src/java/org/apache/sqoop/mapreduce/db/SQLServerDBRecordReader.java - sqoop - Git at Google

 /**
  * 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.
  */
 package org.apache.sqoop.mapreduce.db;

 import java.io.IOException;
 import java.sql.Connection;
 import java.sql.SQLException;

 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.util.ReflectionUtils;
 import org.apache.sqoop.mapreduce.sqlserver.SqlServerRecordReader;
 import org.apache.hadoop.mapreduce.InputSplit;
 import org.apache.hadoop.mapreduce.TaskAttemptContext;

 import com.cloudera.sqoop.mapreduce.db.DBConfiguration;
 import com.cloudera.sqoop.mapreduce.db.DBInputFormat;
 import com.cloudera.sqoop.mapreduce.db.DataDrivenDBInputFormat;

 import  org.apache.sqoop.lib.SqoopRecord;

 /**
  * A RecordReader that reads records from a SQL table.
  * This record reader handles connection failures using the configured
  * connection failure handler
  */
 public class SQLServerDBRecordReader<T extends SqoopRecord> extends
       SqlServerRecordReader<T> {

   private static final Log LOG =
       LogFactory.getLog(SQLServerDBRecordReader.class);

   // The SQL handler to be used for recovering failed read operations
   protected SQLFailureHandler failureHandler = null;

   // Recover failed reads for RETRY_MAX
   protected static final int RETRY_MAX = 3;

   // Name of the split column used to re-generate selectQueries after
   // connection failures
   private String splitColumn;
   private String lastRecordKey;

   public SQLServerDBRecordReader(DBInputFormat.DBInputSplit split,
       Class<T> inputClass, Configuration conf, Connection conn,
       DBConfiguration dbConfig, String cond, String [] fields, String table,
       String dbProduct) throws SQLException {
     super(split, inputClass, conf, conn, dbConfig, cond, fields, table);
   }

   @Override
   /** {@inheritDoc} */
   public T getCurrentValue() {
     T val = super.getCurrentValue();
     // Lookup the key of the last read record to use for recovering
     // As documented, the map may not be null, though it may be empty.
     Object lastRecordSplitCol = val.getFieldMap().get(splitColumn);
     lastRecordKey = (lastRecordSplitCol == null) ? null
         : lastRecordSplitCol.toString();
     return val;
   }

   /**
    * Load the SQLFailureHandler configured for use by the record reader.
    */
   public void initialize(InputSplit inputSplit, TaskAttemptContext context)
       throws IOException, InterruptedException {
     // Load the configured connection failure handler
     Configuration conf = getConf();
     if (conf == null) {
       LOG.error("Configuration cannot be NULL");
     }

     Class connHandlerClass;
     try {
       String className = conf.get(
         SQLServerDBInputFormat.IMPORT_FAILURE_HANDLER_CLASS);

       // Get the class-name set in configuration
       connHandlerClass = conf.getClassByName(className);
     } catch (ClassNotFoundException ex) {
       LOG.error("Failed to find class: "
         + SQLServerDBInputFormat.IMPORT_FAILURE_HANDLER_CLASS);
       throw new IOException(ex);
     }

     // Verify handler class is a subclass of SQLFailureHandler
     if (!SQLFailureHandler.class.isAssignableFrom(connHandlerClass)) {
       String error = "A subclass of " + SQLFailureHandler.class.getName()
         + " is expected. Actual class set is: " + connHandlerClass.getName();
       LOG.error(error);
       throw new IOException(error);
     }
     LOG.trace("Using connection handler class: " + connHandlerClass);

     // Load the configured connection failure handler
     failureHandler = ReflectionUtils.newInstance(
       (Class<? extends SQLFailureHandler>)connHandlerClass, conf);

     // Initialize the connection handler with using job configuration
     failureHandler.initialize(conf);

     // Get the split-by column
     splitColumn = getDBConf().getInputOrderBy();
     if (splitColumn == null || splitColumn.length() == 0) {
       throw new IOException("Split column must be set");
     }

     // Ensure the split-column is not escaped so that we can use it to search
     // in the record map
     int splitColLen = splitColumn.length();
     if (splitColLen > 2 && splitColumn.charAt(0) == '['
       && splitColumn.charAt(splitColLen-1) == ']') {
       splitColumn = splitColumn.substring(1, splitColLen - 1);
     }
   }

   @Override
   /**
    * Read the next key, value pair.
    * Try to recover failed connections using the configured connection failure
    * handler before retrying the failed operation
    */
   public boolean nextKeyValue() throws IOException {
     boolean valueReceived = false;
     int retryCount = RETRY_MAX;
     boolean doRetry = true;

     do {
       try {
         // Try to get the next key/value pairs
         valueReceived = super.nextKeyValue();
         doRetry = false;
       } catch (IOException ioEx) {
         LOG.warn("Trying to recover from DB read failure: ", ioEx);
         Throwable cause = ioEx.getCause();

