I have an async chain in my java code that i want to stop after a certain timeout
so i created a threadPool with some threads and called the CompletableFuture like this
ExecutorService pool = Executors.newFixedThreadPool(10);
than i have a cyclic method that loads data from the db and executes some task on it, once all the CompletableFutures are completed its doing it again
CompletableFuture<MyObject> futureTask =
CompletableFuture.supplyAsync(() -> candidate, pool)
.thenApply(Task1::doWork).thenApply(Task2::doWork).thenApply(Task3::doWork)
.thenApply(Task4::doWork).thenApply(Task5::doWork).orTimeout(30,TimeUnit.SECONDS)
.thenApply(Task6::doWork).orTimeout(30,TimeUnit.SECONDS)
.exceptionally(ExceptionHandlerService::handle);
My problem is in task6, that has a very intensive task (its a network connection task that sometimes hangs forever)
i noticed that my orTimeout is being fired correctly after 30 seconds, but the thread running Task6 is still being running
after few cycles like this, all my threads are drained and my app dies
How can i cancel the running threads on the pool after the timeout has reached?
(without calling pool.shutdown())
UPDATE*
inside the main thread i did a simple check as shown here
for (int i = TIME_OUT_SECONDS; i >= 0; i--) {
unfinishedTasks = handleFutureTasks(unfinishedTasks, totalBatchSize);
if(unfinishedTasks.isEmpty()) {
break;
}
if(i==0) {
//handle cancelation of the tasks
for(CompletableFuture<ComplianceCandidate> task: unfinishedTasks) {
**task.cancel(true);**
log.error("Reached timeout on task, is canceled: {}", task.isCancelled());
}
break;
}
try {
TimeUnit.SECONDS.sleep(1);
} catch (Exception ex) {
}
}
What i see is that after few cycles, all the tasks complain about timeout...
in the first 1-2 cycles, i still get epected responses (while there are threads to process it)
i still feel that the thread pool is exhausted
I know you said without calling pool.shutDown, but there is simply no other way. When you look at your stages though, they will run in either the thread that "appends" them (adding those thenApply) or a thread from that pool that you define. May be an example should make more sense.
public class SO64743332 {
static ExecutorService pool = Executors.newFixedThreadPool(10);
public static void main(String[] args) {
CompletableFuture<String> f1 = CompletableFuture.supplyAsync(() -> dbCall(), pool);
//simulateWork(4);
CompletableFuture<String> f2 = f1.thenApply(x -> {
System.out.println(Thread.currentThread().getName());
return transformationOne(x);
});
CompletableFuture<String> f3 = f2.thenApply(x -> {
System.out.println(Thread.currentThread().getName());
return transformationTwo(x);
});
f3.join();
}
private static String dbCall() {
simulateWork(2);
return "a";
}
private static String transformationOne(String input) {
return input + "b";
}
private static String transformationTwo(String input) {
return input + "b";
}
private static void simulateWork(int seconds) {
try {
Thread.sleep(TimeUnit.SECONDS.toMillis(seconds));
} catch (InterruptedException e) {
System.out.println("Interrupted!");
e.printStackTrace();
}
}
}
They key point of the above code is this : simulateWork(4);. Run the code with it commented out and then uncomment it. See what thread is actually going to execute all those thenApply. It is either main or the same thread from the pool, meaning although you have a pool defined - it's only a single thread from that pool that will execute all those stages.
