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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
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*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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package jdk.internal.net.http;
import java.lang.System.Logger.Level;
import java.util.ArrayList;
import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.concurrent.locks.ReentrantLock;
import jdk.internal.net.http.common.Utils;
/**
* A Send Window Flow-Controller that is used to control outgoing Connection
* and Stream flows, per HTTP/2 connection.
*
* A Http2Connection has its own unique single instance of a WindowController
* that it shares with its Streams. Each stream must acquire the appropriate
* amount of Send Window from the controller before sending data.
*
* WINDOW_UPDATE frames, both connection and stream specific, must notify the
* controller of their increments. SETTINGS frame's INITIAL_WINDOW_SIZE must
* notify the controller so that it can adjust the active stream's window size.
*/
final class WindowController {
static final boolean DEBUG = Utils.DEBUG; // Revisit: temporary developer's flag
static final System.Logger DEBUG_LOGGER =
Utils.getDebugLogger("WindowController"::toString, DEBUG);
/**
* Default initial connection Flow-Control Send Window size, as per HTTP/2.
*/
private static final int DEFAULT_INITIAL_WINDOW_SIZE = 64 * 1024 - 1;
/** The connection Send Window size. */
private int connectionWindowSize;
/** A Map of the active streams, where the key is the stream id, and the
* value is the stream's Send Window size, which may be negative. */
private final Map<Integer,Integer> streams = new HashMap<>();
/** A Map of streams awaiting Send Window. The key is the stream id. The
* value is a pair of the Stream ( representing the key's stream id ) and
* the requested amount of send Window. */
private final Map<Integer, Map.Entry<Stream<?>, Integer>> pending
= new LinkedHashMap<>();
private final ReentrantLock controllerLock = new ReentrantLock();
/** A Controller with the default initial window size. */
WindowController() {
connectionWindowSize = DEFAULT_INITIAL_WINDOW_SIZE;
}
// /** A Controller with the given initial window size. */
// WindowController(int initialConnectionWindowSize) {
// connectionWindowSize = initialConnectionWindowSize;
// }
/** Registers the given stream with this controller. */
void registerStream(int streamid, int initialStreamWindowSize) {
controllerLock.lock();
try {
Integer old = streams.put(streamid, initialStreamWindowSize);
if (old != null)
throw new InternalError("Unexpected entry ["
+ old + "] for streamid: " + streamid);
} finally {
controllerLock.unlock();
}
}
/** Removes/De-registers the given stream with this controller. */
void removeStream(int streamid) {
controllerLock.lock();
try {
Integer old = streams.remove(streamid);
// Odd stream numbers (client streams) should have been registered.
// Even stream numbers (server streams - aka Push Streams) should
// not be registered
final boolean isClientStream = (streamid & 0x1) == 1;
if (old == null && isClientStream) {
throw new InternalError("Expected entry for streamid: " + streamid);
} else if (old != null && !isClientStream) {
throw new InternalError("Unexpected entry for streamid: " + streamid);
}
} finally {
controllerLock.unlock();
}
}
/**
* Attempts to acquire the requested amount of Send Window for the given
* stream.
*
* The actual amount of Send Window available may differ from the requested
* amount. The actual amount, returned by this method, is the minimum of,
* 1) the requested amount, 2) the stream's Send Window, and 3) the
* connection's Send Window.
*
* A negative or zero value is returned if there's no window available.
* When the result is negative or zero, this method arranges for the
* given stream's {@link Stream#signalWindowUpdate()} method to be invoke at
* a later time when the connection and/or stream window's have been
* increased. The {@code tryAcquire} method should then be invoked again to
* attempt to acquire the available window.
*/
int tryAcquire(int requestAmount, int streamid, Stream<?> stream) {
controllerLock.lock();
try {
Integer streamSize = streams.get(streamid);
if (streamSize == null)
throw new InternalError("Expected entry for streamid: "
+ streamid);
int x = Math.min(requestAmount,
Math.min(streamSize, connectionWindowSize));
if (x <= 0) { // stream window size may be negative
DEBUG_LOGGER.log(Level.DEBUG,
"Stream %d requesting %d but only %d available (stream: %d, connection: %d)",
streamid, requestAmount, Math.min(streamSize, connectionWindowSize),
streamSize, connectionWindowSize);
// If there's not enough window size available, put the
// caller in a pending list.
pending.put(streamid, Map.entry(stream, requestAmount));
return x;
}
// Remove the caller from the pending list ( if was waiting ).
pending.remove(streamid);
// Update window sizes and return the allocated amount to the caller.
streamSize -= x;
streams.put(streamid, streamSize);
connectionWindowSize -= x;
DEBUG_LOGGER.log(Level.DEBUG,
"Stream %d amount allocated %d, now %d available (stream: %d, connection: %d)",
streamid, x, Math.min(streamSize, connectionWindowSize),
streamSize, connectionWindowSize);
return x;
} finally {
controllerLock.unlock();
}
}
/**
* Increases the Send Window size for the connection.
