I created a chat application and seems to work just fine except that it takes up 100% cpu. Can this loop take out 100% Cpu? If yes, then what do i do to overcome it?
@Override
public void run(){
try {
_objServerSocket = new ServerSocket(17001, 500);
while (true) {
try {
initializeConnection();
addNewChatClient();
Thread.sleep(1000);
} catch (Exception ex) {
}
}
} catch (IOException ex) {
System.out.println(ex.getCause() + "\n"+ ex.getMessage() + "\n" + ex.getStackTrace());
}
}
Thanks in advance 🙂
Hi Bozho, Phil and Starkey.
This is the exception that i get.
SEVERE: java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
at java.util.AbstractList$Itr.next(AbstractList.java:343)
at misc.ChatRoom.cleanUpStreams(ChatRoom.java:34)
at misc.ChatServer.cleanUpStreams(ChatServer.java:85)
at common.Global.cleanupTasks(Global.java:81)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.sun.ejb.containers.interceptors.BeanCallbackInterceptor.intercept(InterceptorManager.java:1006)
at com.sun.ejb.containers.interceptors.CallbackChainImpl.invokeNext(CallbackChainImpl.java:61)
at com.sun.ejb.containers.interceptors.CallbackInvocationContext.proceed(CallbackInvocationContext.java:109)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doCallback(SystemInterceptorProxy.java:133)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.destroy(SystemInterceptorProxy.java:120)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.sun.ejb.containers.interceptors.CallbackInterceptor.intercept(InterceptorManager.java:961)
at com.sun.ejb.containers.interceptors.CallbackChainImpl.invokeNext(CallbackChainImpl.java:61)
at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:390)
at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:373)
at com.sun.ejb.containers.AbstractSingletonContainer$SingletonContextFactory.destroy(AbstractSingletonContainer.java:727)
at com.sun.ejb.containers.AbstractSingletonContainer.doConcreteContainerShutdown(AbstractSingletonContainer.java:638)
at com.sun.ejb.containers.BaseContainer.onShutdown(BaseContainer.java:4111)
at org.glassfish.ejb.startup.SingletonLifeCycleManager.doShutdown(SingletonLifeCycleManager.java:166)
at org.glassfish.ejb.startup.EjbApplication.stop(EjbApplication.java:240)
at org.glassfish.internal.data.EngineRef.stop(EngineRef.java:165)
at org.glassfish.internal.data.ModuleInfo.stop(ModuleInfo.java:268)
at org.glassfish.internal.data.ApplicationInfo.stop(ApplicationInfo.java:251)
at com.sun.enterprise.v3.server.ApplicationLifecycle.unload(ApplicationLifecycle.java:759)
at com.sun.enterprise.v3.server.ApplicationLifecycle.undeploy(ApplicationLifecycle.java:790)
at org.glassfish.deployment.admin.UndeployCommand.execute(UndeployCommand.java:184)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$1.execute(CommandRunnerImpl.java:305)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:320)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:1176)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.access$900(CommandRunnerImpl.java:83)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1235)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1224)
at com.sun.enterprise.v3.admin.AdminAdapter.doCommand(AdminAdapter.java:365)
at com.sun.enterprise.v3.admin.AdminAdapter.service(AdminAdapter.java:204)
at com.sun.grizzly.tcp.http11.GrizzlyAdapter.service(GrizzlyAdapter.java:166)
at com.sun.enterprise.v3.server.HK2Dispatcher.dispath(HK2Dispatcher.java:100)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:245)
at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791)
at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693)
at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954)
at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170)
at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88)
at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76)
at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53)
at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57)
at com.sun.grizzly.ContextTask.run(ContextTask.java:69)
at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330)
at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309)
at java.lang.Thread.run(Thread.java:619)
SEVERE: java.net.SocketException: Socket closed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.net.SocketInputStream.read(SocketInputStream.java:182)
at java.io.ObjectInputStream$PeekInputStream.peek(ObjectInputStream.java:2249)
at java.io.ObjectInputStream$BlockDataInputStream.peek(ObjectInputStream.java:2542)
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2552)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at misc.ChatClient.run(ChatClient.java:71)
SEVERE: java.net.SocketException: Socket closed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.net.SocketInputStream.read(SocketInputStream.java:182)
