Misc Utils

tryWithSafeFinally

如果我们写代码

try {
    out.write();
    ...
}catch {
    ...
}finally {
    out.close();
}

有个问题是如果out.write出错，那么有可能out.close也会出错，如果out.close抛错就会掩盖out.write的错。 我觉得要是在Java里除非抛出RuntimeException,否则如果是CheckedExceptioin,那么需要catch out.close,那么你可以掩盖掉out.close, 而选择catch block里的。 但是在Scala里是不是就不会这样？

spark这个代码用两段代码合并来放到一个Throwable里

// Utils
def tryWithSafeFinally[T](block: => T)(finallyBlock: => Unit): T = {
    var originalThrowable: Throwable = null
    try {
      block
    } catch {
      case t: Throwable =>
        // Purposefully not using NonFatal, because even fatal exceptions
        // we don't want to have our finallyBlock suppress
        originalThrowable = t
        throw originalThrowable
    } finally {
      try {
        finallyBlock
      } catch {
        case t: Throwable =>
          if (originalThrowable != null) {
            originalThrowable.addSuppressed(t)
            logWarning(s"Suppressing exception in finally: " + t.getMessage, t)
            throw originalThrowable
          } else {
            throw t
          }
      }
    }
  }

使用上这么用

// CheckPoint
def serialize(checkpoint: Checkpoint, conf: SparkConf): Array[Byte] = {
    val compressionCodec = CompressionCodec.createCodec(conf)
    val bos = new ByteArrayOutputStream()
    val zos = compressionCodec.compressedOutputStream(bos)
    val oos = new ObjectOutputStream(zos)
    Utils.tryWithSafeFinally {
      oos.writeObject(checkpoint)
    } {
      oos.close()
    }
    bos.toByteArray
  }