allow implicit initialization

programs/benchmark/Benchmark.cpp

@@ -560,8 +560,6 @@ int mainEntryClickHouseBenchmark(int argc, char ** argv)
             return 1;
         }
 
-        GlobalThreadPool::initialize();
-
         print_stacktrace = options.count("stacktrace");
 
         UseSSL use_ssl;

programs/client/Client.cpp

@@ -439,9 +439,6 @@ private:
         registerFunctions();
         registerAggregateFunctions();
 
-        // Needed for parallel parsing.
-        GlobalThreadPool::initialize();
-
         /// Batch mode is enabled if one of the following is true:
         /// - -e (--query) command line option is present.
         ///   The value of the option is used as the text of query (or of multiple queries).

programs/local/LocalServer.cpp

@@ -147,8 +147,6 @@ try
         return Application::EXIT_OK;
     }
 
-    GlobalThreadPool::initialize();
-
     shared_context = Context::createShared();
     context = std::make_unique<Context>(Context::createGlobal(shared_context.get()));
     context->makeGlobalContext();

programs/obfuscator/Obfuscator.cpp

@@ -1040,9 +1040,6 @@ try
         return 0;
     }
 
-    // Needed for parallel parsing.
-    GlobalThreadPool::initialize();
-
     UInt64 seed = sipHash64(options["seed"].as<std::string>());
 
     std::string structure = options["structure"].as<std::string>();

programs/server/config.xml

@@ -136,7 +136,6 @@
       -->
     <max_server_memory_usage>0</max_server_memory_usage>
 
-    <!-- Maximum thread pool size -->
     <!-- Maximum number of threads in the Global thread pool.
     This will default to a maximum of 10000 threads if not specified.
     This setting will be useful in scenarios where there are a large number

src/Common/ThreadPool.cpp

@@ -269,8 +269,7 @@ std::unique_ptr<GlobalThreadPool> GlobalThreadPool::the_instance;
 
 void GlobalThreadPool::initialize(size_t max_threads)
 {
-    // There should be an assert, but we can't add it because of the unit tests...
+    assert(!the_instance);
-    // assert(!the_instance);
 
     the_instance.reset(new GlobalThreadPool(max_threads,
         1000 /*max_free_threads*/, 10000 /*max_queue_size*/,
@@ -281,8 +280,9 @@ GlobalThreadPool & GlobalThreadPool::instance()
 {
     if (!the_instance)
     {
-        throw DB::Exception(DB::ErrorCodes::LOGICAL_ERROR,
+        // Allow implicit initialization. This is needed for old code that is
-            "The global thread pool is not initalized");
+        // impractical to redo now, especially Arcadia users and unit tests.
+        initialize();
     }
 
     return *the_instance;

src/Common/tests/gtest_thread_pool_global_full.cpp

@@ -13,8 +13,6 @@
 
 TEST(ThreadPool, GlobalFull1)
 {
-    GlobalThreadPool::initialize();
-
     GlobalThreadPool & global_pool = GlobalThreadPool::instance();
 
     static constexpr size_t capacity = 5;
@@ -51,8 +49,6 @@ TEST(ThreadPool, GlobalFull1)
 
 TEST(ThreadPool, GlobalFull2)
 {
-    GlobalThreadPool::initialize();
-
     GlobalThreadPool & global_pool = GlobalThreadPool::instance();
 
     static constexpr size_t capacity = 5;