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A library of tools to assist with safe concurrent java development. Providing a unique priority based thread pool, and ways to distrbute threaded work.
package org.threadly.concurrent.wrapper;
import java.util.ArrayDeque;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Queue;
import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.Executor;
import java.util.concurrent.atomic.AtomicInteger;
import org.threadly.concurrent.RunnableCallableAdapter;
import org.threadly.concurrent.SubmitterExecutor;
import org.threadly.concurrent.future.ListenableFuture;
import org.threadly.concurrent.future.ListenableFutureTask;
import org.threadly.concurrent.future.ListenableRunnableFuture;
import org.threadly.concurrent.lock.StripedLock;
import org.threadly.util.ArgumentVerifier;
import org.threadly.util.ExceptionUtils;
/**
* TaskDistributor is designed such that tasks executed on it for a given key will run in a
* single threaded manner. It needs a multi-threaded pool supplied to it, to then execute those
* tasks on. While the thread which runs those tasks may be different between multiple
* executions, no two tasks for the same key will ever be run in parallel.
*
* Because of that, it is recommended that the executor provided has as many possible threads
* as possible keys that could be provided to be run in parallel. If this class is starved for
* threads some keys may continue to process new tasks, while other keys could be starved.
*
* Assuming that the shared memory (any objects, primitives, etc) are only accessed through the
* same instance of {@link KeyDistributedExecutor}, and assuming that those variables are only
* accessed via the same key. Then the programmer does not need to worry about synchronization, or
* volatile. The {@link KeyDistributedExecutor} will ensure the happens-before relationship.
*
* @author jent - Mike Jensen
* @since 2.5.0 (existed since 1.0.0 as TaskExecutorDistributor)
*/
public class KeyDistributedExecutor {
protected static final short DEFAULT_LOCK_PARALISM = 32;
protected static final float CONCURRENT_HASH_MAP_LOAD_FACTOR = 0.75f; // 0.75 is ConcurrentHashMap default
protected static final short CONCURRENT_HASH_MAP_MIN_SIZE = 8;
protected static final short CONCURRENT_HASH_MAP_MAX_INITIAL_SIZE = 64;
protected static final short CONCURRENT_HASH_MAP_MAX_CONCURRENCY_LEVEL = 32;
protected static final short ARRAY_DEQUE_INITIAL_SIZE = 8; // minimum is 8, should be 2^X
protected final Executor executor;
protected final StripedLock sLock;
protected final int maxTasksPerCycle;
protected final WorkerFactory wFactory;
protected final ConcurrentHashMap taskWorkers;
/**
* Constructor to use a provided executor implementation for running tasks.
*
* This constructs with a default expected level of concurrency of 16. This also does not
* attempt to have an accurate queue size for the {@link #getTaskQueueSize(Object)} call (thus
* preferring high performance).
*
* @param executor A multi-threaded executor to distribute tasks to. Ideally has as many
* possible threads as keys that will be used in parallel.
*/
public KeyDistributedExecutor(Executor executor) {
this(DEFAULT_LOCK_PARALISM, executor, Integer.MAX_VALUE, false);
}
/**
* Constructor to use a provided executor implementation for running tasks.
*
* This constructor allows you to specify if you want accurate queue sizes to be tracked for
* given thread keys. There is a performance hit associated with this, so this should only be
* enabled if {@link #getTaskQueueSize(Object)} calls will be used.
*
* This constructs with a default expected level of concurrency of 16.
*
* @param executor A multi-threaded executor to distribute tasks to. Ideally has as many
* possible threads as keys that will be used in parallel.
* @param accurateQueueSize {@code true} to make {@link #getTaskQueueSize(Object)} more accurate
*/
public KeyDistributedExecutor(Executor executor, boolean accurateQueueSize) {
this(DEFAULT_LOCK_PARALISM, executor, Integer.MAX_VALUE, accurateQueueSize);
}
/**
* Constructor to use a provided executor implementation for running tasks.
*
* This constructor allows you to provide a maximum number of tasks for a key before it yields
* to another key. This can make it more fair, and make it so no single key can starve other
* keys from running. The lower this is set however, the less efficient it becomes in part
* because it has to give up the thread and get it again, but also because it must copy the
* subset of the task queue which it can run.
*
* This also allows you to specify if you want accurate queue sizes to be tracked for given
* thread keys. There is a performance hit associated with this, so this should only be enabled
* if {@link #getTaskQueueSize(Object)} calls will be used.
