内容简介:玩转大数据系列之Apache Pig如何与MySQL集成(三)
上篇介绍了如何把Pig的结果存储到Solr中,那么可能就会有朋友问了,为什么不存到数据库呢? 不支持还是? 其实只要我们愿意,我们可以存储它的结果集到任何地方,只需要重写我们自己的StoreFunc类即可。 关于如何将Pig分析完的结果存储到数据库,在pig的piggy贡献组织里,已经有了对应的UDF了,piggybank是非apache官方提供的 工具 函数,里面的大部分的UDF都是,其他公司或着个人在后来使用时贡献的,这些工具类,虽然没有正式划入pig的源码包里,但是pig每次发行的时候,都会以扩展库的形式附带,编译后会放在pig根目录下一个叫contrib的目录下, piggybank的地址是 https://cwiki.apache.org/confluence/display/PIG/PiggyBank ,感兴趣的朋友们,可以看一看。 将pig分析完的结果存入到数据库,也是非常简单的,需要的条件有: (1)piggybank.jar的jar包 (2)依赖数据库的对应的驱动jar 有一点需要注意下,在将结果存储到数据库之前,一定要确保有访问和写入数据库的权限,否则任务就会失败! 散仙在存储到远程的 MySQL 上,就是由于权限的问题,而写入失败了,具体的异常是这样描述的:
Access denied for user 'root'@'localhost'
当出现上面异常的时候,就意味着权限写入有问题,我们使用以下的授权方法,来给目标机赋予权限: (1)允许所有的机器ip访问 GRANT ALL PRIVILEGES ON *.* TO 'myuser'@'%' IDENTIFIED BY 'mypassword' WITH GRANT OPTION; (2)允许指定的机器ip访问: 1. GRANT ALL PRIVILEGES ON *.* TO 'myuser'@'192.168.1.3' IDENTIFIED BY 'mypassword' WITH GRANT OPTION;
确定有权限之后,我们就可以造一份数据,测试是否可以将HDFS上的数据存储到数据库中,测试数据如下:
1,2,3 1,2,4 2,2,4 3,4,2 8,2,4
提前在对应的MySQL上,建库建表建字段,看下散仙测试表的结构:
最后,在来看下我们的pig脚本是如何定义和使用的:
--注册数据库驱动包和piggybank的jar register ./dependfiles/mysql-connector-java-5.1.23-bin.jar; register ./dependfiles/piggybank.jar --为了能使schemal和数据库对应起来,建议在这个地方给数据加上列名 a = load '/tmp/dongliang/g.txt' using PigStorage(',') as (id:int,name:chararray,count:int) ; --过滤出id大于2的数据 a = filter a by id > 2; --存储结果到数据库里 STORE a INTO '/tmp/dbtest' using org.apache.pig.piggybank.storage.DBStorage('com.mysql.jdbc.Driver', 'jdbc:mysql://192.168.146.63/user', 'root', 'pwd', 'INSERT into pig(id,name,count) values (?,?,?)'); ~
执行成功后,我们再去查看数据库发现已经将pig处理后的数据正确的写入到了数据库中:
最后,附上DBStore类的源码:
/* * 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.pig.piggybank.storage; import org.joda.time.DateTime; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.io.NullWritable; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.JobContext; import org.apache.hadoop.mapreduce.OutputCommitter; import org.apache.hadoop.mapreduce.OutputFormat; import org.apache.hadoop.mapreduce.RecordWriter; import org.apache.hadoop.mapreduce.TaskAttemptContext; import org.apache.pig.StoreFunc; import org.apache.pig.backend.executionengine.ExecException; import org.apache.pig.data.DataByteArray; import org.apache.pig.data.DataType; import org.apache.pig.data.Tuple; import java.io.IOException; import java.sql.*; public class DBStorage extends StoreFunc { private final Log log = LogFactory.getLog(getClass()); private PreparedStatement ps; private Connection con; private String jdbcURL; private String user; private String pass; private int batchSize; private int count = 0; private String insertQuery; public DBStorage(String driver, String jdbcURL, String insertQuery) { this(driver, jdbcURL, null, null, insertQuery, "100"); } public DBStorage(String driver, String jdbcURL, String user, String pass, String insertQuery) throws SQLException { this(driver, jdbcURL, user, pass, insertQuery, "100"); } public DBStorage(String driver, String jdbcURL, String user, String pass, String insertQuery, String batchSize) throws RuntimeException { log.debug("DBStorage(" + driver + "," + jdbcURL + "," + user + ",XXXX," + insertQuery + ")"); try { Class.forName(driver); } catch (ClassNotFoundException e) { log.error("can't load DB driver:" + driver, e); throw new RuntimeException("Can't load DB Driver", e); } this.jdbcURL = jdbcURL; this.user = user; this.pass = pass; this.insertQuery = insertQuery; this.batchSize = Integer.parseInt(batchSize); } /** * Write the tuple to Database directly here. */ public void putNext(Tuple tuple) throws IOException { int sqlPos = 1; try { int size = tuple.size(); for (int i = 0; i < size; i++) { try { Object field = tuple.get(i); switch (DataType.findType(field)) { case DataType.NULL: ps.setNull(sqlPos, java.sql.Types.VARCHAR); sqlPos++; break; case DataType.BOOLEAN: ps.setBoolean(sqlPos, (Boolean) field); sqlPos++; break; case DataType.INTEGER: ps.setInt(sqlPos, (Integer) field); sqlPos++; break; case DataType.LONG: ps.setLong(sqlPos, (Long) field); sqlPos++; break; case DataType.FLOAT: ps.setFloat(sqlPos, (Float) field); sqlPos++; break; case DataType.DOUBLE: ps.setDouble(sqlPos, (Double) field); sqlPos++; break; case DataType.DATETIME: ps.setDate(sqlPos, new Date(((DateTime) field).getMillis())); sqlPos++; break; case DataType.BYTEARRAY: byte[] b = ((DataByteArray) field).get(); ps.setBytes(sqlPos, b); sqlPos++; break; case DataType.CHARARRAY: ps.setString(sqlPos, (String) field); sqlPos++; break; case DataType.BYTE: ps.setByte(sqlPos, (Byte) field); sqlPos++; break; case DataType.MAP: case DataType.TUPLE: case DataType.BAG: throw new RuntimeException("Cannot store a non-flat tuple " + "using DbStorage"); default: throw new RuntimeException("Unknown datatype " + DataType.findType(field)); } } catch (ExecException ee) { throw new RuntimeException(ee); } } ps.addBatch(); count++; if (count > batchSize) { count = 0; ps.executeBatch(); ps.clearBatch(); ps.clearParameters(); } } catch (SQLException e) { try { log .error("Unable to insert record:" + tuple.toDelimitedString("\t"), e); } catch (ExecException ee) { // do nothing } if (e.getErrorCode() == 1366) { // errors that come due to utf-8 character encoding // ignore these kind of errors TODO: Temporary fix - need to find a // better way of handling them in the argument statement itself } else { throw new RuntimeException("JDBC error", e); } } } class MyDBOutputFormat extends OutputFormat<NullWritable, NullWritable> { @Override public void checkOutputSpecs(JobContext context) throws IOException, InterruptedException { // IGNORE } @Override public OutputCommitter getOutputCommitter(TaskAttemptContext context) throws IOException, InterruptedException { return new OutputCommitter() { @Override public void abortTask(TaskAttemptContext context) throws IOException { try { if (ps != null) { ps.close(); } if (con != null) { con.rollback(); con.close(); } } catch (SQLException sqe) { throw new IOException(sqe); } } @Override public void commitTask(TaskAttemptContext context) throws IOException { if (ps != null) { try { ps.executeBatch(); con.commit(); ps.close(); con.close(); ps = null; con = null; } catch (SQLException e) { log.error("ps.close", e); throw new IOException("JDBC Error", e); } } } @Override public boolean needsTaskCommit(TaskAttemptContext context) throws IOException { return true; } @Override public void cleanupJob(JobContext context) throws IOException { // IGNORE } @Override public void setupJob(JobContext context) throws IOException { // IGNORE } @Override public void setupTask(TaskAttemptContext context) throws IOException { // IGNORE } }; } @Override public RecordWriter<NullWritable, NullWritable> getRecordWriter( TaskAttemptContext context) throws IOException, InterruptedException { // We don't use a record writer to write to database return new RecordWriter<NullWritable, NullWritable>() { @Override public void close(TaskAttemptContext context) { // Noop } @Override public void write(NullWritable k, NullWritable v) { // Noop } }; } } @SuppressWarnings("unchecked") @Override public OutputFormat getOutputFormat() throws IOException { return new MyDBOutputFormat(); } /** * Initialise the database connection and prepared statement here. */ @SuppressWarnings("unchecked") @Override public void prepareToWrite(RecordWriter writer) throws IOException { ps = null; con = null; if (insertQuery == null) { throw new IOException("SQL Insert command not specified"); } try { if (user == null || pass == null) { con = DriverManager.getConnection(jdbcURL); } else { con = DriverManager.getConnection(jdbcURL, user, pass); } con.setAutoCommit(false); ps = con.prepareStatement(insertQuery); } catch (SQLException e) { log.error("Unable to connect to JDBC @" + jdbcURL); throw new IOException("JDBC Error", e); } count = 0; } @Override public void setStoreLocation(String location, Job job) throws IOException { // IGNORE since we are writing records to DB. } }
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