         // Use configured connection handler to recover from the connection
         // failure and use the newly constructed connection.
         // If the failure cannot be recovered, an exception is thrown
         if (failureHandler.canHandleFailure(cause)) {
           // Recover from connection failure
           Connection conn = failureHandler.recover();

           // Configure the new connection before using it
           configureConnection(conn);
           setConnection(conn);

           --retryCount;
           doRetry = (retryCount >= 0);
         } else {
           // Cannot recovered using configured handler, re-throw
           throw new IOException("Cannection handler cannot recover failure: ",
               ioEx);
         }
       }
     } while (doRetry);

     // Rethrow the exception if all retry attempts are consumed
     if (retryCount < 0) {
       throw new IOException("Failed to read from database after "
         + RETRY_MAX + " retries.");
     }

     return valueReceived;
   }

   /**
    * Configure the provided Connection for record reads.
    */
   protected void configureConnection(Connection conn) throws IOException {
     try {
       conn.setAutoCommit(false);
       conn.setTransactionIsolation(Connection.TRANSACTION_READ_COMMITTED);
     } catch (SQLException sqlEx) {
       LOG.error("Failed to configure SQL Connection");
       throw new IOException(sqlEx);
     }
   }

   /** Returns the query for selecting the records,
    * For handling connection recovery we always want to start from the last
    * record that was successfully read.
    */
   protected String getSelectQuery() {
     // Last seen record key is only expected to be unavailable if no reads
     // ever happened
     String selectQuery;
     if (lastRecordKey == null) {
       selectQuery = super.getSelectQuery();
     } else {
       // If last record key is available, construct the select query to start
       // from
       DataDrivenDBInputFormat.DataDrivenDBInputSplit dataSplit =
           (DataDrivenDBInputFormat.DataDrivenDBInputSplit) getSplit();
       StringBuilder lowerClause = new StringBuilder();
       lowerClause.append(getDBConf().getInputOrderBy());
       lowerClause.append(" > ");
       lowerClause.append(lastRecordKey.toString());

       // Get the select query with the lowerClause, and split upper clause
       selectQuery = getSelectQuery(lowerClause.toString(),
           dataSplit.getUpperClause());
     }

     return selectQuery;
   }
 }
	/**
	* 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.
	*/
	package org.apache.sqoop.mapreduce.db;

	import java.io.IOException;
	import java.sql.Connection;
	import java.sql.SQLException;

	import org.apache.commons.logging.Log;
	import org.apache.commons.logging.LogFactory;
	import org.apache.hadoop.conf.Configuration;
	import org.apache.hadoop.util.ReflectionUtils;
	import org.apache.sqoop.mapreduce.sqlserver.SqlServerRecordReader;
	import org.apache.hadoop.mapreduce.InputSplit;
	import org.apache.hadoop.mapreduce.TaskAttemptContext;

	import com.cloudera.sqoop.mapreduce.db.DBConfiguration;
	import com.cloudera.sqoop.mapreduce.db.DBInputFormat;
	import com.cloudera.sqoop.mapreduce.db.DataDrivenDBInputFormat;

	import org.apache.sqoop.lib.SqoopRecord;

	/**
	* A RecordReader that reads records from a SQL table.
	* This record reader handles connection failures using the configured
	* connection failure handler
	*/
	public class SQLServerDBRecordReader<T extends SqoopRecord> extends
	SqlServerRecordReader<T> {

	private static final Log LOG =
	LogFactory.getLog(SQLServerDBRecordReader.class);

	// The SQL handler to be used for recovering failed read operations
	protected SQLFailureHandler failureHandler = null;

	// Recover failed reads for RETRY_MAX
	protected static final int RETRY_MAX = 3;

	// Name of the split column used to re-generate selectQueries after
	// connection failures
	private String splitColumn;
	private String lastRecordKey;

	public SQLServerDBRecordReader(DBInputFormat.DBInputSplit split,
	Class<T> inputClass, Configuration conf, Connection conn,
	DBConfiguration dbConfig, String cond, String [] fields, String table,
	String dbProduct) throws SQLException {
	super(split, inputClass, conf, conn, dbConfig, cond, fields, table);
	}

	@Override
	/** {@inheritDoc} */
	public T getCurrentValue() {
	T val = super.getCurrentValue();
	// Lookup the key of the last read record to use for recovering
	// As documented, the map may not be null, though it may be empty.
	Object lastRecordSplitCol = val.getFieldMap().get(splitColumn);
	lastRecordKey = (lastRecordSplitCol == null) ? null
	: lastRecordSplitCol.toString();
	return val;
	}

