From 4c225a66545a2e7baf4b29738441b2957415b76f Mon Sep 17 00:00:00 2001
From: Shai Levi <levishai.g@gmail.com>
Date: Thu, 1 Nov 2018 05:02:14 -0700
Subject: [PATCH] Ability to run periodic operation in logger thread

---
 include/spdlog/details/thread_pool.h | 31 ++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/include/spdlog/details/thread_pool.h b/include/spdlog/details/thread_pool.h
index 0c716c3b..41ca0e9c 100644
--- a/include/spdlog/details/thread_pool.h
+++ b/include/spdlog/details/thread_pool.h
@@ -104,14 +104,23 @@ struct async_msg
     }
 };
 
+class async_logging_periodic_worker
+{
+public:
+    virtual std::chrono::milliseconds get_interval() = 0;
+    virtual void do_periodic_work(std::thread::id thread_id) = 0;
+};
+
 class thread_pool
 {
 public:
     using item_type = async_msg;
     using q_type = details::mpmc_blocking_queue<item_type>;
+    using periodic_worker_ptr_type = std::shared_ptr<async_logging_periodic_worker>;
 
-    thread_pool(size_t q_max_items, size_t threads_n)
+    thread_pool(size_t q_max_items, size_t threads_n, periodic_worker_ptr_type periodic_worker = nullptr)
         : q_(q_max_items)
+        , periodic_worker_(periodic_worker)
     {
         // std::cout << "thread_pool()  q_size_bytes: " << q_size_bytes <<
         // "\tthreads_n: " << threads_n << std::endl;
@@ -167,6 +176,7 @@ public:
 
 private:
     q_type q_;
+    periodic_worker_ptr_type periodic_worker_;
 
     std::vector<std::thread> threads_;
 
@@ -192,8 +202,25 @@ private:
     // was received)
     bool process_next_msg_()
     {
+        using std::chrono::time_point_cast;
+        using std::chrono::milliseconds;
+
+        milliseconds max_time_to_wait_on_queue = milliseconds(10000);
+        milliseconds time_to_wait_on_queue = max_time_to_wait_on_queue;
+        if (periodic_worker_) {
+            static thread_local std::chrono::time_point<std::chrono::system_clock> last_periodic_operation(std::chrono::system_clock::now());
+
+            milliseconds passed_from_last_operation = time_point_cast<milliseconds>(std::chrono::system_clock::now()) -
+                time_point_cast<milliseconds>(last_periodic_operation);
+            if (passed_from_last_operation > periodic_worker_->get_interval()) {
+                periodic_worker_->do_periodic_work(std::this_thread::get_id());
+                last_periodic_operation = std::chrono::system_clock::now();
+            }
+            milliseconds time_left_till_operation = periodic_worker_->get_interval() - passed_from_last_operation;
+            time_to_wait_on_queue = std::min(time_left_till_operation, max_time_to_wait_on_queue);
+        }
         async_msg incoming_async_msg;
-        bool dequeued = q_.dequeue_for(incoming_async_msg, std::chrono::seconds(10));
+        bool dequeued = q_.dequeue_for(incoming_async_msg, time_to_wait_on_queue);
         if (!dequeued)
         {
             return true;