spark sql on hive初探
前一段时间由于shark项目停止更新，sql on spark拆分为两个方向，一个是spark sql on hive,另一个是hive on spark。hive on spark达到可用状态估计还要等很久的时间，所以打算试用下spark sql on hive，用来逐步替代目前mr on hive的工作。
当前试用的版本是spark1.0.0,如果要支持hive,必须重新进行编译，编译的命令有所变化
export MAVEN_OPTS="-Xmx2g -XX:MaxPermSize=512M -XX:ReservedCodeCacheSize=512m" mvn -Pyarn -Phive -Dhadoop.version=2.3.0-cdh5.0.0 -DskipTests clean package
写了段比较简单的代码
val conf = new SparkConf().setAppName("SqlOnHive")
val sc = new SparkContext(conf)
val hiveContext = new HiveContext(sc)
import hiveContext._
hql("FROM tmp.test SELECT id limit 1").foreach(println)
编译后export出jar文件，使用standalone模式，故采用java -cp的方式提交，提交之前需要将hive-site.xml文件copy到$SPARK_HOME/conf目录下
java -XX:PermSize=256M -cp /home/hadoop/hql.jar com.yintai.spark.sql.SqlOnHive spark://h031:7077
提交后会报异常
java.lang.RuntimeException: Error in configuring object at org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:109) at org.apache.hadoop.util.ReflectionUtils.setConf(ReflectionUtils.java:75) at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:133) at org.apache.spark.rdd.HadoopRDD.getInputFormat(HadoopRDD.scala:155) at org.apache.spark.rdd.HadoopRDD$$anon$1.<init>(HadoopRDD.scala:187) at org.apache.spark.rdd.HadoopRDD.compute(HadoopRDD.scala:181) at org.apache.spark.rdd.HadoopRDD.compute(HadoopRDD.scala:93) at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:262) at org.apache.spark.rdd.RDD.iterator(RDD.scala:229) at org.apache.spark.rdd.MappedRDD.compute(MappedRDD.scala:31) at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:262) at org.apache.spark.rdd.RDD.iterator(RDD.scala:229) at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:35) at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:262) at org.apache.spark.rdd.RDD.iterator(RDD.scala:229) at org.apache.spark.rdd.MappedRDD.compute(MappedRDD.scala:31) at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:262) at org.apache.spark.rdd.RDD.iterator(RDD.scala:229) at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:35) at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:262) at org.apache.spark.rdd.RDD.iterator(RDD.scala:229) at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:158) at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:99) at org.apache.spark.scheduler.Task.run(Task.scala:51) at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:187) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918) at java.lang.Thread.run(Thread.java:662) Caused by: java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.hadoop.util.ReflectionUtils.setJobConf(ReflectionUtils.java:106) ... 27 more Caused by: java.lang.IllegalArgumentException: Compression codec com.hadoop.compression.lzo.LzoCodec not found. at org.apache.hadoop.io.compress.CompressionCodecFactory.getCodecClasses(CompressionCodecFactory.java:135) at org.apache.hadoop.io.compress.CompressionCodecFactory.<init>(CompressionCodecFactory.java:175) at org.apache.hadoop.mapred.TextInputFormat.configure(TextInputFormat.java:45) ... 32 more Caused by: java.lang.ClassNotFoundException: Class com.hadoop.compression.lzo.LzoCodec not found at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:1801) at org.apache.hadoop.io.compress.CompressionCodecFactory.getCodecClasses(CompressionCodecFactory.java:128) ... 34 more
解决办法是需要设置相关的环境变量，在spark-env.sh中设置
SPARK_LIBRARY_PATH=$SPARK_LIBRARY_PATH:/path/to/your/hadoop-lzo/libs/native SPARK_CLASSPATH=$SPARK_CLASSPATH:/path/to/your/hadoop-lzo/java/libs
修改过环境变量之后重新提交，继续报错
