Multi-Thread logging with PrintWriter
Hi,
I'm trying to buffer up some log information and flush it out to a log file at the end of servlet.
If I do something like following in a servlet where multiple threaded are doing the same thing, would System.out be a bottleneck? I can see that sometimes, some flush() might get called prematuarely, but I guess that is ok.. any issues with following approach in a servlet?
Thanks
PrintWriter pw = new PrintWriter( System.out );
pw.print( "some info" );
pw.print( "more info" );
pw.print( "more info" );
pw.flush();
If you are writing to a log file...why not use a Logger class.
the latest java JDK come with a Logger class. I prefer log4j (apache.jakarta site). The logger can display the thread name, time, what method is being invoked.
Otherwise, just use a StringBuffer and append the System.out until you are ready to print. then create the printer there and print. IO is expensive.
Similar Messages
-
Multi-threaded server with independent IO
I have designed a multi-threaded server which handles XML via sockets. I am running into the issue that when I try to send data to all of the clients, I have having to iterate through a shared resource where the sockets are stored at. I do not have this problem with reading because it is done in the thread created for this client (I pass the socket into the thread). If one computer freezes, then the iteration (writeToAll) through the client sockets also freeze. I would like to send XML to all clients and have everything fully independent so if it has a problem writing to a client, then it wouldn't halt the server. I would spawn a new thread for each write but that wouldn't be practical and I worry about threads live-locked.
I have looked into JCSP and it looks promising for the common issues associated with thread programming, but this is more of a design issue.
Any robust multi-threaded servers out there for enterprise use and scalability?A basic server which provides an example of what I mean:
http://www.wellho.net/solutions/java-a-multithreaded-server-in-java.html
connectiontable is a non-synchronized static method; I use a synchronized non-static method. I do not know which one I need to use.
The problem: If a socket "lingers" on sending output* (ex if the client is frozen but the socket is still bounded), then it never throws an exception!
*Sending from a shared resource (hashtable) on the parent thread (where the serversocket resides). -
Hi
I have build server with -t for muli-thrread option, it boots fine too. When I
use UD32 < file. ud it does not work.
I get following error in ULOG.
103708.gdev!ProxSvr.26508.4.1: LIBTUX_CAT:6126: INFO: New server dispatched thread
starting
103708.gdev!ProxSvr.26508.1.-2: LIBTUX_CAT:476: WARN: Server 3/511: client process
26500: lost message
103708.gdev!ProxSvr.26508.1.-2: LIBTUX_CAT:477: WARN: SERVICE=PROXSVC MSG_ID=0
REASON=server died
It work when server is not build with -t option.
Any help ?
VijayHere's a huge list of SOAP servers:
http://www.soapware.org/directory/4/implementations
Here's a SOAP/RMI product called XSOAP that might make more sense for you.
http://www.extreme.indiana.edu/xgws/xsoap/ -
Static methods in multi-thread environment.
Sorry for this silly question, but I have no clue...
If you're using classes with static methods in a application server environment, would that imply all threads use that same 'one in the jvm' method and would there be a possibility for performance loss?
Is calling another static method from a static method a good idea in a multi-thread environment, with respect to performance? Somehow I seem to get this java.lang.NoClassDefFoundError. Any ideas? The classes are in the same package. I only get these kind of problems calling static methods from static methods in a multi-thread environmnent. The static methods are pure utility functions and of course do not use class state.
Thanks for your help.Sorry for this question, wasn't thinking straight. I have the answer, won't post question on multiple forums.
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Oracle Multi-threaded libraries and Forte R3
Hello all,
I heard through the grapevine that it would be possible
to use Oracle 7.3 multi-threaded support with Forte 3.0G.
(thus making Load-Balancing obsolete in this case)
Has anyone given a try at this assumption ?
If yes, on what platform and what versions ?
Thanks,
Vincent Figari
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Searchable thread archive <URL:http://pinehurst.sageit.com/listarchive/>Hi,
It is available In R3.0.F.2 also. I tested it this release and it works
very well. But, you need to make a design pattern on it : A Oracle
Session can not be shared between several transactions throught threads.
So You need to manage a pool of DBSessions.
Hope this Helps,
Daniel Nguyen
Freelance Forte Consultant
Vincent R Figari wrote:
>
Hello all,
I heard through the grapevine that it would be possible
to use Oracle 7.3 multi-threaded support with Forte 3.0G.
(thus making Load-Balancing obsolete in this case)
Has anyone given a try at this assumption ?
If yes, on what platform and what versions ?
Thanks,
Vincent Figari
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com
Or call Juno at (800) 654-JUNO [654-5866]
To unsubscribe, email '[email protected]' with
'unsubscribe forte-users' as the body of the message.
Searchable thread archive <URL:http://pinehurst.sageit.com/listarchive/>-
To unsubscribe, email '[email protected]' with
'unsubscribe forte-users' as the body of the message.