In this context, you could define a single thread executor (inside a method let's say) that will run all those stages. This way you could control when to call shutDownNow and potentially interrupt (if your code responds to interrupts) the running task. Here is a made-up example that simulates that:
public class SO64743332 {
public static void main(String[] args) {
execute();
}
public static void execute() {
ExecutorService pool = Executors.newSingleThreadExecutor();
CompletableFuture<String> cf1 = CompletableFuture.supplyAsync(() -> dbCall(), pool);
CompletableFuture<String> cf2 = cf1.thenApply(x -> transformationOne(x));
// give enough time for transformationOne to start, but not finish
simulateWork(2);
try {
CompletableFuture<String> cf3 = cf2.thenApply(x -> transformationTwo(x))
.orTimeout(4, TimeUnit.SECONDS);
cf3.get(10, TimeUnit.SECONDS);
} catch (ExecutionException | InterruptedException | TimeoutException e) {
pool.shutdownNow();
}
}
private static String dbCall() {
System.out.println("Started DB call");
simulateWork(1);
System.out.println("Done with DB call");
return "a";
}
private static String transformationOne(String input) {
System.out.println("Started work");
simulateWork(10);
System.out.println("Done work");
return input + "b";
}
private static String transformationTwo(String input) {
System.out.println("Started transformation two");
return input + "b";
}
private static void simulateWork(int seconds) {
try {
Thread.sleep(TimeUnit.SECONDS.toMillis(seconds));
} catch (InterruptedException e) {
System.out.println("Interrupted!");
e.printStackTrace();
}
}
}
Running this you should notice that transformationOne starts, but it is interrupted because of the shutDownNow.
The drawback of this should be obvious, every invocation of execute will create a new thread pool...
I have a test that is blocking (first block of code). I have a few elements that are all working together. I have a blocking queue that I put events on to, then I have a consumer that takes them off and sends them to Amazon Kinesis. I am pretty sure that my test is getting blocked because the queue is blocking my consumer even though I thought it was running on a separate thread.
// Test.java
#Test
public void testWhileLoop() throws InterruptedException {
ArrayBlockingQueue<Event> testQ = new ArrayBlockingQueue<Event>(1024);
// mockKinesis is a mock at the class level.
KPLPoster kpl = new KPLPoster("TestStream", mockKinesis, testQ);
Event event = new Event("TestMessage", "TestPartition");
ListenableFuture<UserRecordResult> fakeReturn = Mockito.mock(ListenableFuture.class);
final AtomicInteger numberOfWhileLoops = new AtomicInteger();
Mockito.doAnswer(invocation -> {
numberOfWhileLoops.incrementAndGet();
return fakeReturn;
})
.when(mockKinesis)
.addUserRecord("TestStream", "TestPartition", ByteBuffer.wrap("TestMessage".getBytes()));
kpl.run(); // Hangs here
for(int i = 100; i > 0; i--){
testQ.put(event);
}
kpl.stop();
kpl = null;
assert(numberOfWhileLoops.toString()).equals("100");
}
Here is the run method of BaseKinesisPoster which my KPLPoster inherits. It should be noted that BaseKinesisPoster implements the Runnable interface.
//BaseKinesisPoster.java
#Override
public void run() {
shutdown = false;
while (!shutdown && !(Thread.currentThread().isInterrupted())) {
try {
this.runOnce();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}catch (Exception e){
e.printStackTrace();
}
}
}
Finally, here is part of my KPLPoster's (which extends BaseKinesisPoster) relevant runOnce() method.
// KPLPoster.java
#Override
protected void runOnce() throws Exception {
Event event = inputQueue.take();
//other stuff in my method
}
How do I make sure that blocking on my queue consumer doesn't block my test/main thread?
When you call
Thread.run();
it invokes the method called. Nothing special happens and the method is run in the current thread.
When you call
Thread.start();
This starts the thread which in turn calls run() in that new thread.
BTW Thread.stop() will throw an UnsupportedOperationException in Java 8. You shouldn't use it. You should allow it to finish naturally.
I'm trying to find more information on how to bound the running time of a task created using ThreadPoolExecutor.
I want to create a self destructing, e.g. when time has passed (1m for example) then the thread will terminate itself automatically and return a null value. The key point here is that waiting for the thread to finish should not block the main thread (UI thread in our example).
I know I can use the get method, however it will block my application.
I was thinking about running an additional internal thread that will sleep for 1m and then will call interrupt on the main thread.
I attached an example code, it looks like a good idea, but I need another pair of eyes telling me if it makes sense.
public abstract class AbstractTask<T> implements Callable<T> {
private final class StopRunningThread implements Runnable {
/**
* Holds the main thread to interrupt. Cannot be null.
*/
private final Thread mMain;
public StopRunningThread(final Thread main) {
mMain = main;
}
#Override
public void run() {
try {
Thread.sleep(60 * 1000);
// Stop it.
mMain.interrupt();
} catch (final InterruptedException exception) {
// Ignore.
