source tree service: Ensure the Git cache exists

Similarly to just-mr, each SourceTree RPC must ensure that the Git
cache folder exists and the Git cache repository is initialized
before using it.

While there, fix missing shared locks on the Git cache root.

(cherry-picked from 82340791f4362a3a92ea1dfa9ff111c1258be19f)

2 files changed, 90 insertions, 8 deletions

diff --git a/src/buildtool/serve_api/serve_service/source_tree.cpp b/src/buildtool/serve_api/serve_service/source_tree.cpp
index 9fb2dae4..2272cac9 100644
--- a/src/buildtool/serve_api/serve_service/source_tree.cpp
+++ b/src/buildtool/serve_api/serve_service/source_tree.cpp
@@ -97,6 +97,24 @@ auto SymlinksResolveToPragmaSpecial(
 
 }  // namespace
 
+auto SourceTreeService::EnsureGitCacheRoot()
+    -> expected<std::monostate, std::string> {
+    // make sure the git root directory is properly initialized
+    if (not FileSystemManager::CreateDirectory(
+            native_context_->storage_config->GitRoot())) {
+        return unexpected{
+            fmt::format("Could not create Git cache root {}",
+                        native_context_->storage_config->GitRoot().string())};
+    }
+    if (not GitRepo::InitAndOpen(native_context_->storage_config->GitRoot(),
+                                 true)) {
+        return unexpected{
+            fmt::format("Could not initialize Git cache repository {}",
+                        native_context_->storage_config->GitRoot().string())};
+    }
+    return std::monostate{};
+}
+
 auto SourceTreeService::GetSubtreeFromCommit(
     std::filesystem::path const& repo_path,
     std::string const& commit,
@@ -200,6 +218,13 @@ auto SourceTreeService::ServeCommitTree(
     ::grpc::ServerContext* /* context */,
     const ::justbuild::just_serve::ServeCommitTreeRequest* request,
     ServeCommitTreeResponse* response) -> ::grpc::Status {
+    // ensure Git cache exists
+    if (auto done = EnsureGitCacheRoot(); not done) {
+        logger_->Emit(LogLevel::Error, std::move(done).error());
+        response->set_status(ServeCommitTreeResponse::INTERNAL_ERROR);
+        return ::grpc::Status::OK;
+    }
+    // get lock for Git cache
     auto repo_lock = RepositoryGarbageCollector::SharedLock(
         *native_context_->storage_config);
     if (not repo_lock) {
@@ -800,6 +825,13 @@ auto SourceTreeService::ServeArchiveTree(
     ::grpc::ServerContext* /* context */,
     const ::justbuild::just_serve::ServeArchiveTreeRequest* request,
     ServeArchiveTreeResponse* response) -> ::grpc::Status {
+    // ensure Git cache exists
+    if (auto done = EnsureGitCacheRoot(); not done) {
+        logger_->Emit(LogLevel::Error, std::move(done).error());
+        response->set_status(ServeArchiveTreeResponse::INTERNAL_ERROR);
+        return ::grpc::Status::OK;
+    }
+    // get gc lock for Git cache
     auto repo_lock = RepositoryGarbageCollector::SharedLock(
         *native_context_->storage_config);
     if (not repo_lock) {
@@ -1002,14 +1034,6 @@ auto SourceTreeService::DistdirImportToGit(
         content_list,
     bool sync_tree,
     ServeDistdirTreeResponse* response) -> ::grpc::Status {
-    auto repo_lock = RepositoryGarbageCollector::SharedLock(
-        *native_context_->storage_config);
-    if (not repo_lock) {
-        logger_->Emit(LogLevel::Error, "Could not acquire repo gc SharedLock");
-        response->set_status(ServeDistdirTreeResponse::INTERNAL_ERROR);
-        return ::grpc::Status::OK;
-    }
-
     // create tmp directory for the distdir
     auto distdir_tmp_dir =
         native_context_->storage_config->CreateTypedTmpDir("distdir");
@@ -1092,6 +1116,20 @@ auto SourceTreeService::ServeDistdirTree(
     ::grpc::ServerContext* /* context */,
     const ::justbuild::just_serve::ServeDistdirTreeRequest* request,
     ServeDistdirTreeResponse* response) -> ::grpc::Status {
+    // ensure Git cache exists
+    if (auto done = EnsureGitCacheRoot(); not done) {
+        logger_->Emit(LogLevel::Error, std::move(done).error());
+        response->set_status(ServeDistdirTreeResponse::INTERNAL_ERROR);
+        return ::grpc::Status::OK;
+    }
+    // get gc lock for Git cache
+    auto repo_lock = RepositoryGarbageCollector::SharedLock(
+        *native_context_->storage_config);
+    if (not repo_lock) {
+        logger_->Emit(LogLevel::Error, "Could not acquire repo gc SharedLock");
+        response->set_status(ServeDistdirTreeResponse::INTERNAL_ERROR);
+        return ::grpc::Status::OK;
+    }
     // acquire lock for native CAS
     auto lock = GarbageCollector::SharedLock(*native_context_->storage_config);
     if (not lock) {
@@ -1339,6 +1377,13 @@ auto SourceTreeService::ServeContent(
     ServeContentResponse* response) -> ::grpc::Status {
     auto const& content{request->content()};
 
