/**
* Execute the {@link Callable} tasks in parallel (per the configured size of the {@link
* WorkerPool}) and wait for them to complete.
*
* @param tasks a map of {@link Callable}s with keys by which you will be able to access each
* return value
* @return the return values of each {@link Callable}s mapped by their input key
*/
public <K, V> Map<K, V> invokeAll(Map<K, Callable<V>> tasks) {
String caller =
LOGGER.isDebugEnabled() ? Thread.currentThread().getStackTrace()[2].toString() : "n/a";
LOGGER.debug("[%s] is invoking %d mapped tasks", caller, tasks.size());
List<K> orderedKeys = new ArrayList<K>(tasks.size());
List<Callable<V>> orderedTasks = new ArrayList<Callable<V>>(tasks.size());
for (Map.Entry<K, Callable<V>> entry : tasks.entrySet()) {
orderedKeys.add(entry.getKey());
orderedTasks.add(entry.getValue());
}
try {
long start = System.currentTimeMillis();
List<Future<V>> executorResults = executorService.invokeAll(orderedTasks);
long finish = System.currentTimeMillis();
LOGGER.debug("[%s] invoked %d mapped tasks in %d ms", caller, tasks.size(), finish - start);
Map<K, V> mappedResults = new LinkedHashMap<K, V>(tasks.size());
for (int i = 0; i < tasks.size(); i++) {
K key = orderedKeys.get(i);
V result = executorResults.get(i).get();
mappedResults.put(key, result);
}
return mappedResults;
} catch (InterruptedException e) {
throw new RuntimeException(e);
} catch (ExecutionException e) {
throw new RuntimeException(e);
}
}
/**
* Create a pool with the specified number of threads.
*
* @param nThreads
*/
public WorkerPool(int nThreads) {
LOGGER.debug("initializing worker pool with %d threads", nThreads);
executorService =
LOGGER.isDebugEnabled()
? new MetricReportingExecutorService(LOGGER, nThreads)
: Executors.newFixedThreadPool(nThreads);
Runtime.getRuntime()
.addShutdownHook(
new Thread() {
@Override
public void run() {
shutdownAndAwaitTermination(10);
}
});
}
public static void main(String[] args) {
WorkerPool workerPool = new WorkerPool(3);
mapExample(workerPool);
listExample(workerPool);
slowExample(workerPool, 5);
if (LOGGER.isDebugEnabled()) {
((MetricReportingExecutorService) workerPool.executorService).tick();
((MetricReportingExecutorService) workerPool.executorService).report();
}
System.exit(0);
}
/**
* Execute the {@link Callable} tasks in parallel (per the configured size of the {@link
* WorkerPool}) and wait for them to complete.
*
* @param tasks a list of {@link Callable}s
* @return the ordered return values
*/
public <T> List<T> invokeAll(List<Callable<T>> tasks) {
String caller =
LOGGER.isDebugEnabled() ? Thread.currentThread().getStackTrace()[2].toString() : "n/a";
LOGGER.debug("[%s] is invoking %d listed tasks", caller, tasks.size());
try {
long start = System.currentTimeMillis();
List<Future<T>> executorResults = executorService.invokeAll(tasks);
long finish = System.currentTimeMillis();
LOGGER.debug("[%s] invoked %d listed tasks in %d ms", caller, tasks.size(), finish - start);
List<T> results = new ArrayList<T>(tasks.size());
for (Future<T> future : executorResults) {
results.add(future.get());
}
return results;
} catch (InterruptedException e) {
throw new RuntimeException(e);
} catch (ExecutionException e) {
throw new RuntimeException(e);
}
}