*
* A number of awaiting requesters, from unfulfilled tryAcquire requests,
* may have their stream's {@link Stream#signalWindowUpdate()} method
* scheduled to run ( i.e. awake awaiters ).
*
* @return false if, and only if, the addition of the given amount would
* cause the Send Window to exceed 2^31-1 (overflow), otherwise true
*/
boolean increaseConnectionWindow(int amount) {
List<Stream<?>> candidates = null;
controllerLock.lock();
try {
int size = connectionWindowSize;
size += amount;
if (size < 0)
return false;
connectionWindowSize = size;
DEBUG_LOGGER.log(Level.DEBUG, "Connection window size is now %d", size);
// Notify waiting streams, until the new increased window size is
// effectively exhausted.
Iterator<Map.Entry<Integer,Map.Entry<Stream<?>,Integer>>> iter =
pending.entrySet().iterator();
while (iter.hasNext() && size > 0) {
Map.Entry<Integer,Map.Entry<Stream<?>,Integer>> item = iter.next();
Integer streamSize = streams.get(item.getKey());
if (streamSize == null) {
iter.remove();
} else {
Map.Entry<Stream<?>,Integer> e = item.getValue();
int requestedAmount = e.getValue();
// only wakes up the pending streams for which there is
// at least 1 byte of space in both windows
int minAmount = 1;
if (size >= minAmount && streamSize >= minAmount) {
size -= Math.min(streamSize, requestedAmount);
iter.remove();
if (candidates == null)
candidates = new ArrayList<>();
candidates.add(e.getKey());
}
}
}
} finally {
controllerLock.unlock();
}
if (candidates != null) {
candidates.forEach(Stream::signalWindowUpdate);
}
return true;
}
/**
* Increases the Send Window size for the given stream.
*
* If the given stream is awaiting window size, from an unfulfilled
* tryAcquire request, it will have its stream's {@link
* Stream#signalWindowUpdate()} method scheduled to run ( i.e. awoken ).
*
* @return false if, and only if, the addition of the given amount would
* cause the Send Window to exceed 2^31-1 (overflow), otherwise true
*/
boolean increaseStreamWindow(int amount, int streamid) {
Stream<?> s = null;
controllerLock.lock();
try {
Integer size = streams.get(streamid);
if (size == null)
throw new InternalError("Expected entry for streamid: " + streamid);
size += amount;
if (size < 0)
return false;
streams.put(streamid, size);
DEBUG_LOGGER.log(Level.DEBUG,
"Stream %s window size is now %s", streamid, size);
Map.Entry<Stream<?>,Integer> p = pending.get(streamid);
if (p != null) {
int minAmount = 1;
// only wakes up the pending stream if there is at least
// 1 byte of space in both windows
if (size >= minAmount
&& connectionWindowSize >= minAmount) {
pending.remove(streamid);
s = p.getKey();
}
}
} finally {
controllerLock.unlock();
}
if (s != null)
s.signalWindowUpdate();
return true;
}
/**
* Adjusts, either increases or decreases, the active streams registered
* with this controller. May result in a stream's Send Window size becoming
* negative.
*/
void adjustActiveStreams(int adjustAmount) {
assert adjustAmount != 0;
controllerLock.lock();
try {
for (Map.Entry<Integer,Integer> entry : streams.entrySet()) {
int streamid = entry.getKey();
// the API only supports sending on Streams initialed by
// the client, i.e. odd stream numbers
if (streamid != 0 && (streamid % 2) != 0) {
Integer size = entry.getValue();
size += adjustAmount;
streams.put(streamid, size);
DEBUG_LOGGER.log(Level.DEBUG,
"Stream %s window size is now %s", streamid, size);
}
}
} finally {
controllerLock.unlock();
}
}
/** Returns the Send Window size for the connection. */
int connectionWindowSize() {
controllerLock.lock();
try {
return connectionWindowSize;
} finally {
controllerLock.unlock();
}
}
// /** Returns the Send Window size for the given stream. */
// int streamWindowSize(int streamid) {
// controllerLock.lock();
// try {
// Integer size = streams.get(streamid);
// if (size == null)
// throw new InternalError("Expected entry for streamid: " + streamid);
// return size;
// } finally {
// controllerLock.unlock();
// }
// }
}