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Copy pathChannel.java
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package loop.runtime;
import loop.StackTraceSanitizer;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* Concurrent Channels support class for loop's event-driven channel API.
*
* @author [email protected] (Dhanji R. Prasanna)
*/
public class Channel {
private static final ExecutorService GLOBAL_EXECUTOR = Executors.newCachedThreadPool();
private static final int YIELD_FAIRNESS_CYCLES = 15;
private static final String SHUTDOWN = "shutdown";
private static final String DIE = "die";
static {
Runtime.getRuntime().addShutdownHook(new Thread() {
@Override public void run() {
GLOBAL_EXECUTOR.shutdown();
}
});
}
private final String name;
private final Closure actor;
private final ConcurrentLinkedQueue<Object> queue;
private final AtomicBoolean running = new AtomicBoolean();
private final Runnable runnable;
private final ExecutorService executor;
private final boolean isDedicatedPool;
private final Map<String, Object> channelMemory = new HashMap<String, Object>();
public Channel(String name, Closure actor, boolean parallel, int workers) {
this.name = name;
this.actor = actor;
this.queue = new ConcurrentLinkedQueue<Object>();
if (isDedicatedPool = workers > 0) {
this.executor = Executors.newFixedThreadPool(workers);
} else
this.executor = GLOBAL_EXECUTOR;
this.runnable = parallel ? concurrentRunnable : isolatedRunnable;
}
/**
* Isolated runnables allow only one message to be processed at a time, regardless
* of the available worker threads. They are useful for sharding semantics.
*/
private final Runnable isolatedRunnable = new Runnable() {
@Override public void run() {
if (!running.compareAndSet(false, true))
return;
try {
currentChannelMemory.set(channelMemory);
int processed = 0;
while (!queue.isEmpty() && processed < YIELD_FAIRNESS_CYCLES) {
try {
Object result = Caller.callClosure(actor, actor.target, new Object[]{queue.poll()});
// Check if we should shutdown this channel.
// Allows graceful drain of queued messages.
if (SHUTDOWN.equals(result))
shutdown();
else if (DIE.equals(result)) {
// Process no more messages.
die();
break;
}
} catch (Throwable throwable) {
try {
StackTraceSanitizer.clean(throwable);
// Swallow exception if possible.
throwable.printStackTrace(System.err);
} finally {
// Quit VM forcibly on out of memory error.
if (throwable instanceof OutOfMemoryError)
System.exit(1);
}
} finally {
processed++;
}
}
} finally {
currentChannelMemory.remove();
running.compareAndSet(true, false);
// Tail-call ourselves if we're not done with this queue.
if (!queue.isEmpty())
executor.submit(isolatedRunnable);
}
}
};
/**
* Concurrent runnables burst-process tasks as fast as possible. This is
* the default.
*/
private final Runnable concurrentRunnable = new Runnable() {
@Override public void run() {
int processed = 0;
while (!queue.isEmpty() && processed < YIELD_FAIRNESS_CYCLES) {
try {
Object result = Caller.callClosure(actor, actor.target, new Object[]{queue.poll()});
if (SHUTDOWN.equals(result))
shutdown();
else if (DIE.equals(result)) {
// Process no more messages.
die();
break;
}
} catch (Throwable throwable) {
try {
StackTraceSanitizer.clean(throwable);
// Swallow exception if possible.
throwable.printStackTrace(System.err);
} finally {
// Quit VM forcibly on out of memory error.
if (throwable instanceof OutOfMemoryError)
System.exit(1);
}
} finally {
processed++;
}
}
}
};
private static final ThreadLocal<Map<String, Object>> currentChannelMemory = new ThreadLocal<Map<String, Object>>();
public static Object currentMemory() {
Map<String, Object> map = currentChannelMemory.get();
if (map == null)
throw new RuntimeException("Illegal shared memory request. (Hint: use transactional cells instead)");
return map;
}
public void shutdown() {
channels.remove(name);
if (isDedicatedPool)
executor.shutdown();
}
public void die() {
channels.remove(name);
queue.clear();
if (isDedicatedPool)
executor.shutdownNow();
}
public void receive(Object message) {
queue.add(message);
if (!running.get())
executor.submit(runnable);
}
private static final ConcurrentMap<String, Channel> channels =
new ConcurrentHashMap<String, Channel>();
public static Channel named(Object name) {
assert name instanceof String;
Channel channel = channels.get(name);
if (channel == null)
throw new RuntimeException("No such channel established: " + name);
return channel;
}
public static void establish(Object nameObj, Object actor, Object optionsObj) {
assert nameObj instanceof String;
assert actor instanceof Closure;
assert optionsObj instanceof Map;
String name = (String) nameObj;
@SuppressWarnings("unchecked")
Map<String, Object> options = (Map<String, Object>) optionsObj;
Object serialize = options.get("serialize");
Object threads = options.get("workers");
int workers = 0;
if (null != threads)
workers = (Integer)threads;
boolean parallel = serialize == null || !(Boolean) serialize;
channels.put(name, new Channel(name, (Closure)actor, parallel, workers));
}
}