execution_api/serve/utils.hpp"
+#include "src/buildtool/file_system/object_type.hpp"
+#include "src/buildtool/logging/log_level.hpp"
+#include "src/buildtool/logging/logger.hpp"
+#include "src/utils/cpp/expected.hpp"
+
+MRGitApi::MRGitApi(
+    gsl::not_null<RepositoryConfig const*> const& repo_config,
+    gsl::not_null<StorageConfig const*> const& native_storage_config,
+    StorageConfig const* compatible_storage_config,
+    Storage const* compatible_storage,
+    IExecutionApi const* compatible_local_api) noexcept
+    : repo_config_{repo_config},
+      native_storage_config_{native_storage_config},
+      compat_storage_config_{compatible_storage_config},
+      compat_storage_{compatible_storage},
+      compat_local_api_{compatible_local_api} {}
+
+auto MRGitApi::RetrieveToCas(
+    std::vector<Artifact::ObjectInfo> const& artifacts_info,
+    IExecutionApi const& api) const noexcept -> bool {
+    // Return immediately if target CAS is this CAS
+    if (this == &api) {
+        return true;
+    }
+
+    // in native mode: dispatch to regular GitApi
+    if (compat_storage_config_ == nullptr) {
+        GitApi const git_api{repo_config_};
+        return git_api.RetrieveToCas(artifacts_info, api);
+    }
+
+    // in compatible mode: set up needed callbacks for caching digest mappings
+    auto read_rehashed =
+        [native_sc = native_storage_config_,
+         compat_sc = compat_storage_config_](ArtifactDigest const& digest)
+        -> expected<std::optional<Artifact::ObjectInfo>, std::string> {
+        return MRApiUtils::ReadRehashedDigest(
+            digest, *native_sc, *compat_sc, /*from_git=*/true);
+    };
+    auto store_rehashed =
+        [native_sc = native_storage_config_,
+         compat_sc = compat_storage_config_](
+            ArtifactDigest const& source_digest,
+            ArtifactDigest const& target_digest,
+            ObjectType obj_type) -> std::optional<std::string> {
+        return MRApiUtils::StoreRehashedDigest(source_digest,
+                                               target_digest,
+                                               obj_type,
+                                               *native_sc,
+                                               *compat_sc,
+                                               /*from_git=*/true);
+    };
+
+    // collect the native blobs and rehash them as compatible to be able to
+    // check what is missing in the other api
+    std::vector<Artifact::ObjectInfo> compat_artifacts;
+    compat_artifacts.reserve(artifacts_info.size());
+    for (auto const& native_obj : artifacts_info) {
+        // check if we know already the compatible digest
+        auto cached_obj = read_rehashed(native_obj.digest);
+        if (not cached_obj) {
+            Logger::Log(
+                LogLevel::Error, "MRGitApi: {}", std::move(cached_obj).error());
+            return false;
+        }
+        if (*cached_obj) {
+            // add object to the vector of compatible artifacts
+            compat_artifacts.emplace_back(std::move(cached_obj)->value());
+        }
+        else {
+            // process object; trees need to be handled appropriately
+            if (IsTreeObject(native_obj.type)) {
+                // set up all the callbacks needed
+                auto read_git = [repo_config = repo_config_](
+                                    ArtifactDigest const& digest,
+                                    ObjectType /*type*/)
+                    -> std::optional<
+                        std::variant<std::filesystem::path, std::string>> {
+                    return repo_config->ReadBlobFromGitCAS(digest.hash());
+                };
+                auto store_file =
+                    [cas = &compat_storage_->CAS()](
+                        std::variant<std::filesystem::path, std::string> const&
+                            data,
+                        bool is_exec) -> std::optional<ArtifactDigest> {
+                    if (not std::holds_alternative<std::string>(data)) {
+                        return std::nullopt;
+                    }
+                    return cas->StoreBlob(std::get<std::string>(data), is_exec);
+                };
+                BazelMsgFactory::TreeStoreFunc store_dir =
+                    [cas = &compat_storage_->CAS()](std::string const& content)
+                    -> std::optional<ArtifactDigest> {
+                    return cas->StoreTree(content);