}
}
}
call() is called via a ThreadPool
public T call() {
try {
// Before running any task initialize the result so that the user
// won't
// think he/she has something.
mResult = null;
mException = null;
// Stop running thread.
mStopThread = new Thread(new StopRunningThread(
Thread.currentThread()));
mStopThread.start();
mResult = execute(); <-- A subclass implements this one
} catch (final Exception e) {
// An error occurred, ignore any result.
mResult = null;
mException = e;
// Log it.
Ln.e(e);
}
// In case it's out of memory do a special catch.
catch (final OutOfMemoryError e) {
// An error occurred, ignore any result.
mResult = null;
mException = new UncheckedException(e);
// Log it.
Ln.e(e);
} finally {
// Stop counting.
mStopThread.interrupt();
}
return mResult;
}
There are couple of points which I'm afraid of:
What will happen if execute() has an exception and immediately afterwards my external thread will interrupt, then I'll never catch the exception.
Memory/CPU consumption, I am using a thread pool to avoid the creation of new threads.
Do you see a better idea for reaching the same functionality ?
Doing this would be somewhat involved. First, you'd need to extend the ThreadPoolExecutor class. You'll need to override the "beforeExecute" and "afterExecute" methods. They would keep track of thread start times, and do cleanup after. Then you'd need a reaper to periodically check to see which threads need cleaning up.
This example uses a Map to record when each thread is started. The beforeExecute method populates this, and the afterExecute method cleans it up. There is a TimerTask which periodically executes and looks at all the current entries (ie. all the running threads), and calls Thread.interrupt() on all of them that have exceeded the given time limit.
Notice that I have given two extra constructor parameters: maxExecutionTime, and reaperInterval to control how long tasks are given, and how often to check for tasks to kill. I've omitted some constructors here for the the sake of brevity.
Keep in mind the tasks you submit have to play nice and allow themselves to be killed. This means you have to:
Check Thread.currentThread().isInterrupted() at regular intervals
during execution.
Try to avoid any blocking operation that does not declare
InterruptedException in it's throws clause. A prime example of this
would be InputStream/OutputStream usage, and you would use NIO
Channels instead. If you have to use these methods, check the interrupted flag immediately after returning from such an operation.
.
public class TimedThreadPoolExecutor extends ThreadPoolExecutor {
private Map<Thread, Long> threads = new HashMap<Thread, Long>();
private Timer timer;
public TimedThreadPoolExecutor(int corePoolSize, int maximumPoolSize,
long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue,
long maxExecutionTime,
long reaperInterval) {
super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
startReaper(maxExecutionTime, reaperInterval);
}
#Override
protected void afterExecute(Runnable r, Throwable t) {
threads.remove(Thread.currentThread());
System.out.println("after: " + Thread.currentThread().getName());
super.afterExecute(r, t);
}
#Override
protected void beforeExecute(Thread t, Runnable r) {
super.beforeExecute(t, r);
System.out.println("before: " + t.getName());
threads.put(t, System.currentTimeMillis());
}
#Override
protected void terminated() {
if (timer != null) {
timer.cancel();
}
super.terminated();
}
private void startReaper(final long maxExecutionTime, long reaperInterval) {
timer = new Timer();
TimerTask timerTask = new TimerTask() {
#Override
public void run() {
// make a copy to avoid concurrency issues.
List<Map.Entry<Thread, Long>> entries =
new ArrayList<Map.Entry<Thread, Long>>(threads.entrySet());
for (Map.Entry<Thread, Long> entry : entries) {
Thread thread = entry.getKey();
long start = entry.getValue();
if (System.currentTimeMillis() - start > maxExecutionTime) {
System.out.println("interrupting thread : " + thread.getName());
thread.interrupt();
}
}
}
};
timer.schedule(timerTask, reaperInterval, reaperInterval);
}
public static void main(String args[]) throws Exception {
TimedThreadPoolExecutor executor = new TimedThreadPoolExecutor(5,5, 1000L, TimeUnit.MILLISECONDS, new ArrayBlockingQueue<Runnable>(20),
1000L,
200L);
for (int i=0;i<10;i++) {
executor.execute(new Runnable() {
public void run() {
try {
Thread.sleep(5000L);
}
catch (InterruptedException e) {
}
}
});
}
executor.shutdown();
while (! executor.isTerminated()) {
executor.awaitTermination(1000L, TimeUnit.MILLISECONDS);
}
}
}
Is it possible to force Java to throw an Exception after some block of code runs longer than acceptable?
