added leader follower thread pool

source/core/utils/leader_follower_thread_pool.cpp

@@ -0,0 +1,102 @@
+#include "matador/utils/leader_follower_thread_pool.hpp"
+
+#include <algorithm>
+
+namespace matador::utils {
+
+leader_follower_thread_pool::~leader_follower_thread_pool()
+{
+  shutdown();
+}
+
+void leader_follower_thread_pool::start()
+{
+  is_running_ = true;
+  for (std::size_t i = 0; i < num_threads_; ++i) {
+    threads_.emplace_back([this] { execute(); });
+  }
+}
+
+void leader_follower_thread_pool::stop()
+{
+  is_running_ = false;
+}
+
+void leader_follower_thread_pool::promote_new_leader()
+{
+  std::lock_guard<std::mutex> l(mutex_);
+
+  if (leader_ != std::this_thread::get_id()) {
+    return;
+  }
+
+  leader_ = null_id;
+
+  signal_ready_ = true;
+  condition_synchronizer_.notify_one();
+}
+
+std::size_t leader_follower_thread_pool::size() const
+{
+  return threads_.size();
+}
+
+void leader_follower_thread_pool::shutdown()
+{
+  {
+    const std::lock_guard<std::mutex> l(mutex_);
+//    if (!is_running_) {
+//      return;
+//    }
+    stop();
+    signal_shutdown_ = true;
+    condition_synchronizer_.notify_all();
+  }
+
+  std::for_each(threads_.begin(), threads_.end(), [](thread_vector_t::reference item) {
+    if (item.joinable()) {
+      item.join();
+    }
+  });
+}
+
+std::thread::id leader_follower_thread_pool::leader() {
+  const std::lock_guard<std::mutex> l(mutex_);
+  return leader_;
+}
+
+std::size_t leader_follower_thread_pool::num_follower() const {
+  return follower_;
+}
+
+bool leader_follower_thread_pool::is_running() const
+{
+  return is_running_;
+}
+
+void leader_follower_thread_pool::execute() {
+  std::unique_lock<std::mutex> l(mutex_);
+  while (is_running_) {
+    while (leader_ != null_id) {
+//      log_.info("thread <%d> waiting for synchronizer (leader %d)",
+//                acquire_thread_index(std::this_thread::get_id()),
+//                acquire_thread_index(leader_));
+      condition_synchronizer_.wait(l, [this]() { return signal_ready_ || signal_shutdown_; });
+      signal_ready_ = false;
+      if (!is_running_) {
+        return;
+      }
+    }
+
+//    log_.info("new leader <%d> (thread <%d> is now follower)",acquire_thread_index(std::this_thread::get_id()) , acquire_thread_index(leader_));
+    leader_ = std::this_thread::get_id();
+
+    l.unlock();
+
+    join_();
+
+//    log_.info("thread <%d> finished work", acquire_thread_index(std::this_thread::get_id()));
+    l.lock();
+  }
+}
+}