org.apache.sqoop.mapreduce.db.SQLServerConnectionFailureHandler.java Source code

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Here is the source code for org.apache.sqoop.mapreduce.db.SQLServerConnectionFailureHandler.java

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/**
 * 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.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Connection failure handler for SQL Server which extends basic retry
 * mechanism for handling connection failures. Retry settings are embedded
 * in job configuration
 */
public class SQLServerConnectionFailureHandler extends BasicRetrySQLFailureHandler {

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

    protected static final String CONNECTION_RESET_ERR_REGEX = "(^Connection reset)(.*?)";
    protected static final String SQLSTATE_CODE_CONNECTION_RESET = "08S01";

    protected static final String VALIDATION_QUERY = "SELECT CONVERT(NVARCHAR, CONTEXT_INFO()) AS contextInfo";

    public SQLServerConnectionFailureHandler() {
    }

    /**
     * Handle only connection reset or TCP exceptions.
     */
    public boolean canHandleFailure(Throwable failureCause) {
        if (!super.canHandleFailure(failureCause)) {
            return false;
        }
        SQLException sqlEx = (SQLException) failureCause;
        String errStateCode = sqlEx.getSQLState();
        boolean canHandle = false;
        // By default check SQLState code if available
        if (errStateCode != null) {
            canHandle = errStateCode == SQLSTATE_CODE_CONNECTION_RESET;
        } else {
            errStateCode = "NULL";
            // In case SQLState code is not available, check the exception message
            String errMsg = sqlEx.getMessage();
            canHandle = errMsg.matches(CONNECTION_RESET_ERR_REGEX);
        }

        if (!canHandle) {
            LOG.warn("Cannot handle error with SQL State: " + errStateCode);
        }
        return canHandle;
    }

    /**
     * Verify the provided connection is valid. For SQL Server we test the
     * connection by querying the session context.
     */
    protected boolean validateConnection(Connection connection) throws SQLException {
        boolean isValid = false;
        String contextInfo = null;
        if (super.validateConnection(connection)) {
            // Execute the validation query
            PreparedStatement stmt = connection.prepareStatement(VALIDATION_QUERY);
            ResultSet results = stmt.executeQuery();

            // Read the context from the result set
            if (results.next()) {
                contextInfo = results.getString("contextInfo");
                LOG.info("Session context is: " + ((contextInfo == null) ? "NULL" : contextInfo));
                isValid = true;
            }
        }
        return isValid;
    }
}