Here's the simplest way that I know of to do this:
final Runnable stuffToDo = new Thread() {
#Override
public void run() {
/* Do stuff here. */
}
};
final ExecutorService executor = Executors.newSingleThreadExecutor();
final Future future = executor.submit(stuffToDo);
executor.shutdown(); // This does not cancel the already-scheduled task.
try {
future.get(5, TimeUnit.MINUTES);
}
catch (InterruptedException ie) {
/* Handle the interruption. Or ignore it. */
}
catch (ExecutionException ee) {
/* Handle the error. Or ignore it. */
}
catch (TimeoutException te) {
/* Handle the timeout. Or ignore it. */
}
if (!executor.isTerminated())
executor.shutdownNow(); // If you want to stop the code that hasn't finished.
Alternatively, you can create a TimeLimitedCodeBlock class to wrap this functionality, and then you can use it wherever you need it as follows:
new TimeLimitedCodeBlock(5, TimeUnit.MINUTES) { #Override public void codeBlock() {
// Do stuff here.
}}.run();
I compiled some of the other answers into a single utility method:
public class TimeLimitedCodeBlock {
public static void runWithTimeout(final Runnable runnable, long timeout, TimeUnit timeUnit) throws Exception {
runWithTimeout(new Callable<Object>() {
#Override
public Object call() throws Exception {
runnable.run();
return null;
}
}, timeout, timeUnit);
}
public static <T> T runWithTimeout(Callable<T> callable, long timeout, TimeUnit timeUnit) throws Exception {
final ExecutorService executor = Executors.newSingleThreadExecutor();
final Future<T> future = executor.submit(callable);
executor.shutdown(); // This does not cancel the already-scheduled task.
try {
return future.get(timeout, timeUnit);
}
catch (TimeoutException e) {
//remove this if you do not want to cancel the job in progress
//or set the argument to 'false' if you do not want to interrupt the thread
future.cancel(true);
throw e;
}
catch (ExecutionException e) {
//unwrap the root cause
Throwable t = e.getCause();
if (t instanceof Error) {
throw (Error) t;
} else if (t instanceof Exception) {
throw (Exception) t;
} else {
throw new IllegalStateException(t);
}
}
}
}
Sample code making use of this utility method:
public static void main(String[] args) throws Exception {
final long startTime = System.currentTimeMillis();
log(startTime, "calling runWithTimeout!");
try {
TimeLimitedCodeBlock.runWithTimeout(new Runnable() {
#Override
public void run() {
try {
log(startTime, "starting sleep!");
Thread.sleep(10000);
log(startTime, "woke up!");
}
catch (InterruptedException e) {
log(startTime, "was interrupted!");
}
}
}, 5, TimeUnit.SECONDS);
}
catch (TimeoutException e) {
log(startTime, "got timeout!");
}
log(startTime, "end of main method!");
}
private static void log(long startTime, String msg) {
long elapsedSeconds = (System.currentTimeMillis() - startTime);
System.out.format("%1$5sms [%2$16s] %3$s\n", elapsedSeconds, Thread.currentThread().getName(), msg);
}
Output from running the sample code on my machine:
0ms [ main] calling runWithTimeout!
13ms [ pool-1-thread-1] starting sleep!
5015ms [ main] got timeout!
5016ms [ main] end of main method!
5015ms [ pool-1-thread-1] was interrupted!
Yes, but its generally a very bad idea to force another thread to interrupt on a random line of code. You would only do this if you intend to shutdown the process.
What you can do is to use Thread.interrupt() for a task after a certain amount of time. However, unless the code checks for this it won't work. An ExecutorService can make this easier with Future.cancel(true)
Its much better for the code to time itself and stop when it needs to.
