* Licensed to the Apache Software Foundation (ASF) under one

* or more contributor license agreements.  See the NOTICE file

* distributed with this work for additional information

* regarding copyright ownership.  The ASF licenses this file

* to you under the Apache License, Version 2.0 (the

* "License"); you may not use this file except in compliance

* with the License.  You may obtain a copy of the License at

*

*     http://www.apache.org/licenses/LICENSE-2.0

*

* Unless required by applicable law or agreed to in writing,

* software distributed under the License is distributed on an

* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

* KIND, either express or implied.  See the License for the

* specific language governing permissions and limitations

* under the License.

*/

* Implementation of

* {@link org.apache.hadoop.hive.metastore.MetaStoreEventListener} It sends

* message on two type of topics. One has name of form dbName.tblName On this

* topic, two kind of messages are sent: add/drop partition and

* finalize_partition message. Second topic has name "HCAT" and messages sent on

* it are: add/drop database and add/drop table. All messages also has a

* property named "HCAT_EVENT" set on them whose value can be used to configure

* message selector on subscriber side.

*/

  private static final Logger LOG = LoggerFactory.getLogger(NotificationListener.class);

  protected Connection conn;

  private static MessageFactory messageFactory = MessageFactory.getInstance();

  public static final int NUM_RETRIES = 1;

  private static final String HEALTH_CHECK_TOPIC_SUFFIX = "jms_health_check";

  private static final String HEALTH_CHECK_MSG = "HCAT_JMS_HEALTH_CHECK_MESSAGE";

  protected final ThreadLocal<Session> session = new ThreadLocal<Session>() {

    @Override

    protected Session initialValue() {

      try {

        return createSession();

      } catch (Exception e) {

        LOG.error("Couldn't create JMS Session", e);

        return null;

      }

    }

    @Override

    public void remove() {

      if (get() != null) {

        try {

          get().close();

        } catch (Exception e) {

          LOG.error("Unable to close bad JMS session, ignored error", e);

        }

      }

      super.remove();

    }

  };

  /**

   * Create message bus connection and session in constructor.

   */

  public NotificationListener(final Configuration conf) {

    super(conf);

    testAndCreateConnection();

  }

  private static String getTopicName(Partition partition,

                     ListenerEvent partitionEvent) throws MetaException {

    try {

      return partitionEvent.getHandler()

        .get_table(partition.getDbName(), partition.getTableName())

        .getParameters().get(HCatConstants.HCAT_MSGBUS_TOPIC_NAME);

    } catch (NoSuchObjectException e) {

      throw new MetaException(e.toString());

    }

  }

  @Override

  public void onAddPartition(AddPartitionEvent partitionEvent)

    throws MetaException {

    // Subscriber can get notification of newly add partition in a

    // particular table by listening on a topic named "dbName.tableName"

    // and message selector string as "HCAT_EVENT = HCAT_ADD_PARTITION"

    if (partitionEvent.getStatus()) {

      Partition partition = partitionEvent.getPartition();

      String topicName = getTopicName(partition, partitionEvent);

      if (topicName != null && !topicName.equals("")) {

        send(messageFactory.buildAddPartitionMessage(partitionEvent.getTable(), partition), topicName);

      } else {

        LOG.info("Topic name not found in metastore. Suppressing HCatalog notification for "

          + partition.getDbName()

          + "."

          + partition.getTableName()

          + " To enable notifications for this table, please do alter table set properties ("

          + HCatConstants.HCAT_MSGBUS_TOPIC_NAME

          + "=<dbname>.<tablename>) or whatever you want topic name to be.");

      }

    }

  }

  /**

   * Send dropped partition notifications. Subscribers can receive these notifications for a

   * particular table by listening on a topic named "dbName.tableName" with message selector

   * string {@value org.apache.hive.hcatalog.common.HCatConstants#HCAT_EVENT} =

   * {@value org.apache.hive.hcatalog.common.HCatConstants#HCAT_DROP_PARTITION_EVENT}.

