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17 package org.apache.activemq.store.jdbc;
18
19 import org.apache.activemq.Service;
20 import org.apache.activemq.broker.BrokerService;
21 import org.apache.commons.logging.Log;
22 import org.apache.commons.logging.LogFactory;
23
24 import javax.sql.DataSource  ;
25
26 import java.sql.Connection ;
27 import java.sql.PreparedStatement ;
28 import java.sql.SQLException ;
29
30
36 public class DefaultDatabaseLocker implements DatabaseLocker {
37 private static final Log log = LogFactory.getLog(DefaultDatabaseLocker.class);
38
39 private final DataSource dataSource;
40 private final Statements statements;
41 private long sleepTime = 1000;
42 private Connection connection;
43 private boolean stopping;
44
45 public DefaultDatabaseLocker(DataSource dataSource, Statements statements) {
46 this.dataSource = dataSource;
47 this.statements = statements;
48 }
49
50 public void start() throws Exception {
51 stopping = false;
52 connection = dataSource.getConnection();
53 connection.setAutoCommit(false);
54
55 log.info("Attempting to acquire the exclusive lock to become the Master broker");
56 String sql = statements.getLockCreateStatement();
57 PreparedStatement statement = connection.prepareStatement(sql);
58 while (true) {
59 try {
60 statement.execute();
61 break;
62 }
63 catch (Exception e) {
64 if (stopping) {
65 throw new Exception ("Cannot start broker as being asked to shut down. Interupted attempt to acquire lock: " + e, e);
66 }
67 log.error("Failed to acquire lock: " + e, e);
68 }
69 log.debug("Sleeping for " + sleepTime + " milli(s) before trying again to get the lock...");
70 Thread.sleep(sleepTime);
71 }
72
73 log.info("Becoming the master on dataSource: " + dataSource);
74 }
75
76 public void stop() throws Exception {
77 stopping = true;
78 if (connection != null) {
79 connection.rollback();
80 connection.close();
81 }
82 }
83
84 public boolean keepAlive() {
85 try {
86 PreparedStatement statement = connection.prepareStatement(statements.getLockUpdateStatement());
87 statement.setLong(1, System.currentTimeMillis());
88 int rows = statement.executeUpdate();
89 if (rows == 1) {
90 return true;
91 }
92 }
93 catch (Exception e) {
94 log.error("Failed to update database lock: " + e, e);
95 }
96 return false;
97 }
98 }
99 |
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