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Easy Redis Java client and Real-Time Data Platform. Valkey compatible. Sync/Async/RxJava3/Reactive API. Client side caching. Over 50 Redis based Java objects and services: JCache API, Apache Tomcat, Hibernate, Spring, Set, Multimap, SortedSet, Map, List, Queue, Deque, Semaphore, Lock, AtomicLong, Map Reduce, Bloom filter, Scheduler, RPC
/*
* Copyright 2014 The Netty Project
*
* The Netty Project licenses this file to you 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:
*
* https://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 io.netty.channel.epoll;
import io.netty.channel.Channel;
import io.netty.channel.EventLoop;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.EventLoopTaskQueueFactory;
import io.netty.channel.SelectStrategy;
import io.netty.channel.SingleThreadEventLoop;
import io.netty.channel.epoll.AbstractEpollChannel.AbstractEpollUnsafe;
import io.netty.channel.unix.FileDescriptor;
import io.netty.channel.unix.IovArray;
import io.netty.util.IntSupplier;
import io.netty.util.collection.IntObjectHashMap;
import io.netty.util.collection.IntObjectMap;
import io.netty.util.concurrent.RejectedExecutionHandler;
import io.netty.util.internal.ObjectUtil;
import io.netty.util.internal.PlatformDependent;
import io.netty.util.internal.SystemPropertyUtil;
import io.netty.util.internal.UnstableApi;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;
import java.io.IOException;
import java.util.Iterator;
import java.util.Queue;
import java.util.concurrent.Executor;
import java.util.concurrent.atomic.AtomicLong;
import static java.lang.Math.min;
/**
* {@link EventLoop} which uses epoll under the covers. Only works on Linux!
*/
public class EpollEventLoop extends SingleThreadEventLoop {
private static final InternalLogger logger = InternalLoggerFactory.getInstance(EpollEventLoop.class);
private static final long EPOLL_WAIT_MILLIS_THRESHOLD =
SystemPropertyUtil.getLong("io.netty.channel.epoll.epollWaitThreshold", 10);
static {
// Ensure JNI is initialized by the time this class is loaded by this time!
// We use unix-common methods in this class which are backed by JNI methods.
Epoll.ensureAvailability();
}
private FileDescriptor epollFd;
private FileDescriptor eventFd;
private FileDescriptor timerFd;
private final IntObjectMap channels = new IntObjectHashMap(4096);
private final boolean allowGrowing;
private final EpollEventArray events;
// These are initialized on first use
private IovArray iovArray;
private NativeDatagramPacketArray datagramPacketArray;
private final SelectStrategy selectStrategy;
private final IntSupplier selectNowSupplier = new IntSupplier() {
@Override
public int get() throws Exception {
return epollWaitNow();
}
};
private static final long AWAKE = -1L;
private static final long NONE = Long.MAX_VALUE;
// nextWakeupNanos is:
// AWAKE when EL is awake
// NONE when EL is waiting with no wakeup scheduled
// other value T when EL is waiting with wakeup scheduled at time T
private final AtomicLong nextWakeupNanos = new AtomicLong(AWAKE);
private boolean pendingWakeup;
private volatile int ioRatio = 50;
// See https://man7.org/linux/man-pages/man2/timerfd_create.2.html.
private static final long MAX_SCHEDULED_TIMERFD_NS = 999999999;
EpollEventLoop(EventLoopGroup parent, Executor executor, int maxEvents,
SelectStrategy strategy, RejectedExecutionHandler rejectedExecutionHandler,
EventLoopTaskQueueFactory taskQueueFactory, EventLoopTaskQueueFactory tailTaskQueueFactory) {
super(parent, executor, false, newTaskQueue(taskQueueFactory), newTaskQueue(tailTaskQueueFactory),
rejectedExecutionHandler);
selectStrategy = ObjectUtil.checkNotNull(strategy, "strategy");
if (maxEvents == 0) {
allowGrowing = true;
events = new EpollEventArray(4096);
} else {
allowGrowing = false;
events = new EpollEventArray(maxEvents);
}
openFileDescriptors();
}
/**
* This method is intended for use by a process checkpoint/restore
* integration, such as OpenJDK CRaC.
*/
@UnstableApi
public void openFileDescriptors() {
boolean success = false;
FileDescriptor epollFd = null;
FileDescriptor eventFd = null;
FileDescriptor timerFd = null;
try {
this.epollFd = epollFd = Native.newEpollCreate();
this.eventFd = eventFd = Native.newEventFd();
try {
// It is important to use EPOLLET here as we only want to get the notification once per
// wakeup and don't call eventfd_read(...).