Searchable thread archive <URL:http://pinehurst.sageit.com/listarchive/> -
Multi-thread application recompile object with make but runs with old value
Hi. I am working on a simulation in Java, and there is some behavior going on that I cannot understand. Granted, I'm a mechanical engineer, not a CS student (a fact that is probably made obvious by the code I'm posting below). The simulation comprises three parts: a controller, a robot, and a 3-d sensor. Here's the code for the "Simulation" application.
class Simulation {
void go() {
ThreeDSensor sensorRunner = new ThreeDSensor();
VSController controllerRunner = new VSController();
KukaKR15SL robotRunner = new KukaKR15SL();
Thread sensorThread = new Thread(sensorRunner);
Thread controllerThread = new Thread(controllerRunner);
Thread robotThread = new Thread(robotRunner);
sensorThread.start();
try {
Thread.sleep(1000); // Give sensorThread time to start in order to catch first triggers
} catch(InterruptedException ex) {
ex.printStackTrace();
controllerThread.start();
try {
Thread.sleep(1000); // Give controllerThread time to open the socket for communication with robotThread
} catch(InterruptedException ex) {
ex.printStackTrace();
robotThread.start();
public static void main(String[] args) {
Simulation sim = new Simulation();
sim.go();
}I guess the big reason I'm using multi-threading is that once this simulation is working I want to be able to just run VSController alone and have it interface with a robot controller and a PC performing image processing. So with multiple threads I'm sending TCP and UDP messages around just like the final system will.
I have made an object for my VSController that just stores values used by the simulation. That way I could have them all in one place instead of hunting through methods to change them. One example is "double noiseThreshold". Quickly, here is the code for "ControllerSettings.java".
class ControllerSettings {
final double cameraXOffset = 0; // If > 0 then the origin of the camera CS is not on the center line of the lens
final double cameraYOffset = 0; // If > 0 then the origin of the camera CS is not on the center line of the lens
final double cameraZOffset = 700; // The distance that must be kept between the camera and the target
// Error magnitude less than this is disregarded (in centimeters if roundingData else in millimeters)
final double noiseThreshold = 60;
final boolean estimatingEndPoints = false; // If the controller is using two images per cycle then true
final boolean roundingData = false;
final boolean using3DData = true; // How double[] sent from Matlab image processing is used
* If the robot controller uses the output of this controller to command
* motions in cartesian space then true. This is used in two places: 1) initial guess of Jacobian,
* and 2) "commandType" element sent to robot controller.
final boolean useRobotControllerModel = false;
final double thetaBumpValueForEstimationOfJacobian = .1; // Distance each joint is jogged in estimation process
final double bumpDistance = 50; // Distance robot moves each time (magnitude of translation in mm)
final double limitAngular = .5; // Max amout robot joint will be commanded to rotate (in degrees)
}And here is some pertinent code from "VSController.java".
class VSController implements Runnable{
ControllerSettings cSettings; // Stores all the preferences used by the controller
NGN controller; // This is the controller algorithm.
int dof; // The degrees of freedom of the robot being controlled
KukaSendData ksd; // This provides communication to the robot.
protected DatagramSocket socketForVisionSystem = null;
ImageFeaturesData ifd; // This parses and stores data from the image system.
double[] errorVector; // This is what's acted on by the algorithm
PrintWriter errorTrackerOut = null; // For analysis of error vector
public void run() {
VSController vsc = new VSController();
vsc.go();
public void go() {
initWriters();
cSettings = new ControllerSettings();
public boolean isNoise() {
boolean ret = false;
double magnitude = 0;
for (int i = 0; i < errorVector.length; i++) {
magnitude += errorVector[i] * errorVector;
magnitude = Math.sqrt(magnitude);
if (magnitude <= cSettings.noiseThreshold) {
System.out.println("VSController: magnitude (of errorVector) = " + magnitude +
", threshold = " + cSettings.noiseThreshold); // Debug
Now here's my issue: I change the value for "noiseThreshold" in "ControllerSettings.java" then run make from terminal (makefile code posted below) and rerun "Simulation". However, despite my changes to "ControllerSettings.java" the value for "noiseThreshold" is not changed, as evidenced by the output on the terminal screen:VSController: magnitude (of errorVector) = 6.085046125925263, threshold = 10.0 See, that value of 10.0 is what I used to have for noiseThreshold. I do not know why this value does not update even though I save the java file and execute make in between executions of Simulation. I would love it if someone could explain this problem to me.
Here's the contents of makefile.
JFLAGS = -cp ../Jama\-1\.0\.2.jar:../utils/:/usr/share/java/vecmath\-1\.5\.2.jar:.
JC = javac
.SUFFIXES: .java .class
.java.class:
$(JC) $(JFLAGS) $*.java
CLASSES = \
ControllerSettings.java \
ImageFeaturesData.java \
KukaKR15SL.java \
../utils/KukaSendData.java \
NGN.java \
Puma560.java \
Robot.java \
RobotSettings.java \
Simulation.java \
SimulationSettings.java \
SixRRobot.java \
Targets.java \
TargetsSettings.java \
ThreeDData.java \
ThreeDSensor.java \
VSController.java
default: classes
classes: $(CLASSES:.java=.class)
clean:
$(RM) *.classEdited by: raequin on Apr 5, 2010 1:43 PMI saw this explanation about what's causing my problem.
