由于预处理的数据都存储在cassandra里面,所以想要用spark进行数据分析的话，需要读取cassandra数据，并把分析结果也一并存回到cassandra；因此需要研究一下spark如何读写cassandra。
话说这个单词敲起来好累，说是spark，其实就是看你开发语言是否有对应的driver了。
因为cassandra是datastax主打的，所以该公司也提供了spark的对应的driver了，见这里。
我就参考它的demo，使用scala语言来测试一把。
1.执行代码
//CassandraTest.scala
import org.apache.spark.{Logging, SparkContext, SparkConf} import com.datastax.spark.connector.cql.CassandraConnector object CassandraTestApp { def main(args: Array[String]) {
#配置spark，cassandra的ip，这里都是本机 val SparkMasterHost = "127.0.0.1" val CassandraHost = "127.0.0.1" // Tell Spark the address of one Cassandra node: val conf = new SparkConf(true) .set("spark.cassandra.connection.host", CassandraHost) .set("spark.cleaner.ttl", "3600") .setMaster("local[12]") .setAppName("CassandraTestApp") // Connect to the Spark cluster: lazy val sc = new SparkContext(conf)
//预处理脚本,连接的时候就执行这些 CassandraConnector(conf).withSessionDo { session => session.execute("CREATE KEYSPACE IF NOT EXISTS test WITH REPLICATION = {'class': 'SimpleStrategy', 'replication_factor': 1 }") session.execute("CREATE TABLE IF NOT EXISTS test.key_value (key INT PRIMARY KEY, value VARCHAR)") session.execute("TRUNCATE test.key_value") session.execute("INSERT INTO test.key_value(key, value) VALUES (1, 'first row')") session.execute("INSERT INTO test.key_value(key, value) VALUES (2, 'second row')") session.execute("INSERT INTO test.key_value(key, value) VALUES (3, 'third row')") }
//加载connector import com.datastax.spark.connector._ // Read table test.kv and print its contents: val rdd = sc.cassandraTable("test", "key_value").select("key", "value") rdd.collect().foreach(row => println(s"Existing Data: $row")) // Write two new rows to the test.kv table: val col = sc.parallelize(Seq((4, "fourth row"), (5, "fifth row"))) col.saveToCassandra("test", "key_value", SomeColumns("key", "value")) // Assert the two new rows were stored in test.kv table: assert(col.collect().length == 2) col.collect().foreach(row => println(s"New Data: $row")) println(s"Work completed, stopping the Spark context.") sc.stop() } }
2.目录结构
由于构建工具是用sbt，所以目录结构也必须遵循sbt规范，主要是build.sbt 和 src目录， 其它目录会自动生成。
qpzhang@qpzhangdeMac-mini:~/scala_code/CassandraTest $ll total 8 drwxr-xr-x 6 qpzhang staff 204 11 26 12:14 ./ drwxr-xr-x 10 qpzhang staff 340 11 25 17:30 ../ -rw-r--r-- 1 qpzhang staff 460 11 26 10:11 build.sbt drwxr-xr-x 3 qpzhang staff 102 11 25 17:42 project/ drwxr-xr-x 3 qpzhang staff 102 11 25 17:32 src/ drwxr-xr-x 6 qpzhang staff 204 11 25 17:55 target/ qpzhang@qpzhangdeMac-mini:~/scala_code/CassandraTest $tree src/ src/ └── main └── scala └── CassandraTest.scala
qpzhang@qpzhangdeMac-mini:~/scala_code/CassandraTest $cat build.sbt name := "CassandraTest" version := "1.0" scalaVersion := "2.10.4" libraryDependencies += "org.apache.spark" %% "spark-core" % "1.5.2" % "provided" libraryDependencies += "com.datastax.spark" %% "spark-cassandra-connector" % "1.5.0-M2" assemblyMergeStrategy in assembly := { case PathList(ps @ _*) if ps.last endsWith ".properties" => MergeStrategy.first case x => val oldStrategy = (assemblyMergeStrategy in assembly).value oldStrategy(x) }
