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From "kjhawierhjbasdf (Jira)" <j...@apache.org>
Subject [jira] [Commented] (DIRMINA-1135) Connections hanging around in CLOSE_WAIT state, not getting cleaned up properly
Date Mon, 05 Oct 2020 10:21:00 GMT

    [ https://issues.apache.org/jira/browse/DIRMINA-1135?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17207980#comment-17207980

kjhawierhjbasdf commented on DIRMINA-1135:

we tried the same setup with using standalone program, and we can see that connections are
getting cleaned up.

// import java.io.IOException;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;/**
 * A server program which accepts requests from clients to capitalize strings.
 * When a client connects, a new thread is started to handle it. Receiving
 * client data, capitalizing it, and sending the response back is all done on
 * the thread, allowing much greater throughput because more clients can be
 * handled concurrently.
public class ServerAccpetance {    /**
     * Runs the server. When a client connects, the server spawns a new thread to do
     * the servicing and immediately returns to listening. The application limits
     * the number of threads via a thread pool (otherwise millions of clients could
     * cause the server to run out of resources by allocating too many threads).
    public static void main(String[] args) throws Exception {
        try (ServerSocket listener = new ServerSocket(6516)) {
            System.out.println("The capitalization server is running...");
            ExecutorService pool = Executors.newFixedThreadPool(1000);
            while (true) {
                pool.execute(new ServerAccpetanc(listener.accept()));
    }    private static class ServerAccpetanc implements Runnable {
        private Socket socket;        ServerAccpetanc(Socket socket) {
            this.socket = socket;
        }        @Override
        public void run() {
            System.out.println("Connected: " + socket);
            try {
                Scanner in = new Scanner(socket.getInputStream());
                PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
                while (in.hasNextLine()) {
            } catch (Exception e) {
                System.out.println("Error:" + socket);
            } finally {
                try {
                } catch (Exception e) {
                System.out.println("Closed: " + socket);

> Connections hanging around in CLOSE_WAIT state, not getting cleaned up properly
> -------------------------------------------------------------------------------
>                 Key: DIRMINA-1135
>                 URL: https://issues.apache.org/jira/browse/DIRMINA-1135
>             Project: MINA
>          Issue Type: Bug
>            Reporter: kjhawierhjbasdf
>            Assignee: Jonathan Valliere
>            Priority: Major
>         Attachments: Screenshot 2020-10-05 at 8.31.37 AM.png, Screenshot 2020-10-05 at
9.10.31 AM.png
> Hello Team,
> We are using Apache MINA(v2.0.21) for tcp tls server implementation.
> I tried with running following operations in loop,
> establishing 200-300 connections 
> sending data
> closing connections
> And I observed that, closed connections were getting cleaned up properly.
> In another scenario, We tried configuring AWS ALB and target group, which was establishing
connection for healthcheck. These were not valid tls connections, but only tcp connections.
And In this case, we observed that, connections were in CLOSE_WAIT state, And these CLOSE_WAITs
are hanging around far too long. This was impacting our service.
> I did debug the TCP server code, I found that when the sessionClosed method is never
getting called. Then I tried closing session from sessionIdle method, Even after that session.isConnected
is showing true, connection is not getting closed.
> Our product owner is raising concern about, we should be able to avoid denial of service
> Can you please provide pointers to investigate further.
> Thanks,
> Rupesh Shah

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