   * </br>

   * TODO: DataNucleus 2.0.3, currently used by the HiveMetaStore for persistence, has been

   * found to throw NPE when serializing objects that contain null. For this reason we override

   * some fields in the StorageDescriptor of this notification. This should be fixed after

   * HIVE-2084 "Upgrade datanucleus from 2.0.3 to 3.0.1" is resolved.

   */

  @Override

  public void onDropPartition(DropPartitionEvent partitionEvent) throws MetaException {

    if (partitionEvent.getStatus()) {

      Partition partition = partitionEvent.getPartition();

      StorageDescriptor sd = partition.getSd();

      sd.setBucketCols(new ArrayList<String>());

      sd.setSortCols(new ArrayList<Order>());

      sd.setParameters(new HashMap<String, String>());

      sd.getSerdeInfo().setParameters(new HashMap<String, String>());

      sd.getSkewedInfo().setSkewedColNames(new ArrayList<String>());

      String topicName = getTopicName(partition, partitionEvent);

      if (topicName != null && !topicName.equals("")) {

        send(messageFactory.buildDropPartitionMessage(partitionEvent.getTable(), partition), topicName);

      } else {

        LOG.info("Topic name not found in metastore. Suppressing HCatalog notification for "

          + partition.getDbName()

          + "."

          + partition.getTableName()

          + " To enable notifications for this table, please do alter table set properties ("

          + HCatConstants.HCAT_MSGBUS_TOPIC_NAME

          + "=<dbname>.<tablename>) or whatever you want topic name to be.");

      }

    }

  }

  @Override

  public void onCreateDatabase(CreateDatabaseEvent dbEvent)

    throws MetaException {

    // Subscriber can get notification about addition of a database in HCAT

    // by listening on a topic named "HCAT" and message selector string

    // as "HCAT_EVENT = HCAT_ADD_DATABASE"

    if (dbEvent.getStatus()) {

      String topicName = getTopicPrefix(dbEvent.getHandler().getHiveConf());

      send(messageFactory.buildCreateDatabaseMessage(dbEvent.getDatabase()), topicName);

    }

  }

  @Override

  public void onDropDatabase(DropDatabaseEvent dbEvent) throws MetaException {

    // Subscriber can get notification about drop of a database in HCAT

    // by listening on a topic named "HCAT" and message selector string

    // as "HCAT_EVENT = HCAT_DROP_DATABASE"

    if (dbEvent.getStatus()) {

      String topicName = getTopicPrefix(dbEvent.getHandler().getHiveConf());

      send(messageFactory.buildDropDatabaseMessage(dbEvent.getDatabase()), topicName);

    }

  }

  @Override

  public void onCreateTable(CreateTableEvent tableEvent) throws MetaException {

    // Subscriber can get notification about addition of a table in HCAT

    // by listening on a topic named "HCAT" and message selector string

    // as "HCAT_EVENT = HCAT_ADD_TABLE"

    if (tableEvent.getStatus()) {

      Table tbl = tableEvent.getTable();

      HMSHandler handler = tableEvent.getHandler();

      HiveConf conf = handler.getHiveConf();

      Table newTbl;

      try {

        newTbl = handler.get_table(tbl.getDbName(), tbl.getTableName())

          .deepCopy();

        newTbl.getParameters().put(

          HCatConstants.HCAT_MSGBUS_TOPIC_NAME,

          getTopicPrefix(conf) + "." + newTbl.getDbName().toLowerCase() + "."