	/**
	* Load the SQLFailureHandler configured for use by the record reader.
	*/
	public void initialize(InputSplit inputSplit, TaskAttemptContext context)
	throws IOException, InterruptedException {
	// Load the configured connection failure handler
	Configuration conf = getConf();
	if (conf == null) {
	LOG.error("Configuration cannot be NULL");
	}

	Class connHandlerClass;
	try {
	String className = conf.get(
	SQLServerDBInputFormat.IMPORT_FAILURE_HANDLER_CLASS);

	// Get the class-name set in configuration
	connHandlerClass = conf.getClassByName(className);
	} catch (ClassNotFoundException ex) {
	LOG.error("Failed to find class: "
	+ SQLServerDBInputFormat.IMPORT_FAILURE_HANDLER_CLASS);
	throw new IOException(ex);
	}

	// Verify handler class is a subclass of SQLFailureHandler
	if (!SQLFailureHandler.class.isAssignableFrom(connHandlerClass)) {
	String error = "A subclass of " + SQLFailureHandler.class.getName()
	+ " is expected. Actual class set is: " + connHandlerClass.getName();
	LOG.error(error);
	throw new IOException(error);
	}
	LOG.trace("Using connection handler class: " + connHandlerClass);

	// Load the configured connection failure handler
	failureHandler = ReflectionUtils.newInstance(
	(Class<? extends SQLFailureHandler>)connHandlerClass, conf);

	// Initialize the connection handler with using job configuration
	failureHandler.initialize(conf);

	// Get the split-by column
	splitColumn = getDBConf().getInputOrderBy();
	if (splitColumn == null \|\| splitColumn.length() == 0) {
	throw new IOException("Split column must be set");
	}

	// Ensure the split-column is not escaped so that we can use it to search
	// in the record map
	int splitColLen = splitColumn.length();
	if (splitColLen > 2 && splitColumn.charAt(0) == '['
	&& splitColumn.charAt(splitColLen-1) == ']') {
	splitColumn = splitColumn.substring(1, splitColLen - 1);
	}
	}

	@Override
	/**
	* Read the next key, value pair.
	* Try to recover failed connections using the configured connection failure
	* handler before retrying the failed operation
	*/
	public boolean nextKeyValue() throws IOException {
	boolean valueReceived = false;
	int retryCount = RETRY_MAX;
	boolean doRetry = true;

	do {
	try {
	// Try to get the next key/value pairs
	valueReceived = super.nextKeyValue();
	doRetry = false;
	} catch (IOException ioEx) {
	LOG.warn("Trying to recover from DB read failure: ", ioEx);
	Throwable cause = ioEx.getCause();

	// Use configured connection handler to recover from the connection
	// failure and use the newly constructed connection.
	// If the failure cannot be recovered, an exception is thrown
	if (failureHandler.canHandleFailure(cause)) {
	// Recover from connection failure
	Connection conn = failureHandler.recover();

	// Configure the new connection before using it
	configureConnection(conn);
	setConnection(conn);

	--retryCount;
	doRetry = (retryCount >= 0);
	} else {
	// Cannot recovered using configured handler, re-throw
	throw new IOException("Cannection handler cannot recover failure: ",
	ioEx);
	}
	}
	} while (doRetry);

	// Rethrow the exception if all retry attempts are consumed
	if (retryCount < 0) {
	throw new IOException("Failed to read from database after "
	+ RETRY_MAX + " retries.");
	}

	return valueReceived;
	}

	/**
	* Configure the provided Connection for record reads.
	*/
	protected void configureConnection(Connection conn) throws IOException {
	try {
	conn.setAutoCommit(false);
	conn.setTransactionIsolation(Connection.TRANSACTION_READ_COMMITTED);
	} catch (SQLException sqlEx) {
	LOG.error("Failed to configure SQL Connection");
	throw new IOException(sqlEx);
	}
	}

	/** Returns the query for selecting the records,
	* For handling connection recovery we always want to start from the last
	* record that was successfully read.
	*/
	protected String getSelectQuery() {
	// Last seen record key is only expected to be unavailable if no reads
	// ever happened
	String selectQuery;
	if (lastRecordKey == null) {
	selectQuery = super.getSelectQuery();
	} else {
	// If last record key is available, construct the select query to start
	// from
	DataDrivenDBInputFormat.DataDrivenDBInputSplit dataSplit =
	(DataDrivenDBInputFormat.DataDrivenDBInputSplit) getSplit();
	StringBuilder lowerClause = new StringBuilder();
	lowerClause.append(getDBConf().getInputOrderBy());
	lowerClause.append(" > ");
	lowerClause.append(lastRecordKey.toString());

	// Get the select query with the lowerClause, and split upper clause
	selectQuery = getSelectQuery(lowerClause.toString(),
	dataSplit.getUpperClause());
	}

	return selectQuery;
	}
	}