If it is test code you want to time, then you can use the time attribute:
#Test(timeout = 1000)
public void shouldTakeASecondOrLess()
{
}
If it is production code, there is no simple mechanism, and which solution you use depends upon whether you can alter the code to be timed or not.
If you can change the code being timed, then a simple approach is is to have your timed code remember it's start time, and periodically the current time against this. E.g.
long startTime = System.currentTimeMillis();
// .. do stuff ..
long elapsed = System.currentTimeMillis()-startTime;
if (elapsed>timeout)
throw new RuntimeException("tiomeout");
If the code itself cannot check for timeout, you can execute the code on another thread, and wait for completion, or timeout.
Callable<ResultType> run = new Callable<ResultType>()
{
#Override
public ResultType call() throws Exception
{
// your code to be timed
}
};
RunnableFuture<ResultType> future = new FutureTask<>(run);
ExecutorService service = Executors.newSingleThreadExecutor();
service.execute(future);
ResultType result = null;
try
{
result = future.get(1, TimeUnit.SECONDS); // wait 1 second
}
catch (TimeoutException ex)
{
// timed out. Try to stop the code if possible.
future.cancel(true);
}
service.shutdown();
}
I can suggest two options.
Within the method, assuming it is looping and not waiting for an external event, add a local field and test the time each time around the loop.
void method() {
long endTimeMillis = System.currentTimeMillis() + 10000;
while (true) {
// method logic
if (System.currentTimeMillis() > endTimeMillis) {
// do some clean-up
return;
}
}
}
Run the method in a thread, and have the caller count to 10 seconds.
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
method();
}
});
thread.start();
long endTimeMillis = System.currentTimeMillis() + 10000;
while (thread.isAlive()) {
if (System.currentTimeMillis() > endTimeMillis) {
// set an error flag
break;
}
try {
Thread.sleep(500);
}
catch (InterruptedException t) {}
}
The drawback to this approach is that method() cannot return a value directly, it must update an instance field to return its value.
EDIT: Peter Lawrey is completely right: it's not as simple as interrupting a thread (my original suggestion), and Executors & Callables are very useful ...
Rather than interrupting threads, you could set a variable on the Callable once the timeout is reached. The callable should check this variable at appropriate points in task execution, to know when to stop.
Callables return Futures, with which you can specify a timeout when you try to 'get' the future's result. Something like this:
try {
future.get(timeoutSeconds, TimeUnit.SECONDS)
} catch(InterruptedException e) {
myCallable.setStopMeAtAppropriatePlace(true);
}
See Future.get, Executors, and Callable ...
https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/Future.html#get-long-java.util.concurrent.TimeUnit-
https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/Callable.html
https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/Executors.html#newFixedThreadPool%28int%29
I created a very simple solution without using any frameworks or APIs. This looks more elegant and understandable. The class is called TimeoutBlock.
public class TimeoutBlock {
private final long timeoutMilliSeconds;
private long timeoutInteval=100;
public TimeoutBlock(long timeoutMilliSeconds){
this.timeoutMilliSeconds=timeoutMilliSeconds;
}
public void addBlock(Runnable runnable) throws Throwable{
long collectIntervals=0;
Thread timeoutWorker=new Thread(runnable);
timeoutWorker.start();
do{
if(collectIntervals>=this.timeoutMilliSeconds){
timeoutWorker.stop();
throw new Exception("<<<<<<<<<<****>>>>>>>>>>> Timeout Block Execution Time Exceeded In "+timeoutMilliSeconds+" Milli Seconds. Thread Block Terminated.");
}
collectIntervals+=timeoutInteval;
Thread.sleep(timeoutInteval);
}while(timeoutWorker.isAlive());
System.out.println("<<<<<<<<<<####>>>>>>>>>>> Timeout Block Executed Within "+collectIntervals+" Milli Seconds.");
}
/**
* #return the timeoutInteval
*/
public long getTimeoutInteval() {
return timeoutInteval;
}
/**
* #param timeoutInteval the timeoutInteval to set
*/
public void setTimeoutInteval(long timeoutInteval) {
this.timeoutInteval = timeoutInteval;
}
}
example :
try {
TimeoutBlock timeoutBlock = new TimeoutBlock(10 * 60 * 1000);//set timeout in milliseconds
Runnable block=new Runnable() {
#Override
public void run() {
//TO DO write block of code to execute
}
};
timeoutBlock.addBlock(block);// execute the runnable block
} catch (Throwable e) {
//catch the exception here . Which is block didn't execute within the time limit
}
This was so much useful for me when i had to connect to a FTP account. Then download and upload stuff. sometimes FTP connection hangs or totally breaks. This caused whole system to go down. and i needed a way to detect it and prevent it from happening . So i created this and used it. Works pretty well.