            + newTbl.getTableName().toLowerCase());

        handler.alter_table(newTbl.getDbName(), newTbl.getTableName(), newTbl);

      } catch (InvalidOperationException e) {

        MetaException me = new MetaException(e.toString());

        me.initCause(e);

        throw me;

      } catch (NoSuchObjectException e) {

        MetaException me = new MetaException(e.toString());

        me.initCause(e);

        throw me;

      }

      String topicName = getTopicPrefix(conf) + "." + newTbl.getDbName().toLowerCase();

      send(messageFactory.buildCreateTableMessage(newTbl), topicName);

    }

  }

  private String getTopicPrefix(Configuration conf) {

    return conf.get(HCatConstants.HCAT_MSGBUS_TOPIC_PREFIX,

      HCatConstants.HCAT_DEFAULT_TOPIC_PREFIX);

  }

  /**

   * Send dropped table notifications. Subscribers can receive these notifications for

   * dropped tables by listening on topic "HCAT" with message selector string

   * {@value org.apache.hive.hcatalog.common.HCatConstants#HCAT_EVENT} =

   * {@value org.apache.hive.hcatalog.common.HCatConstants#HCAT_DROP_TABLE_EVENT}

   * </br>

   * TODO: DataNucleus 2.0.3, currently used by the HiveMetaStore for persistence, has been

   * found to throw NPE when serializing objects that contain null. For this reason we override

   * some fields in the StorageDescriptor of this notification. This should be fixed after

   * HIVE-2084 "Upgrade datanucleus from 2.0.3 to 3.0.1" is resolved.

   */

  @Override

  public void onDropTable(DropTableEvent tableEvent) throws MetaException {

    // Subscriber can get notification about drop of a table in HCAT

    // by listening on a topic named "HCAT" and message selector string

    // as "HCAT_EVENT = HCAT_DROP_TABLE"

    // Datanucleus throws NPE when we try to serialize a table object

    // retrieved from metastore. To workaround that we reset following objects

    if (tableEvent.getStatus()) {

      Table table = tableEvent.getTable();

      String topicName = getTopicPrefix(tableEvent.getHandler().getHiveConf()) + "." + table.getDbName().toLowerCase();

      send(messageFactory.buildDropTableMessage(table), topicName);

    }

  }

  /**

   * @param hCatEventMessage The HCatEventMessage being sent over JMS.

   * @param topicName is the name on message broker on which message is sent.

   */

  protected void send(HCatEventMessage hCatEventMessage, String topicName) {

    send(hCatEventMessage, topicName, NUM_RETRIES);

  }

  /**

   * @param hCatEventMessage The HCatEventMessage being sent over JMS, this method is threadsafe

   * @param topicName is the name on message broker on which message is sent.

   * @param retries the number of retry attempts

   */

  protected void send(HCatEventMessage hCatEventMessage, String topicName, int retries) {

    try {

      if (session.get() == null) {

        // Need to reconnect

        throw new JMSException("Invalid JMS session");

      }

      Destination topic = createTopic(topicName);

      Message msg = session.get().createTextMessage(hCatEventMessage.toString());

      msg.setStringProperty(HCatConstants.HCAT_EVENT, hCatEventMessage.getEventType().toString());

      msg.setStringProperty(HCatConstants.HCAT_MESSAGE_VERSION, messageFactory.getVersion());

      msg.setStringProperty(HCatConstants.HCAT_MESSAGE_FORMAT, messageFactory.getMessageFormat());

      MessageProducer producer = createProducer(topic);

      producer.send(msg);

      // Message must be transacted before we return.

      session.get().commit();

    } catch (Exception e) {

      if (retries >= 0) {

        // this may happen if we were able to establish connection once, but its no longer valid

        LOG.error("Seems like connection is lost. Will retry. Retries left : " + retries + ". error was:", e);

        testAndCreateConnection();

        send(hCatEventMessage, topicName, retries - 1);

      } else {

        // Gobble up the exception. Message delivery is best effort.

        LOG.error("Failed to send message on topic: " + topicName +

          " event: " + hCatEventMessage.getEventType() + " after retries: " + NUM_RETRIES, e);

      }

    }

  }

  /**

   * Get the topic object for the topicName

   *

   * @param topicName The String identifying the message-topic.

   * @return A {@link Topic} object corresponding to the specified topicName.