"When the Java compiler sees a reference to a final static primitive or String, it inserts the actual value of that constant into the class that uses it. If you then change the constant value in the defining class but don't recompile the using class, it will continue to use the old value."
I verified that the value updates if I also change something in VSController.java, forcing it to recompile. I think I will solve this problem by just making the variables in ControllerSettings no longer final (and then recompile VSController to make sure it takes effect!). Is there another solution? I saw intern(), but that seems to only apply to Strings.
Thanks. -
What's wrong with my multi-threaded Matrix Mult. code? 1 thread is fastest
For some reason, 1 thread performs the best. What's wrong with my implementation?
import java.util.Random;
import java.util.Date;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class Matrix {
private int values[][];
private int rows;
private int columns;
public Matrix(int r, int c) {
this.rows = r;
this.columns = c;
this.values = new int[r][c];
private void randomize() {
Random generator = new Random();
for (int r = 0; r < this.rows; r++) {
for (int c = 0; c < this.columns; c++) {
this.values[r][c] = generator.nextInt(10);
public String toString() {
String out = "";
for (int r = 0; r < this.rows; r++) {
for (int c = 0; c < this.columns; c++) {
if (c == 0) out += "[";
else out += "\t";
out += this.values[r][c];
out += "]\n";
return out;
public boolean equals(Object obj) {
Matrix other = (Matrix) obj;
if (this.columns != other.columns || this.rows != other.rows) {
return false;
for (int r = 0; r < this.rows; r++) {
for (int c = 0; c < this.columns; c++) {
if (this.values[r][c] != other.values[r][c]) {
return false;
return true;
// matrix multiplication using single thread
public Matrix times(Matrix other) {
assert(this.columns == other.rows);
Matrix out = new Matrix(this.rows, other.columns);
for (int r = 0; r < this.rows; r++) {
for (int c = 0; c < other.columns; c++) {
int dotProduct = 0;
for (int z = 0; z < this.columns; z++) {
dotProduct += this.values[r][z] * other.values[z][c];
out.values[r][c] = dotProduct;
return out;
// matrix multiplication with many threads
public Matrix ptimes(Matrix other, int numberOfThreads) throws InterruptedException { // parallel
assert(this.columns == other.rows);
Matrix out = new Matrix(this.rows, other.columns);
ExecutorService threadExecutor = Executors.newFixedThreadPool(numberOfThreads);
for (int r = 0; r < this.rows; r++) {
for (int c = 0; c < other.columns; c++) {
threadExecutor.execute(new HelperThread(r, c, this, other, out));
threadExecutor.shutdown();
threadExecutor.awaitTermination(2, TimeUnit.DAYS);
return out;
private class HelperThread implements Runnable {
private int row;
private int col;
private Matrix a;
private Matrix b;
private Matrix out;
HelperThread(int r, int c, Matrix a, Matrix b, Matrix o) {
this.row = r;
this.col = c;
this.a = a;
this.b = b;
this.out = o;
public void run() {
int dotProduct = 0;
for (int z = 0; z < a.columns; z++) {
dotProduct += this.a.values[row][z] * this.b.values[z][col];
this.out.values[row][col] = dotProduct;
public static void main(String[] args) throws InterruptedException {
int size = 100;
Matrix a = new Matrix(size, size);
a.randomize();
Matrix b = new Matrix(size, size);
b.randomize();
for (int t = 1; t < 15; t++) {
long start = new Date().getTime();
System.out.print(t + " threads: ");
Matrix c = a.ptimes(b, t);
//System.out.println(c);
long finish = new Date().getTime();
System.out.println((finish - start) + " milliseconds");
Matrix d = a.times(b);
assert(c.equals(d));
}This one is even faster. On my dual core I get:
Warmup
Single Threaded
5.20616 milliseconds
5.52872 milliseconds
5.12708 milliseconds
5.59048 milliseconds
5.16104 milliseconds
5.1838 milliseconds
5.37104 milliseconds
5.1788 milliseconds
5.18636 milliseconds
5.15736 milliseconds
Multi Threaded with 2 threads
3.22184 milliseconds
2.86552 milliseconds
2.86284 milliseconds
3.67032 milliseconds
3.08032 milliseconds
2.97388 milliseconds
2.93084 milliseconds
3.44012 milliseconds
2.89744 milliseconds
2.88136 milliseconds
As you can see the Multi-Threaded versions are now faster.
