fix(mdbx): report initialization failures

Notify the configured error callback for constructor-time storage failures so logger registration can surface the cause before the exception prevents a broken backend from being added.

Constraint: Keep MdbxLogger C++17-compatible and preserve constructor rethrow semantics

Confidence: high

Scope-risk: narrow

Not-tested: Full test suite; only mdbx_logger_test was run

Co-Authored-By: Claude Opus 4.8 <[email protected]>

Author: LimiNode

include/logit_cpp/logit/loggers/MdbxLogger.hpp

@@ -45,7 +45,7 @@ namespace logit {
             bool store_large_payloads_separately = true;///< Store large messages in `log_payloads`.
             MdbxPayloadCompression payload_compression = MdbxPayloadCompression::None; ///< Payload compression.
             int payload_compression_level = 6; ///< Compression level for gzip/zstd.
-            std::function<void(const std::string&)> on_error; ///< Optional callback invoked on write errors instead of stderr.
+            std::function<void(const std::string&)> on_error; ///< Optional callback invoked on initialization and write errors instead of stderr.
         };
 
         /// \struct SessionView
@@ -70,12 +70,20 @@ namespace logit {
 
         explicit MdbxLogger(const Config& config)
             : m_config(config) {
-            normalize_config();
-            validate_compression_config();
-            open_storage();
-            m_session_id = open_session();
-            if (m_config.async) {
-                m_worker = std::thread(&MdbxLogger::worker_loop, this);
+            try {
+                normalize_config();
+                validate_compression_config();
+                open_storage();
+                m_session_id = open_session();
+                if (m_config.async) {
+                    m_worker = std::thread(&MdbxLogger::worker_loop, this);
+                }
+            } catch (const std::exception& e) {
+                report_init_error(std::string("MdbxLogger initialization error: ") + e.what());
+                throw;
+            } catch (...) {
+                report_init_error("MdbxLogger initialization error");
+                throw;
             }
         }
 
@@ -623,12 +631,28 @@ namespace logit {
             db_config.no_subdir = true;
             db_config.sync_durable = true;
 
+            ensure_storage_parent(db_config);
             m_connection = mdbxc::Connection::create(db_config);
             m_sessions.reset(new SessionTable(m_connection, "log_sessions"));
             m_records.reset(new RecordTable(m_connection, "log_records_by_time"));
             m_payloads.reset(new PayloadTable(m_connection, "log_payloads"));
         }
 
+        void ensure_storage_parent(const mdbxc::Config& db_config) const {
+            if (!db_config.read_only && db_config.no_subdir) {
+                mdbxc::create_directories(db_config.pathname);
+            }
+        }
+
+        void report_init_error(const std::string& message) const noexcept {
+            if (m_config.on_error) {
+                try {
+                    m_config.on_error(message);
+                } catch (...) {
+                }
+            }
+        }
+
         uint64_t open_session() {
             std::lock_guard<std::mutex> db_lock(m_db_mutex);
             auto txn = m_connection->transaction(mdbxc::TransactionMode::WRITABLE);

tests/mdbx_logger_test.cpp

@@ -9,6 +9,9 @@
 #include <sstream>
 #include <string>
 #include <vector>
+#if __cplusplus >= 201703L
+#include <filesystem>
+#endif
 
 namespace {
 
@@ -23,11 +26,29 @@ std::string make_db_path(const std::string& suffix) {
     return os.str();
 }
 
+std::string make_nested_db_path(const std::string& suffix) {
+    std::ostringstream os;
+    os << logit::get_exec_dir()
+       << "/mdbx_logger_test_"
+       << suffix
+       << "_"
+       << LOGIT_CURRENT_TIMESTAMP_MS()
+       << "/nested/logs.mdbx";
+    return os.str();
+}
+
 void cleanup_db(const std::string& path) {
     std::remove(path.c_str());
     std::remove((path + "-lck").c_str());
 }
 
+void cleanup_path_tree(const std::string& path) {
+    cleanup_db(path);
+#if __cplusplus >= 201703L
+    std::filesystem::remove_all(std::filesystem::u8path(path).parent_path().parent_path());
+#endif
+}
+
 logit::LogRecord make_record(logit::LogLevel level, int64_t timestamp_ms, int line) {
     return logit::LogRecord(
         level,
@@ -223,6 +244,59 @@ void test_on_error_callback() {
     cleanup_db(path);
 }
 
+void test_nested_parent_directory_created() {
+    const std::string path = make_nested_db_path("nested");
+    cleanup_path_tree(path);
+
+    {
+        logit::MdbxLogger::Config config;
+        config.path = path;
+        config.async = false;
+
+        logit::MdbxLogger logger(config);
+        logger.log(make_record(logit::LogLevel::LOG_LVL_INFO, 6100, 51), "nested-ok");
+
+        auto records = logger.read_range(6100, 6101);
+        assert(records.size() == 1);
+        assert(records[0].message == "nested-ok");
+        logger.shutdown();
+    }
+
+    cleanup_path_tree(path);
+}
+
+void test_init_error_callback_and_rethrow() {
+    const std::string path = make_nested_db_path("init_error");
+    cleanup_path_tree(path);
+
+    std::vector<std::string> errors;
+    logit::MdbxLogger::Config config;
+    config.path = path;
+    config.async = false;
+    config.on_error = [&errors](const std::string& msg) {
+        errors.push_back(msg);
+    };
+
+    const std::string blocker = path.substr(0, path.find("/nested/logs.mdbx"));
+    FILE* blocker_file = std::fopen(blocker.c_str(), "wb");
+    assert(blocker_file != nullptr);
+    std::fclose(blocker_file);
+
+    bool thrown = false;
+    try {
+        logit::MdbxLogger logger(config);
+    } catch (const std::exception&) {
+        thrown = true;
+    }
+
+    assert(thrown);
+    assert(!errors.empty());
+    assert(errors[0].find("MdbxLogger initialization error") != std::string::npos);
+
+    std::remove(blocker.c_str());
+    cleanup_path_tree(path);
+}
+
 void test_read_range_empty_and_limits() {
     const std::string path = make_db_path("range");
     cleanup_db(path);
@@ -412,6 +486,8 @@ int main() {
 #endif
     test_counters_zero_for_sync_writes();
     test_on_error_callback();
+    test_nested_parent_directory_created();
+    test_init_error_callback_and_rethrow();
     test_read_range_empty_and_limits();
     test_read_recent();
     test_callback_sync();