   * @throws JMSException

   */

  protected Topic createTopic(final String topicName) throws JMSException {

    return session.get().createTopic(topicName);

  }

  /**

   * Does a health check on the connection by sending a dummy message.

   * Create the connection if the connection is found to be bad

   * Also recreates the session

   */

  protected synchronized void testAndCreateConnection() {

    if (conn != null) {

      // This method is reached when error occurs while sending msg, so the session must be bad

      session.remove();

      if (!isConnectionHealthy()) {

        // I am the first thread to detect the error, cleanup old connection & reconnect

        try {

          conn.close();

        } catch (Exception e) {

          LOG.error("Unable to close bad JMS connection, ignored error", e);

        }

        conn = createConnection();

      }

    } else {

      conn = createConnection();

    }

    try {

      session.set(createSession());

    } catch (JMSException e) {

      LOG.error("Couldn't create JMS session, ignored the error", e);

    }

  }

  /**

   * Create the JMS connection

   * @return newly created JMS connection

   */

  protected Connection createConnection() {

    LOG.info("Will create new JMS connection");

    Context jndiCntxt;

    Connection jmsConnection = null;

    try {

      jndiCntxt = new InitialContext();

      ConnectionFactory connFac = (ConnectionFactory) jndiCntxt.lookup("ConnectionFactory");

      jmsConnection = connFac.createConnection();

      jmsConnection.start();

      jmsConnection.setExceptionListener(new ExceptionListener() {

        @Override

        public void onException(JMSException jmse) {

          LOG.error("JMS Exception listener received exception. Ignored the error", jmse);

        }

      });

    } catch (NamingException e) {

      LOG.error("JNDI error while setting up Message Bus connection. "

        + "Please make sure file named 'jndi.properties' is in "

        + "classpath and contains appropriate key-value pairs.", e);

    } catch (JMSException e) {

      LOG.error("Failed to initialize connection to message bus", e);

    } catch (Throwable t) {

      LOG.error("Unable to connect to JMS provider", t);

    }

    return jmsConnection;

  }

  /**

   * Send a dummy message to probe if the JMS connection is healthy

   * @return true if connection is healthy, false otherwise

   */

  protected boolean isConnectionHealthy() {

    try {

      Topic topic = createTopic(getTopicPrefix(getConf()) + "." + HEALTH_CHECK_TOPIC_SUFFIX);

      MessageProducer producer = createProducer(topic);

      Message msg = session.get().createTextMessage(HEALTH_CHECK_MSG);

      producer.send(msg, DeliveryMode.NON_PERSISTENT, 4, 0);

    } catch (Exception e) {

      return false;

    }

    return true;

  }

  /**

   * Creates a JMS session

   * @return newly create JMS session

   * @throws JMSException

   */

  protected Session createSession() throws JMSException {

    // We want message to be sent when session commits, thus we run in

    // transacted mode.

    return conn.createSession(true, Session.SESSION_TRANSACTED);

  }

  /**

   * Create a JMS producer

   * @param topic

   * @return newly created message producer

   * @throws JMSException

   */

  protected MessageProducer createProducer(Destination topic) throws JMSException {

    return session.get().createProducer(topic);

  }

  @Override

  protected void finalize() throws Throwable {

    if (conn != null) {

      try {

        conn.close();

      } catch (Exception e) {

        LOG.error("Couldn't close jms connection, ignored the error", e);

      }

    }

  }

  @Override

  public void onLoadPartitionDone(LoadPartitionDoneEvent lpde)

    throws MetaException {

//        if(lpde.getStatus())

//            send(lpde.getPartitionName(),lpde.getTable().getParameters().get(HCatConstants.HCAT_MSGBUS_TOPIC_NAME),HCatConstants.HCAT_PARTITION_DONE_EVENT);

  }

  @Override

  public void onAlterPartition(AlterPartitionEvent ape) throws MetaException {

    // no-op

  }

  @Override

  public void onAlterTable(AlterTableEvent ate) throws MetaException {

    // no-op

  }

}