// matrix multiplication with many threads
ExecutorService threadExecutor = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());
public Matrix ptimes(Matrix other) throws InterruptedException, ExecutionException {
assert (this.columns == other.rows);
Matrix out = new Matrix(this.rows, other.columns);
Future futures[] = new Future[rows];
for (int r = 0; r < this.rows; r++) {
futures[r] = threadExecutor.submit(new HelperThread(r, this, other, out));
for(Future f : futures) {
f.get();
return out;
private class HelperThread implements Callable<Object> {
private int row;
private Matrix a;
private Matrix b;
private Matrix out;
HelperThread(int r, Matrix a, Matrix b, Matrix o) {
this.row = r;
this.a = a;
this.b = b;
this.out = o;
public String call() throws Exception {
int dotProduct = 0;
for (int c = 0; c < b.columns; c++) {
for (int z = 0; z < a.columns; z++) {
dotProduct += this.a.values[row][z] * this.b.values[z][c];
this.out.values[row][c] = dotProduct;
return null;
public static void main(String[] args) throws InterruptedException, ExecutionException {
int size = 100;
Matrix a = new Matrix(size, size);
a.randomize();
Matrix b = new Matrix(size, size);
b.randomize();
System.out.println("Warmup");
for (int t = 0; t < 1000; t++) {
Matrix c = a.ptimes(b);
Matrix d = a.times(b);
assert (c.equals(d));
System.out.println("Single Threaded");
for (int t = 0; t < 10; t++) {
long start = System.nanoTime();
Matrix d = a.times(b);
long finish = System.nanoTime();
System.out.println((finish - start)/1000000.0 + " milliseconds");
System.out.println("Multi Threaded with " + Runtime.getRuntime().availableProcessors() + " threads");
for (int t = 0; t < 10; t++) {
long start = System.nanoTime();
Matrix c = a.ptimes(b);
long finish = System.nanoTime();
System.out.println((finish - start)/1000000.0 + " milliseconds");
Matrix d = a.times(b);
assert (c.equals(d));
System.exit(0);
} -
Proble with multi-threaded app using the same connection
have a multi-threaded app. The threads all share the
same connection. They all do some selects / updates.
The OS is NT 4.0 and the application server is weblogic
Some times I am getting the error "java.sql.SQLException: Io exception: not in streaming mode"
and some times I am getting "java.sql.SQLException: Io exception: Protocal violation
Any Ideas?
Regards
SureshDon't create threads.... Your threads should if they are necessary be reusable, your threads should call the connections it needs from the cache service with let's say a max number of N pools (each pool a max number of M connections), if the connection domain asked exists on cache a connection is asked for corresponding pool, if the connection domain is not on cache the less used domain is thrown away (all inner connections closed first) and substituted by the new one requested. While the pool is not full keep creating connections as the request came (and all existing connections are being held and not released), when M connections exists, a request should wait till a connection is released.
If you can have 20 threads asking for the same connection and the max number of connections on pool is M=10, then yopur threads will wait for a connection being released. All this must be synchronized. You should set M the closest as possible to the normal number of requests you can imagine to happen the same time. You should get connection use it and release it right away if you can have a lot of requests.
I hope this helps you. -
Multi-threaded program hangs in Linux with green thread when doing I/O
Hi,
I am using green thread(jdk1.3.1) on Linux. My program is in multi-threaded model and has some I/O operations. I am runing one java program using Runtime.exec("java <program>"). Actually the <program> prompts user with some question like "enter location" and waits for the input. Now in my code I am constantly reading the input stream of the process. Once I get the string like "enter location", immediately I send the location through Process o/p stream. But the process is not able to read this and hangs there for ever.
Please help, what could be the problem? If you need the source code, pls let me know.
Thanks in advance,
SisirI had a similar issue few weeks back... If I could see the source I would have a better understanding of the problem and think I could help out. If you want to send it, send it to [email protected]
thanks,
JP -
Help with understanding multi-threaded code
Hi Everyone,
I am currently reading a book on multi-threading and up until recently I have been able to understand what is going on. The thing is the complexity of the code has just jumped up about two gears without warning. The code is now using inner classes which I am trying to develop an understanding of but I am not finding it easy going, and the book has been lite on explanations. If anybody can help with the following code it will be really appreciated.
public class SetPriority extends Object
private static Runnable makeRunnable()
Runnable r = new Runnable()
public void run()
for(int i=0; i<5; i++)
Thread t = Thread.currentThread();
System.out.println("in run() - priority=" + t.getPriority() +
", name=" + t.getName());
try{
Thread.sleep(2000);
}catch(InterruptedException x){
//ignore
return r;
public static void main(String[] args)
Thread threadA = new Thread(makeRunnable(), "threadA");
threadA.setPriority(8);
threadA.start();
Thread threadB = new Thread(makeRunnable(), "threadB");
threadB.setPriority(2);
threadB.start();
Runnable r = new Runnable()
public void run()
Thread threadC = new Thread(makeRunnable(), "threadC");
threadC.start();
Thread threadD = new Thread(r, "threadD");
threadD.setPriority(7);
threadD.start();
try{
Thread.sleep(3000);
}catch(InterruptedException x){
//ignore
threadA.setPriority(3);
System.out.println("in main() - threadA.getPriority()=" + threadA.getPriority());
}My greatest challenge is understanding how the makeRunnable() method works. I don't understand how this inner class can be declared static and then multiple "instances" created from it. I know that I have no idea what is going on, please help!!!
Thanks for your time.
Regards
Davo
P.S.: If you know of any really good references on inner classes, particularly URL resources, please let me know. Thanks again.Yikes!! The good news is that you're unlikely to see such convoluted code in real life. But here we go.
"private static Runnable makeRunnable()" declares a method that returns objects of type Runnable. The fact that the method is declared "static" is pretty irrelevant - I'll describe what that means later.