+                };
+                BazelMsgFactory::SymlinkStoreFunc store_symlink =
+                    [cas = &compat_storage_->CAS()](std::string const& content)
+                    -> std::optional<ArtifactDigest> {
+                    return cas->StoreBlob(content);
+                };
+                // get the directory digest
+                auto tree_digest =
+                    BazelMsgFactory::CreateDirectoryDigestFromGitTree(
+                        native_obj.digest,
+                        read_git,
+                        store_file,
+                        store_dir,
+                        store_symlink,
+                        read_rehashed,
+                        store_rehashed);
+                if (not tree_digest) {
+                    Logger::Log(LogLevel::Error,
+                                "MRGitApi: {}",
+                                std::move(tree_digest).error());
+                    return false;
+                }
+                // add object to the vector of compatible artifacts
+                compat_artifacts.emplace_back(
+                    Artifact::ObjectInfo{.digest = *std::move(tree_digest),
+                                         .type = ObjectType::Tree});
+            }
+            else {
+                // blobs are read from repo and added to compatible CAS
+                auto const blob_content =
+                    repo_config_->ReadBlobFromGitCAS(native_obj.digest.hash());
+                if (not blob_content) {
+                    Logger::Log(LogLevel::Error,
+                                "MRGitApi: failed reading Git entry {}",
+                                native_obj.digest.hash());
+                    return false;
+                }
+                auto blob_digest = compat_storage_->CAS().StoreBlob(
+                    *blob_content, IsExecutableObject(native_obj.type));
+                if (not blob_digest) {
+                    Logger::Log(LogLevel::Error,
+                                "MRGitApi: failed to rehash Git entry {}",
+                                native_obj.digest.hash());
+                    return false;
+                }
+                // cache the digest association
+                if (auto error_msg = store_rehashed(
+                        native_obj.digest, *blob_digest, native_obj.type)) {
+                    Logger::Log(
+                        LogLevel::Error, "MRGitApi: {}", *std::move(error_msg));
+                    return false;
+                }
+                // add object to the vector of compatible artifacts
+                compat_artifacts.emplace_back(
+                    Artifact::ObjectInfo{.digest = *std::move(blob_digest),
+                                         .type = native_obj.type});
+            }
+        }
+    }
+    // now that we have gathered all the compatible object infos, simply pass
+    // them to a local api that can interact with the remote
+    return compat_local_api_->RetrieveToCas(compat_artifacts, api);
+}
diff --git a/src/buildtool/execution_api/serve/mr_git_api.hpp b/src/buildtool/execution_api/serve/mr_git_api.hpp
new file mode 100644
index 00000000..74864218
--- /dev/null
+++ b/src/buildtool/execution_api/serve/mr_git_api.hpp
@@ -0,0 +1,143 @@
+// Copyright 2024 Huawei Cloud Computing Technology Co., Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef INCLUDED_SRC_BUILDTOOL_EXECUTION_API_SERVE_MR_GIT_API_HPP
+#define INCLUDED_SRC_BUILDTOOL_EXECUTION_API_SERVE_MR_GIT_API_HPP
+
+#include <filesystem>
+#include <map>
+#include <optional>
+#include <string>
+#include <vector>
+
+#include "gsl/gsl"
+#include "src/buildtool/common/artifact.hpp"
+#include "src/buildtool/common/artifact_digest.hpp"
+#include "src/buildtool/common/repository_config.hpp"
+#include "src/buildtool/crypto/hash_function.hpp"
+#include "src/buildtool/execution_api/common/artifact_blob_container.hpp"
+#include "src/buildtool/execution_api/common/execution_api.hpp"
+#include "src/buildtool/execution_engine/dag/dag.hpp"
+#include "src/buildtool/storage/config.hpp"
+#include "src/buildtool/storage/storage.hpp"
+
+/// \brief Multi-repo-specific implementation of the abstract Execution API.
+/// Handles interaction between the Git CAS and another api, irrespective of the
+/// remote-execution protocol used. This instance cannot create actions or store
+/// anything to the Git CAS, but has access to local storages.
