本文介绍如何配置Spark使用OSS Select加速数据查询，以及使用OSS Select查询数据的优势。
背景信息
说明 文中所有
${}的内容为环境变量，请根据您实际的环境修改。
步骤一：配置Spark支持读写OSS
由于Spark默认没有将OSS的支持包放到它的CLASSPATH里面，所以我们需要配置Spark支持读写OSS。您需要在所有的CDH节点执行以下操作：
步骤二：配置Spark支持OSS Select
OSS Select详情请参见OSS Select，以下内容基于oss-cn-shenzhen.aliyuncs.com这个OSS EndPoint来进行。您需要在所有的CDH节点执行以下操作：
对比测试
测试环境：使用spark on yarn进行对比测试，其中Node Manager节点是4个，每个节点最多可以运行4个container，每个container配备的资源是1核2GB内存。
测试数据：共630MB，包含3列，分别是姓名、公司和年龄。
ot@cdh-master jars]# hadoop fs -ls oss://select-test-sz/people/ Found 10 items -rw-rw-rw- 1 63079930 2018-10-30 17:03 oss://select-test-sz/people/part-00000 -rw-rw-rw- 1 63079930 2018-10-30 17:03 oss://select-test-sz/people/part-00001 -rw-rw-rw- 1 63079930 2018-10-30 17:05 oss://select-test-sz/people/part-00002 -rw-rw-rw- 1 63079930 2018-10-30 17:05 oss://select-test-sz/people/part-00003 -rw-rw-rw- 1 63079930 2018-10-30 17:06 oss://select-test-sz/people/part-00004 -rw-rw-rw- 1 63079930 2018-10-30 17:12 oss://select-test-sz/people/part-00005 -rw-rw-rw- 1 63079930 2018-10-30 17:14 oss://select-test-sz/people/part-00006 -rw-rw-rw- 1 63079930 2018-10-30 17:14 oss://select-test-sz/people/part-00007 -rw-rw-rw- 1 63079930 2018-10-30 17:15 oss://select-test-sz/people/part-00008 -rw-rw-rw- 1 63079930 2018-10-30 17:16 oss://select-test-sz/people/part-00009
进入到
${CDH_HOME}/lib/spark/，启动spark-shell ，分别测试使用OSS Select查询数据和不使用OSS Select查询数据：
[root@cdh-master spark]# ./bin/spark-shell
WARNING: User-defined SPARK_HOME (/opt/cloudera/parcels/CDH-6.0.1-1.cdh6.0.1.p0.590678/lib/spark) overrides detected (/opt/cloudera/parcels/CDH/lib/spark).
WARNING: Running spark-class from user-defined location.
Setting default log level to "WARN".
To adjust logging level use sc.setLogLevel(newLevel). For SparkR, use setLogLevel(newLevel).
Spark context Web UI available at http://x.x.x.x:4040
Spark context available as 'sc' (master = yarn, app id = application_1540887123331_0008).
Spark session available as 'spark'.
Welcome to
____ __
/ __/__ ___ _____/ /__
_\ \/ _ \/ _ `/ __/ '_/
/___/ .__/\_,_/_/ /_/\_\ version 2.2.0-cdh6.0.1
/_/
Using Scala version 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_152)
Type in expressions to have them evaluated.
Type :help for more information.