The body of the method creates and returns an object of type Runnable. Not much special about it, except that you can give such an object to the constructor of class Thread and as a result the run() method of this Runnable object will be called on a new thread of execution (think - in parallel).
Now the way it creates this Runnable object is by using the "anonymous inner class" syntax. In effect the method is doing the same as
public class MyNewClass implements Runnable {
public void run() {
// All the same code inside run()
public class SetPriority {
private static Runnable makeRunnable() {
Runnable r = new MyNewClass();
return r;
// The rest of the original code
}Except you don't bother declaring MyNewClass. You're not interested in defining any new method signatures. You just want to create an object that implements Runnable and has certain instructions that you want inside the run() method. Think of the whole approach as shorthand.
Think about this for a while. In the mean time I'll write up the "static". -
Multi-task data logging with DAQmx
I was wonder is it possible to use 'DAQmx Configure Logging' VI and 'DAQmx Start New File' VI for multiple tasks? I'm doing synchronized high speed DAQ with NI PXI-6133 cards. Each card (there are 16) must have its own task. Although the DAQ is continuous, the user (software trigger) determines when data is saved to the disk and for how long.
In my scenario the test length could be up to an hour with various test events scatter throughout. The users want to display the data during the entire test length. However they only want to write the data to disk during an event. The event could last from 10 sec to 1 min. That is why the users want to control when data is written to the disk.
DAQmx Logging seems to work for a single task only, but I need to do multiple tasks.I've attempted to implement your suggestion, but I still do not acquire data for all channels for all tasks. I've enclosed my VI.
Attachments:
TDMS Logging with Pause LoggingFSPR.vi 55 KB -
Multi-threaded performance server using 2 ports to two-way communication
Hi, I'm new in the forums so welcome everyone. I'm developing now an online computer game based on orginal Polish board-game, but it doesn't mean. Important is that I need to develope a high-performance multi-threaded server, which can serve... let's say few hundres of games, and a thousend of players simulateously. My server works on two ports/sockets.
First one is represented by "ServerSocketChannel clientConSsc" in my code. The main thread in my server class which invokes the method "run()" (which You can see below), registers clientConSsc with Selector and then repeatingly accepts incoming connections from clients on this socket. When connection(channel) is estabilished and clients wants to write some request to this channel, the main thread on server creates a new instance of class "RequestHandler" which extends Thread and handles this request (reads the request from channel, makes some changes on server, spreads some new messages to other clients in the same game and so on... everything on the same socket/port/channel). Then the channel/connection is closed by the server - I call such connections: "a short connections". In the same time the main thread continues the loop and is still able to accept connections from another players. That's the idea of multi-threaded server, right? :) And to this point, everything works fine, but... what if the server wants to trigger some new command, write new information to client?
Server could have tried to open a SocketChannel to client's IP address, but then the client programme would have to create and ServerSocketChannel object, bind it to some InetAddress and then... and then client becomes a server! - that breaks the idea of client-server cooperation and demands on players of my game to have routed some port on their machines. To resolve this problem I made some sort of "system" which, when some player/client is logging into my server, accepts second (this time constant, not "short") connection on the second port I mentoined on the beginning. This connection is held in variable "SocketChannel serverCon" of class "Player" - which reflects a player logged onto server. Server maintains every such connection till the client logs off. After the connection is accepted, the player whom connection it was is added to collection called "playersToRegisterToWrite". After the Selector.selectNow() is invoked (as You can see in the code below), each and every player's connection is registered in selector (with selection key - OP_WRITE and attachment pointing on owning player). In the same time client's code is trying to read some bytes from this connection and blocks on it until some bytes are written to this connection. When server wants to "tell" something to client, deliver some message/command, it creates a new instance of class which extends an abstract class called "ServerAction" (another new thread) and adds it to collection "actionsToDo". In ServerAction's method "run()" there are whole code to interact with client (e.g. send an update of players' list, an update of games' list, a chat message). Finnaly when Selector informs the server that some connection is writable (some client is waiting for commands), then server checks if there's any "actionToDo" involving this client/player. If there is, it unregisters the connection from Selector (so no other ServerAction (thread) can write on this connection) and starts the action. At the end of every "run()" method of subclass of ServerAction there's a code, which again adds the player to collection "playersToRegisterToWrite", so the player's connection can again be registered in Selector and the player can again receive informations from server - after it consumed THIS "ServerAction".
It looks to me like it should be working fine, but it's not. When I test my server and clients on the same machine (no ping/latency) everything seems to be working fine. But when it comes to play my game with somebody even on LAN or through the Internet there comes the problems. My first socket I describe (and first type of connections - short connections) works perfectly fine, so the requests triggered by client are delivered and handled properly. But the second socket is cirppling. For example: the server triggers a command refering to an update of clients logged to server' list. It is triggered by Selector so the client should be ready to read data from server, so the server sends data! And the client never receives it... Why?
It experimented a whole lot of time on SocketChannel's method "configureBlocking(boolean)", but it never helps. I think the client should always block it's listening thread on connection, contratry to server which is ment to be fast, so it should send the data through non-blocking channels. Am I right? Are there any rules refering blocking configuration of SocketChannels?
