heron/api/src/scala/com/twitter/heron/streamlet/scala/SerializableTransformer.scala

//  Copyright 2018 Twitter. All rights reserved.
//
//  Licensed under the Apache License, Version 2.0 (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
//
//  http://www.apache.org/licenses/LICENSE-2.0
//
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS,
//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//  See the License for the specific language governing permissions and
//  limitations under the License.
package com.twitter.heron.streamlet.scala

import com.twitter.heron.streamlet.Context

/**
  * All user supplied transformation functions have to be serializable.
  * Thus all Streamlet transformation definitions take Serializable
  * Functions as their input. We simply decorate java.util. function
  * definitions with a Serializable tag to ensure that any supplied
  * lambda functions automatically become serializable.
  */
trait SerializableTransformer[I, O] extends Serializable {
  def setup(context: Context): Unit

  def transform(i: I, f: O => Unit): Unit

  def cleanup(): Unit
}