Gist to stream strings to a akka queue that gzips and stores

GzipCompressor.scala

import akka.actor._
import akka.actor.ActorLogging
import akka.actor.ActorSystem
import akka.stream._
import akka.stream.actor.ActorSubscriberMessage._
import akka.stream.actor._
import akka.stream.scaladsl._
import akka.{ NotUsed, Done }
import akka.util.ByteString
import java.io._
import scala.concurrent._
import scala.concurrent.ExecutionContext.Implicits.global
import akka.stream.scaladsl._

class GzipCompressor( 
        ofile : String , 
        bufferMaxSize:Int = 100, 
        queueSize:Int = 1000
    )(implicit val materializer : ActorMaterializer ){
    
    var isOpen = true
    val buffer = new StringBuilder(capacity = bufferMaxSize) 

//    val overflowStrategy = akka.stream.OverflowStrategy.fail
    val overflowStrategy = akka.stream.OverflowStrategy.backpressure
    assert(ofile.endsWith(".gz"))
    val fileSink =  FileIO.toPath((new File(ofile)).toPath)

    var queue = akka.stream.scaladsl.Source.queue[String](queueSize, overflowStrategy).
        map(x=> {
            ByteString.fromArray(x.getBytes("UTF-8"))
        }).via( Compression.gzip ).
        to( fileSink).run

    def add(z:String) : Unit = {
        assert(isOpen)
        z.sliding( bufferMaxSize, bufferMaxSize).foreach( s=> {
            if( ( s.size + buffer.size ) >= bufferMaxSize ){
                queue offer buffer.toString
                buffer.clear
            }
            buffer ++= s
        })
    }
    def close = {
        queue offer buffer.toString
        isOpen = false
        queue complete
    }
 
}
 
/*
implicit val system = ActorSystem("AkkaGzipCompressor")
implicit val materializer = ActorMaterializer()

val gz = new GzipCompressor("wow.gz")
gz.add("sfsds1")
gz.add("sfsds2")
gz.add("sfsds3")
gz.close

*/
 /*

val gz1 = new GzipCompressor("wow1.gz")
val gz2 = new GzipCompressor("wow2.gz")
val gz3 = new GzipCompressor("wow3.gz")

for( i <- 1 to 1000000 ){
gz1.add("sfsds1")
gz2.add("sfsds2sfsds2sfsds2")
gz3.add("sfsds3sfsds2sfsds2sfsds2")
}
gz3.close
gz1.close
gz2.close
 

 */