Scheduler - removed templatization

Summary: Because it was unnecessary and also implemented wrong (if someone tried using a Schduler with something other then std::mutex, it would not compile). We can trivially add this if it ever becomes necessary.

Reviewers: buda, mislav.bradac

Reviewed By: buda, mislav.bradac

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D666

src/database/graph_db.hpp

@@ -115,9 +115,9 @@ class GraphDb {
   Snapshooter snapshooter_;
 
   // Schedulers
-  Scheduler<std::mutex> gc_scheduler_;
+  Scheduler gc_scheduler_;
-  Scheduler<std::mutex> snapshot_creator_;
+  Scheduler snapshot_creator_;
   // Periodically wakes up and hints to transactions that are running for a long
   // time to stop their execution.
-  Scheduler<std::mutex> transaction_killer_;
+  Scheduler transaction_killer_;
 };

src/utils/executioner.hpp

@@ -84,6 +84,6 @@ class Executioner {
   int64_t count_{0};
   std::mutex execute_mutex_;
   std::mutex update_mutex_;
-  Scheduler<std::mutex> scheduler_;
+  Scheduler scheduler_;
   std::vector<std::pair<int, std::function<void()>>> id_job_pairs_;
 };

src/utils/scheduler.hpp

@@ -13,7 +13,6 @@
  * mutex class TMutex which is used to synchronize threads. Default template
  * value is std::mutex.
  */
-template <typename TMutex = std::mutex>
 class Scheduler {
  public:
   Scheduler() {}
@@ -74,7 +73,7 @@ class Scheduler {
   /**
    * Mutex used to synchronize threads using condition variable.
    */
-  TMutex mutex_;
+  std::mutex mutex_;
 
   /**
    * Condition variable is used to stop waiting until the end of the

tests/unit/scheduler.cpp

@@ -15,7 +15,7 @@ TEST(Scheduler, TestFunctionExecuting) {
     EXPECT_EQ(y.load(), x.load());
     x++;
   }};
-  Scheduler<> scheduler;
+  Scheduler scheduler;
   scheduler.Run(std::chrono::seconds(1), func);
 
   std::this_thread::sleep_for(std::chrono::milliseconds(980));