*
* This constructs with a default expected level of concurrency of 16. This also does not
* attempt to have an accurate queue size for the "getTaskQueueSize" call (thus preferring
* high performance).
*
* @param executor A multi-threaded executor to distribute tasks to. Ideally has as many
* possible threads as keys that will be used in parallel.
* @param maxTasksPerCycle maximum tasks run per key before yielding for other keys
*/
public KeyDistributedExecutor(Executor executor, int maxTasksPerCycle) {
this(DEFAULT_LOCK_PARALISM, executor, maxTasksPerCycle, false);
}
/**
* Constructor to use a provided executor implementation for running tasks.
*
* This constructor allows you to provide a maximum number of tasks for a key before it yields
* to another key. This can make it more fair, and make it so no single key can starve other
* keys from running. The lower this is set however, the less efficient it becomes in part
* because it has to give up the thread and get it again, but also because it must copy the
* subset of the task queue which it can run.
*
* This also allows you to specify if you want accurate queue sizes to be tracked for given
* thread keys. There is a performance hit associated with this, so this should only be enabled
* if {@link #getTaskQueueSize(Object)} calls will be used.
*
* This constructs with a default expected level of concurrency of 16.
*
* @param executor A multi-threaded executor to distribute tasks to. Ideally has as many
* possible threads as keys that will be used in parallel.
* @param maxTasksPerCycle maximum tasks run per key before yielding for other keys
* @param accurateQueueSize {@code true} to make {@link #getTaskQueueSize(Object)} more accurate
*/
public KeyDistributedExecutor(Executor executor, int maxTasksPerCycle,
boolean accurateQueueSize) {
this(DEFAULT_LOCK_PARALISM, executor, maxTasksPerCycle, accurateQueueSize);
}
/**
* Constructor to use a provided executor implementation for running tasks.
*
* This constructor does not attempt to have an accurate queue size for the
* {@link #getTaskQueueSize(Object)} call (thus preferring high performance).
*
* @param expectedParallism level of expected quantity of threads adding tasks in parallel
* @param executor A multi-threaded executor to distribute tasks to. Ideally has as many
* possible threads as keys that will be used in parallel.
*/
public KeyDistributedExecutor(int expectedParallism, Executor executor) {
this(expectedParallism, executor, Integer.MAX_VALUE, false);
}
/**
* Constructor to use a provided executor implementation for running tasks.
*
* This constructor allows you to specify if you want accurate queue sizes to be tracked for
* given thread keys. There is a performance hit associated with this, so this should only be
* enabled if {@link #getTaskQueueSize(Object)} calls will be used.
*
* @param expectedParallism level of expected quantity of threads adding tasks in parallel
* @param executor A multi-threaded executor to distribute tasks to. Ideally has as many
* possible threads as keys that will be used in parallel.
* @param accurateQueueSize {@code true} to make {@link #getTaskQueueSize(Object)} more accurate
*/
public KeyDistributedExecutor(int expectedParallism, Executor executor,
boolean accurateQueueSize) {
this(expectedParallism, executor, Integer.MAX_VALUE, accurateQueueSize);
}
/**
* Constructor to use a provided executor implementation for running tasks.
*
* This constructor allows you to provide a maximum number of tasks for a key before it yields
* to another key. This can make it more fair, and make it so no single key can starve other
* keys from running. The lower this is set however, the less efficient it becomes in part
* because it has to give up the thread and get it again, but also because it must copy the
* subset of the task queue which it can run.
*
* This constructor does not attempt to have an accurate queue size for the
* {@link #getTaskQueueSize(Object)} call (thus preferring high performance).
*
* @param expectedParallism level of expected quantity of threads adding tasks in parallel
* @param executor A multi-threaded executor to distribute tasks to. Ideally has as many
* possible threads as keys that will be used in parallel.
* @param maxTasksPerCycle maximum tasks run per key before yielding for other keys
*/
public KeyDistributedExecutor(int expectedParallism, Executor executor, int maxTasksPerCycle) {
this(expectedParallism, executor, maxTasksPerCycle, false);
}
/**
* Constructor to use a provided executor implementation for running tasks.
*
* This constructor allows you to provide a maximum number of tasks for a key before it yields
* to another key. This can make it more fair, and make it so no single key can starve other
* keys from running. The lower this is set however, the less efficient it becomes in part
* because it has to give up the thread and get it again, but also because it must copy the
* subset of the task queue which it can run.