at java.io.ObjectInputStream$PeekInputStream.peek(ObjectInputStream.java:2249)
at java.io.ObjectInputStream$BlockDataInputStream.peek(ObjectInputStream.java:2542)
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2552)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at misc.ChatClient.run(ChatClient.java:71)
SEVERE: java.net.SocketException: Socket closed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.net.SocketInputStream.read(SocketInputStream.java:182)
at java.io.ObjectInputStream$PeekInputStream.peek(ObjectInputStream.java:2249)
at java.io.ObjectInputStream$BlockDataInputStream.peek(ObjectInputStream.java:2542)
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2552)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at misc.ChatClient.run(ChatClient.java:71)
SEVERE: java.net.SocketException: Socket closed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.net.SocketInputStream.read(SocketInputStream.java:182)
at java.io.ObjectInputStream$PeekInputStream.peek(ObjectInputStream.java:2249)
at java.io.ObjectInputStream$BlockDataInputStream.peek(ObjectInputStream.java:2542)
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2552)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at misc.ChatClient.run(ChatClient.java:71)
SEVERE: java.net.SocketException: Socket closed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.net.SocketInputStream.read(SocketInputStream.java:182)
at java.io.ObjectInputStream$PeekInputStream.peek(ObjectInputStream.java:2249)
at java.io.ObjectInputStream$BlockDataInputStream.peek(ObjectInputStream.java:2542)
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2552)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at misc.ChatClient.run(ChatClient.java:71)
SEVERE: java.net.SocketException: Socket closed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.net.SocketInputStream.read(SocketInputStream.java:182)
at java.io.ObjectInputStream$PeekInputStream.peek(ObjectInputStream.java:2249)
at java.io.ObjectInputStream$BlockDataInputStream.peek(ObjectInputStream.java:2542)
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2552)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at misc.ChatClient.run(ChatClient.java:71)
SEVERE: java.net.SocketException: Socket closed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.net.SocketInputStream.read(SocketInputStream.java:182)
at java.io.ObjectInputStream$PeekInputStream.peek(ObjectInputStream.java:2249)
at java.io.ObjectInputStream$BlockDataInputStream.peek(ObjectInputStream.java:2542)
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2552)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at misc.ChatClient.run(ChatClient.java:71)
SEVERE: java.net.SocketException: Socket closed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.net.SocketInputStream.read(SocketInputStream.java:182)
at java.io.ObjectInputStream$PeekInputStream.peek(ObjectInputStream.java:2249)
at java.io.ObjectInputStream$BlockDataInputStream.peek(ObjectInputStream.java:2542)
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2552)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at misc.ChatClient.run(ChatClient.java:71)
SEVERE: java.net.SocketException: Socket closed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.net.SocketInputStream.read(SocketInputStream.java:182)
at java.io.ObjectInputStream$PeekInputStream.peek(ObjectInputStream.java:2249)
at java.io.ObjectInputStream$BlockDataInputStream.peek(ObjectInputStream.java:2542)
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2552)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at misc.ChatClient.run(ChatClient.java:71)
SEVERE: java.net.SocketException: Socket closed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.net.SocketInputStream.read(SocketInputStream.java:182)
at java.io.ObjectInputStream$PeekInputStream.peek(ObjectInputStream.java:2249)
at java.io.ObjectInputStream$BlockDataInputStream.peek(ObjectInputStream.java:2542)
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2552)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at misc.ChatClient.run(ChatClient.java:71)
And this exception continues endlessly as it is in loop. I would like to add that everything works fine. But this starts if some client is connected to serversocket and i again redeploy my application :d. I know you woulnt’t want to do that, but still how should i avoid it? Should i remove the inner try catch? so that once any error comes it is directly thrown out of loop? But this doesn’t seem practical. Does it? Since one client may face some problem connecting to the serversocket, does not mean that i should terminate my application only. Now can you all help me?
