1.sbt是什么
对于sbt 我也是小白, 为了搞spark看了一下scala，学习scala时指定的构建工具就是sbt（因为sbt也是用scala开发的嘛），起初在我眼里就是一个maven（虽然maven我也没怎么用），后面构建2个项目之后，发现还是蛮强大的，就是学习成本有点高。
哎，但是现在什么东东没有学习成本呢。扯远了，0.13版本的入门之旅参考：http://www.scala-sbt.org/0.13/tutorial/zh-cn/index.html
2.assembly是sbt的一个打包插件
下面是一个入门之旅里面的例子：
/* SimpleApp.scala */ import org.apache.spark.SparkContext import org.apache.spark.SparkContext._ import org.apache.spark.SparkConf object SimpleApp { def main(args: Array[String]) { val logFile = "YOUR_SPARK_HOME/README.md" // Should be some file on your system val conf = new SparkConf().setAppName("Simple Application") val sc = new SparkContext(conf) val logData = sc.textFile(logFile, 2).cache() val numAs = logData.filter(line => line.contains("a")).count() val numBs = logData.filter(line => line.contains("b")).count() println("Lines with a: %s, Lines with b: %s".format(numAs, numBs)) } }
#simple.sbt
name := "Simple Project" version := "1.0" scalaVersion := "2.10.4" libraryDependencies += "org.apache.spark" %% "spark-core" % "1.5.2"
# Your directory layout should look like this $ find . . ./simple.sbt ./src ./src/main ./src/main/scala ./src/main/scala/SimpleApp.scala # Package a jar containing your application $ sbt package ... [info] Packaging {..}/{..}/target/scala-2.10/simple-project_2.10-1.0.jar # Use spark-submit to run your application $ YOUR_SPARK_HOME/bin/spark-submit --class "SimpleApp" --master local[4] target/scala-2.10/simple-project_2.10-1.0.jar ... Lines with a: 46, Lines with b: 23
到目前为止，都很happy，因为都能顺利通过，因为你依赖的spark库，在spark master和worker上面都有。但是如果依赖mysql的jdbc这些第三方库, 只使用sbt的 package 命令打包，是不会把这些第三方库打包进去的。
这样在spark上面运行就会报错，而且如果你有多台wroker机器的话，需要把其它机器都撞上同样的运行环境（jar包依赖）。
所以，这个时候我们就需要sbt的assembly pulgin。它的任务，就是负责把所有依赖的jar包都打成一个 fat jar。
但是，它也不是万能的，特别当你遇到重名的文件时候，就非常尴尬。
3.assembly如何解决 SBT Assembly - Deduplicate error & Exclude error
我们先来看个错误例子：
[error] 1 error was encountered during merge [trace] Stack trace suppressed: run last *:assembly for the full output. [error] (*:assembly) deduplicate: different file contents found in the following: [error] /Users/qpzhang/.ivy2/cache/io.netty/netty-handler/jars/netty-handler-4.0.27.Final.jar:META-INF/io.netty.versions.properties [error] /Users/qpzhang/.ivy2/cache/io.netty/netty-buffer/jars/netty-buffer-4.0.27.Final.jar:META-INF/io.netty.versions.properties [error] /Users/qpzhang/.ivy2/cache/io.netty/netty-common/jars/netty-common-4.0.27.Final.jar:META-INF/io.netty.versions.properties [error] /Users/qpzhang/.ivy2/cache/io.netty/netty-transport/jars/netty-transport-4.0.27.Final.jar:META-INF/io.netty.versions.properties [error] /Users/qpzhang/.ivy2/cache/io.netty/netty-codec/jars/netty-codec-4.0.27.Final.jar:META-INF/io.netty.versions.properties [error] Total time: 5 s, completed 2015-11-25 20:20:23
大概是说，这里面有很多路径一样的重复文件，它处理不了。怎么办?
只好手动来进行判断，assembly提供了不打包文件的规则，这些可以用脚本写在build.sbt文件中。
参考：https://github.com/sbt/sbt-assembly#excluding-jars-and-files
在我们这里，脚本是这样的（注意：sbt是当时最新的 0.13版本）：
qpzhang@qpzhangdeMac-mini:~/scala_code/CassandraTest $cat build.sbt name := "CassandraTest" version := "1.0" scalaVersion := "2.10.4"
#spark的依赖直接忽略, 使用关键词provided表示运行环境已经有，不需要打包 libraryDependencies += "org.apache.spark" %% "spark-core" % "1.5.2" % "provided"
#依赖spark-cassandra-connector的库 libraryDependencies += "com.datastax.spark" %% "spark-cassandra-connector" % "1.5.0-M2"
#如果后缀是.properties的文件，合并策略采用（MergeStrategy.first）第一个出现的文件 assemblyMergeStrategy in assembly := { case PathList(ps @ _*) if ps.last endsWith ".properties" => MergeStrategy.first case x => val oldStrategy = (assemblyMergeStrategy in assembly).value oldStrategy(x) }
这样就搞定了，其它的情况，再根据修改一下合并策略咯。
> 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.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.