I will be grateful for every answer. To help You out I attach also drafts from run()'s methods of my classes.
Server's main method - main thread :
public void run() {
try {
selector = Selector.open();
clientConSsc.configureBlocking(false);
clientConSsc.register(selector , SelectionKey.OP_ACCEPT);
while(serverRunning) {
try {
selector.selectNow();
Iterator it;
synchronized(playersToRegisterToWrite) {
it = playersToRegisterToWrite.iterator();
while(it.hasNext()) {
Player player = (Player)it.next();
it.remove();
player.serverCon.configureBlocking(false);
player.serverCon.register(selector , SelectionKey.OP_WRITE , player);
Set keys = selector.selectedKeys() {
it = keys.iterator();
while(it.hasNext()) {
SelectionKey key = (SelectionKey)it.next();
if(key.isAcceptable()) {
it.remove();
clientCon = clientConSsc.accept();
clientCon.configureBlocking(false);
clientCon.register(selector , SelectionKey.OP_READ);
continue;
if(key.isReadable()) {
it.remove();
key.cancel();
new RequestHandler(this , (SocketChannel)key.channel()).start();
continue;
if(key.isWritable()) {
if(key.attachment() != null ) {
ServerAction action = null;
synchronized(actionsToDo) {
Iterator aIt = actionsToDo.iterator();
while(aIt.hasNext()) {
ServerAction temp = (ServerAction)aIt.next();
if(temp.getPlayer().equals((Player)key.attachment())) {
action = temp;
aIt.remove();
break;
if(action != null) {
key.channel().configureBlocking(false);
it.remove();
key.cancel();
action.start();
continue;
} catch(Exception e) {
statusArea.append(e.toString() + "\n");
e.printStackTrace();
continue;
} catch(ClosedChannelException e) {
statusArea.append(e.toString() + "\n");
} catch(IOException e) {
statusArea.append(e.toString() + "\n");
A part of server's RequestHandler's class' method run() - the method which handles requests triggered by client on first port:
public void run() {
boolean served = false;
try {
channel.configureBlocking(true);
retryCount++;
retry = false;
String command = ns.readText(channel).trim();
ns.statusArea.append("ktos przesyla komende: " + command + "\n");
if(command != null && !command.equals("ERROR")) {
String[] cmd = command.split("�");
ns.statusArea.append("komenda: " + cmd[0] + "\n");
if(cmd[0].equals("CHAT")) {
if(cmd.length != 5) {
retry();
} else {
if(cmd[2].equals("NOGAME")) { // jezeli nie ma okreslonej gry czyli rozsylamy do wszystkich
for(int i = 0 ; i < ns.loggedPlayersListItems.size() ; i++) {
Player current = (Player)ns.loggedPlayersListItems.get(i);
if(current.state == Player.CHOOSING && !current.equals(new Player(Integer.parseInt(cmd[1])))) // jezeli gracz jest w okienku wybierania gry to wysylamy mu broadcast
ns.actionsToDo.add(new SendMsg(ns , current , "CHAT�" + cmd[1] + "�" + cmd[3] + "�" + cmd[4]));
} else {
Game game = (Game)ns.gamesListItems.get(ns.gamesListItems.indexOf(new Game(Integer.parseInt(cmd[2]))));
for(int i = 0 ; i < game.players.size() ; i++) {
Player current = (Player)game.players.get(i);
if(!current.equals(new Player(Integer.parseInt(cmd[1]))))
ns.actionsToDo.add(new SendMsg(ns , current , "CHAT�" + cmd[1] + "�" + cmd[3] + "�" + cmd[4]));
served = true;
} else if(cmd[0].equals("GETGAMEINFO")) {
if(cmd.length != 3)
retry();
else {
int gameID = Integer.parseInt(cmd[2]);
ns.statusArea.append("poproszono o informacje o grze nr: " + gameID + "\n");
Game checkedGame = new Game(gameID);
if(ns.gamesListItems.contains(checkedGame)) {
Game game = (Game)ns.gamesListItems.get(ns.gamesListItems.indexOf(checkedGame));
channel.configureBlocking(true);
ObjectOutputStream oos = new ObjectOutputStream(channel.socket().getOutputStream());
oos.writeObject(game);
oos.writeObject(game.players);
oos.flush();
ns.statusArea.append("wyslano informacje o grze nr: " + gameID + "\n");
} else {
ns.statusArea.append("brak gry o nr: " + gameID + "\n");
served = true;
} catch(IOException e) {
e.printStackTrace();
if(!served) {
ns.findAndDisconnectPlayer(channel);
try {
channel.close();
} catch(IOException e) {
e.printStackTrace();
}An example of ServerAction's subclass - the class which triggers server commands to client on second port:
class UpdateLoggedPlayersList extends ServerAction {
public UpdateLoggedPlayersList(NeuroServer ns , Player player) {
super(ns , player);
public void run() {
try {