This is my whole ChatRoom class :-
package misc;
import java.io.IOException;
import java.util.ArrayList;
public class ChatRoom {
private ArrayList<ChatClient> _objChatMembers;
private int roomId = 0;
public ChatRoom(int roomId){
this.roomId = roomId;
this._objChatMembers = new ArrayList<ChatClient>();
System.out.println("Chat ROom created :" + roomId);
}
public ArrayList<ChatClient> getObjChatMembers() {
return _objChatMembers;
}
public int getRoomId() {
return roomId;
}
public void setRoomId(int roomId) {
this.roomId = roomId;
}
public void setObjChatMembers(ArrayList<ChatClient> _objChatMembers) {
this._objChatMembers = _objChatMembers;
}
public void cleanUpStreams() throws IOException{
for(ChatClient objChatClient : _objChatMembers)
objChatClient.releaseStreams();
}
}
This is my ChatServer’s cleanupStreams:-
//clean up streams
public void cleanUpStreams() throws IOException{
_objServerSocket.close();
for(ChatRoom objChatRoom : _objChatRooms)
objChatRoom.cleanUpStreams();
}
This is my Singleton bean which starts up as soon as application is deployed :-
package common;
import entity.UserProfile;
import java.util.Date;
import java.util.List;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import javax.annotation.Resource;
import javax.ejb.EJB;
import javax.ejb.LocalBean;
import javax.ejb.SessionContext;
import javax.ejb.Singleton;
import javax.ejb.Startup;
import javax.ejb.Timeout;
import javax.ejb.TimerService;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import misc.ChatServer;
@Startup
@Singleton
@LocalBean
public class Global{
@EJB
private EmailManagerRemote _objEmailManager;
@EJB
private Utils _objUtils;
@Resource
private SessionContext _objSessionContext;
@PersistenceContext
private EntityManager _objEntityManager;
private TimerService _objTimerService;
private ChatServer _objChatServer;
@PostConstruct
public void init(){
final int TWENTY_FOUR_HOURS = 1000 * 60 * 60 * 24 ;
_objTimerService = _objSessionContext.getTimerService();
_objTimerService.createIntervalTimer(new Date(), TWENTY_FOUR_HOURS , null);
//start chat server
this._objChatServer = new ChatServer();
this._objChatServer.start();
}
@Timeout
public void sendBirthdayGreetingsAndBackupDatabase(){
//send birthday reminders
try{
List<UserProfile> userProfileList = _objEntityManager.createNamedQuery("UserProfile.findByBirthdate").setParameter("birthdate", new Date()).getResultList();
//List<UserProfile> userProfileList = _objEntityManager.createNamedQuery("UserProfile.findAll").getResultList();
for(UserProfile objUserProfile : userProfileList)
_objEmailManager.sendMail(EMAIL_TEMPLATE_CONSTANTS.REGISTRATION,objUserProfile.getUser());
}
catch(Exception ex){
ex.printStackTrace();
}
//backup BMS database
try{
_objUtils.backupBMSDB();
}
catch(Exception ex){
}
}
@PreDestroy
public void cleanupTasks(){
try{
if(_objChatServer != null)
_objChatServer.cleanUpStreams();
}
catch(Exception ex){
ex.printStackTrace();
}
}
}
Please ask me if anything else too is needed.
This is my ChatClient’s releaseStreams :-
public void releaseStreams() throws IOException {
multicastData(_objChatUser);
this._objChatRoom.getObjChatMembers().remove(this);
_objObjectOutputStream.close();
_objObjectInputStream.close();
_clientSocket.close();
}
I concurr that exceptions will cause the loop to spin continually with no pause – putting Thread.sleep() at the start of the loop will improve things.
That you are getting a ConcurrentModificationException hints that you are either modifying the collection during iteration over them in cleanupStreams() or some other thread is modifying the collection.
This seems a bit suspect, and a potential cause of the concurrent modification. If clients only need read access then change this to
If the list of ChatClients can be modified, then you should take steps to ensure modifications are done in a thread-safe manner. This is a deep subject, but for starters, you can use
Collections.synchronizedList()to ensure all operations are synchronized.Your iterator will also need to on this list, see the javadoc for that method for details.