I faced a similar kind of issue where my task was to push a message to SQS within a particular timeout. I used the trivial logic of executing it via another thread and waiting on its future object by specifying the timeout. This would give me a TIMEOUT exception in case of timeouts.
final Future<ISendMessageResult> future =
timeoutHelperThreadPool.getExecutor().submit(() -> {
return getQueueStore().sendMessage(request).get();
});
try {
sendMessageResult = future.get(200, TimeUnit.MILLISECONDS);
logger.info("SQS_PUSH_SUCCESSFUL");
return true;
} catch (final TimeoutException e) {
logger.error("SQS_PUSH_TIMEOUT_EXCEPTION");
}
But there are cases where you can't stop the code being executed by another thread and you get true negatives in that case.
For example - In my case, my request reached SQS and while the message was being pushed, my code logic encountered the specified timeout. Now in reality my message was pushed into the Queue but my main thread assumed it to be failed because of the TIMEOUT exception.
This is a type of problem which can be avoided rather than being solved. Like in my case I avoided it by providing a timeout which would suffice in nearly all of the cases.
If the code you want to interrupt is within you application and is not something like an API call then you can simply use
future.cancel(true)
However do remember that java docs says that it does guarantee that the execution will be blocked.
"Attempts to cancel execution of this task. This attempt will fail if the task has already completed, has already been cancelled,or could not be cancelled for some other reason. If successful,and this task has not started when cancel is called,this task should never run. If the task has already started,then the mayInterruptIfRunning parameter determines whether the thread executing this task should be interrupted inan attempt to stop the task."
If you want a CompletableFuture way you could have a method like
public MyResponseObject retrieveDataFromEndpoint() {
CompletableFuture<MyResponseObject> endpointCall
= CompletableFuture.supplyAsync(() ->
yourRestService.callEnpoint(withArg1, withArg2));
try {
return endpointCall.get(10, TimeUnit.MINUTES);
} catch (TimeoutException
| InterruptedException
| ExecutionException e) {
throw new RuntimeException("Unable to fetch data", e);
}
}
If you're using spring, you could annotate the method with a #Retryable so that it retries the method three times if an exception is thrown.
Instead of having the task in the new thread and the timer in the main thread, have the timer in the new thread and the task in the main thread:
public static class TimeOut implements Runnable{
public void run() {
Thread.sleep(10000);
if(taskComplete ==false) {
System.out.println("Timed Out");
return;
}
else {
return;
}
}
}
public static boolean taskComplete = false;
public static void main(String[] args) {
TimeOut timeOut = new TimeOut();
Thread timeOutThread = new Thread(timeOut);
timeOutThread.start();
//task starts here
//task completed
taskComplete =true;
while(true) {//do all other stuff }
}
There is a hacky way to do it.
Set some boolean field to indicate whether the work was completed. Then before the block of code, set a timer to run a piece of code after your timeout. The timer will check if the block of code had finished executing, and if not, throw an exception. Otherwise it will do nothing.
The end of the block of code should, of course, set the field to true to indicate the work was done.
There's a very simple option that nobody's mentioned yet:
Duration timeout = Duration.ofMinutes(5);
Thread thread = new Thread(() -> {
// your code here
});
thread.start();
thread.join(timeout.toMillis());
if (thread.isAlive()) {
thread.interrupt();
throw new MyTimeoutException();
}
If the thread running your code block fails to complete within the timeout, it is interrupted and whatever exception you want can be thrown.
It is possible to write code that will simply ignore the interruption and carry on. If you're dealing with this can cannot fix it then there is thread.stop(), but that can break any synchronisation mechanisms that you are relying on. See its deprecation notice.
