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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  package org.apache.hadoop.hbase.procedure;
19  
20  import java.io.IOException;
21  import java.util.Collection;
22  import java.util.HashSet;
23  import java.util.List;
24  import java.util.Set;
25  import java.util.concurrent.ConcurrentMap;
26  import java.util.concurrent.ExecutorService;
27  import java.util.concurrent.Future;
28  import java.util.concurrent.RejectedExecutionException;
29  import java.util.concurrent.SynchronousQueue;
30  import java.util.concurrent.ThreadPoolExecutor;
31  import java.util.concurrent.TimeUnit;
32  
33  import org.apache.commons.logging.Log;
34  import org.apache.commons.logging.LogFactory;
35  import org.apache.hadoop.classification.InterfaceAudience;
36  import org.apache.hadoop.hbase.DaemonThreadFactory;
37  import org.apache.hadoop.hbase.errorhandling.ForeignException;
38  import org.apache.hadoop.hbase.errorhandling.ForeignExceptionDispatcher;
39  
40  import com.google.common.collect.MapMaker;
41  
42  /**
43   * This is the master side of a distributed complex procedure execution.
44   * <p>
45   * The {@link Procedure} is generic and subclassing or customization shouldn't be
46   * necessary -- any customization should happen just in {@link Subprocedure}s.
47   */
48  @InterfaceAudience.Private
49  public class ProcedureCoordinator {
50    private static final Log LOG = LogFactory.getLog(ProcedureCoordinator.class);
51  
52    final static long KEEP_ALIVE_MILLIS_DEFAULT = 5000;
53    final static long TIMEOUT_MILLIS_DEFAULT = 60000;
54    final static long WAKE_MILLIS_DEFAULT = 500;
55  
56    private final ProcedureCoordinatorRpcs rpcs;
57    private final ExecutorService pool;
58    private final long wakeTimeMillis;
59    private final long timeoutMillis;
60  
61    // Running procedure table.  Maps procedure name to running procedure reference
62    private final ConcurrentMap<String, Procedure> procedures =
63        new MapMaker().concurrencyLevel(4).weakValues().makeMap();
64  
65    /**
66     * Create and start a ProcedureCoordinator.
67     *
68     * The rpc object registers the ProcedureCoordinator and starts any threads in this
69     * constructor.
70     *
71     * @param rpcs
72     * @param pool Used for executing procedures.
73     */
74    public ProcedureCoordinator(ProcedureCoordinatorRpcs rpcs, ThreadPoolExecutor pool) {
75      this(rpcs, pool, TIMEOUT_MILLIS_DEFAULT, WAKE_MILLIS_DEFAULT);
76    }
77  
78    /**
79     * Create and start a ProcedureCoordinator.
80     *
81     * The rpc object registers the ProcedureCoordinator and starts any threads in
82     * this constructor.
83     *
84     * @param rpcs
85     * @param pool Used for executing procedures.
86     * @param timeoutMillis
87     */
88    public ProcedureCoordinator(ProcedureCoordinatorRpcs rpcs, ThreadPoolExecutor pool,
89        long timeoutMillis, long wakeTimeMillis) {
90      this.timeoutMillis = timeoutMillis;
91      this.wakeTimeMillis = wakeTimeMillis;
92      this.rpcs = rpcs;
93      this.pool = pool;
94      this.rpcs.start(this);
95    }
96  
97    /**
98     * Default thread pool for the procedure
99     *
100    * @param coordName
101    * @param opThreads the maximum number of threads to allow in the pool
102    */
103   public static ThreadPoolExecutor defaultPool(String coordName, int opThreads) {
104     return defaultPool(coordName, opThreads, KEEP_ALIVE_MILLIS_DEFAULT);
105   }
106 
107   /**
108    * Default thread pool for the procedure
109    *
110    * @param coordName
111    * @param opThreads the maximum number of threads to allow in the pool
112    * @param keepAliveMillis the maximum time (ms) that excess idle threads will wait for new tasks
113    */
114   public static ThreadPoolExecutor defaultPool(String coordName, int opThreads,
115       long keepAliveMillis) {
116     return new ThreadPoolExecutor(1, opThreads, keepAliveMillis, TimeUnit.MILLISECONDS,
117         new SynchronousQueue<Runnable>(),
118         new DaemonThreadFactory("(" + coordName + ")-proc-coordinator-pool"));
119   }
120 
121   /**
122    * Shutdown the thread pools and release rpc resources
123    * @throws IOException
124    */
125   public void close() throws IOException {
126     // have to use shutdown now to break any latch waiting
127     pool.shutdownNow();
128     rpcs.close();
129   }
130 
131   /**
132    * Submit an procedure to kick off its dependent subprocedures.
133    * @param proc Procedure to execute
134    * @return <tt>true</tt> if the procedure was started correctly, <tt>false</tt> if the
135    *         procedure or any subprocedures could not be started.  Failure could be due to
136    *         submitting a procedure multiple times (or one with the same name), or some sort
137    *         of IO problem.  On errors, the procedure's monitor holds a reference to the exception
138    *         that caused the failure.