14/07/23 10:25:19 ERROR RetryingHMSHandler: NoSuchObjectException(message:There is no database named tmp) at org.apache.hadoop.hive.metastore.ObjectStore.getMDatabase(ObjectStore.java:431) at org.apache.hadoop.hive.metastore.ObjectStore.getDatabase(ObjectStore.java:441) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.hadoop.hive.metastore.RetryingRawStore.invoke(RetryingRawStore.java:124) at com.sun.proxy.$Proxy9.getDatabase(Unknown Source) at org.apache.hadoop.hive.metastore.HiveMetaStore$HMSHandler.get_database(HiveMetaStore.java:628) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.hadoop.hive.metastore.RetryingHMSHandler.invoke(RetryingHMSHandler.java:103) at com.sun.proxy.$Proxy10.get_database(Unknown Source) at org.apache.hadoop.hive.metastore.HiveMetaStoreClient.getDatabase(HiveMetaStoreClient.java:810) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.hadoop.hive.metastore.RetryingMetaStoreClient.invoke(RetryingMetaStoreClient.java:89) at com.sun.proxy.$Proxy11.getDatabase(Unknown Source) at org.apache.hadoop.hive.ql.metadata.Hive.getDatabase(Hive.java:1139) at org.apache.hadoop.hive.ql.metadata.Hive.databaseExists(Hive.java:1128) at org.apache.hadoop.hive.ql.exec.DDLTask.switchDatabase(DDLTask.java:3479) at org.apache.hadoop.hive.ql.exec.DDLTask.execute(DDLTask.java:237) at org.apache.hadoop.hive.ql.exec.Task.executeTask(Task.java:151) at org.apache.hadoop.hive.ql.exec.TaskRunner.runSequential(TaskRunner.java:65) at org.apache.hadoop.hive.ql.Driver.launchTask(Driver.java:1414) at org.apache.hadoop.hive.ql.Driver.execute(Driver.java:1192) at org.apache.hadoop.hive.ql.Driver.runInternal(Driver.java:1020) at org.apache.hadoop.hive.ql.Driver.run(Driver.java:888) at org.apache.spark.sql.hive.HiveContext.runHive(HiveContext.scala:185) at org.apache.spark.sql.hive.HiveContext.runSqlHive(HiveContext.scala:160) at org.apache.spark.sql.hive.HiveContext$QueryExecution.toRdd$lzycompute(HiveContext.scala:249) at org.apache.spark.sql.hive.HiveContext$QueryExecution.toRdd(HiveContext.scala:246) at org.apache.spark.sql.hive.HiveContext.hiveql(HiveContext.scala:85) at org.apache.spark.sql.hive.HiveContext.hql(HiveContext.scala:90) at com.yintai.spark.sql.SqlOnHive$.main(SqlOnHive.scala:20) at com.yintai.spark.sql.SqlOnHive.main(SqlOnHive.scala) 14/07/23 10:25:19 ERROR DDLTask: org.apache.hadoop.hive.ql.metadata.HiveException: Database does not exist: tmp at org.apache.hadoop.hive.ql.exec.DDLTask.switchDatabase(DDLTask.java:3480) at org.apache.hadoop.hive.ql.exec.DDLTask.execute(DDLTask.java:237) at org.apache.hadoop.hive.ql.exec.Task.executeTask(Task.java:151) at org.apache.hadoop.hive.ql.exec.TaskRunner.runSequential(TaskRunner.java:65) at org.apache.hadoop.hive.ql.Driver.launchTask(Driver.java:1414) at org.apache.hadoop.hive.ql.Driver.execute(Driver.java:1192) at org.apache.hadoop.hive.ql.Driver.runInternal(Driver.java:1020) at org.apache.hadoop.hive.ql.Driver.run(Driver.java:888) at org.apache.spark.sql.hive.HiveContext.runHive(HiveContext.scala:185) at org.apache.spark.sql.hive.HiveContext.runSqlHive(HiveContext.scala:160) at org.apache.spark.sql.hive.HiveContext$QueryExecution.toRdd$lzycompute(HiveContext.scala:249) at org.apache.spark.sql.hive.HiveContext$QueryExecution.toRdd(HiveContext.scala:246) at org.apache.spark.sql.hive.HiveContext.hiveql(HiveContext.scala:85) at org.apache.spark.sql.hive.HiveContext.hql(HiveContext.scala:90) at com.yintai.spark.sql.SqlOnHive$.main(SqlOnHive.scala:20) at com.yintai.spark.sql.SqlOnHive.main(SqlOnHive.scala)
造成这个错误的原因就是spark程序无法加载到hive-site.xml，从而无法获取到远程metastore服务的地址，只能在本地的derby数据库中查找，自然找不到相关库表的元数据信息。spark sql实际上是通过实例化HiveConf类来加载hive-site.xml文件的，这个跟hive cli的方式是一致的，代码如下
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
if (classLoader == null) {
classLoader = HiveConf.class.getClassLoader();
}
hiveDefaultURL = classLoader.getResource("hive-default.xml");
// Look for hive-site.xml on the CLASSPATH and log its location if found.
hiveSiteURL = classLoader.getResource("hive-site.xml");
使用java -cp提交的方式不能正确的设置环境变量，在1.0.0版本中，新增了使用spark-submit脚本进行提交的方式，后来改为使用此脚本来提交
/usr/lib/spark/bin/spark-submit --class com.yintai.spark.sql.SqlOnHive \ --master spark://h031:7077 \ --executor-memory 1g \ --total-executor-cores 1 \ /home/hadoop/hql.jar
这个脚本在提交过程中会设置SparkConf中的spark.executor.extraClassPath和spark.driver.extraClassPath属性，从而保证可以正确加载到所需的配置文件，到此测试成功。
目前spark sql on hive兼容了大部分hive的语法和UDF，在SQL解析的时候使用了Catalyst框架，作业在运行效率上高出hive很多，不过目前的版本还存在一些BUG，稳定性上会有一些问题，需要等到新的稳定版发布再进行进一步的测试。
参考资料
http://spark.apache.org/docs/1.0.0/sql-programming-guide.html
http://hsiamin.com/posts/2014/05/03/enable-lzo-compression-on-hadoop-pig-and-spark/