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A set of basic utilities used in Jitsi projects
/*
* Copyright @ 2018 - present 8x8, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jitsi.utils.queue;
import org.jitsi.utils.logging.*;
import org.json.simple.*;
import org.jetbrains.annotations.*;
import java.lang.*;
import java.lang.SuppressWarnings;
import java.time.*;
import java.util.*;
import java.util.concurrent.*;
/**
* An abstract queue of packets.
*
* @author Boris Grozev
* @author Yura Yaroshevich
*/
public class PacketQueue
{
/**
* The {@link Logger} used by the {@link PacketQueue} class and its
* instances for logging output.
*/
private static final Logger logger = Logger.getLogger(PacketQueue.class);
/**
* The default value for the {@code enableStatistics} constructor argument.
*/
private static boolean enableStatisticsDefault = false;
/**
* Sets the default value for the {@code enableStatistics} constructor
* parameter.
*
* @param enable the value to set.
*/
public static void setEnableStatisticsDefault(boolean enable)
{
enableStatisticsDefault = enable;
}
public static boolean getEnableStatisticsDefault()
{
return enableStatisticsDefault;
}
/**
* The underlying {@link BlockingQueue} which holds packets.
*/
@NotNull private final BlockingQueue queue;
/**
* The {@link Observer} instance optionally used to collect and print
* detailed statistics about this queue.
*/
protected final Observer observer;
/**
* The {@link AsyncQueueHandler} to perpetually read packets
* from {@link #queue} on separate thread and handle them with provided
* packet handler.
*/
@NotNull private final AsyncQueueHandler asyncQueueHandler;
/**
* A string used to identify this {@link PacketQueue} for logging purposes.
*/
@NotNull private final String id;
/**
* Whether this queue has been closed. Field is denoted as volatile,
* because it is set in one thread and could be read in while loop in other.
*/
private volatile boolean closed = false;
/**
* The maximum number of items the queue can contain before it starts
* dropping items.
*/
private final int capacity;
/**
* Handles dropped packets and exceptions thrown while processing.
*/
@NotNull
private ErrorHandler errorHandler = new ErrorHandler(){};
/**
* Creates a queue observer.
*/
protected Observer createObserver(Clock clock)
{
return new QueueStatisticsObserver<>(this, clock);
}
/**
* Initializes a new {@link PacketQueue} instance.
* @param capacity the capacity of the queue. {@link Integer#MAX_VALUE} for
* unbounded.
* @param enableStatistics whether detailed statistics should be gathered by
* constructing an {@link Observer}.
* (In the base {@link PacketQueue} class this will be a {@link QueueStatisticsObserver}
* but subclasses can override this).
* This might affect performance. A value of {@code null} indicates that
* the default {@link #enableStatisticsDefault} value will be used.
* @param id the ID of the packet queue, to be used for logging.
* @param packetHandler An handler to be used by the queue for
* packets read from it. The queue will start its own tasks on
* {@param executor}, which will read packets from the queue and execute
* {@code handler.handlePacket} on them.
* @param executor An executor service to use to execute
* packetHandler for items added to queue.
* @param clock If {@param enableStatistics} is true (or resolves as true),
* a clock to use to construct the {@link Observer}.
*/
public PacketQueue(
int capacity,
Boolean enableStatistics,
@NotNull String id,
@NotNull PacketHandler packetHandler,
ExecutorService executor,
Clock clock)
{
this(capacity, enableStatistics, id, packetHandler, executor, clock, true);
}
/**
* Initializes a new {@link PacketQueue} instance.
* @param capacity the capacity of the queue. {@link Integer#MAX_VALUE} for
* unbounded.
* @param enableStatistics whether detailed statistics should be gathered by
* constructing an {@link Observer}.
* (In the base {@link PacketQueue} class this will be a {@link QueueStatisticsObserver}
* but subclasses can override this).
* This might affect performance. A value of {@code null} indicates that
* the default {@link #enableStatisticsDefault} value will be used.
* @param id the ID of the packet queue, to be used for logging.
* @param packetHandler An handler to be used by the queue for
* packets read from it. The queue will start its own tasks on
* {@param executor}, which will read packets from the queue and execute
* {@code handler.handlePacket} on them.
* @param executor An executor service to use to execute
* packetHandler for items added to queue.
* @param clock If {@param enableStatistics} is true (or resolves as true),
* a clock to use to construct the {@link Observer}.
* @param interruptOnClose whether the running task (if any) should be interrupted when the queue is closed. This
* is useful when the queue is closed from within a task.
*/
public PacketQueue(
int capacity,
Boolean enableStatistics,
@NotNull String id,
@NotNull PacketHandler packetHandler,
ExecutorService executor,
Clock clock,
boolean interruptOnClose)
{
this.id = id;
this.capacity = capacity;
queue = new LinkedBlockingQueue<>(capacity);
asyncQueueHandler = new AsyncQueueHandler<>(
queue,
new HandlerAdapter(packetHandler),
id,
executor,
packetHandler.maxSequentiallyProcessedPackets(),
interruptOnClose);
if (enableStatistics == null)
{
enableStatistics = enableStatisticsDefault;
}
observer = enableStatistics ? createObserver(clock) : null;
logger.debug("Initialized a PacketQueue instance with ID " + id);
}
/**
* Initializes a new {@link PacketQueue} instance.