+class MRGitApi final : public IExecutionApi {
+  public:
+    MRGitApi(gsl::not_null<RepositoryConfig const*> const& repo_config,
+             gsl::not_null<StorageConfig const*> const& native_storage_config,
+             StorageConfig const* compatible_storage_config = nullptr,
+             Storage const* compatible_storage = nullptr,
+             IExecutionApi const* compatible_local_api = nullptr) noexcept;
+
+    /// \brief Not supported.
+    [[nodiscard]] auto CreateAction(
+        ArtifactDigest const& /*root_digest*/,
+        std::vector<std::string> const& /*command*/,
+        std::string const& /*cwd*/,
+        std::vector<std::string> const& /*output_files*/,
+        std::vector<std::string> const& /*output_dirs*/,
+        std::map<std::string, std::string> const& /*env_vars*/,
+        std::map<std::string, std::string> const& /*properties*/) const noexcept
+        -> IExecutionAction::Ptr final {
+        // Execution not supported.
+        return nullptr;
+    }
+
+    /// \brief Not supported.
+    // NOLINTNEXTLINE(google-default-arguments)
+    [[nodiscard]] auto RetrieveToPaths(
+        std::vector<Artifact::ObjectInfo> const& /*artifacts_info*/,
+        std::vector<std::filesystem::path> const& /*output_paths*/,
+        IExecutionApi const* /*alternative*/ = nullptr) const noexcept
+        -> bool final {
+        // Retrieval to paths not suported.
+        return false;
+    }
+
+    /// \brief Not supported.
+    [[nodiscard]] auto RetrieveToFds(
+        std::vector<Artifact::ObjectInfo> const& /*artifacts_info*/,
+        std::vector<int> const& /*fds*/,
+        bool /*raw_tree*/) const noexcept -> bool final {
+        // Retrieval to file descriptors not supported.
+        return false;
+    }
+
+    /// \brief Passes artifacts from Git CAS to specified (remote) api. In
+    /// compatible mode, it must rehash the native digests to be able to upload
+    /// to a compatible remote. Expects native digests.
+    /// \note Caller is responsible for passing vectors with artifacts of the
+    /// same digest type.
+    [[nodiscard]] auto RetrieveToCas(
+        std::vector<Artifact::ObjectInfo> const& artifacts_info,
+        IExecutionApi const& api) const noexcept -> bool final;
+
+    /// \brief Not supported.
+    [[nodiscard]] auto RetrieveToMemory(
+        Artifact::ObjectInfo const& /*artifact_info*/) const noexcept
+        -> std::optional<std::string> final {
+        // Retrieval to memory not supported.
+        return std::nullopt;
+    }
+
+    /// \brief Not supported.
+    // NOLINTNEXTLINE(google-default-arguments)
+    [[nodiscard]] auto Upload(ArtifactBlobContainer&& /*blobs*/,
+                              bool /*skip_find_missing*/ = false) const noexcept
+        -> bool final {
+        // Upload not suppoorted.
+        return false;
+    }
+
+    /// \brief Not supported.
+    [[nodiscard]] auto UploadTree(
+        std::vector<DependencyGraph::NamedArtifactNodePtr> const& /*artifacts*/)
+        const noexcept -> std::optional<ArtifactDigest> final {
+        // Upload tree not supported.
+        return std::nullopt;
+    }
+
+    /// \brief Not supported.
+    [[nodiscard]] auto IsAvailable(
+        ArtifactDigest const& /*digest*/) const noexcept -> bool final {
+        // Not supported.
+        return false;
+    }
+
+    /// \brief Not implemented.
+    [[nodiscard]] auto IsAvailable(
+        std::vector<ArtifactDigest> const& /*digests*/) const noexcept
+        -> std::vector<ArtifactDigest> final {
+        // Not supported.
+        return {};
+    }
+
+  private:
+    gsl::not_null<const RepositoryConfig*> repo_config_;
+
+    // retain references to needed storages and configs
+    gsl::not_null<StorageConfig const*> native_storage_config_;
+    StorageConfig const* compat_storage_config_;
+    Storage const* compat_storage_;
+
+    // an api accessing compatible storage, used purely to communicate with a
+    // compatible remote; only instantiated if in compatible mode
+    IExecutionApi const* compat_local_api_;
+};
+
+#endif  // INCLUDED_SRC_BUILDTOOL_EXECUTION_API_SERVE_MR_GIT_API_HPP