Attach to current thread in threadpool.

dbms/programs/server/TCPHandler.cpp

@@ -32,6 +32,7 @@
 #include <Compression/CompressionFactory.h>
 
 #include <Processors/Formats/LazyOutputFormat.h>
+#include <Interpreters/ThreadGroupThreadPoolCallbacks.h>
 
 #include "TCPHandler.h"
 
@@ -487,6 +488,7 @@ void TCPHandler::processOrdinaryQueryWithProcessors(size_t num_threads)
         CurrentMetrics::Increment query_thread_metric_increment{CurrentMetrics::QueryThread};
         setThreadName("QueryPipelineEx");
 
+        /// Manually attach and detach thread_group in order to collect metrics after pool.wait() call.
         if (thread_group)
             CurrentThread::attachTo(thread_group);
 
@@ -495,7 +497,7 @@ void TCPHandler::processOrdinaryQueryWithProcessors(size_t num_threads)
                 CurrentThread::detachQueryIfNotDetached();
         );
 
-        ThreadPool inner_pool(num_threads, thread_group);
+        ThreadPool inner_pool(num_threads, std::make_unique<ThreadGroupThreadPoolCallbacks>(thread_group));
 
         try
         {

dbms/src/Common/ThreadPool.cpp

@@ -17,14 +17,14 @@ namespace DB
 
 
 template <typename Thread>
-ThreadPoolImpl<Thread>::ThreadPoolImpl(size_t max_threads, DB::ThreadGroupStatusPtr thread_group)
-    : ThreadPoolImpl(max_threads, max_threads, max_threads, thread_group)
+ThreadPoolImpl<Thread>::ThreadPoolImpl(size_t max_threads, ThreadPoolCallbacksPtr callbacks_)
+    : ThreadPoolImpl(max_threads, max_threads, max_threads, std::move(callbacks_))
 {
 }
 
 template <typename Thread>
-ThreadPoolImpl<Thread>::ThreadPoolImpl(size_t max_threads, size_t max_free_threads, size_t queue_size, DB::ThreadGroupStatusPtr thread_group)
-    : max_threads(max_threads), max_free_threads(max_free_threads), queue_size(queue_size), thread_group(thread_group)
+ThreadPoolImpl<Thread>::ThreadPoolImpl(size_t max_threads, size_t max_free_threads, size_t queue_size, ThreadPoolCallbacksPtr callbacks_)
+    : max_threads(max_threads), max_free_threads(max_free_threads), queue_size(queue_size), callbacks(std::move(callbacks_))
 {
 }
 
@@ -142,12 +142,12 @@ size_t ThreadPoolImpl<Thread>::active() const
 template <typename Thread>
 void ThreadPoolImpl<Thread>::worker(typename std::list<Thread>::iterator thread_it)
 {
-    if (thread_group)
-        DB::CurrentThread::attachToIfDetached(thread_group);
+    if (callbacks)
+        callbacks->onThreadStart();
 
     SCOPE_EXIT(
-            if (thread_group)
-                DB::CurrentThread::detachQueryIfNotDetached()
+        if (callbacks)
+            callbacks->onThreadFinish();
     );
 
     while (true)

dbms/src/Common/ThreadPool.h

@@ -13,11 +13,18 @@
 #include <Poco/Event.h>
 #include <Common/ThreadStatus.h>
 
-namespace DB
+
+/// Callbacks which can be passed to ThreadPool.
+/// Are used to calculate metrics on thread.
+class ThreadPoolCallbacks
 {
-    class ThreadGroupStatus;
-    using ThreadGroupStatusPtr = std::shared_ptr<ThreadGroupStatus>;
-}
+public:
+    virtual void onThreadStart() = 0;
+    virtual void onThreadFinish() = 0;
+    virtual ~ThreadPoolCallbacks() = default;
+};
+
+using ThreadPoolCallbacksPtr = std::unique_ptr<ThreadPoolCallbacks>;
 
 /** Very simple thread pool similar to boost::threadpool.
   * Advantages:
@@ -36,10 +43,10 @@ public:
     using Job = std::function<void()>;
 