serverCon.configureBlocking(true);
ns.sendText("UPDATELOGGEDPLAYERSLIST" , serverCon);
if(ns.readText(serverCon).equals("OK")) {
ObjectOutputStream oos = new ObjectOutputStream(serverCon.socket().getOutputStream());
oos.writeObject(ns.loggedPlayersListItems);
oos.flush();
synchronized(ns.playersToRegisterToWrite) {
ns.playersToRegisterToWrite.add(player);
} catch(IOException e) {
e.printStackTrace();
}A part of client's CmdHandler's class' method run() - the method which handles commands triggered by server:
public void run() {
try {
while(works) {
String command = nc.readText(nc.serverCon);
System.out.println("Server przesyla komende: " + command + "\n");
String[] cmd = command.split("�");
if(cmd[0] != null && !cmd[0].equals("ERROR")) {
if(cmd[0].equals("CHAT")) {
if(nc.chooseGameDialog != null && nc.chooseGameDialog.isVisible()) { // jezeli na wybieraniu gry
newChatEntry(cmd[2] , null , cmd[3] , nc.chooseGameDialog.chatPane);
} else if(nc.readyDialog != null && nc.readyDialog.isVisible()) { // jesli na przygotowywaniu
Player sender = (Player)nc.actGame.players.get(nc.actGame.players.indexOf(new Player(Integer.parseInt(cmd[1]))));
newChatEntry(cmd[2] , sender.fraction , cmd[3] , nc.readyDialog.chatPane);
} else if(nc.ng != null) { // jesli w grze
Player sender = (Player)nc.actGame.players.get(nc.actGame.players.indexOf(new Player(Integer.parseInt(cmd[1]))));
newChatEntry(cmd[2] , sender.fraction , cmd[3] , nc.ng.inGameChatPane);
} else if(cmd[0].equals("UPDATELOGGEDPLAYERSLIST")) {
nc.sendText("OK" , nc.serverCon , false);
nc.serverCon.configureBlocking(true);
ObjectInputStream ois = new ObjectInputStream(nc.serverCon.socket().getInputStream());
DefaultListModel players = (DefaultListModel)ois.readObject();
nc.chooseGameDialog.updateLoggedPlayersList(players);
} catch(IndexOutOfBoundsException e) {
System.out.println(e);
} catch(IOException e) {
System.out.println(e);
} catch(ClassNotFoundException e) {
System.out.println(e);
}And two methods I used in codes above: sendText(String text , SocketChannel sc) and readText(SocketChannel sc) - they are my "utility" methods, which I use to send and receive Strings through specified SocketChannels.
boolean sendText(String text , SocketChannel sc) {
ByteBuffer bbuf = ByteBuffer.allocate(BSIZE);
boolean sendRetry;
boolean sent = false;
do {
sendRetry = false;
try {
StringBuffer cmd = new StringBuffer();
cmd.setLength(0);
if(text.length()+4 < 100)
cmd.append("0");
if(text.length()+4 < 10)
cmd.append("0");
cmd.append(Integer.toString(text.length()+4) + "�");
cmd.append(text);
cmd.append("\n");
bbuf = charset.encode(CharBuffer.wrap(cmd));
sc.write(bbuf);
bbuf.clear();
int n = sc.read(bbuf);
if(n == 1) {
bbuf.flip();
Byte re = bbuf.get();
if(re == 1) {
sendRetry = true;
} else {
sent = true;
} catch(Exception e) {
findAndDisconnectPlayer(sc);
try {
sc.close();
} catch(IOException f) {
f.printStackTrace();
return false;
} while(!sent && sendRetry);
return true;
String readText(SocketChannel sc) {
ByteBuffer bbuf = ByteBuffer.allocate(BSIZE);
int readRetryCount = -1;
boolean readRetry;
do {
readRetry = false;
readRetryCount++;
StringBuffer cmd = new StringBuffer();
cmd.setLength(0);
bbuf.clear();
try {
readLoop:
while(true) {
int n = sc.read(bbuf);
if(n > 0) {
bbuf.flip();
CharBuffer cbuf = charset.decode(bbuf);
while(cbuf.hasRemaining()) {
char c = cbuf.get();
if(c == '\r' || c == '\n') break readLoop;
cmd.append(c);
} else break;
statusArea.append(Thread.currentThread().getId() + " readText() odczytuje: " + cmd.toString() + "\n");
if(cmd.length() < 3 || Integer.parseInt(cmd.substring(0 , 3)) != cmd.length()) {
sc.write(ByteBuffer.wrap(new byte[] {1}));
readRetry = true;
} else {
sc.write(ByteBuffer.wrap(new byte[] {0})); // length OK
return cmd.toString().substring(4 , cmd.toString().length());
} catch(Exception e) {
findAndDisconnectPlayer(sc);
try {
sc.close();
} catch(IOException f) {
f.printStackTrace();
return "ERROR";
} while(readRetry && readRetryCount < 3);
findAndDisconnectPlayer(sc);
try {
sc.close();
} catch(IOException e) {
e.printStackTrace();
return "ERROR";
}Edited by: Kakalec on Jul 23, 2008 11:04 AMYou seem to be using a horrendous mixture of PrintWriters, BufferedReaders, ObjectOutputStreams, and no doubt ObjectInputStreams. You can't do that.
