Merge pull request #3760 from yandex/fix-database-ordinary-load-table-deadlock

Fix database ordinary load table deadlock

dbms/programs/server/Server.cpp

@@ -376,13 +376,21 @@ int Server::main(const std::vector<std::string> & /*args*/)
     format_schema_path.createDirectories();
 
     LOG_INFO(log, "Loading metadata.");
-    loadMetadataSystem(*global_context);
-    /// After attaching system databases we can initialize system log.
-    global_context->initializeSystemLogs();
-    /// After the system database is created, attach virtual system tables (in addition to query_log and part_log)
-    attachSystemTablesServer(*global_context->getDatabase("system"), has_zookeeper);
-    /// Then, load remaining databases
-    loadMetadata(*global_context);
+    try
+    {
+        loadMetadataSystem(*global_context);
+        /// After attaching system databases we can initialize system log.
+        global_context->initializeSystemLogs();
+        /// After the system database is created, attach virtual system tables (in addition to query_log and part_log)
+        attachSystemTablesServer(*global_context->getDatabase("system"), has_zookeeper);
+        /// Then, load remaining databases
+        loadMetadata(*global_context);
+    }
+    catch (...)
+    {
+        tryLogCurrentException(log, "Caught exception while loading metadata");
+        throw;
+    }
     LOG_DEBUG(log, "Loaded metadata.");
 
     global_context->setCurrentDatabase(default_database);

dbms/src/Databases/DatabaseOrdinary.cpp

@@ -21,6 +21,7 @@
 #include <IO/ReadBufferFromFile.h>
 #include <IO/WriteHelpers.h>
 #include <IO/ReadHelpers.h>
+#include <ext/scope_guard.h>
 
 
 namespace DB
@@ -164,9 +165,15 @@ void DatabaseOrdinary::loadTables(
     AtomicStopwatch watch;
     std::atomic<size_t> tables_processed {0};
     Poco::Event all_tables_processed;
+    ExceptionHandler exception_handler;
 
     auto task_function = [&](const String & table)
     {
+        SCOPE_EXIT(
+            if (++tables_processed == total_tables)
+                all_tables_processed.set()
+        );
+
         /// Messages, so that it's not boring to wait for the server to load for a long time.
         if ((tables_processed + 1) % PRINT_MESSAGE_EACH_N_TABLES == 0
             || watch.compareAndRestart(PRINT_MESSAGE_EACH_N_SECONDS))
@@ -176,14 +183,11 @@ void DatabaseOrdinary::loadTables(
         }
 
         loadTable(context, metadata_path, *this, name, data_path, table, has_force_restore_data_flag);
-
-        if (++tables_processed == total_tables)
-            all_tables_processed.set();
     };
 
     for (const auto & filename : file_names)
     {
-        auto task = std::bind(task_function, filename);
+        auto task = createExceptionHandledJob(std::bind(task_function, filename), exception_handler);
 
         if (thread_pool)
             thread_pool->schedule(task);
@@ -194,6 +198,8 @@ void DatabaseOrdinary::loadTables(
     if (thread_pool)
         all_tables_processed.wait();
 
+    exception_handler.throwIfException();
+
     /// After all tables was basically initialized, startup them.
     startupTables(thread_pool);
 }
@@ -207,12 +213,18 @@ void DatabaseOrdinary::startupTables(ThreadPool * thread_pool)
     std::atomic<size_t> tables_processed {0};
     size_t total_tables = tables.size();
     Poco::Event all_tables_processed;
+    ExceptionHandler exception_handler;
 
     if (!total_tables)
         return;
 
     auto task_function = [&](const StoragePtr & table)
     {
+        SCOPE_EXIT(
+            if (++tables_processed == total_tables)
+                all_tables_processed.set()
+        );
+
         if ((tables_processed + 1) % PRINT_MESSAGE_EACH_N_TABLES == 0
             || watch.compareAndRestart(PRINT_MESSAGE_EACH_N_SECONDS))
         {
@@ -221,14 +233,11 @@ void DatabaseOrdinary::startupTables(ThreadPool * thread_pool)
         }
 
         table->startup();
-
-        if (++tables_processed == total_tables)
-            all_tables_processed.set();
     };
 
     for (const auto & name_storage : tables)
     {
-        auto task = std::bind(task_function, name_storage.second);
+        auto task = createExceptionHandledJob(std::bind(task_function, name_storage.second), exception_handler);
 
         if (thread_pool)
             thread_pool->schedule(task);
@@ -238,6 +247,8 @@ void DatabaseOrdinary::startupTables(ThreadPool * thread_pool)
 
     if (thread_pool)
         all_tables_processed.wait();
+
+    exception_handler.throwIfException();
 }
 
 

libs/libcommon/include/common/ThreadPool.h

@@ -58,3 +58,17 @@ private:
     void worker();
 };
 
+
+/// Allows to save first catched exception in jobs and postpone its rethrow.
+class ExceptionHandler
+{
+public:
+    void setException(std::exception_ptr && exception);
+    void throwIfException();
+
+private:
+    std::exception_ptr first_exception;
+    std::mutex mutex;
+};
+
+ThreadPool::Job createExceptionHandledJob(ThreadPool::Job job, ExceptionHandler & handler);

libs/libcommon/src/ThreadPool.cpp

@@ -112,3 +112,34 @@ void ThreadPool::worker()
     }
 }
 
+
+void ExceptionHandler::setException(std::exception_ptr && exception)
+{
+    std::unique_lock<std::mutex> lock(mutex);
+    if (!first_exception)
+        first_exception = std::move(exception);
+}
+
+void ExceptionHandler::throwIfException()
+{
+    std::unique_lock<std::mutex> lock(mutex);
+    if (first_exception)
+        std::rethrow_exception(first_exception);
+}
+
+
+ThreadPool::Job createExceptionHandledJob(ThreadPool::Job job, ExceptionHandler & handler)
+{
+    return [job{std::move(job)}, &handler] ()
+    {
+        try
+        {
+            job();
+        }
+        catch (...)
+        {
+            handler.setException(std::current_exception());
+        }
+    };
+}
+