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1   /**
2    *
3    * Licensed to the Apache Software Foundation (ASF) under one
4    * or more contributor license agreements.  See the NOTICE file
5    * distributed with this work for additional information
6    * regarding copyright ownership.  The ASF licenses this file
7    * to you under the Apache License, Version 2.0 (the
8    * "License"); you may not use this file except in compliance
9    * with the License.  You may obtain a copy of the License at
10   *
11   *     http://www.apache.org/licenses/LICENSE-2.0
12   *
13   * Unless required by applicable law or agreed to in writing, software
14   * distributed under the License is distributed on an "AS IS" BASIS,
15   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16   * See the License for the specific language governing permissions and
17   * limitations under the License.
18   */
19  package org.apache.hadoop.hbase.regionserver;
20  
21  import java.io.IOException;
22  
23  import org.apache.commons.logging.Log;
24  import org.apache.commons.logging.LogFactory;
25  import org.apache.hadoop.hbase.classification.InterfaceAudience;
26  import org.apache.hadoop.hbase.RemoteExceptionHandler;
27  import org.apache.hadoop.hbase.master.TableLockManager.TableLock;
28  import org.apache.hadoop.hbase.util.Bytes;
29  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
30  import org.apache.hadoop.hbase.util.Strings;
31  import org.apache.hadoop.util.StringUtils;
32  
33  import com.google.common.base.Preconditions;
34  
35  /**
36   * Handles processing region splits. Put in a queue, owned by HRegionServer.
37   */
38  @InterfaceAudience.Private
39  class SplitRequest implements Runnable {
40    static final Log LOG = LogFactory.getLog(SplitRequest.class);
41    private final HRegion parent;
42    private final byte[] midKey;
43    private final HRegionServer server;
44    private TableLock tableLock;
45  
46    SplitRequest(HRegion region, byte[] midKey, HRegionServer hrs) {
47      Preconditions.checkNotNull(hrs);
48      this.parent = region;
49      this.midKey = midKey;
50      this.server = hrs;
51    }
52  
53    @Override
54    public String toString() {
55      return "regionName=" + parent + ", midKey=" + Bytes.toStringBinary(midKey);
56    }
57  
58    @Override
59    public void run() {
60      if (this.server.isStopping() || this.server.isStopped()) {
61        LOG.debug("Skipping split because server is stopping=" +
62          this.server.isStopping() + " or stopped=" + this.server.isStopped());
63        return;
64      }
65      boolean success = false;
66      long startTime = EnvironmentEdgeManager.currentTimeMillis();
67      SplitTransaction st = new SplitTransaction(parent, midKey);
68      try {
69        //acquire a shared read lock on the table, so that table schema modifications
70        //do not happen concurrently
71        tableLock = server.getTableLockManager().readLock(parent.getTableDesc().getTableName()
72            , "SPLIT_REGION:" + parent.getRegionNameAsString());
73        try {
74          tableLock.acquire();
75        } catch (IOException ex) {
76          tableLock = null;
77          throw ex;
78        }
79  
80        // If prepare does not return true, for some reason -- logged inside in
81        // the prepare call -- we are not ready to split just now. Just return.
82        if (!st.prepare()) return;
83        try {
84          st.execute(this.server, this.server);
85          success = true;
86        } catch (Exception e) {
87          if (this.server.isStopping() || this.server.isStopped()) {
88            LOG.info(
89                "Skip rollback/cleanup of failed split of "
90                    + parent.getRegionNameAsString() + " because server is"
91                    + (this.server.isStopping() ? " stopping" : " stopped"), e);
92            return;
93          }
94          try {
95            LOG.info("Running rollback/cleanup of failed split of " +
96              parent.getRegionNameAsString() + "; " + e.getMessage(), e);
97            if (st.rollback(this.server, this.server)) {
98              LOG.info("Successful rollback of failed split of " +
99                parent.getRegionNameAsString());
100           } else {
101             this.server.abort("Abort; we got an error after point-of-no-return");
102           }
103         } catch (RuntimeException ee) {
104           String msg = "Failed rollback of failed split of " +
105             parent.getRegionNameAsString() + " -- aborting server";
106           // If failed rollback, kill this server to avoid having a hole in table.
107           LOG.info(msg, ee);
108           this.server.abort(msg + " -- Cause: " + ee.getMessage());
109         }
110         return;
111       }
112     } catch (IOException ex) {
113       LOG.error("Split failed " + this, RemoteExceptionHandler.checkIOException(ex));
114       server.checkFileSystem();
115     } finally {
116       if (this.parent.getCoprocessorHost() != null) {
117         try {
118           this.parent.getCoprocessorHost().postCompleteSplit();
119         } catch (IOException io) {
120           LOG.error("Split failed " + this,
121               RemoteExceptionHandler.checkIOException(io));
122         }
123       }
124       if (parent.shouldForceSplit()) {
125         parent.clearSplit();
126       }
127       releaseTableLock();
128       long endTime = EnvironmentEdgeManager.currentTimeMillis();
129       // Update regionserver metrics with the split transaction total running time
130       server.getMetrics().updateSplitTime(endTime - startTime);
131       if (success) {
132         // Log success
133         LOG.info("Region split, hbase:meta updated, and report to master. Parent="
134             + parent.getRegionNameAsString() + ", new regions: "
135             + st.getFirstDaughter().getRegionNameAsString() + ", "
136             + st.getSecondDaughter().getRegionNameAsString() + ". Split took "
137             + StringUtils.formatTimeDiff(EnvironmentEdgeManager.currentTimeMillis(), startTime));
138       }
139       // Always log the split transaction journal
140       LOG.info("Split transaction journal:\n\t" + Strings.join("\n\t", st.getJournal()));
141     }
142   }
143 
144   protected void releaseTableLock() {
145     if (this.tableLock != null) {
146       try {
147         this.tableLock.release();
148       } catch (IOException ex) {
149         LOG.error("Could not release the table lock (something is really wrong). " 
150            + "Aborting this server to avoid holding the lock forever.");
151         this.server.abort("Abort; we got an error when releasing the table lock "
152                          + "on " + parent.getRegionNameAsString());
153       }
154     }
155   }
156 }