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Adding database locking functionality
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mcuthbert
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Jun 4, 2020
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142 changes: 142 additions & 0 deletions
142
osmosis-core/src/main/java/org/openstreetmap/osmosis/core/database/DatabaseLocker.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,142 @@ | ||
| // This software is released into the Public Domain. See copying.txt for details. | ||
| package org.openstreetmap.osmosis.core.database; | ||
|
|
||
| import java.net.InetAddress; | ||
| import java.net.UnknownHostException; | ||
| import java.sql.Connection; | ||
| import java.sql.PreparedStatement; | ||
| import java.sql.ResultSet; | ||
| import java.sql.SQLException; | ||
| import java.sql.Statement; | ||
| import java.util.logging.Logger; | ||
|
|
||
| import javax.sql.DataSource; | ||
|
|
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| /** | ||
| * A check against the database to see if it is locked. | ||
| * | ||
| * @author mcuthbert | ||
| */ | ||
| public class DatabaseLocker implements AutoCloseable { | ||
|
|
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| private static Logger logger = Logger.getLogger(DatabaseLocker.class.getSimpleName()); | ||
| private final DataSource source; | ||
| private final boolean writeLock; | ||
| private boolean enabled = true; | ||
| private int lockedIdentifier = -1; | ||
|
|
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| /** | ||
| * Static function to fully unlock the database. | ||
| * | ||
| * @param source {@link DataSource} to execute the query | ||
| */ | ||
| public static void fullUnlockDatabase(final DataSource source) { | ||
| unlockDatabase(-1, source); | ||
| } | ||
|
|
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| private static void unlockDatabase(final int identifier, final DataSource source) { | ||
| try (Connection connection = source.getConnection(); | ||
| PreparedStatement statement = connection.prepareStatement("SELECT unlock_database(?)")) { | ||
| statement.setInt(1, identifier); | ||
| final ResultSet result = statement.executeQuery(); | ||
| if (result.next()) { | ||
| final boolean unlocked = result.getBoolean(1); | ||
| if (unlocked) { | ||
| logger.info(String.format("Unlocked database using identifier %d.", identifier)); | ||
| return; | ||
| } | ||
| } | ||
| throw new RuntimeException("Failed to unlock the database"); | ||
| } catch (final SQLException e) { | ||
| throw new RuntimeException("Failed to unlock the database", e); | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * Default Constructor. | ||
| * | ||
| * @param source The DataSource for the connection | ||
| * @param writeLock Whether the lock that is being requested is a write lock | ||
| */ | ||
| public DatabaseLocker(final DataSource source, final boolean writeLock) { | ||
| this.source = source; | ||
| this.writeLock = writeLock; | ||
| // check to see if the function exists in the database and if it doesn't then throw a | ||
| // warning on the log and don't try any locking | ||
| try (Connection connection = source.getConnection(); | ||
| Statement statement = connection.createStatement()) { | ||
| statement.executeQuery("SELECT 'lock_database'::regproc, 'unlock_database'::regproc"); | ||
| } catch (final Exception e) { | ||
| logger.warning("Locking functions do not exist in database. Disabling locking."); | ||
| this.enabled = false; | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * Helper function for primary lock database function that simply sets the source to empty string. | ||
| * | ||
| * @param process The process that is locking the database | ||
| */ | ||
| public void lockDatabase(final String process) { | ||
| this.lockDatabase(process, ""); | ||
| } | ||
|
|
||
| /** | ||
| * Will attempt to lock the database. | ||
| * | ||
| * @param process | ||
| * The process that will lock the database. This would be something like "Extracts" or "Replication". | ||
| * @param description | ||
| * The source of the process. This is basically a description for the process, like | ||
| * "Pipeline Extraction for Build X". | ||
| */ | ||
| public void lockDatabase(final String process, final String description) { | ||
| if (this.enabled) { | ||
| String lockName = "read"; | ||
| if (this.writeLock) { | ||
| lockName = "write"; | ||
| } | ||
| try (Connection connection = source.getConnection(); | ||
| PreparedStatement statement = connection.prepareStatement("SELECT lock_database(?, ?, ?, ?)")) { | ||
| statement.setString(1, process); | ||
| statement.setString(2, description); | ||
| statement.setString(3, InetAddress.getLocalHost().getHostName()); | ||
| statement.setBoolean(4, this.writeLock); | ||
| final ResultSet result = statement.executeQuery(); | ||
| if (result.next()) { | ||
| this.lockedIdentifier = result.getInt(1); | ||
| logger.info(String.format("Obtained %s lock to database for process: %s " | ||
| + "from source: '%s', with lockedID: %d", | ||
| lockName, process, description, this.lockedIdentifier)); | ||
| } else { | ||
| throw new RuntimeException("Failed to retrieve lock for the database."); | ||
| } | ||
| } catch (final SQLException | UnknownHostException e) { | ||
| throw new RuntimeException("Failed to lock the database.", e); | ||
| } | ||
| } | ||
| } | ||
|
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| /** | ||
| * Will attempt to unlock the database with the given locked identifier. | ||
| */ | ||
| public void unlockDatabase() { | ||
| if (this.enabled && this.lockedIdentifier > 0) { | ||
| unlockDatabase(this.lockedIdentifier, this.source); | ||
| } | ||
| } | ||
|
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| /** | ||
| * Does a full unlock of the database. So no matter what is locking it, this will unlock it. | ||
| */ | ||
| public void fullUnlockDatabase() { | ||
| if (this.enabled) { | ||
| fullUnlockDatabase(this.source); | ||
| } | ||
| } | ||
|
|
||
| @Override | ||
| public void close() throws Exception { | ||
| this.unlockDatabase(); | ||
| } | ||
| } |
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