这里需要注意的是，sbt安装的是当时最新版本 0.13 , 并且安装了 assembly插件(这里要吐槽一下sbt，下载一坨坨的jar包，最好有FQ代理，否则下载等待时间很长)。
qpzhang@qpzhangdeMac-mini:~/scala_code/CassandraTest $cat ~/.sbt/0.13/plugins/plugins.sbt addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "2.5.0") addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.14.1")
3.sbt编译打包
在build.sbt 目录下，使用sbt命令启动。
然后使用 compile 命令进行编译，使用assembly进行打包。
在次期间，遇到了sbt-assembly-deduplicate-error的问题，参考这里。
> compile [success] Total time: 0 s, completed 2015-11-26 10:11:50 >> assembly [info] Including from cache: slf4j-api-1.7.5.jar [info] Including from cache: metrics-core-3.0.2.jar [info] Including from cache: netty-codec-4.0.27.Final.jar [info] Including from cache: netty-handler-4.0.27.Final.jar [info] Including from cache: netty-common-4.0.27.Final.jar [info] Including from cache: joda-time-2.3.jar [info] Including from cache: netty-buffer-4.0.27.Final.jar [info] Including from cache: commons-lang3-3.3.2.jar [info] Including from cache: jsr166e-1.1.0.jar [info] Including from cache: cassandra-clientutil-2.1.5.jar [info] Including from cache: joda-convert-1.2.jar [info] Including from cache: netty-transport-4.0.27.Final.jar [info] Including from cache: guava-16.0.1.jar [info] Including from cache: spark-cassandra-connector_2.10-1.5.0-M2.jar [info] Including from cache: cassandra-driver-core-2.2.0-rc3.jar [info] Including from cache: scala-reflect-2.10.5.jar [info] Including from cache: scala-library-2.10.5.jar [info] Checking every *.class/*.jar file's SHA-1. [info] Merging files... [warn] Merging 'META-INF/INDEX.LIST' with strategy 'discard' [warn] Merging 'META-INF/MANIFEST.MF' with strategy 'discard' [warn] Merging 'META-INF/io.netty.versions.properties' with strategy 'first' [warn] Merging 'META-INF/maven/com.codahale.metrics/metrics-core/pom.xml' with strategy 'discard' [warn] Merging 'META-INF/maven/com.datastax.cassandra/cassandra-driver-core/pom.xml' with strategy 'discard' [warn] Merging 'META-INF/maven/com.google.guava/guava/pom.xml' with strategy 'discard' [warn] Merging 'META-INF/maven/com.twitter/jsr166e/pom.xml' with strategy 'discard' [warn] Merging 'META-INF/maven/io.netty/netty-buffer/pom.xml' with strategy 'discard' [warn] Merging 'META-INF/maven/io.netty/netty-codec/pom.xml' with strategy 'discard' [warn] Merging 'META-INF/maven/io.netty/netty-common/pom.xml' with strategy 'discard' [warn] Merging 'META-INF/maven/io.netty/netty-handler/pom.xml' with strategy 'discard' [warn] Merging 'META-INF/maven/io.netty/netty-transport/pom.xml' with strategy 'discard' [warn] Merging 'META-INF/maven/joda-time/joda-time/pom.xml' with strategy 'discard' [warn] Merging 'META-INF/maven/org.apache.commons/commons-lang3/pom.xml' with strategy 'discard' [warn] Merging 'META-INF/maven/org.joda/joda-convert/pom.xml' with strategy 'discard' [warn] Merging 'META-INF/maven/org.slf4j/slf4j-api/pom.xml' with strategy 'discard' [warn] Strategy 'discard' was applied to 15 files [warn] Strategy 'first' was applied to a file [info] SHA-1: d2cb403e090e6a3ae36b08c860b258c79120fc90 [info] Packaging /Users/qpzhang/scala_code/CassandraTest/target/scala-2.10/CassandraTest-assembly-1.0.jar ... [info] Done packaging. [success] Total time: 19 s, completed 2015-11-26 10:12:22
