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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  
19  package org.apache.hadoop.hbase.procedure2.store;
20  
21  import java.io.IOException;
22  
23  import org.apache.hadoop.hbase.classification.InterfaceAudience;
24  import org.apache.hadoop.hbase.classification.InterfaceStability;
25  import org.apache.hadoop.hbase.ProcedureInfo;
26  import org.apache.hadoop.hbase.procedure2.Procedure;
27  
28  /**
29   * The ProcedureStore is used by the executor to persist the state of each procedure execution.
30   * This allows to resume the execution of pending/in-progress procedures in case
31   * of machine failure or service shutdown.
32   */
33  @InterfaceAudience.Private
34  @InterfaceStability.Evolving
35  public interface ProcedureStore {
36    /**
37     * Store listener interface.
38     * The main process should register a listener and respond to the store events.
39     */
40    public interface ProcedureStoreListener {
41      /**
42       * triggered when the store sync is completed.
43       */
44      void postSync();
45  
46      /**
47       * triggered when the store is not able to write out data.
48       * the main process should abort.
49       */
50      void abortProcess();
51    }
52  
53    /**
54     * An Iterator over a collection of Procedure
55     */
56    public interface ProcedureIterator {
57      /**
58       * Reset the Iterator by seeking to the beginning of the list.
59       */
60      void reset();
61  
62      /**
63       * Returns true if the iterator has more elements.
64       * (In other words, returns true if next() would return a Procedure
65       * rather than throwing an exception.)
66       * @return true if the iterator has more procedures
67       */
68      boolean hasNext();
69  
70      /**
71       * @return true if the iterator next element is a completed procedure.
72       */
73      boolean isNextCompleted();
74  
75      /**
76       * Skip the next procedure
77       */
78      void skipNext();
79  
80      /**
81       * Returns the next procedure in the iteration.
82       * @throws IOException if there was an error fetching/deserializing the procedure
83       * @return the next procedure in the iteration.
84       */
85      Procedure nextAsProcedure() throws IOException;
86  
87      /**
88       * @return the next procedure in the iteration as ProcedureInfo.
89       */
90      ProcedureInfo nextAsProcedureInfo();
91    }
92  
93    /**
94     * Interface passed to the ProcedureStore.load() method to handle the store-load events.
95     */
96    public interface ProcedureLoader {
97      /**
98       * Called by ProcedureStore.load() to notify about the maximum proc-id in the store.
99       * @param maxProcId the highest proc-id in the store
100      */
101     void setMaxProcId(long maxProcId);
102 
103     /**
104      * Called by the ProcedureStore.load() every time a set of procedures are ready to be executed.
105      * The ProcedureIterator passed to the method, has the procedure sorted in replay-order.
106      * @param procIter iterator over the procedures ready to be added to the executor.
107      */
108     void load(ProcedureIterator procIter) throws IOException;
109 
110     /**
111      * Called by the ProcedureStore.load() in case we have procedures not-ready to be added to
112      * the executor, which probably means they are corrupted since some information/link is missing.
113      * @param procIter iterator over the procedures not ready to be added to the executor, corrupted
114      */
115     void handleCorrupted(ProcedureIterator procIter) throws IOException;
116   }
117 
118   /**
119    * Add the listener to the notification list.
120    * @param listener The AssignmentListener to register
121    */
122   void registerListener(ProcedureStoreListener listener);
123 
124   /**
125    * Remove the listener from the notification list.
126    * @param listener The AssignmentListener to unregister
127    * @return true if the listner was in the list and it was removed, otherwise false.
128    */
129   boolean unregisterListener(ProcedureStoreListener listener);
130 
131   /**
132    * Start/Open the procedure store
133    * @param numThreads
134    */
135   void start(int numThreads) throws IOException;
136 
137   /**
138    * Stop/Close the procedure store
139    * @param abort true if the stop is an abort
140    */
141   void stop(boolean abort);
142 
143   /**
144    * @return true if the store is running, otherwise false.
145    */
146   boolean isRunning();
147 
148   /**
149    * @return the number of threads/slots passed to start()
150    */
151   int getNumThreads();
152 
153   /**
154    * Acquire the lease for the procedure store.
155    */
156   void recoverLease() throws IOException;
157 
158   /**
159    * Load the Procedures in the store.
160    * @param loader the ProcedureLoader that will handle the store-load events
161    */
162   void load(ProcedureLoader loader) throws IOException;
163 
164   /**
165    * When a procedure is submitted to the executor insert(proc, null) will be called.
166    * 'proc' has a 'RUNNABLE' state and the initial information required to start up.
167    *
168    * When a procedure is executed and it returns children insert(proc, subprocs) will be called.
169    * 'proc' has a 'WAITING' state and an update state.
170    * 'subprocs' are the children in 'RUNNABLE' state with the initial information.
171    *
172    * @param proc the procedure to serialize and write to the store.
173    * @param subprocs the newly created child of the proc.
174    */
175   void insert(Procedure proc, Procedure[] subprocs);
176 
177   /**
178    * The specified procedure was executed,
179    * and the new state should be written to the store.
180    * @param proc the procedure to serialize and write to the store.
181    */
182   void update(Procedure proc);
183 
184   /**
185    * The specified procId was removed from the executor,
186    * due to completion, abort or failure.
187    * The store implementor should remove all the information about the specified procId.
188    * @param procId the ID of the procedure to remove.
189    */
190   void delete(long procId);
191 }