/* * Copyright 2012 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: * * 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 io.netty.channel.nio; import io.netty.channel.Channel; import io.netty.channel.ChannelException; import io.netty.channel.EventLoop; import io.netty.channel.EventLoopException; import io.netty.channel.SelectStrategy; import io.netty.channel.SingleThreadEventLoop; import io.netty.util.IntSupplier; import io.netty.util.concurrent.RejectedExecutionHandler; import io.netty.util.internal.PlatformDependent; import io.netty.util.internal.ReflectionUtil; import io.netty.util.internal.SystemPropertyUtil; import io.netty.util.internal.logging.InternalLogger; import io.netty.util.internal.logging.InternalLoggerFactory; import java.io.IOException; import java.lang.reflect.Field; import java.nio.channels.CancelledKeyException; import java.nio.channels.SelectableChannel; import java.nio.channels.SelectionKey; import java.nio.channels.Selector; import java.nio.channels.spi.SelectorProvider; import java.security.AccessController; import java.security.PrivilegedAction; import java.util.ArrayList; import java.util.Collection; import java.util.Iterator; import java.util.Queue; import java.util.Set; import java.util.concurrent.Callable; import java.util.concurrent.Executor; import java.util.concurrent.TimeUnit; import java.util.concurrent.atomic.AtomicBoolean; /** * {@link SingleThreadEventLoop} implementation which register the {@link Channel}'s to a * {@link Selector} and so does the multi-plexing of these in the event loop. * */ public final class NioEventLoop extends SingleThreadEventLoop { private static final InternalLogger logger = InternalLoggerFactory.getInstance(NioEventLoop.class); private static final int CLEANUP_INTERVAL = 256; // XXX Hard-coded value, but won't need customization. private static final boolean DISABLE_KEYSET_OPTIMIZATION = SystemPropertyUtil.getBoolean("io.netty.noKeySetOptimization", false); private static final int MIN_PREMATURE_SELECTOR_RETURNS = 3; private static final int SELECTOR_AUTO_REBUILD_THRESHOLD; private final IntSupplier selectNowSupplier = new IntSupplier() { @Override public int get() throws Exception { return selectNow(); } }; private final Callable<Integer> pendingTasksCallable = new Callable<Integer>() { @Override public Integer call() throws Exception { return NioEventLoop.super.pendingTasks(); } }; // Workaround for JDK NIO bug. // // See: // - http://bugs.sun.com/view_bug.do?bug_id=6427854 // - https://github.com/netty/netty/issues/203 static { final String key = "sun.nio.ch.bugLevel"; final String buglevel = SystemPropertyUtil.get(key); if (buglevel == null) { try { AccessController.doPrivileged(new PrivilegedAction<Void>() { @Override public Void run() { System.setProperty(key, ""); return null; } }); } catch (final SecurityException e) { logger.debug("Unable to get/set System Property: " + key, e); } } int selectorAutoRebuildThreshold = SystemPropertyUtil.getInt("io.netty.selectorAutoRebuildThreshold", 512); if (selectorAutoRebuildThreshold < MIN_PREMATURE_SELECTOR_RETURNS) { selectorAutoRebuildThreshold = 0; } SELECTOR_AUTO_REBUILD_THRESHOLD = selectorAutoRebuildThreshold; if (logger.isDebugEnabled()) { logger.debug("-Dio.netty.noKeySetOptimization: {}", DISABLE_KEYSET_OPTIMIZATION); logger.debug("-Dio.netty.selectorAutoRebuildThreshold: {}", SELECTOR_AUTO_REBUILD_THRESHOLD); } } /** * The NIO {@link Selector}. */ private Selector selector; private Selector unwrappedSelector; private SelectedSelectionKeySet selectedKeys; private final SelectorProvider provider; /** * Boolean that controls determines if a blocked Selector.select should * break out of its selection process. In our case we use a timeout for * the select method and the select method will block for that time unless * waken up. */ private final AtomicBoolean wakenUp = new