Class SlaveDatabase

  • All Implemented Interfaces:
    Database, Database, LocaleFinder, JarReader, ModuleControl, ModuleSupportable, PropertySetCallback

    public class SlaveDatabase
    extends BasicDatabase
    SlaveDatabase is an instance of Database, and is booted instead of BasicDatabase if this database will have the replication slave role. SlaveDatabase differs from BasicDatabase in the following ways: 1: When starting a non-replicated database (i.e., BasicDatabase), only one thread is used to start all modules of the database. When booted in slave mode, the thread that boots the store module will be blocked during log recovery. To remedy this, SlaveDatabase runs the boot method of BasicDatabase in a separate thread. This ensures that the connection attempt that started slave replication mode will not hang. 2: While the database is in replication slave mode, the authentication services are not available because these require that the store module has been booted first. Calling getAuthenticationService when in slave mode will raise an exception. 3: While the database is in replication slave mode, connections are not accepted since the database cannot process transaction requests. Calling setupConnection when in slave mode will raise an exception. 4: If the failover command has been executed for this database, it is no longer in replication slave mode. When this has happened, SlaveDatabase works exactly as BasicDatabase.
    • Field Detail

      • inReplicationSlaveMode

        private volatile boolean inReplicationSlaveMode
        True until SlaveDatabaseBootThread has successfully booted the database. Does not happen until the failover command has been executed for this database
      • shutdownInitiated

        private volatile boolean shutdownInitiated
      • inBoot

        private volatile boolean inBoot
        True until this database has been successfully booted. Any exception that occurs while inBoot is true will be handed to the client thread booting this database.
      • bootException

        private volatile StandardException bootException
        Set by the database boot thread if it fails before slave mode has been started properly (i.e., if inBoot is true). This exception will then be reported to the client connection.
      • dbname

        private java.lang.String dbname
    • Constructor Detail

      • SlaveDatabase

        public SlaveDatabase()
    • Method Detail

      • canSupport

        public boolean canSupport​(java.util.Properties startParams)
        Determines whether this Database implementation should be used to boot the database.
        Specified by:
        canSupport in interface ModuleSupportable
        Overrides:
        canSupport in class BasicDatabase
        Parameters:
        startParams - The properties used to decide if SlaveDatabase is the correct implementation of Database for the database to be booted.
        Returns:
        true if the database is updatable (not read-only) and replication slave mode is specified in startParams
      • boot

        public void boot​(boolean create,
                         java.util.Properties startParams)
                  throws StandardException
        Description copied from interface: ModuleControl
        Boot this module with the given properties. Creates a module instance that can be found using the findModule() methods of Monitor. The module can only be found using one of these findModule() methods once this method has returned.

        An implementation's boot method can throw StandardException. If it is thrown the module is not registered by the monitor and therefore cannot be found through a findModule(). In this case the module's stop() method is not called, thus throwing this exception must free up any resources.

        When create is true the contents of the properties object will be written to the service.properties of the persistent service. Thus any code that requires an entry in service.properties must explicitly place the value in this properties set using the put method.
        Typically the properties object contains one or more default properties sets, which are not written out to service.properties. These default sets are how callers modify the create process. In a JDBC connection database create the first set of defaults is a properties object that contains the attributes that were set on the jdbc:derby: URL. This attributes properties set has the second default properties set as its default. This set (which could be null) contains the properties that the user set on their DriverManager.getConnection() call, and are thus not owned by Derby code, and thus must not be modified by Derby code.

        When create is false the properties object contains all the properties set in the service.properties file plus a limited number of attributes from the JDBC URL attributes or connection properties set. This avoids properties set by the user compromising the boot process. An example of a property passed in from the JDBC world is the bootPassword for encrypted databases.

        Code should not hold onto the passed in properties reference after boot time as its contents may change underneath it. At least after the complete boot is completed, the links to all the default sets will be removed.