*
* This also allows you to specify if you want accurate queue sizes to be tracked for given
* thread keys. There is a performance hit associated with this, so this should only be enabled
* if {@link #getTaskQueueSize(Object)} calls will be used.
*
* @param expectedParallism level of expected quantity of threads adding tasks in parallel
* @param executor A multi-threaded executor to distribute tasks to. Ideally has as many
* possible threads as keys that will be used in parallel.
* @param maxTasksPerCycle maximum tasks run per key before yielding for other keys
* @param accurateQueueSize {@code true} to make {@link #getTaskQueueSize(Object)} more accurate
*/
public KeyDistributedExecutor(int expectedParallism, Executor executor,
int maxTasksPerCycle, boolean accurateQueueSize) {
this(executor, new StripedLock(expectedParallism), maxTasksPerCycle, accurateQueueSize);
}
/**
* Constructor to be used in unit tests.
*
* This constructor allows you to provide a maximum number of tasks for a key before it yields
* to another key. This can make it more fair, and make it so no single key can starve other
* keys from running. The lower this is set however, the less efficient it becomes in part
* because it has to give up the thread and get it again, but also because it must copy the
* subset of the task queue which it can run.
*
* @param executor executor to be used for task worker execution
* @param sLock lock to be used for controlling access to workers
* @param maxTasksPerCycle maximum tasks run per key before yielding for other keys
* @param accurateQueueSize {@code true} to make {@link #getTaskQueueSize(Object)} more accurate
*/
protected KeyDistributedExecutor(Executor executor, StripedLock sLock,
int maxTasksPerCycle, boolean accurateQueueSize) {
ArgumentVerifier.assertNotNull(executor, "executor");
ArgumentVerifier.assertNotNull(sLock, "sLock");
ArgumentVerifier.assertGreaterThanZero(maxTasksPerCycle, "maxTasksPerCycle");
this.executor = executor;
this.sLock = sLock;
this.maxTasksPerCycle = maxTasksPerCycle;
int mapInitialSize = Math.min(sLock.getExpectedConcurrencyLevel(),
CONCURRENT_HASH_MAP_MAX_INITIAL_SIZE);
if (mapInitialSize < CONCURRENT_HASH_MAP_MIN_SIZE) {
mapInitialSize = CONCURRENT_HASH_MAP_MIN_SIZE;
}
int mapConcurrencyLevel = Math.min(sLock.getExpectedConcurrencyLevel() / 2,
CONCURRENT_HASH_MAP_MAX_CONCURRENCY_LEVEL);
if (mapConcurrencyLevel < 1) {
mapConcurrencyLevel = 1;
}
if (accurateQueueSize) {
wFactory = new WorkerFactory() {
@Override
public TaskQueueWorker build(Object mapKey, Object workerLock, Runnable firstTask) {
return new StatisticWorker(mapKey, workerLock, firstTask);
}
};
} else {
wFactory = new WorkerFactory() {
@Override
public TaskQueueWorker build(Object mapKey, Object workerLock, Runnable firstTask) {
return new TaskQueueWorker(mapKey, workerLock, firstTask);
}
};
}
this.taskWorkers = new ConcurrentHashMap(mapInitialSize,
CONCURRENT_HASH_MAP_LOAD_FACTOR,
mapConcurrencyLevel);
}
/**
* Getter for the executor being used behind the scenes.
*
* @return executor tasks are being distributed to
*/
public Executor getExecutor() {
return executor;
}
/**
* Returns a {@link SubmitterExecutor} implementation where all tasks submitted on this executor
* will run on the provided key.
*
* @param threadKey object key where hashCode will be used to determine execution thread
* @return executor which will only execute based on the provided key
*/
public SubmitterExecutor getExecutorForKey(Object threadKey) {
ArgumentVerifier.assertNotNull(threadKey, "threadKey");
return new KeySubmitter(threadKey);
}
/**
* Call to check how many tasks have been queued up for a given key. Depending on what
* constructor was used, and if a {@code true} was passed in for {@code accurateQueueSize}, the
* accuracy of this call varies dramatically.
*
* If {@code true} was not supplied in the constructor for {@code accurateQueueSize}, this will
* only report how many tasks have not been accepted by the worker yet. The accepting of those
* tasks occur in batches, so this number will vary dramatically (and probably be unusable).
*
* So it is highly recommended that if your interested in this functionality you supply a
* {@code true} into the constructor.
*
* Supplying a {@code true} for {@code accurateQueueSize} in the constructor does involve some
* performance cost, but that overhead should be minimal (just no reason to accept any loss if
* not interested in this feature).