* @param capacity the capacity of the queue.
* @param enableStatistics whether detailed statistics should be gathered
* using a {@link QueueStatisticsObserver} as a default queue observer.
* This might affect performance. A value of {@code null} indicates that
* the default {@link #enableStatisticsDefault} value will be used.
* @param id the ID of the packet queue, to be used for logging.
* @param packetHandler An handler to be used by the queue for
* packets read from it. The queue will start its own tasks on
* {@param executor}, which will read packets from the queue and execute
* {@code handler.handlePacket} on them.
* @param executor An executor service to use to execute
* packetHandler for items added to queue.
*/
public PacketQueue(
int capacity,
Boolean enableStatistics,
@NotNull String id,
@NotNull PacketHandler packetHandler,
ExecutorService executor)
{
this(capacity, enableStatistics, id, packetHandler, executor, Clock.systemUTC());
}
/**
* Adds a specific packet ({@code T}) instance to the queue.
* @param pkt the packet to add.
*/
public void add(T pkt)
{
if (closed)
return;
while (!queue.offer(pkt))
{
// Drop from the head of the queue.
T p = queue.poll();
if (p != null)
{
if (observer != null)
{
observer.dropped(p);
}
errorHandler.packetDropped();
// Call release on dropped packet to allow proper implementation
// of object pooling by PacketQueue users
releasePacket(p);
}
}
if (observer != null)
{
observer.added(pkt);
}
asyncQueueHandler.handleQueueItemsUntilEmpty();
}
/**
* Closes current PacketQueue instance. No items will be added
* to queue when it's closed. Asynchronous queue processing by
* {@link #asyncQueueHandler} is stopped.
*/
public void close()
{
if (!closed)
{
closed = true;
asyncQueueHandler.cancel();
T item;
while ((item = queue.poll()) != null) {
releasePacket(item);
}
}
}
/**
* Releases packet when it is handled by provided packet handler.
* This method is not called when PacketQueue was created without
* handler and hence no automatic queue processing is done.
* Default implementation is empty, but it might be used to implement
* packet pooling to re-use them.
* @param pkt packet to release
*/
protected void releasePacket(T pkt)
{
}
/** Get the current number of packets queued in this queue. */
public int size()
{
return queue.size();
}
/** Get the maximum number of packets queued in this queue. */
public int capacity()
{
return capacity;
}
/** Get the ID of this queue. */
public String id()
{
return id;
}
/**
* Gets a JSON representation of the parts of this object's state that
* are deemed useful for debugging.
*/
@SuppressWarnings("unchecked")
public JSONObject getDebugState()
{
JSONObject debugState = new JSONObject();
debugState.put("id", id);
debugState.put("capacity", capacity);
debugState.put("closed", closed);
debugState.put(
"statistics",
observer == null
? null : observer.getStats());
return debugState;
}
/**
* Sets the handler of errors (packets dropped or exceptions caught while
* processing).
* @param errorHandler the handler to set.
*/
public void setErrorHandler(@NotNull ErrorHandler errorHandler)
{
this.errorHandler = errorHandler;
}
/**
* A simple interface to handle packets.
* @param the type of the packets.
*/
public interface PacketHandler
{
/**
* Does something with a packet.
* @param pkt the packet to do something with.
* @return {@code true} if the operation was successful, and
* {@code false} otherwise.
*/
boolean handlePacket(T pkt);
/**
* Specifies the number of packets allowed to be processed sequentially
* without yielding control to executor's thread. Specifying positive
* number will allow other possible queues sharing same
* {@link ExecutorService} to process their packets.
* @return positive value to specify max number of packets which allows
* implementation of cooperative multi-tasking between different
* {@link PacketQueue} sharing same {@link ExecutorService}.
*/
default long maxSequentiallyProcessedPackets()
{
return -1;
}
}
/**
* An interface to observe a queue, to collect statistics or similar.
*/
public interface Observer
{
/** Called when a packet is added to a queue. */
void added(T pkt);
/** Called when a packet is removed from a queue. */
void removed(T pkt);
/** Called when a packet is dropped from a queue. */
void dropped(T pkt);
/** Get statistics gathered by this observer. */
Map getStats();
}
/**
* An adapter class implementing {@link AsyncQueueHandler.Handler}
* to wrap {@link PacketHandler}.
*/
private final class HandlerAdapter implements AsyncQueueHandler.Handler
{
/**
* An actual handler of packets.
*/
private final PacketHandler handler;
/**
* Constructs adapter of {@link PacketHandler} to
* {@link AsyncQueueHandler.Handler} interface.
* @param handler an handler instance to adapt
*/
HandlerAdapter(PacketHandler handler)
{
this.handler = handler;
}
/**
* {@inheritDoc}
*/
@Override
public void handleItem(T item)
{
if (observer != null)
{
observer.removed(item);
}
try
{
handler.handlePacket(item);
}
catch (Throwable t)
{
errorHandler.packetHandlingFailed(t);
}
}
}
}
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