Native.epollCtlAdd(epollFd.intValue(), eventFd.intValue(), Native.EPOLLIN | Native.EPOLLET);
} catch (IOException e) {
throw new IllegalStateException("Unable to add eventFd filedescriptor to epoll", e);
}
this.timerFd = timerFd = Native.newTimerFd();
try {
// It is important to use EPOLLET here as we only want to get the notification once per
// wakeup and don't call read(...).
Native.epollCtlAdd(epollFd.intValue(), timerFd.intValue(), Native.EPOLLIN | Native.EPOLLET);
} catch (IOException e) {
throw new IllegalStateException("Unable to add timerFd filedescriptor to epoll", e);
}
success = true;
} finally {
if (!success) {
closeFileDescriptor(epollFd);
closeFileDescriptor(eventFd);
closeFileDescriptor(timerFd);
}
}
}
private static void closeFileDescriptor(FileDescriptor fd) {
if (fd != null) {
try {
fd.close();
} catch (Exception e) {
// ignore
}
}
}
private static Queue newTaskQueue(
EventLoopTaskQueueFactory queueFactory) {
if (queueFactory == null) {
return newTaskQueue0(DEFAULT_MAX_PENDING_TASKS);
}
return queueFactory.newTaskQueue(DEFAULT_MAX_PENDING_TASKS);
}
/**
* Return a cleared {@link IovArray} that can be used for writes in this {@link EventLoop}.
*/
IovArray cleanIovArray() {
if (iovArray == null) {
iovArray = new IovArray();
} else {
iovArray.clear();
}
return iovArray;
}
/**
* Return a cleared {@link NativeDatagramPacketArray} that can be used for writes in this {@link EventLoop}.
*/
NativeDatagramPacketArray cleanDatagramPacketArray() {
if (datagramPacketArray == null) {
datagramPacketArray = new NativeDatagramPacketArray();
} else {
datagramPacketArray.clear();
}
return datagramPacketArray;
}
@Override
protected void wakeup(boolean inEventLoop) {
if (!inEventLoop && nextWakeupNanos.getAndSet(AWAKE) != AWAKE) {
// write to the evfd which will then wake-up epoll_wait(...)
Native.eventFdWrite(eventFd.intValue(), 1L);
}
}
@Override
protected boolean beforeScheduledTaskSubmitted(long deadlineNanos) {
// Note this is also correct for the nextWakeupNanos == -1 (AWAKE) case
return deadlineNanos < nextWakeupNanos.get();
}
@Override
protected boolean afterScheduledTaskSubmitted(long deadlineNanos) {
// Note this is also correct for the nextWakeupNanos == -1 (AWAKE) case
return deadlineNanos < nextWakeupNanos.get();
}
/**
* Register the given epoll with this {@link EventLoop}.
*/
void add(AbstractEpollChannel ch) throws IOException {
assert inEventLoop();
int fd = ch.socket.intValue();
Native.epollCtlAdd(epollFd.intValue(), fd, ch.flags);
AbstractEpollChannel old = channels.put(fd, ch);
// We either expect to have no Channel in the map with the same FD or that the FD of the old Channel is already
// closed.
assert old == null || !old.isOpen();
}
/**
* The flags of the given epoll was modified so update the registration
*/
void modify(AbstractEpollChannel ch) throws IOException {
assert inEventLoop();
Native.epollCtlMod(epollFd.intValue(), ch.socket.intValue(), ch.flags);
}
/**
* Deregister the given epoll from this {@link EventLoop}.
*/
void remove(AbstractEpollChannel ch) throws IOException {
assert inEventLoop();
int fd = ch.socket.intValue();
AbstractEpollChannel old = channels.remove(fd);
if (old != null && old != ch) {
// The Channel mapping was already replaced due FD reuse, put back the stored Channel.
channels.put(fd, old);
// If we found another Channel in the map that is mapped to the same FD the given Channel MUST be closed.
assert !ch.isOpen();
} else if (ch.isOpen()) {
// Remove the epoll. This is only needed if it's still open as otherwise it will be automatically
// removed once the file-descriptor is closed.
Native.epollCtlDel(epollFd.intValue(), fd);
}
}
@Override
protected Queue newTaskQueue(int maxPendingTasks) {
return newTaskQueue0(maxPendingTasks);
}
private static Queue newTaskQueue0(int maxPendingTasks) {
// This event loop never calls takeTask()
return maxPendingTasks == Integer.MAX_VALUE ? PlatformDependent.newMpscQueue()
: PlatformDependent.newMpscQueue(maxPendingTasks);
}
/**
* Returns the percentage of the desired amount of time spent for I/O in the event loop.
*/
public int getIoRatio() {
return ioRatio;
}
/**
* Sets the percentage of the desired amount of time spent for I/O in the event loop. The default value is
* {@code 50}, which means the event loop will try to spend the same amount of time for I/O as for non-I/O tasks.