139    */
140   boolean submitProcedure(Procedure proc) {
141     // if the submitted procedure was null, then we don't want to run it
142     if (proc == null) {
143       return false;
144     }
145     String procName = proc.getName();
146 
147     // make sure we aren't already running a procedure of that name
148     synchronized (procedures) {
149       Procedure oldProc = procedures.get(procName);
150       if (oldProc != null) {
151         // procedures are always eventually completed on both successful and failed execution
152         if (oldProc.completedLatch.getCount() != 0) {
153           LOG.warn("Procedure " + procName + " currently running.  Rejecting new request");
154           return false;
155         }
156         LOG.debug("Procedure " + procName + " was in running list but was completed.  Accepting new attempt.");
157         procedures.remove(procName);
158       }
159     }
160 
161     // kick off the procedure's execution in a separate thread
162     Future<Void> f = null;
163     try {
164       synchronized (procedures) {
165         this.procedures.put(procName, proc);
166         f = this.pool.submit(proc);
167       }
168       return true;
169     } catch (RejectedExecutionException e) {
170       LOG.warn("Procedure " + procName + " rejected by execution pool.  Propagating error and " +
171           "cancelling operation.", e);
172       // Remove the procedure from the list since is not started
173       this.procedures.remove(procName);
174       // the thread pool is full and we can't run the procedure
175       proc.receive(new ForeignException(procName, e));
176 
177       // cancel procedure proactively
178       if (f != null) {
179         f.cancel(true);
180       }
181     }
182     return false;
183   }
184 
185   /**
186    * The connection to the rest of the procedure group (members and coordinator) has been
187    * broken/lost/failed. This should fail any interested procedures, but not attempt to notify other
188    * members since we cannot reach them anymore.
189    * @param message description of the error
190    * @param cause the actual cause of the failure
191    */
192   void rpcConnectionFailure(final String message, final IOException cause) {
193     Collection<Procedure> toNotify = procedures.values();
194 
195     for (Procedure proc : toNotify) {
196       if (proc == null) {
197         continue;
198       }
199       // notify the elements, if they aren't null
200       proc.receive(new ForeignException(proc.getName(), cause));
201     }
202   }
203 
204   /**
205    * Abort the procedure with the given name
206    * @param procName name of the procedure to abort
207    * @param reason serialized information about the abort
208    */
209   public void abortProcedure(String procName, ForeignException reason) {
210     // if we know about the Procedure, notify it
211     synchronized(procedures) {
212       Procedure proc = procedures.get(procName);
213       if (proc == null) {
214         return;
215       }
216       proc.receive(reason);
217     }
218   }
219 
220   /**
221    * Exposed for hooking with unit tests.
222    * @param procName
223    * @param procArgs
224    * @param expectedMembers
225    * @return the newly created procedure
226    */
227   Procedure createProcedure(ForeignExceptionDispatcher fed, String procName, byte[] procArgs,
228       List<String> expectedMembers) {
229     // build the procedure
230     return new Procedure(this, fed, wakeTimeMillis, timeoutMillis,
231         procName, procArgs, expectedMembers);
232   }
233 
234   /**
235    * Kick off the named procedure
236    * @param procName name of the procedure to start
237    * @param procArgs arguments for the procedure
238    * @param expectedMembers expected members to start
239    * @return handle to the running procedure, if it was started correctly, <tt>null</tt> otherwise
240    * @throws RejectedExecutionException if there are no more available threads to run the procedure
241    */
242   public Procedure startProcedure(ForeignExceptionDispatcher fed, String procName, byte[] procArgs,
243       List<String> expectedMembers) throws RejectedExecutionException {
244     Procedure proc = createProcedure(fed, procName, procArgs, expectedMembers);
245     if (!this.submitProcedure(proc)) {
246       LOG.error("Failed to submit procedure '" + procName + "'");
247       return null;
248     }
249     return proc;
250   }
251 
252   /**
253    * Notification that the procedure had the specified member acquired its part of the barrier
254    * via {@link Subprocedure#acquireBarrier()}.
255    * @param procName name of the procedure that acquired
256    * @param member name of the member that acquired
257    */
258   void memberAcquiredBarrier(String procName, final String member) {
259     Procedure proc = procedures.get(procName);
260     if (proc == null) {
261       LOG.warn("Member '"+ member +"' is trying to acquire an unknown procedure '"+ procName +"'");
262       return;
263     }
264 
265     proc.barrierAcquiredByMember(member);
266   }
267 
268   /**
269    * Notification that the procedure had another member finished executing its in-barrier subproc
270    * via {@link Subprocedure#insideBarrier()}.
271    * @param procName name of the subprocedure that finished
272    * @param member name of the member that executed and released its barrier
273    */
274   void memberFinishedBarrier(String procName, final String member) {
275     Procedure proc = procedures.get(procName);
276     if (proc == null) {
277       LOG.warn("Member '"+ member +"' is trying to release an unknown procedure '"+ procName +"'");
278       return;
279     }
280     proc.barrierReleasedByMember(member);
281   }
282 
283   /**
284    * @return the rpcs implementation for all current procedures
285    */
286   ProcedureCoordinatorRpcs getRpcs() {
287     return rpcs;
288   }
289 
290   /**
291    * Returns the procedure.  This Procedure is a live instance so should not be modified but can
292    * be inspected.
293    * @param name Name of the procedure
294    * @return Procedure or null if not present any more
295    */
296   public Procedure getProcedure(String name) {
297     return procedures.get(name);
298   }
299 
300   /**
301    * @return Return set of all procedure names.
302    */
303   public Set<String> getProcedureNames() {
304     return new HashSet<String>(procedures.keySet());
305   }
306 }