scala> val sqlContext = spark.sqlContext
sqlContext: org.apache.spark.sql.SQLContext = org.apache.spark.sql.SQLContext@4bdef487
scala> sqlContext.sql("CREATE TEMPORARY VIEW people USING com.aliyun.oss " +
| "OPTIONS (" +
| "oss.bucket 'select-test-sz', " +
| "oss.prefix 'people', " + // objects with this prefix belong to this table
| "oss.schema 'name string, company string, age long'," + // like 'column_a long, column_b string'
| "oss.data.format 'csv'," + // we only support csv now
| "oss.input.csv.header 'None'," +
| "oss.input.csv.recordDelimiter '\r\n'," +
| "oss.input.csv.fieldDelimiter ','," +
| "oss.input.csv.commentChar '#'," +
| "oss.input.csv.quoteChar '\"'," +
| "oss.output.csv.recordDelimiter '\n'," +
| "oss.output.csv.fieldDelimiter ','," +
| "oss.output.csv.quoteChar '\"'," +
| "oss.endpoint 'oss-cn-shenzhen.aliyuncs.com', " +
| "oss.accessKeyId 'Your Access Key Id', " +
| "oss.accessKeySecret 'Your Access Key Secret')")
res0: org.apache.spark.sql.DataFrame = []
scala> val sql: String = "select count(*) from people where name like 'Lora%'"
sql: String = select count(*) from people where name like 'Lora%'
scala> sqlContext.sql(sql).show()
+--------+
|count(1)|
+--------+
| 31770|
+--------+
scala> val textFile = sc.textFile("oss://select-test-sz/people/")
textFile: org.apache.spark.rdd.RDD[String] = oss://select-test-sz/people/ MapPartitionsRDD[8] at textFile at <console>:24
scala> textFile.map(line => line.split(',')).filter(_(0).startsWith("Lora")).count()
res3: Long = 31770
从下图可看到：使用OSS Select查询数据耗时为15s，不使用OSS Select查询数据耗时为54s，使用OSS Select能大幅度加快查询速度。
Spark对接OSS Select支持包的实现（Preview）
通过扩展Spark的
DataSource API 可以实现Spark对接OSS Select。通过实现PrunedFilteredScan，可以把需要的列和过滤条件下推到OSS Select执行。目前这个支持包还在开发中，定义的规范和支持的过滤条件如下：
- 定义的规范：
scala> sqlContext.sql("CREATE TEMPORARY VIEW people USING com.aliyun.oss " + | "OPTIONS (" + | "oss.bucket 'select-test-sz', " + | "oss.prefix 'people', " + // objects with this prefix belong to this table | "oss.schema 'name string, company string, age long'," + // like 'column_a long, column_b string' | "oss.data.format 'csv'," + // we only support csv now | "oss.input.csv.header 'None'," + | "oss.input.csv.recordDelimiter '\r\n'," + | "oss.input.csv.fieldDelimiter ','," + | "oss.input.csv.commentChar '#'," + | "oss.input.csv.quoteChar '\"'," + | "oss.output.csv.recordDelimiter '\n'," + | "oss.output.csv.fieldDelimiter ','," + | "oss.output.csv.quoteChar '\"'," + | "oss.endpoint 'oss-cn-shenzhen.aliyuncs.com', " + | "oss.accessKeyId 'Your Access Key Id', " + | "oss.accessKeySecret 'Your Access Key Secret')")字段 说明 oss.bucket 数据所在的Bucket。 oss.prefix 拥有这个前缀的Object都属于定义的这个TEMPORARY VIEW。 oss.schema 这个TEMPORARY VIEW的schema，目前通过字符串指定，后续会通过一个文件来指定schema。 oss.data.format 数据内容的格式，目前支持CSV格式，其他格式也会陆续支持。 oss.input.csv.* 定义CSV输入格式参数。 oss.output.csv.* 定义CSV输出格式参数。 oss.endpoint Bucket所在的Endpoint。 oss.accessKeyId 填写AccessKeyId。 oss.accessKeySecret 填写AccessKeySecret。 说明 目前只定义了基本参数，详情请参见 SelectObject，其余参数将陆续支持。 - 支持的过滤条件：
=,<,>,<=, >=,||,or,not,and,in,like(StringStartsWith,StringEndsWith,StringContains)。对于不能下推的过滤条件，例如算术运算、字符串拼接等通过PrunedFilteredScan获取不到的条件，则只下推需要的列到OSS Select。说明OSS Select还支持其他过滤条件，详情请参见 SelectObject。
对比TPC-H的查询
通过测试TPC-H中query1.sql对于lineitem这个table的查询性能，来检验配置效果。为了能使OSS Select过滤更多的数据，我们将where条件由l_shipdate <= '1998-09-16'改为where l_shipdate > '1997-09-16'，测试数据大小为2.27 GB。仅使用Spark SQL查询和在Spark SQL上使用OSS Select查询的方式如下：
- 仅使用Spark SQL查询
[root@cdh-master ~]# hadoop fs -ls oss://select-test-sz/data/lineitem.csv -rw-rw-rw- 1 2441079322 2018-10-31 11:18 oss://select-test-sz/data/lineitem.csv