+    // ensure Git cache exists
+    if (auto done = EnsureGitCacheRoot(); not done) {
+        logger_->Emit(LogLevel::Error, std::move(done).error());
+        response->set_status(ServeContentResponse::INTERNAL_ERROR);
+        return ::grpc::Status::OK;
+    }
+
     // acquire locks
     auto repo_lock = RepositoryGarbageCollector::SharedLock(
         *native_context_->storage_config);
@@ -1441,6 +1486,13 @@ auto SourceTreeService::ServeTree(
     ServeTreeResponse* response) -> ::grpc::Status {
     auto const& tree_id{request->tree()};
 
+    // ensure Git cache exists
+    if (auto done = EnsureGitCacheRoot(); not done) {
+        logger_->Emit(LogLevel::Error, std::move(done).error());
+        response->set_status(ServeTreeResponse::INTERNAL_ERROR);
+        return ::grpc::Status::OK;
+    }
+
     // acquire locks
     auto repo_lock = RepositoryGarbageCollector::SharedLock(
         *native_context_->storage_config);
@@ -1542,6 +1594,14 @@ auto SourceTreeService::CheckRootTree(
     const ::justbuild::just_serve::CheckRootTreeRequest* request,
     CheckRootTreeResponse* response) -> ::grpc::Status {
     auto const& tree_id{request->tree()};
+
+    // ensure Git cache exists
+    if (auto done = EnsureGitCacheRoot(); not done) {
+        logger_->Emit(LogLevel::Error, std::move(done).error());
+        response->set_status(CheckRootTreeResponse::INTERNAL_ERROR);
+        return ::grpc::Status::OK;
+    }
+
     // acquire locks
     auto repo_lock = RepositoryGarbageCollector::SharedLock(
         *native_context_->storage_config);
@@ -1662,7 +1722,23 @@ auto SourceTreeService::GetRemoteTree(
     ::grpc::ServerContext* /* context */,
     const ::justbuild::just_serve::GetRemoteTreeRequest* request,
     GetRemoteTreeResponse* response) -> ::grpc::Status {
+
+    // ensure Git cache exists
+    if (auto done = EnsureGitCacheRoot(); not done) {
+        logger_->Emit(LogLevel::Error, std::move(done).error());
+        response->set_status(GetRemoteTreeResponse::INTERNAL_ERROR);
+        return ::grpc::Status::OK;
+    }
+
     // acquire locks
+    auto repo_lock = RepositoryGarbageCollector::SharedLock(
+        *native_context_->storage_config);
+    if (not repo_lock) {
+        logger_->Emit(LogLevel::Error, "Could not acquire repo gc SharedLock");
+        response->set_status(GetRemoteTreeResponse::INTERNAL_ERROR);
+        return ::grpc::Status::OK;
+    }
+
     auto lock = GarbageCollector::SharedLock(*native_context_->storage_config);
     if (not lock) {
         logger_->Emit(LogLevel::Error, "Could not acquire gc SharedLock");
diff --git a/src/buildtool/serve_api/serve_service/source_tree.hpp b/src/buildtool/serve_api/serve_service/source_tree.hpp
index 24ef59c2..2989d65a 100644
--- a/src/buildtool/serve_api/serve_service/source_tree.hpp
+++ b/src/buildtool/serve_api/serve_service/source_tree.hpp
@@ -23,6 +23,7 @@
 #include <type_traits>
 #include <unordered_map>
 #include <utility>
+#include <variant>
 #include <vector>
 
 #include "gsl/gsl"
@@ -142,6 +143,11 @@ class SourceTreeService final
     // symlinks resolver map
     ResolveSymlinksMap resolve_symlinks_map_{CreateResolveSymlinksMap()};
 
+    /// \brief Ensure that the Git cache repository exists.
+    /// \returns Error message on failure.
+    [[nodiscard]] auto EnsureGitCacheRoot()
+        -> expected<std::monostate, std::string>;
+
     /// \brief Check if commit exists and tries to get the subtree if found.
     /// \returns The subtree hash on success or an unexpected error (fatal or
     /// commit was not found).