4.提交到spark，执行结果
qpzhang@qpzhangdeMac-mini:~/project/spark-1.5.2-bin-hadoop2.6 $./bin/spark-submit --class "CassandraTestApp" --master local[4] ~/scala_code/CassandraTest/target/scala-2.10/CassandraTest-assembly-1.0.jar //........................... 5/11/26 11:40:23 INFO TaskSetManager: Starting task 0.0 in stage 0.0 (TID 0, localhost, NODE_LOCAL, 26660 bytes) 15/11/26 11:40:23 INFO Executor: Running task 0.0 in stage 0.0 (TID 0) 15/11/26 11:40:23 INFO Executor: Fetching http://10.60.215.42:57683/jars/CassandraTest-assembly-1.0.jar with timestamp 1448509221160 15/11/26 11:40:23 INFO CassandraConnector: Disconnected from Cassandra cluster: Test Cluster 15/11/26 11:40:23 INFO Utils: Fetching http://10.60.215.42:57683/jars/CassandraTest-assembly-1.0.jar to /private/var/folders/2l/195zcc1n0sn2wjfjwf9hl9d80000gn/T/spark-4030cadf-8489-4540-976e-e98eedf50412/userFiles-63085bda-aa04-4906-9621-c1cedd98c163/fetchFileTemp7487594 894647111926.tmp 15/11/26 11:40:23 INFO Executor: Adding file:/private/var/folders/2l/195zcc1n0sn2wjfjwf9hl9d80000gn/T/spark-4030cadf-8489-4540-976e-e98eedf50412/userFiles-63085bda-aa04-4906-9621-c1cedd98c163/CassandraTest-assembly-1.0.jar to class loader 15/11/26 11:40:24 INFO Cluster: New Cassandra host localhost/127.0.0.1:9042 added 15/11/26 11:40:24 INFO CassandraConnector: Connected to Cassandra cluster: Test Cluster 15/11/26 11:40:25 INFO Executor: Finished task 0.0 in stage 0.0 (TID 0). 2676 bytes result sent to driver 15/11/26 11:40:25 INFO TaskSetManager: Finished task 0.0 in stage 0.0 (TID 0) in 2462 ms on localhost (1/1) 15/11/26 11:40:25 INFO TaskSchedulerImpl: Removed TaskSet 0.0, whose tasks have all completed, from pool 15/11/26 11:40:25 INFO DAGScheduler: ResultStage 0 (collect at CassandraTest.scala:32) finished in 2.481 s 15/11/26 11:40:25 INFO DAGScheduler: Job 0 finished: collect at CassandraTest.scala:32, took 2.940601 s Existing Data: CassandraRow{key: 1, value: first row} Existing Data: CassandraRow{key: 2, value: second row} Existing Data: CassandraRow{key: 3, value: third row} //.................... 5/11/26 11:40:27 INFO TaskSchedulerImpl: Removed TaskSet 3.0, whose tasks have all completed, from pool 15/11/26 11:40:27 INFO DAGScheduler: ResultStage 3 (collect at CassandraTest.scala:41) finished in 0.032 s 15/11/26 11:40:27 INFO DAGScheduler: Job 3 finished: collect at CassandraTest.scala:41, took 0.046502 s New Data: (4,fourth row) New Data: (5,fifth row) Work completed, stopping the Spark context.
cassandra中的数据
cqlsh:test> select * from key_value ; key | value -----+------------ 5 | fifth row 1 | first row 2 | second row 4 | fourth row 3 | third row (5 rows)
到此位置，还算顺利，除了assembly 重复文件的问题，都还算ok。
