Hello,Every Hacker:
 I am a junior software engineer. I tried to rewrite Stream as a sink and 
found that when I read a large update of the database, I throw an exception 
OutOfMemory. Can anyone give me some advice? Why am I wrong, thanks :-)

def run(url: String, user: String, password: String, replUser: String, 
replPass: String): Unit = {
  implicit val system: ActorSystem = ActorSystem("log-analyzer")
  implicit val materializer: ActorMaterializer = ActorMaterializer()
  implicit val ec: ExecutionContextExecutor = system.dispatcher

  class DeadLetterListener extends Actor {
    def receive: PartialFunction[Any, Unit] = {
      case dl: DeadLetter ⇒
        logger.error("dead letter: {}", dl)

  val listener = system.actorOf(Props[DeadLetterListener])
  system.eventStream.subscribe(listener, classOf[DeadLetter])


  // check last confirmed lsn
  val sqlConnection: Connection = this.getSqlConnection(url, user, password)
  val lastLSNOpt: Option[LogSequenceNumber] = 

  var stream: PGReplicationStream = null
  var replConnection: PGConnection = this.getReplicationConnection(url, 
replUser, replPass)

  if (lastLSNOpt.isEmpty) {
    logger.info(s"未发现slot信息,初始化slot: $SLOT_NAME")
  } else {
    logger.info(s"从 ${lastLSNOpt.get} 开始")

  // start stream flow process
  //    val counter = new AtomicInteger(0)

  var lastTs = System.currentTimeMillis()
  var lastReceiveLSN = LogSequenceNumber.INVALID_LSN

  while (true) {
    try {
      if (replConnection == null || 
replConnection.asInstanceOf[Connection].isClosed) {
        replConnection = this.getReplicationConnection(url, replUser, replPass)

      stream = replConnection
        .withSlotOption("include-xids", false)
        //          .withSlotOption("skip-empty-xacts", true) 
        .start() // start replication stream

      object stream2iter extends Iterator[(LogSequenceNumber, String)] {
        override def next: (LogSequenceNumber, String) = {
          try {
            //outofmemory when big update in database
            val msg = stream.read
            val offset = msg.arrayOffset
            val src = msg.array
            val len = src.length - offset
            val log = new String(src, offset, len)
            val tmpLSN = stream.getLastReceiveLSN

            (tmpLSN, log)
          } catch {
            case e: Throwable =>
              println("localhost: " + e)
              (LogSequenceNumber.INVALID_LSN, "")

        override def hasNext: Boolean = !stream.isClosed

      val srcStream: Source[(LogSequenceNumber, String), NotUsed] = 
Source.fromIterator(() => stream2iter)

      val sink: Sink[LogRecord, Future[Done]] = Sink.foreach(log => {
        logger.debug(s"LSN: ${log.lsn}, target: ${log.target.fullname}")
        if (log.lsn != LogSequenceNumber.INVALID_LSN)
          lastReceiveLSN = log.lsn


      val totalG: RunnableGraph[NotUsed] = srcStream.via(graph(system)).to(sink)
      val res = totalG.run()
    } catch {
      // 断连常态化
      case e: PSQLException =>
        logger.warn("Connection closed, retrying...", e)
        val conn = replConnection.asInstanceOf[Connection]
        if (!conn.isClosed) {
        replConnection = null
      case e: Throwable =>
        logger.error("Connection can not be established!", e)
        shutdown(system, e)


** New discussion forum: https://discuss.akka.io/ replacing akka-user 
google-group soon.
** This group will soon be put into read-only mode, and replaced by 
** More details: https://akka.io/blog/news/2018/03/13/discuss.akka.io-announced
>>>>>>>>>>      Read the docs: http://akka.io/docs/
>>>>>>>>>>      Check the FAQ: 
>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html
>>>>>>>>>>      Search the archives: https://groups.google.com/group/akka-user
You received this message because you are subscribed to the Google Groups "Akka 
User List" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to akka-user+unsubscr...@googlegroups.com.
To post to this group, send email to akka-user@googlegroups.com.
Visit this group at https://groups.google.com/group/akka-user.
For more options, visit https://groups.google.com/d/optout.

Reply via email to