*/
public void setIoRatio(int ioRatio) {
if (ioRatio <= 0 || ioRatio > 100) {
throw new IllegalArgumentException("ioRatio: " + ioRatio + " (expected: 0 < ioRatio <= 100)");
}
this.ioRatio = ioRatio;
}
@Override
public int registeredChannels() {
return channels.size();
}
@Override
public Iterator registeredChannelsIterator() {
assert inEventLoop();
IntObjectMap ch = channels;
if (ch.isEmpty()) {
return ChannelsReadOnlyIterator.empty();
}
return new ChannelsReadOnlyIterator(ch.values());
}
private long epollWait(long deadlineNanos) throws IOException {
if (deadlineNanos == NONE) {
return Native.epollWait(epollFd, events, timerFd,
Integer.MAX_VALUE, 0, EPOLL_WAIT_MILLIS_THRESHOLD); // disarm timer
}
long totalDelay = deadlineToDelayNanos(deadlineNanos);
int delaySeconds = (int) min(totalDelay / 1000000000L, Integer.MAX_VALUE);
int delayNanos = (int) min(totalDelay - delaySeconds * 1000000000L, MAX_SCHEDULED_TIMERFD_NS);
return Native.epollWait(epollFd, events, timerFd, delaySeconds, delayNanos, EPOLL_WAIT_MILLIS_THRESHOLD);
}
private int epollWaitNoTimerChange() throws IOException {
return Native.epollWait(epollFd, events, false);
}
private int epollWaitNow() throws IOException {
return Native.epollWait(epollFd, events, true);
}
private int epollBusyWait() throws IOException {
return Native.epollBusyWait(epollFd, events);
}
private int epollWaitTimeboxed() throws IOException {
// Wait with 1 second "safeguard" timeout
return Native.epollWait(epollFd, events, 1000);
}
@Override
protected void run() {
long prevDeadlineNanos = NONE;
for (;;) {
try {
int strategy = selectStrategy.calculateStrategy(selectNowSupplier, hasTasks());
switch (strategy) {
case SelectStrategy.CONTINUE:
continue;
case SelectStrategy.BUSY_WAIT:
strategy = epollBusyWait();
break;
case SelectStrategy.SELECT:
if (pendingWakeup) {
// We are going to be immediately woken so no need to reset wakenUp
// or check for timerfd adjustment.
strategy = epollWaitTimeboxed();
if (strategy != 0) {
break;
}
// We timed out so assume that we missed the write event due to an
// abnormally failed syscall (the write itself or a prior epoll_wait)
logger.warn("Missed eventfd write (not seen after > 1 second)");
pendingWakeup = false;
if (hasTasks()) {
break;
}
// fall-through
}
long curDeadlineNanos = nextScheduledTaskDeadlineNanos();
if (curDeadlineNanos == -1L) {
curDeadlineNanos = NONE; // nothing on the calendar
}
nextWakeupNanos.set(curDeadlineNanos);
try {
if (!hasTasks()) {
if (curDeadlineNanos == prevDeadlineNanos) {
// No timer activity needed
strategy = epollWaitNoTimerChange();
} else {
// Timerfd needs to be re-armed or disarmed
long result = epollWait(curDeadlineNanos);
// The result contains the actual return value and if a timer was used or not.
// We need to "unpack" using the helper methods exposed in Native.
strategy = Native.epollReady(result);
prevDeadlineNanos = Native.epollTimerWasUsed(result) ? curDeadlineNanos : NONE;
}
}
} finally {
// Try get() first to avoid much more expensive CAS in the case we
// were woken via the wakeup() method (submitted task)
if (nextWakeupNanos.get() == AWAKE || nextWakeupNanos.getAndSet(AWAKE) == AWAKE) {
pendingWakeup = true;
}
}
// fallthrough
default:
}
final int ioRatio = this.ioRatio;
if (ioRatio == 100) {
try {
if (strategy > 0 && processReady(events, strategy)) {
prevDeadlineNanos = NONE;
}
} finally {
// Ensure we always run tasks.
runAllTasks();
}
} else if (strategy > 0) {
final long ioStartTime = System.nanoTime();
try {
if (processReady(events, strategy)) {
prevDeadlineNanos = NONE;
}
} finally {
// Ensure we always run tasks.
final long ioTime = System.nanoTime() - ioStartTime;
runAllTasks(ioTime * (100 - ioRatio) / ioRatio);
}
} else {
runAllTasks(0); // This will run the minimum number of tasks
}
if (allowGrowing && strategy == events.length()) {
//increase the size of the array as we needed the whole space for the events
events.increase();
}
} catch (Error e) {
throw e;
} catch (Throwable t) {
handleLoopException(t);
} finally {
// Always handle shutdown even if the loop processing threw an exception.
try {
if (isShuttingDown()) {
closeAll();
if (confirmShutdown()) {
break;
}
}
} catch (Error e) {
throw e;
} catch (Throwable t) {
handleLoopException(t);
}
}
}
}
/**
* Visible only for testing!