Some rules about this:
(a) Whenever you use a stream or reader or writer on a socket, you must allocate it once for the life of the socket, not every time you want to do an I/O.
There are many reasons for this including losing buffered data in the old stream and auto-closure of the socket on garbage-collection of the old stream.
(b) You can't mix stream types on the same socket. (i) If you're writing objects, use an ObjectOutputStream, you must read with an ObjectInputStream, and you can't read or write anything that isn't supported by the API of ObjectOutputStream. (ii) If you're writing lines, use a BufferedWriter and a BufferedReader at the other end. If you're writing characters, use a Writer and a Reader. (iii) If you're writing primitive data or UTF strings, use a DataOutputStream and a DataInputStream. (iv) If you're writing bytes, use DataOutputStream and a DataInputStream or an OutputStream and an InputStream. You can't mix (i), (ii), (iii), and (iv).
(c) Don't use PrintWriter or PrintStream over the network. They swallow exceptions that you need to know about. They are for writing to the console, or log files, where you don't really care about exceptions.
(d) Call flush() before reading.
(e) Always close the 'outermost' output stream or writer of a socket, never the input stream or the socket itself. Closing any of these closes the socket and therefore makes the other stream unusable, but only closing the output stream/writer will flush it. -
Multi Thread Server over TCP/IP
Multi Thread Server over TCP/IP. Does it work?
In my box it works only over IPC protocol.
nullS C Maturi (guest) wrote:
: Mark Malakanov (guest) wrote:
: : Multi Thread Server over TCP/IP. Does it work?
: : In my box it works only over IPC protocol.
: Mark,
: Multi threaded server over TCP/IP will not work with
: the current distribution of Oracle 8.0.5 on Linux.
: This is corrected and a patch would be released soon.
: Maturi
tcp 0 0 bock.nettek-ll:listener bock.nettek-
llc.co:4196 ESTABLISHED
tcp 0 0 bock.nettek-llc.co:4196 bock.nettek-
ll:listener ESTABLISHED
(I have serveral of these)
TNS Ping Utility for Linux: Version 8.0.5.0.0 - Production on 07-
JAN-99 18:45:52
(c) Copyright 1997 Oracle Corporation. All rights reserved.
Attempting to contact (ADDRESS=(PROTOCOL=TCP)(HOST=localhost)
(PORT=1521))
OK (440 msec)
...and from my install log you see that I selected MTS:
-[ YESNO
Q> Would you like MTS (Multi-Threaded Server) configured
and the SQL*Net$
A> TRUE
Please explain? Will TCP/IP MTS work via the loopback adapter
only? So far I have not tried a remote TCP/IP connection.
-STEVEl
null -
Multi-threaded agent not being used
Solaris 9, Oracle 9.2.0.1
The docs say the multi-threaded agent avoids processes starting every time a user opens a database connection. Except it doesn't seem to.
I've started up the agent;
ps -ef |grep hsodbc
oracle 6193 1 0 14:21:07 ? 0:00 hsodbcMYSQL_R -mt
But, when I establish 2 user connections across a database link, I see this;
ps -ef |grep hsodbc
oracle 6201 1 0 14:21:40 ? 0:00 hsodbcMYSQL_R (LOCAL=NO)
oracle 6216 1 1 14:23:08 ? 0:00 hsodbcMYSQL_L (LOCAL=NO)
oracle 6193 1 0 14:21:07 ? 0:00 hsodbcMYSQL_R -mt
The multi-threaded agent isn't picking up and processing the connections as I would expect. Processes are being spawned in exactly the same way as when the mt agent is not running.
I have checked the listener logs and the agent is registering ok at startup [and every 10 secs too!!!].
Can anyone shed any light on why I am not seeing the benefits of the mt agent?
TIA
SteveSteve,
MTA is not supported with Generic Connectivity. -
I am quite new to multi threaded programming.
The problem I am facing in my code is as follows:
I can instantiate 1-10 threads from my controller class. For example if my controller class generates 10 threads, 5 threads
finish the task they are assigned to do(i.e send SMS and Update the Database) and the other 5 threads eventhough send SMS but
get stuck when they are supposed to update the Database (this is inferred from the logs).
Due to this problem my controller class remains in a wait state as I am using the join() method and some of the threads never
join.
Another interesting observation is that it always happens that the thread numbered 0-5 always get stuck at the exact point
where database has to be updated and thread number 6-10 complete their task. Same is the case when i instantiate 2 threads, i
thread completes its task and another thread gets stuck, again at the same point.
I am using Connection Pooling to connect to the database.
I am sure that the problem is with the query
int j=dbObject.execute_pst("UPDATE table SET flag='true' WHERE message IN("+trueFlag+")",con);
where true flag is a comma seperated string containing some ID's.
What i cannot understand is why some of the threads (almost 50% of them), work fine with this query and the others get stuck
(i.e. just wait at this query during runtime)The problem must lie in the connection, as the SQL statement is to basic to cause an endless loop inside the DBMS. If you are in doubt, try the setMaxRows() method of the Statement interface, I'm using Sybase and it also limits the number of rows processed in update and delete statements (which I'm pretty sure is buggy, but you can still try it).
Which DBMS are you using by the way?
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