hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/ProcedureScheduler.java

   1 /**
   2  * Licensed to the Apache Software Foundation (ASF) under one
   3  * or more contributor license agreements.  See the NOTICE file
   4  * distributed with this work for additional information
   5  * regarding copyright ownership.  The ASF licenses this file
   6  * to you under the Apache License, Version 2.0 (the
   7  * "License"); you may not use this file except in compliance
   8  * with the License.  You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  */
  18 package org.apache.hadoop.hbase.procedure2;
  19
  20 import java.util.Iterator;
  21 import java.util.List;
  22 import java.util.concurrent.TimeUnit;
  23 import org.apache.yetus.audience.InterfaceAudience;
  24
  25 /**
  26  * Keep track of the runnable procedures
  27  */
  28 @InterfaceAudience.Private
  29 public interface ProcedureScheduler {
  30   /**
  31    * Start the scheduler
  32    */
  33   void start();
  34
  35   /**
  36    * Stop the scheduler
  37    */
  38   void stop();
  39
  40   /**
  41    * In case the class is blocking on poll() waiting for items to be added,
  42    * this method should awake poll() and poll() should return.
  43    */
  44   void signalAll();
  45
  46   /**
  47    * Inserts the specified element at the front of this queue.
  48    * @param proc the Procedure to add
  49    */
  50   void addFront(Procedure proc);
  51
  52   /**
  53    * Inserts the specified element at the front of this queue.
  54    * @param proc the Procedure to add
  55    * @param notify whether need to notify worker
  56    */
  57   void addFront(Procedure proc, boolean notify);
  58
  59   /**
  60    * Inserts all elements in the iterator at the front of this queue.
  61    */
  62   void addFront(Iterator<Procedure> procedureIterator);
  63
  64   /**
  65    * Inserts the specified element at the end of this queue.
  66    * @param proc the Procedure to add
  67    */
  68   void addBack(Procedure proc);
  69
  70   /**
  71    * Inserts the specified element at the end of this queue.
  72    * @param proc the Procedure to add
  73    * @param notify whether need to notify worker
  74    */
  75   void addBack(Procedure proc, boolean notify);
  76
  77   /**
  78    * The procedure can't run at the moment.
  79    * add it back to the queue, giving priority to someone else.
  80    * @param proc the Procedure to add back to the list
  81    */
  82   void yield(Procedure proc);
  83
  84   /**
  85    * The procedure in execution completed.
  86    * This can be implemented to perform cleanups.
  87    * @param proc the Procedure that completed the execution.
  88    */
  89   void completionCleanup(Procedure proc);
  90
  91   /**
  92    * @return true if there are procedures available to process, otherwise false.
  93    */
  94   boolean hasRunnables();
  95
  96   /**
  97    * Fetch one Procedure from the queue
  98    * @return the Procedure to execute, or null if nothing present.
  99    */
 100   Procedure poll();
 101
 102   /**
 103    * Fetch one Procedure from the queue
 104    * @param timeout how long to wait before giving up, in units of unit
 105    * @param unit a TimeUnit determining how to interpret the timeout parameter
 106    * @return the Procedure to execute, or null if nothing present.
 107    */
 108   Procedure poll(long timeout, TimeUnit unit);
 109
 110   /**
 111    * List lock queues.
 112    * @return the locks
 113    */
 114   List<LockedResource> getLocks();
 115
 116   /**
 117    * @return {@link LockedResource} for resource of specified type & name. null if resource is not
 118    *         locked.
 119    */
 120   LockedResource getLockResource(LockedResourceType resourceType, String resourceName);
 121
 122   /**
 123    * Returns the number of elements in this queue.
 124    * @return the number of elements in this queue.
 125    */
 126   int size();
 127
 128   /**
 129    * Clear current state of scheduler such that it is equivalent to newly created scheduler.
 130    * Used for testing failure and recovery. To emulate server crash/restart,
 131    * {@link ProcedureExecutor} resets its own state and calls clear() on scheduler.
 132    */
 133   void clear();
 134 }