*/
void handleLoopException(Throwable t) {
logger.warn("Unexpected exception in the selector loop.", t);
// Prevent possible consecutive immediate failures that lead to
// excessive CPU consumption.
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// Ignore.
}
}
private void closeAll() {
// Using the intermediate collection to prevent ConcurrentModificationException.
// In the `close()` method, the channel is deleted from `channels` map.
AbstractEpollChannel[] localChannels = channels.values().toArray(new AbstractEpollChannel[0]);
for (AbstractEpollChannel ch: localChannels) {
ch.unsafe().close(ch.unsafe().voidPromise());
}
}
// Returns true if a timerFd event was encountered
private boolean processReady(EpollEventArray events, int ready) {
boolean timerFired = false;
for (int i = 0; i < ready; i ++) {
final int fd = events.fd(i);
if (fd == eventFd.intValue()) {
pendingWakeup = false;
} else if (fd == timerFd.intValue()) {
timerFired = true;
} else {
final long ev = events.events(i);
AbstractEpollChannel ch = channels.get(fd);
if (ch != null) {
// Don't change the ordering of processing EPOLLOUT | EPOLLRDHUP / EPOLLIN if you're not 100%
// sure about it!
// Re-ordering can easily introduce bugs and bad side-effects, as we found out painfully in the
// past.
AbstractEpollUnsafe unsafe = (AbstractEpollUnsafe) ch.unsafe();
// First check for EPOLLOUT as we may need to fail the connect ChannelPromise before try
// to read from the file descriptor.
// See https://github.com/netty/netty/issues/3785
//
// It is possible for an EPOLLOUT or EPOLLERR to be generated when a connection is refused.
// In either case epollOutReady() will do the correct thing (finish connecting, or fail
// the connection).
// See https://github.com/netty/netty/issues/3848
if ((ev & (Native.EPOLLERR | Native.EPOLLOUT)) != 0) {
// Force flush of data as the epoll is writable again
unsafe.epollOutReady();
}
// Check EPOLLIN before EPOLLRDHUP to ensure all data is read before shutting down the input.
// See https://github.com/netty/netty/issues/4317.
//
// If EPOLLIN or EPOLLERR was received and the channel is still open call epollInReady(). This will
// try to read from the underlying file descriptor and so notify the user about the error.
if ((ev & (Native.EPOLLERR | Native.EPOLLIN)) != 0) {
// The Channel is still open and there is something to read. Do it now.
unsafe.epollInReady();
}
// Check if EPOLLRDHUP was set, this will notify us for connection-reset in which case
// we may close the channel directly or try to read more data depending on the state of the
// Channel and als depending on the AbstractEpollChannel subtype.
if ((ev & Native.EPOLLRDHUP) != 0) {
unsafe.epollRdHupReady();
}
} else {
// We received an event for an fd which we not use anymore. Remove it from the epoll_event set.
try {
Native.epollCtlDel(epollFd.intValue(), fd);
} catch (IOException ignore) {
// This can happen but is nothing we need to worry about as we only try to delete
// the fd from the epoll set as we not found it in our mappings. So this call to
// epollCtlDel(...) is just to ensure we cleanup stuff and so may fail if it was
// deleted before or the file descriptor was closed before.
}
}
}
}
return timerFired;
}
@Override
protected void cleanup() {
try {
closeFileDescriptors();
} finally {
// release native memory
if (iovArray != null) {
iovArray.release();
iovArray = null;
}
if (datagramPacketArray != null) {
datagramPacketArray.release();
datagramPacketArray = null;
}
events.free();
}
}
/**
* This method is intended for use by process checkpoint/restore
* integration, such as OpenJDK CRaC.
* It's up to the caller to ensure that there is no concurrent use
* of the FDs while these are closed, e.g. by blocking the executor.
*/
@UnstableApi
public void closeFileDescriptors() {
// Ensure any in-flight wakeup writes have been performed prior to closing eventFd.
while (pendingWakeup) {
try {
int count = epollWaitTimeboxed();
if (count == 0) {
// We timed-out so assume that the write we're expecting isn't coming
break;
}
for (int i = 0; i < count; i++) {
if (events.fd(i) == eventFd.intValue()) {
pendingWakeup = false;
break;
}
}
} catch (IOException ignore) {
// ignore
}
}
try {
eventFd.close();
} catch (IOException e) {
logger.warn("Failed to close the event fd.", e);
}
try {
timerFd.close();
} catch (IOException e) {
logger.warn("Failed to close the timer fd.", e);
}
try {
epollFd.close();
} catch (IOException e) {
logger.warn("Failed to close the epoll fd.", e);
}
}
}
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