        Specified by:
        boot in interface ModuleControl
        Overrides:
        boot in class BasicDatabase
        Throws:
        StandardException - Module cannot be started.
        See Also:
        Monitor, ModuleFactory
      • stop

        public void stop()
        Called by Monitor when this module is stopped, i.e. when the database is shut down. When the database is shut down using the stopSlave command, the stopReplicationSlave method has already been called when this method is called. In this case, the replication functionality has already been stopped. If the database is shutdown as part of a system shutdown, however, we need to cleanup slave replication as part of database shutdown.
        Specified by:
        stop in interface ModuleControl
        Overrides:
        stop in class BasicDatabase
        See Also:
        Monitor, ModuleFactory
      • isInSlaveMode

        public boolean isInSlaveMode()
        Description copied from interface: Database
        Used to indicated whether the database is in the replication slave mode.
        Specified by:
        isInSlaveMode in interface Database
        Overrides:
        isInSlaveMode in class BasicDatabase
        Returns:
        true if this database is in replication slave mode, false otherwise.
      • setupConnection

        public LanguageConnectionContext setupConnection​(ContextManager cm,
                                                         java.lang.String user,
                                                         java.lang.String drdaID,
                                                         java.lang.String dbname)
                                                  throws StandardException
        Description copied from interface: Database
        Sets up a connection to the Database, owned by the given user. The JDBC version of getConnection takes a URL. The purpose of the URL is to tell the driver where the database system is. By the time we get here, we have found the database system (that's how we're making this method call), so the URL is not necessary to establish the connection here. The driver should remember the URL that was used to establish the connection, so it can implement the DatabaseMetaData.getURL() method.
        Specified by:
        setupConnection in interface Database
        Overrides:
        setupConnection in class BasicDatabase
        user - The UserID of the user getting the connection
        drdaID - The drda id of the connection (from network server)
        dbname - The database name
        Returns:
        A new LanguageConnectionContext
        Throws:
        StandardException - thrown if unable to create the connection.
      • verifyShutdownSlave

        public void verifyShutdownSlave()
                                 throws StandardException
        Verify that a connection to stop the slave has been made from here. If verified, the database context is given to the method caller. This will ensure this database is shutdown when an exception with database severity is thrown. If not verified, an exception is thrown.
        Throws:
        StandardException - Thrown if a stop slave connection attempt was not made from this class
      • stopReplicationSlave

        public void stopReplicationSlave()
                                  throws java.sql.SQLException
        Stop replication slave mode if replication slave mode is active and the network connection with the master is down
        Specified by:
        stopReplicationSlave in interface Database
        Overrides:
        stopReplicationSlave in class BasicDatabase
        Throws:
        java.sql.SQLException - Thrown on error, if not in replication slave mode or if the network connection with the master is not down
      • failover

        public void failover​(java.lang.String dbname)
                      throws StandardException
        Description copied from interface: Database
        Start failover for the given database.
        Specified by:
        failover in interface Database
        Overrides:
        failover in class BasicDatabase
        Parameters:
        dbname - the replication database that is being failed over.
        Throws:
        StandardException - 1) If the failover succeeds, an exception is thrown to indicate that the master database was shutdown after a successful failover 2) If a failure occurs during network communication with slave.
        See Also:
        Database.failover(String)
      • verifySuccessfulBoot

        private void verifySuccessfulBoot()
                                   throws StandardException
        Verify that the slave functionality has been properly started. This method will block until a successful slave startup has been confirmed, or it will throw the exception that caused it to fail.
        Throws:
        StandardException
      • isSlaveFactorySet

        private boolean isSlaveFactorySet()
        If slaveFac (the reference to the SlaveFactory) has not already been set, this method will try to set it by calling Monitor.findServiceModule. If slavFac was already set, the method does not do anything.
        Returns:
        true if slaveFac is set after calling this method, false otherwise
      • handleShutdown

        private void handleShutdown​(StandardException shutdownCause)
        Used to shutdown this database. If an error occurs as part of the database boot process, we hand the exception that caused boot to fail to the client thread. The client thread will in turn shut down this database. If an error occurs at a later stage than during boot, we shut down the database by setting up a connection with the shutdown attribute. The internal connection is required because database shutdown requires EmbedConnection to do cleanup.
        Parameters:
        shutdownCause - the reason why the database needs to be shutdown
      • getContextService

        private static ContextService getContextService()
        Privileged lookup of the ContextService. Must be private so that user code can't call this entry point.
      • findServiceModule

        private static java.lang.Object findServiceModule​(java.lang.Object serviceModule,
                                                          java.lang.String factoryInterface)
                                                   throws StandardException
        Privileged startup. Must be private so that user code can't call this entry point.
        Throws:
        StandardException