I write UDP server and client in Java to send message from client to server. In my case, every message from client will be stored in database. I tried to make a multithread UDP server using fixed thread pool. But now I encountered a problem, I found out that one message from client can be processed by more than one thread. My server look like this :
DatagramSocket serverSocket = new DatagramSocket(9876); Map<String, Integer> retryMap = new ConcurrentHashMap<>(); byte[] receiveData = new byte[1024]; ExecutorService executor = Executors.newFixedThreadPool(2); while(true){ DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length); serverSocket.receive(receivePacket); executor.execute(new ThreadServer(receivePacket, retryMap)); } ThreadServer class :
public void run(){ String temp = new String(packet.getData(), 0, packet.getLength()); long threadId = Thread.currentThread().getId(); System.out.println("Thread Id = "+threadId+" Message = "+temp); // insert message to db } And my client look like this :
public class UDPClient1{ String message; public UDPClient1(String message){ this.message = message; try{ byte[] sendData; DatagramSocket clientSocket = new DatagramSocket(); InetAddress IPAddress = InetAddress.getByName("localhost"); sendData = message.getBytes("UTF-8"); DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876); clientSocket.send(sendPacket); clientSocket.close(); }catch(Exception e){ e.printStackTrace(); } } public static void main(String args[]) throws InterruptedException{ int i = 0; while(i < 1000){ new UDPClient1("T000"+i+"_"+i); System.out.println(i); i++; Thread.sleep(2); } }} The output from the server show that sometimes one message from client will be processed by 2 thread or more.
Thread Id = 18 Routing Id = T000975 09:54:11,759 ERROR LogRoutingFileDaoImpl:59 - AMS - Error insert to database org.springframework.dao.DuplicateKeyException: PreparedStatementCallback; SQL [INSERT INTO LOG_ROUTING_FILE (ID_ROUTING_FILE, FILE_NM , PATH, TYPES, PROTOCOL, SOURCE_NM, TARGET_NM) VALUES (?,?,?,?,?,?,?)]; ERROR: duplicate key value violates unique constraint "log_routing_file_id_routing_file_key"; nested exception is org.postgresql.util.PSQLException: ERROR: duplicate key value violates unique constraint "log_routing_file_id_routing_file_key" Thread Id = 9 Routing Id = T000975 09:54:11,759 ERROR LogRoutingFileDaoImpl:59 - AMS - Error insert to database org.springframework.dao.DuplicateKeyException: PreparedStatementCallback; SQL [INSERT INTO LOG_ROUTING_FILE (ID_ROUTING_FILE, FILE_NM , PATH, TYPES, PROTOCOL, SOURCE_NM, TARGET_NM) VALUES (?,?,?,?,?,?,?)]; ERROR: duplicate key value violates unique constraint "log_routing_file_id_routing_file_key"; nested exception is org.postgresql.util.PSQLException: ERROR: duplicate key value violates unique constraint "log_routing_file_id_routing_file_key" The message T000975 is processed by thread 9 and 18.. Can anyone help me to solve this? :)
