为什么在我的build.sbt中没有正确遮蔽番石榴？这里

Posted 2021-04-12

tl;dr: Here's a repo containing the problem.

---

Cassandra和HDFS都在内部使用番石榴，但由于各种原因，它们都不会影响依赖性。因为番石榴的版本不是二进制兼容的，所以我在运行时找到了NoSuchMethodErrors。

我试图在我的build.sbt中自己遮蔽番石榴：

val HadoopVersion =  "2.6.0-cdh5.11.0"

// ...

val hadoopHdfs = "org.apache.hadoop" % "hadoop-hdfs" % HadoopVersion
val hadoopCommon = "org.apache.hadoop" % "hadoop-common" % HadoopVersion
val hadoopHdfsTest = "org.apache.hadoop" % "hadoop-hdfs" % HadoopVersion % "test" classifier "tests"
val hadoopCommonTest = "org.apache.hadoop" % "hadoop-common" % HadoopVersion % "test" classifier "tests"
val hadoopMiniDFSCluster = "org.apache.hadoop" % "hadoop-minicluster" % HadoopVersion % Test

// ...

assemblyShadeRules in assembly := Seq(
  ShadeRule.rename("com.google.common.**" -> "shade.com.google.common.@1").inLibrary(hadoopHdfs).inProject,
  ShadeRule.rename("com.google.common.**" -> "shade.com.google.common.@1").inLibrary(hadoopCommon).inProject,
  ShadeRule.rename("com.google.common.**" -> "shade.com.google.common.@1").inLibrary(hadoopHdfsTest).inProject,
  ShadeRule.rename("com.google.common.**" -> "shade.com.google.common.@1").inLibrary(hadoopCommonTest).inProject,
  ShadeRule.rename("com.google.common.**" -> "shade.com.google.common.@1").inLibrary(hadoopMiniDFSCluster).inProject
)

assemblyJarName in assembly := s"${name.value}-${version.value}.jar"

assemblyMergeStrategy in assembly := {
  case PathList("META-INF", "MANIFEST.MF") => MergeStrategy.discard
  case _ => MergeStrategy.first
}

但运行时异常仍然存在（哈 - 这是一个cassandra笑话，人们）。

具体的例外是

[info] HdfsEntitySpec *** ABORTED ***
[info]   java.lang.NoSuchMethodError: com.google.common.base.Objects.toStringHelper(Ljava/lang/Object;)Lcom/google/common/base/Objects$ToStringHelper;
[info]   at org.apache.hadoop.metrics2.lib.MetricsRegistry.toString(MetricsRegistry.java:406)
[info]   at java.lang.String.valueOf(String.java:2994)
[info]   at java.lang.StringBuilder.append(StringBuilder.java:131)
[info]   at org.apache.hadoop.ipc.metrics.RetryCacheMetrics.<init>(RetryCacheMetrics.java:46)
[info]   at org.apache.hadoop.ipc.metrics.RetryCacheMetrics.create(RetryCacheMetrics.java:53)
[info]   at org.apache.hadoop.ipc.RetryCache.<init>(RetryCache.java:202)
[info]   at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.initRetryCache(FSNamesystem.java:1038)
[info]   at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.<init>(FSNamesystem.java:949)
[info]   at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.<init>(FSNamesystem.java:796)
[info]   at org.apache.hadoop.hdfs.server.namenode.NameNode.format(NameNode.java:1040)
[info]   ...

如何正确遮挡番石榴以阻止运行时错误？

答案

着色规则仅适用于构建胖罐的情况。在其他sbt任务期间不会应用它。

如果你想在hadoop依赖项中隐藏一些库，你可以创建一个只包含hadoop依赖项的新项目，遮蔽库，并发布一个带有所有着色hadoop依赖项的胖jar。

这不是一个完美的解决方案，因为新的hadoop jar中的所有依赖项对于使用它们的人来说都是“未知”，并且您需要手动处理冲突。

这是您在build.sbt中需要的代码，用于发布胖的hadoop jar（使用您的代码和sbt程序集docs）：

val HadoopVersion =  "2.6.0-cdh5.11.0"

val hadoopHdfs = "org.apache.hadoop" % "hadoop-hdfs" % HadoopVersion
val hadoopCommon = "org.apache.hadoop" % "hadoop-common" % HadoopVersion
val hadoopHdfsTest = "org.apache.hadoop" % "hadoop-hdfs" % HadoopVersion classifier "tests"
val hadoopCommonTest = "org.apache.hadoop" % "hadoop-common" % HadoopVersion %  classifier "tests"
val hadoopMiniDFSCluster = "org.apache.hadoop" % "hadoop-minicluster" % HadoopVersion 

lazy val fatJar = project
  .enablePlugins(AssemblyPlugin)
  .settings(
    libraryDependencies ++= Seq(
        hadoopHdfs,
        hadoopCommon,
        hadoopHdfsTest,
        hadoopCommonTest,
        hadoopMiniDFSCluster
    ),
      assemblyShadeRules in assembly := Seq(
      ShadeRule.rename("com.google.common.**" -> "shade.@0").inAll
    ),
    assemblyMergeStrategy in assembly := {
      case PathList("META-INF", "MANIFEST.MF") => MergeStrategy.discard
      case _ => MergeStrategy.first
    },
    artifact in (Compile, assembly) := {
      val art = (artifact in (Compile, assembly)).value
      art.withClassifier(Some("assembly"))
    },
    addArtifact(artifact in (Compile, assembly), assembly),
    crossPaths := false, // Do not append Scala versions to the generated artifacts
    autoScalaLibrary := false, // This forbids including Scala related libraries into the dependency
    skip in publish := true
  )

lazy val shaded_hadoop = project
  .settings(
    name := "shaded-hadoop",
    packageBin in Compile := (assembly in (fatJar, Compile)).value
  )

我没有测试它，但这是它的要点。

---

我想指出我注意到的另一个问题，你的合并策略可能会给你带来问题，因为你想对某些文件应用不同的策略。看到默认策略here。 我建议使用这样的东西来保留原来的策略，不是deduplicate

assemblyMergeStrategy in assembly := {
          entry: String => {
            val strategy = (assemblyMergeStrategy in assembly).value(entry)
            if (strategy == MergeStrategy.deduplicate) MergeStrategy.first
            else strategy
          }
      }