WL#3337 (Event scheduler new architecture)

This patch makes the relationship between Event_scheduler and Event_queue
unidirectional from the former to the latter.




The change is that the conditional on which the scheduler sleeped has been
moved to the Event_queue and the latter does not call anymore
Event_scheduler::queue_changed(), which in turn has be removed.


sql/event_queue.cc:
  Remove dependency of Event_queue on Event_scheduler but not vice versa.
  Event_scheduler polls whether there is time to execute an event.
  
  Removed notify_observers() as the way of calling has changed.
  Added Event_queue::cond_wait() similar to Event_scheduler::cond_wait().
sql/event_queue.h:
  init_queue() does not need anymore Event_scheduler object because
  the relationship is now one-way. Event_scheduler knows about Event_queue
  but not vice versa.
  
  get_top_execution_if_time() does by itself the waiting instead of
  returning abstime. This simplifies the code in Event_scheduler::run()
  get_top_execution_if_time() returns only if job_data != NULL or if
  the scheduler thread was killed.
  
  notify_observers() is no more used and therefore removed.
  
  Added Event_queue::cond_wait() because now there is waiting on a
  conditional variable in Event_queue too (like in Event_scheduler for
  ::stop()).
sql/event_scheduler.cc:
  Change the relationship between Event_scheduler & Event_queue.
  Event_queue does not know anymore about Event_scheduler. When
  the scheduler calls get_top_element_if_time() it may fall asleep
  on a conditional of Event_queue, if either the queue is empty or
  it's still not time for activation. When the method returns it
  will return a non-null address, namely an object to be executed.
  If the return value is NULL, the thread was killed by a call to
  Event_scheduler::stop() (we assert this).
sql/event_scheduler.h:
  Remove queue_changed() as it is obsoleted by making the relationship
  between Event_scheduler and Event_queue one-way, from the former to the
  latter. Event_queue now does not know about Event_scheduler.
  
  get_state() is changed to is_running(). The state enum should be private,
  as it is not needed to be seen from outside anymore.
sql/events.cc:
  Event_queue does not need anymore a pointer to Event_scheduler.

1 files changed, 12 insertions, 21 deletions

diff --git a/sql/event_scheduler.h b/sql/event_scheduler.h
index 18a805eb6f6..fc41e345dfd 100644
--- a/sql/event_scheduler.h
+++ b/sql/event_scheduler.h
@@ -34,14 +34,6 @@ public:
   Event_scheduler():state(UNINITIALIZED){}
   ~Event_scheduler(){}
 
-  enum enum_state
-  {
-    UNINITIALIZED = 0,
-    INITIALIZED,
-    RUNNING,
-    STOPPING
-  };
-
   /* State changing methods follow */
 
   bool
@@ -70,12 +62,8 @@ public:
   deinit_mutexes();
 
   /* Information retrieving methods follow */
-
-  enum enum_state
-  get_state();
-
-  void
-  queue_changed();
+  bool
+  is_running();
 
   bool
   dump_internal_status(THD *thd);
@@ -84,6 +72,7 @@ private:
   uint
   workers_count();
 
+
   /* helper functions */
   bool
   execute_top(THD *thd, Event_job_data *job_data);
@@ -101,16 +90,18 @@ private:
 
   pthread_mutex_t LOCK_scheduler_state;
 
+  enum enum_state
+  {
+    UNINITIALIZED = 0,
+    INITIALIZED,
+    RUNNING,
+    STOPPING
+  };
+
   /* This is the current status of the life-cycle of the scheduler. */
   enum enum_state state;
 
-  /*
-    Holds the thread id of the executor thread or 0 if the scheduler is not
-    running. It is used by ::shutdown() to know which thread to kill with
-    kill_one_thread(). The latter wake ups a thread if it is waiting on a
-    conditional variable and sets thd->killed to non-zero.
-  */
-  ulong thread_id;
+  THD *scheduler_thd;
 
   pthread_cond_t COND_state;