Improved the Scheduler.

Adds nag message when async tasks are not properly shut down and adds a limiter for sync tasks. Once they use 35ms in a single tick, any remaining tasks are not executed until later ticks. Adds a method to report the pending tasks and one to report active worker threads

By: Raphfrk <raphfrk@gmail.com>

paper-api/src/main/java/org/bukkit/scheduler/BukkitScheduler.java

@@ -3,6 +3,7 @@ package org.bukkit.scheduler;
 import org.bukkit.plugin.Plugin;
 import java.util.concurrent.Callable;
 import java.util.concurrent.Future;
+import java.util.List;
 
 public interface BukkitScheduler {
 
@@ -22,7 +23,7 @@ public interface BukkitScheduler {
      * This task will be executed by the main server thread
      *
      * @param Plugin Plugin that owns the task
-     * @param Runnable Task to be executed 
+     * @param Runnable Task to be executed
      * @return int Task id number (-1 if scheduling failed)
      */
     public int scheduleSyncDelayedTask(Plugin plugin, Runnable task);
@@ -32,7 +33,7 @@ public interface BukkitScheduler {
      * This task will be executed by the main server thread
      *
      * @param Plugin Plugin that owns the task
-     * @param Runnable Task to be executed 
+     * @param Runnable Task to be executed
      * @param long Delay in server ticks before executing first repeat
      * @param long Period in server ticks of the task
      * @return int Task id number (-1 if scheduling failed)
@@ -106,27 +107,44 @@ public interface BukkitScheduler {
 
     /**
      * Check if the task currently running.
-     * 
+     *
      * A repeating task might not be running currently, but will be running in the future.
      * A task that has finished, and does not repeat, will not be running ever again.
-     * 
+     *
      * Explicitly, a task is running if there exists a thread for it, and that thread is alive.
-     * 
+     *
      * @param taskId The task to check.
-     * 
+     *
      * @return If the task is currently running.
      */
     public boolean isCurrentlyRunning(int taskId);
 
     /**
      * Check if the task queued to be run later.
-     * 
+     *
      * If a repeating task is currently running, it might not be queued now but could be in the future.
      * A task that is not queued, and not running, will not be queued again.
-     * 
+     *
      * @param taskId The task to check.
-     * 
+     *
      * @return If the task is queued to be run.
      */
     public boolean isQueued(int taskId);
+
+    /**
+     * Returns a list of all active workers.
+     *
+     * This list contains asynch tasks that are being executed by separate threads.
+     *
+     * @return Active workers
+     */
+    public List<BukkitWorker> getActiveWorkers();
+
+    /**
+     * Returns a list of all pending tasks.  The ordering of the tasks is not related to their order of execution.
+     *
+     * @return Active workers
+     */
+    public List<BukkitTask> getPendingTasks();
+
 }

paper-api/src/main/java/org/bukkit/scheduler/BukkitTask.java

@@ -0,0 +1,31 @@
+package org.bukkit.scheduler;
+
+import org.bukkit.plugin.Plugin;
+
+/**
+ * Represents a task being executed by the scheduler
+ */
+
+public interface BukkitTask {
+
+    /**
+     * Returns the taskId for the task
+     *
+     * @return Task id number
+     */
+    public int getTaskId();
+
+    /**
+     * Returns the Plugin that owns this task
+     *
+     * @return The Plugin that owns the task
+     */
+    public Plugin getOwner();
+
+    /**
+     * Returns true if the Task is a sync task
+     *
+     * @return true if the task is run by main thread
+     */
+    public boolean isSync();
+}

paper-api/src/main/java/org/bukkit/scheduler/BukkitWorker.java

@@ -0,0 +1,35 @@
+package org.bukkit.scheduler;
+
+import org.bukkit.plugin.Plugin;
+
+/**
+ * Represents a worker thread for the scheduler.  This gives information about
+ * the Thread object for the task, owner of the task and the taskId.
+ *
+ * Workers are used to execute async tasks.
+ */
+
+public interface BukkitWorker {
+
+    /**
+     * Returns the taskId for the task being executed by this worker
+     *
+     * @return Task id number
+     */
+    public int getTaskId();
+
+    /**
+     * Returns the Plugin that owns this task
+     *
+     * @return The Plugin that owns the task
+     */
+    public Plugin getOwner();
+
+    /**
+     * Returns the thread for the worker
+     *
+     * @return The Thread object for the worker
+     */
+    public Thread getThread();
+
+}