You can also capture exceptions from the thread:
AtomicReference<Throwable> uncaughtException = new AtomicReference<>();
thread.setUncaughtExceptionHandler((t, ex) -> uncaughtException.setRelease(ex));
// ...
Throwable ex = uncaughtException.getAcquire();
if (ex != null) {
throw ex;
}
I had this problem too, my logs print out with ‘’Unexpected end of stream‘’.and ‘’Could not get a resource from the pool‘’，
I set the timeout of brpop to 30s, redis to 31s, and mysql database connection pool to 300s. For now, this error is not printed on the log, but I don't know if this error will be reported in the future.I don't know if it has a bad effect on my writing to the database
I'm implementing a GUI for a console application, and I need to do some actions (for example, parse an XML file) in a specified time interval. I decided to use javax.swing.Timer alongside SwingWorker to be sure that these actions will not make my application unresponsive.
I had implemented the timer this way:
public class DataUpdateTimer extends Timer {
private String dataFlowControllerXML = null;
private DataUpdateWorker dataUpdateWorker = null;
public class DataUpdateWorker extends SwingWorker {
private String dataFlowControllerXML = null;
DataUpdateWorker(String dataFlowControllerXML) {
super();
this.dataFlowControllerXML = dataFlowControllerXML;
}
#Override
protected Boolean doInBackground() throws Exception {
Thread.sleep(300);
return Boolean.TRUE;
}
}
public class DataUpdateIntervalListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
DataUpdateTimer timer = (DataUpdateTimer)e.getSource();
DataUpdateWorker dataUpdateWorker = timer.getDataUpdateWorker();
if (dataUpdateWorker != null)
if (dataUpdateWorker.isDone()) {
Boolean updateResult = Boolean.FALSE;
try {
updateResult = (Boolean)dataUpdateWorker.get();
} catch (InterruptedException ex) {
} catch (ExecutionException ex) {
}
dataUpdateWorker = null;
}
// Creating new worker thread here
if (dataUpdateWorker == null) {
timer.dataUpdateWorker = new DataUpdateWorker(timer.dataFlowControllerXML);
// Starting a new worker thread for parsing Data Flow Controller's XML
timer.dataUpdateWorker.execute();
return;
}
}
}
DataUpdateTimer(Integer dataUpdateInterval, String dataFlowControllerXML) {
super(dataUpdateInterval.intValue(), null);
this.dataFlowControllerXML = dataFlowControllerXML;
addActionListener(new DataUpdateIntervalListener());
}
#Override
public void stop() {
super.stop();
if (dataUpdateWorker != null) {
if (!dataUpdateWorker.isDone() || !dataUpdateWorker.isCancelled())
dataUpdateWorker.cancel(true);
}
}
}
...and use it as follows:
new DataUpdateTimer(1000, dataFlowControllerXML).start();
Everything works as I wish. Timer creates new a SwingWorker instance and executes it. After the worker is done, the new one is created and executed.
The thing I'm confused by is that after the worker's thread is done I still can see it running in Netbeans' debugging window (for example, as SwingWorker-pool-3-thread-1) or in Windows Task Manager (the number of running threads doesn't decrease after the thread is done). The number of SwingWorker threads is limited to 10, but having them running embarrasses me.
In the case of simple thread usage:
Thread th = new Thread(new Runnable() {
public void run() {
int a = 0;
}
});
th.start();
This thread automatically disappears after execution.
Is this SwingWorker behavior normal?
Yes, this is normal. As the thread's name suggests, the swing workers' model (background) actions are being delegated to a thread pool. When the work is done the thread is returned to the pool so another worker can use it. This eliminates some overhead in creating/destroying threads which can be expensive.
By the way, the background threads won't stick around forever. Looking at the source for SwingWorker I see:
//from SwingWorker.java (c) Sun Microsystems/Oracle 2009
executorService =
new ThreadPoolExecutor(1, MAX_WORKER_THREADS,
10L, TimeUnit.MINUTES,
new LinkedBlockingQueue<Runnable>(),
threadFactory);
This indicates that the threads will die off after being idle for 10 minutes.