     /// Size is constant. Up to num_threads are created on demand and then run until shutdown.
-    explicit ThreadPoolImpl(size_t max_threads, DB::ThreadGroupStatusPtr thread_group = nullptr);
+    explicit ThreadPoolImpl(size_t max_threads, ThreadPoolCallbacksPtr callbacks_ = nullptr);
 
     /// queue_size - maximum number of running plus scheduled jobs. It can be greater than max_threads. Zero means unlimited.
-    ThreadPoolImpl(size_t max_threads, size_t max_free_threads, size_t queue_size, DB::ThreadGroupStatusPtr thread_group = nullptr);
+    ThreadPoolImpl(size_t max_threads, size_t max_free_threads, size_t queue_size, ThreadPoolCallbacksPtr callbacks_ = nullptr);
 
     /// Add new job. Locks until number of scheduled jobs is less than maximum or exception in one of threads was thrown.
     /// If an exception in some thread was thrown, method silently returns, and exception will be rethrown only on call to 'wait' function.
@@ -95,7 +102,7 @@ private:
     std::list<Thread> threads;
     std::exception_ptr first_exception;
 
-    DB::ThreadGroupStatusPtr thread_group;
+    ThreadPoolCallbacksPtr callbacks;
 
     template <typename ReturnType>
     ReturnType scheduleImpl(Job job, int priority, std::optional<uint64_t> wait_microseconds);

dbms/src/Interpreters/ThreadGroupThreadPoolCallbacks.cpp

@@ -0,0 +1,24 @@
+#include <Interpreters/ThreadGroupThreadPoolCallbacks.h>
+#include <Common/CurrentThread.h>
+
+namespace DB
+{
+
+ThreadGroupThreadPoolCallbacks::ThreadGroupThreadPoolCallbacks(ThreadGroupStatusPtr thread_group_)
+    : thread_group(std::move(thread_group_))
+{
+}
+
+void ThreadGroupThreadPoolCallbacks::onThreadStart()
+{
+    if (thread_group)
+        DB::CurrentThread::attachToIfDetached(thread_group);
+}
+
+void ThreadGroupThreadPoolCallbacks::onThreadFinish()
+{
+    if (thread_group)
+        DB::CurrentThread::detachQueryIfNotDetached();
+}
+
+}

dbms/src/Interpreters/ThreadGroupThreadPoolCallbacks.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include <Common/ThreadPool.h>
+
+namespace DB
+{
+
+class ThreadGroupStatus;
+using ThreadGroupStatusPtr = std::shared_ptr<ThreadGroupStatus>;
+
+/// Attach/detach thread from ThreadPool to specified thread_group.
+class ThreadGroupThreadPoolCallbacks : public ThreadPoolCallbacks
+{
+public:
+    explicit ThreadGroupThreadPoolCallbacks(ThreadGroupStatusPtr thread_group_);
+
+    void onThreadStart() override;
+    void onThreadFinish() override;
+
+private:
+    ThreadGroupStatusPtr thread_group;
+};
+
+}
+

dbms/src/Interpreters/executeQuery.cpp

@@ -27,7 +27,8 @@
 #include <Interpreters/QueryLog.h>
 #include <Interpreters/InterpreterSetQuery.h>
 #include <Interpreters/executeQuery.h>
-#include "DNSCacheUpdater.h"
+#include <Interpreters/DNSCacheUpdater.h>
+#include <Interpreters/ThreadGroupThreadPoolCallbacks.h>
 
 #include <Processors/Transforms/LimitsCheckingTransform.h>
 #include <Processors/Transforms/MaterializingTransform.h>
@@ -624,7 +625,8 @@ void executeQuery(
 
             auto executor = pipeline.execute();
             {
-                ThreadPool pool(context.getSettingsRef().max_threads, CurrentThread::getGroup());
+                ThreadPool pool(context.getSettingsRef().max_threads,
+                        std::make_unique<ThreadGroupThreadPoolCallbacks>(CurrentThread::getGroup()));
                 executor->execute(&pool);
             }
             pipeline.finalize();