*
* @since 1.2.0
*
* @param threadKey key for task queue to examine
* @return the number of tasks queued for the key
*/
public int getTaskQueueSize(Object threadKey) {
TaskQueueWorker worker = taskWorkers.get(threadKey);
if (worker == null) {
return 0;
} else {
return worker.getQueueSize();
}
}
/**
* Get a map of all the keys and how many tasks are queued per key. This map is generated
* without locking. Due to that, this may be inaccurate as task queue sizes changed while
* iterating all key's active workers.
*
* Because this requires an iteration of all task workers, if only a single key's queue size is
* needed, use {@link #getTaskQueueSize(Object)} as a cheaper alternative.
*
* If {@code true} was not supplied in the constructor for {@code accurateQueueSize}, this will
* only report how many tasks have not been accepted by the worker yet. The accepting of those
* tasks occur in batches, so this number will vary dramatically (and probably be unusable).
*
* So it is highly recommended that if your interested in this functionality you supply a
* {@code true} into the constructor.
*
* Supplying a {@code true} for {@code accurateQueueSize} in the constructor does involve some
* performance cost, but that overhead should be minimal (just no reason to accept any loss if
* not interested in this feature).
*
* @return Map of task key's to their respective queue size
*/
public Map getTaskQueueSizeMap() {
Map result = new HashMap();
for (Map.Entry e : taskWorkers.entrySet()) {
result.put(e.getKey(), e.getValue().getQueueSize());
}
return result;
}
/**
* Provide a task to be run with a given thread key.
*
* @param threadKey object key where {@code equals()} will be used to determine execution thread
* @param task Task to be executed
*/
public void execute(Object threadKey, Runnable task) {
ArgumentVerifier.assertNotNull(threadKey, "threadKey");
ArgumentVerifier.assertNotNull(task, "task");
addTask(threadKey, task, executor);
}
/**
* This is a protected implementation to add the task to a worker. No safety checks are done at
* this point, so only provide non-null inputs.
*
* You can supply the executor in case extending classes want to use different executors than
* the class was constructed with.
*
* @param threadKey object key where {@code equals()} will be used to determine execution thread
* @param task Task to be added to worker
* @param Executor to run worker on (if it needs to be started)
*/
protected void addTask(Object threadKey, Runnable task, Executor executor) {
TaskQueueWorker worker;
Object workerLock = sLock.getLock(threadKey);
synchronized (workerLock) {
worker = taskWorkers.get(threadKey);
if (worker == null) {
worker = wFactory.build(threadKey, workerLock, task);
taskWorkers.put(threadKey, worker);
} else {
worker.add(task);
// return so we wont start worker
return;
}
}
// must run execute outside of lock
executor.execute(worker);
}
/**
* Submit a task to be run with a given thread key.
*
* @param threadKey object key where {@code equals()} will be used to determine execution thread
* @param task Task to be executed
* @return Future to represent when the execution has occurred
*/
public ListenableFuture submit(Object threadKey, Runnable task) {
return submit(threadKey, task, null);
}
/**
* Submit a task to be run with a given thread key.
*
* @param type of result returned from the future
* @param threadKey object key where {@code equals()} will be used to determine execution thread
* @param task Runnable to be executed
* @param result Result to be returned from future when task completes
* @return Future to represent when the execution has occurred and provide the given result
*/
public ListenableFuture submit(Object threadKey, Runnable task, T result) {
return submit(threadKey, new RunnableCallableAdapter(task, result));
}
/**
* Submit a callable to be run with a given thread key.
*
* @param type of result returned from the future
* @param threadKey object key where {@code equals()} will be used to determine execution thread
* @param task Callable to be executed
* @return Future to represent when the execution has occurred and provide the result from the callable
*/
public ListenableFuture submit(Object threadKey, Callable task) {
ArgumentVerifier.assertNotNull(threadKey, "threadKey");
ArgumentVerifier.assertNotNull(task, "task");
ListenableRunnableFuture rf = new ListenableFutureTask(false, task);
addTask(threadKey, rf, executor);
return rf;
}
/**
* Simple factory interface so we can build the most efficient {@link TaskQueueWorker}
* implementation for the settings provided at construction.
*
* @author jent - Mike Jensen
* @since 1.2.0
*/
private interface WorkerFactory {
public TaskQueueWorker build(Object mapKey, Object workerLock, Runnable firstTask);
}
/**
* Worker which will consume through a given queue of tasks. Each key is represented by one
* worker at any given time.
