HBase Class Loading Trick

HbaseClassloader.scala

  /**
    * Hacky Workaround for Getting the Current Context Classloader
    * Executing Some arbitrary Sync with the Hbase Classloader
    * Then reseting that thread to how it was previously.
    *
    * The moments I believe this is neccessary is when connections or
    * configurations are being created to HBase. At these times it
    * needs to have the hbase-default.xml which it will be lacking
    * otherwise.
    *
    * NOTICE: If your F is an Async and you pass this function something that
    * forks you are defeating the purpose and likely screwing up your threads.
    * You want the thread that is executing any action to have a classpath.
    * So Fork inside what is passed to this function at your own risk.
    *
    * Fixes: java.lang.RuntimeException: hbase-default.xml file seems to be for and old version of HBase (null)
    * Solution Modified From:
    * https://stackoverflow.com/questions/18272268/hbase-default-xml-file-seems-to-be-for-and-old-version-of-hbase-null-this-ver
    *
    */
  private[hbase] def withHBaseClassLoader[F[_]: Sync, A](a: F[A]): F[A] =
    for {
      initialClassLoader <- Sync[F].delay(
        Thread.currentThread.getContextClassLoader())
      _ <- Sync[F].delay(
        Thread
          .currentThread()
          .setContextClassLoader(classOf[HBaseConfiguration].getClassLoader()))
      aE <- a.attempt
      _ <- Sync[F].delay(
        Thread.currentThread().setContextClassLoader(initialClassLoader))
      a <- Sync[F].pure(aE).rethrow
} yield a