- 在Spark SQL上使用OSS Select查询
scala> import org.apache.spark.sql.types.{IntegerType, LongType, StringType, StructField, StructType, DoubleType} import org.apache.spark.sql.types.{IntegerType, LongType, StringType, StructField, StructType, DoubleType} scala> import org.apache.spark.sql.{Row, SQLContext} import org.apache.spark.sql.{Row, SQLContext} scala> val sqlContext = spark.sqlContext sqlContext: org.apache.spark.sql.SQLContext = org.apache.spark.sql.SQLContext@74e2cfc5 scala> val textFile = sc.textFile("oss://select-test-sz/data/lineitem.csv") textFile: org.apache.spark.rdd.RDD[String] = oss://select-test-sz/data/lineitem.csv MapPartitionsRDD[1] at textFile at <console>:26 scala> val dataRdd = textFile.map(_.split('|')) dataRdd: org.apache.spark.rdd.RDD[Array[String]] = MapPartitionsRDD[2] at map at <console>:28 scala> val schema = StructType( | List( | StructField("L_ORDERKEY",LongType,true), | StructField("L_PARTKEY",LongType,true), | StructField("L_SUPPKEY",LongType,true), | StructField("L_LINENUMBER",IntegerType,true), | StructField("L_QUANTITY",DoubleType,true), | StructField("L_EXTENDEDPRICE",DoubleType,true), | StructField("L_DISCOUNT",DoubleType,true), | StructField("L_TAX",DoubleType,true), | StructField("L_RETURNFLAG",StringType,true), | StructField("L_LINESTATUS",StringType,true), | StructField("L_SHIPDATE",StringType,true), | StructField("L_COMMITDATE",StringType,true), | StructField("L_RECEIPTDATE",StringType,true), | StructField("L_SHIPINSTRUCT",StringType,true), | StructField("L_SHIPMODE",StringType,true), | StructField("L_COMMENT",StringType,true) | ) | ) schema: org.apache.spark.sql.types.StructType = StructType(StructField(L_ORDERKEY,LongType,true), StructField(L_PARTKEY,LongType,true), StructField(L_SUPPKEY,LongType,true), StructField(L_LINENUMBER,IntegerType,true), StructField(L_QUANTITY,DoubleType,true), StructField(L_EXTENDEDPRICE,DoubleType,true), StructField(L_DISCOUNT,DoubleType,true), StructField(L_TAX,DoubleType,true), StructField(L_RETURNFLAG,StringType,true), StructField(L_LINESTATUS,StringType,true), StructField(L_SHIPDATE,StringType,true), StructField(L_COMMITDATE,StringType,true), StructField(L_RECEIPTDATE,StringType,true), StructField(L_SHIPINSTRUCT,StringType,true), StructField(L_SHIPMODE,StringType,true), StructField(L_COMMENT,StringType,true)) scala> val dataRowRdd = dataRdd.map(p => Row(p(0).toLong, p(1).toLong, p(2).toLong, p(3).toInt, p(4).toDouble, p(5).toDouble, p(6).toDouble, p(7).toDouble, p(8), p(9), p(10), p(11), p(12), p(13), p(14), p(15))) dataRowRdd: org.apache.spark.rdd.RDD[org.apache.spark.sql.Row] = MapPartitionsRDD[3] at map at <console>:30 scala> val dataFrame = sqlContext.createDataFrame(dataRowRdd, schema) dataFrame: org.apache.spark.sql.DataFrame = [L_ORDERKEY: bigint, L_PARTKEY: bigint ... 14 more fields] scala> dataFrame.createOrReplaceTempView("lineitem") scala> spark.sql("select l_returnflag, l_linestatus, sum(l_quantity) as sum_qty, sum(l_extendedprice) as sum_base_price, sum(l_extendedprice * (1 - l_discount)) as sum_disc_price, sum(l_extendedprice * (1 - l_discount) * (1 + l_tax)) as sum_charge, avg(l_quantity) as avg_qty, avg(l_extendedprice) as avg_price, avg(l_discount) as avg_disc, count(*) as count_order from lineitem where l_shipdate > '1997-09-16' group by l_returnflag, l_linestatus order by l_returnflag, l_linestatus").show() +------------+------------+-----------+--------------------+--------------------+--------------------+------------------+------------------+-------------------+-----------+ |l_returnflag|l_linestatus| sum_qty| sum_base_price| sum_disc_price| sum_charge| avg_qty| avg_price| avg_disc|count_order| +------------+------------+-----------+--------------------+--------------------+--------------------+------------------+------------------+-------------------+-----------+ | N| O|7.5697385E7|1.135107538838699...