*
* @author jent - Mike Jensen
* @since 1.0.0
*/
protected class TaskQueueWorker implements Runnable {
protected final Object mapKey;
protected final Object workerLock;
// we treat the first task special to attempt to avoid constructing the ArrayDeque
protected volatile Runnable firstTask;
protected Queue queue; // locked around workerLock
protected TaskQueueWorker(Object mapKey, Object workerLock, Runnable firstTask) {
this.mapKey = mapKey;
this.workerLock = workerLock;
this.queue = null;
this.firstTask = firstTask;
}
/**
* Call to get this workers current queue size.
*
* @return How many tasks are waiting to be executed.
*/
public int getQueueSize() {
// the default implementation is very inaccurate
synchronized (workerLock) {
return (firstTask == null ? 0 : 1) + (queue == null ? 0 : queue.size());
}
}
/**
* You MUST hold the workerLock before calling into this. This is designed to be overridden
* if you need to track how tasks are being added.
*
* @param task Runnable to add to the worker's queue
*/
protected void add(Runnable task) {
if (queue == null) {
queue = new ArrayDeque(ARRAY_DEQUE_INITIAL_SIZE);
}
queue.add(task);
}
/**
* Runs the provided task in the invoking thread. This is designed to be overridden if
* needed. No exceptions will ever be thrown from this call.
*
* @param task Runnable to run
*/
protected void runTask(Runnable task) {
ExceptionUtils.runRunnable(task);
}
@Override
public void run() {
int consumedItems = 0;
// firstTask may be null if we exceeded our maxTasksPerCycle
if (firstTask != null) {
consumedItems++;
// we need to set firstTask to null before we run the task (for semi-accurate queue size)
Runnable task = firstTask;
// set to null to allow GC
firstTask = null;
runTask(task);
}
while (true) {
Queue nextQueue;
synchronized (workerLock) {
if (queue == null) { // nothing left to run
taskWorkers.remove(mapKey);
return;
} else if (consumedItems < maxTasksPerCycle) {
// we can run at least one task...let's figure out how much we can run
if (queue.size() + consumedItems <= maxTasksPerCycle) {
// we can run the entire next queue
nextQueue = queue;
queue = null;
} else {
// we need to run a subset of the queue, so copy and remove what we can run
int nextListSize = maxTasksPerCycle - consumedItems;
nextQueue = new ArrayDeque(nextListSize);
Iterator it = queue.iterator();
do {
nextQueue.add(it.next());
it.remove();
} while (nextQueue.size() < nextListSize);
}
consumedItems += nextQueue.size();
} else {
// re-execute this worker to give other works a chance to run
executor.execute(this);
/* notice that we never removed from taskWorkers, and thus wont be
* executed from people adding new tasks
*/
return;
}
}
for (Runnable r : nextQueue) {
runTask(r);
}
}
}
}
/**
* Extending class that will accurately track how many tasks have been added, and how many
* have been run. Thus providing an accurate queue size statistic.
*
* @author jent - Mike Jensen
* @since 1.2.0
*/
protected class StatisticWorker extends TaskQueueWorker {
private final AtomicInteger queueSize;
protected StatisticWorker(Object mapKey, Object workerLock, Runnable firstTask) {
super(mapKey, workerLock, firstTask);
queueSize = new AtomicInteger(1);
}
@Override
public int getQueueSize() {
return queueSize.get();
}
@Override
protected void add(Runnable task) {
queueSize.incrementAndGet();
super.add(task);
}
@Override
protected void runTask(Runnable task) {
queueSize.decrementAndGet();
super.runTask(task);
}
}
/**
* Simple {@link SubmitterExecutor} implementation that submits for a given key.
*
* @author jent - Mike Jensen
* @since 2.5.0
*/
protected class KeySubmitter implements SubmitterExecutor {
protected final Object threadKey;
protected KeySubmitter(Object threadKey) {
this.threadKey = threadKey;
}
@Override
public void execute(Runnable command) {
KeyDistributedExecutor.this.execute(threadKey, command);
}
@Override
public ListenableFuture submit(Runnable task) {
return KeyDistributedExecutor.this.submit(threadKey, task);
}
@Override
public ListenableFuture submit(Runnable task, T result) {
return KeyDistributedExecutor.this.submit(threadKey, task, result);
}
@Override
public ListenableFuture submit(Callable task) {
return KeyDistributedExecutor.this.submit(threadKey, task);
}
}
}
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