Class ReplicationMessageTransmit

java.lang.Object
org.apache.derby.impl.store.replication.net.ReplicationMessageTransmit

public class ReplicationMessageTransmit extends Object
Used to send replication messages to the slave. Called by the Master controller to transmit replication messages wrapped in a ReplicationMessage object to a receiver. The receiver is implemented by the ReplicationMessageReceive class.
  • Field Details

    • DEFAULT_MESSAGE_RESPONSE_TIMEOUT

      private final int DEFAULT_MESSAGE_RESPONSE_TIMEOUT
      Number of millis to wait for a response message before timing out
      See Also:
    • receiveSemaphore

      private final Object receiveSemaphore
      Used to synchronize when waiting for a response message from the slave
    • receivedMsg

      private ReplicationMessage receivedMsg
      The message received from the slave as a response to sending a message.
    • stopMessageReceiver

      private volatile boolean stopMessageReceiver
      Whether or not to keep the message receiver thread alive. Set to true to terminate the thread
    • slaveAddress

      private final SlaveAddress slaveAddress
      Contains the address (hostname and port number) of the slave to replicate to.
    • socketConn

      private SocketConnection socketConn
      Used to write/read message objects to/from a connection.
    • dbname

      private String dbname
      The name of the replicated database
  • Constructor Details

    • ReplicationMessageTransmit

      public ReplicationMessageTransmit(SlaveAddress slaveAddress)
      Constructor initializes the slave address used in replication.
      Parameters:
      slaveAddress - contains the address (host name and port number) of the slave to connect to.
  • Method Details

    • initConnection

      public void initConnection(int timeout, long synchOnInstant) throws IOException, StandardException, ClassNotFoundException
      Used to create a Socket connection to the slave and establish compatibility with the database version of the slave by comparing the UID's of the ReplicationMessage classes of the master and the slave.
      Parameters:
      timeout - the amount of time for which the connection should block before being established.
      synchOnInstant - the master log instant, used to check that the master and slave log files are in synch. If no chunks of log records have been shipped to the slave yet, this is the end position in the current log file. If a chunk of log has been shipped, this is the instant of the log record shipped last. Note that there is a difference!
      Throws:
      IOException - if an exception occurs while trying to create the SocketConnection class or open a connection.
      StandardException - If an error message is received from the server indicating incompatible software versions of master and slave.
      ClassNotFoundException - Class of a serialized object cannot be found.
    • tearDown

      public void tearDown() throws IOException
      Tear down the network connection established with the other replication peer
      Throws:
      IOException - if an exception occurs while trying to tear down the network connection
    • sendMessage

      public void sendMessage(ReplicationMessage message) throws IOException
      Used to send a replication message to the slave.
      Parameters:
      message - a ReplicationMessage object that contains the message to be transmitted.
      Throws:
      IOException - 1) if an exception occurs while transmitting the message. 2) if the connection handle is invalid.
    • sendMessageWaitForReply

      public ReplicationMessage sendMessageWaitForReply(ReplicationMessage message) throws IOException, StandardException
      Send a replication message to the slave and return the message received as a response. Will only wait DEFAULT_MESSAGE_RESPONSE_TIMEOUT millis for the response message. If not received when the wait times out, no message is returned. The method is synchronized to guarantee that only one thread will be waiting for a response message at any time.
      Parameters:
      message - a ReplicationMessage object that contains the message to be transmitted.
      Returns:
      the response message
      Throws:
      IOException - 1) if an exception occurs while sending or receiving a message. 2) if the connection handle is invalid.
      StandardException - if the response message has not been received after DEFAULT_MESSAGE_RESPONSE_TIMEOUT millis
    • brokerConnection

      private void brokerConnection(long synchOnInstant) throws IOException, StandardException, ClassNotFoundException
      Used to send initiator messages to the slave and receive information about the compatibility of the slave with the master. One message is used to check that the slave and master have the same software versions. A second message is used to check that the master and slave log files are in synch.
      Parameters:
      synchOnInstant - the master log instant, used to check that the master and slave log files are in synch. If no chunks of log records have been shipped to the slave yet, this is the end position in the current log file. If a chunk of log has been shipped, this is the instant of the log record shipped last. Note that there is a difference!
      Throws:
      IOException - if an exception occurs during the sending or reading of the message.
      StandardException - If an error message is received from the server indicating a mis-match in serialVersionUID or log files out of synch.
      ClassNotFoundException - Class of a serialized object cannot be found.
    • verifyMessageType

      private boolean verifyMessageType(ReplicationMessage message, int expectedType) throws StandardException
      Used to parse a message received from the slave. If the message is an ack of the last shipped message, this method terminates quietly. Otherwise, it throws the exception received in the message from the slave describing why the last message could not be acked.
      Throws:
      StandardException - If an error message is received from the server
      ClassNotFoundException - Class of a serialized object cannot be found.
    • checkSocketConnection

      private void checkSocketConnection() throws IOException
      Verifies if the SocketConnection is valid.
      Throws:
      IOException - If the socket connection object is not valid (is null).
    • startMessageReceiverThread

      private void startMessageReceiverThread(String dbname)