|1.078345555027154...|1.121504616321447...|25.501957856643052|38241.036487881756|0.04999335309103123| 2968297| +------------+------------+-----------+--------------------+--------------------+--------------------+------------------+------------------+-------------------+-----------+ scala> sqlContext.sql("CREATE TEMPORARY VIEW item USING com.aliyun.oss " + | "OPTIONS (" + | "oss.bucket 'select-test-sz', " + | "oss.prefix 'data', " + | "oss.schema 'L_ORDERKEY long, L_PARTKEY long, L_SUPPKEY long, L_LINENUMBER int, L_QUANTITY double, L_EXTENDEDPRICE double, L_DISCOUNT double, L_TAX double, L_RETURNFLAG string, L_LINESTATUS string, L_SHIPDATE string, L_COMMITDATE string, L_RECEIPTDATE string, L_SHIPINSTRUCT string, L_SHIPMODE string, L_COMMENT string'," + | "oss.data.format 'csv'," + // we only support csv now | "oss.input.csv.header 'None'," + | "oss.input.csv.recordDelimiter '\n'," + | "oss.input.csv.fieldDelimiter '|'," + | "oss.input.csv.commentChar '#'," + | "oss.input.csv.quoteChar '\"'," + | "oss.output.csv.recordDelimiter '\n'," + | "oss.output.csv.fieldDelimiter ','," + | "oss.output.csv.commentChar '#'," + | "oss.output.csv.quoteChar '\"'," + | "oss.endpoint 'oss-cn-shenzhen.aliyuncs.com', " + | "oss.accessKeyId 'Your Access Key Id', " + | "oss.accessKeySecret 'Your Access Key Secret')") res2: org.apache.spark.sql.DataFrame = [] scala> sqlContext.sql("select l_returnflag, l_linestatus, sum(l_quantity) as sum_qty, sum(l_extendedprice) as sum_base_price, sum(l_extendedprice * (1 - l_discount)) as sum_disc_price, sum(l_extendedprice * (1 - l_discount) * (1 + l_tax)) as sum_charge, avg(l_quantity) as avg_qty, avg(l_extendedprice) as avg_price, avg(l_discount) as avg_disc, count(*) as count_order from item where l_shipdate > '1997-09-16' group by l_returnflag, l_linestatus order by l_returnflag, l_linestatus").show() scala> sqlContext.sql("select l_returnflag, l_linestatus, sum(l_quantity) as sum_qty, sum(l_extendedprice) as sum_base_price, sum(l_extendedprice * (1 - l_discount)) as sum_disc_price, sum(l_extendedprice * (1 - l_discount) * (1 + l_tax)) as sum_charge, avg(l_quantity) as avg_qty, avg(l_extendedprice) as avg_price, avg(l_discount) as avg_disc, count(*) as count_order from item where l_shipdate > '1997-09-16' group by l_returnflag, l_linestatus order by l_returnflag, l_linestatus").show() +------------+------------+-----------+--------------------+--------------------+--------------------+------------------+-----------------+-------------------+-----------+ |l_returnflag|l_linestatus| sum_qty| sum_base_price| sum_disc_price| sum_charge| avg_qty| avg_price| avg_disc|count_order| +------------+------------+-----------+--------------------+--------------------+--------------------+------------------+-----------------+-------------------+-----------+ | N| O|7.5697385E7|1.135107538838701E11|1.078345555027154...|1.121504616321447...|25.501957856643052|38241.03648788181|0.04999335309103024| 2968297| +------------+------------+-----------+--------------------+--------------------+--------------------+------------------+-----------------+-------------------+-----------+
从下图可以看出：在Spark SQL上使用OSS Select查询数据耗时为38s，在Spark SQL上不使用OSS Select查询数据耗时为2.5min，使用OSS Select可大幅度加快查询速度。