AtomicBoolean(); private final SelectStrategy selectStrategy; private volatile int ioRatio = 50; private int cancelledKeys; private boolean needsToSelectAgain; NioEventLoop(NioEventLoopGroup parent, Executor executor, SelectorProvider selectorProvider, SelectStrategy strategy, RejectedExecutionHandler rejectedExecutionHandler) { super(parent, executor, false, DEFAULT_MAX_PENDING_TASKS, rejectedExecutionHandler); if (selectorProvider == null) { throw new NullPointerException("selectorProvider"); } if (strategy == null) { throw new NullPointerException("selectStrategy"); } provider = selectorProvider; final SelectorTuple selectorTuple = openSelector(); selector = selectorTuple.selector; unwrappedSelector = selectorTuple.unwrappedSelector; selectStrategy = strategy; } private static final class SelectorTuple { final Selector unwrappedSelector; final Selector selector; SelectorTuple(Selector unwrappedSelector) { this.unwrappedSelector = unwrappedSelector; this.selector = unwrappedSelector; } SelectorTuple(Selector unwrappedSelector, Selector selector) { this.unwrappedSelector = unwrappedSelector; this.selector = selector; } } private SelectorTuple openSelector() { final Selector unwrappedSelector; try { unwrappedSelector = provider.openSelector(); } catch (IOException e) { throw new ChannelException("failed to open a new selector", e); } if (DISABLE_KEYSET_OPTIMIZATION) { return new SelectorTuple(unwrappedSelector); } final SelectedSelectionKeySet selectedKeySet = new SelectedSelectionKeySet(); Object maybeSelectorImplClass = AccessController.doPrivileged(new PrivilegedAction<Object>() { @Override public Object run() { try { return Class.forName( "sun.nio.ch.SelectorImpl", false, PlatformDependent.getSystemClassLoader()); } catch (Throwable cause) { return cause; } } }); if (!(maybeSelectorImplClass instanceof Class) || // ensure the current selector implementation is what we can instrument. !((Class<?>) maybeSelectorImplClass).isAssignableFrom(unwrappedSelector.getClass())) { if (maybeSelectorImplClass instanceof Throwable) { Throwable t = (Throwable) maybeSelectorImplClass; logger.trace("failed to instrument a special java.util.Set into: {}", unwrappedSelector, t); } return new SelectorTuple(unwrappedSelector); } final Class<?> selectorImplClass = (Class<?>) maybeSelectorImplClass; Object maybeException = AccessController.doPrivileged(new PrivilegedAction<Object>() { @Override public Object run() { try { Field selectedKeysField = selectorImplClass.getDeclaredField("selectedKeys"); Field publicSelectedKeysField = selectorImplClass.getDeclaredField("publicSelectedKeys"); Throwable cause = ReflectionUtil.trySetAccessible(selectedKeysField); if (cause != null) { return cause; } cause = ReflectionUtil.trySetAccessible(publicSelectedKeysField); if (cause != null) { return cause; } selectedKeysField.set(unwrappedSelector, selectedKeySet); publicSelectedKeysField.set(unwrappedSelector, selectedKeySet); return null; } catch (NoSuchFieldException e) { return e; } catch (IllegalAccessException e) { return e; } } }); if (maybeException instanceof Exception) { selectedKeys = null; Exception e = (Exception) maybeException; logger.trace("failed to instrument a special java.util.Set into: {}", unwrappedSelector, e); return new SelectorTuple(unwrappedSelector); } selectedKeys = selectedKeySet; logger.trace("instrumented a special java.util.Set into: {}", unwrappedSelector); return new SelectorTuple(unwrappedSelector, new SelectedSelectionKeySetSelector(unwrappedSelector, selectedKeySet)); } /** * Returns the {@link SelectorProvider} used by this {@link NioEventLoop} to obtain the {@link Selector}. */ public SelectorProvider selectorProvider() { return provider; } @Override protected Queue<Runnable> newTaskQueue(int maxPendingTasks) { // This event loop never calls takeTask() return PlatformDependent.newMpscQueue(maxPendingTasks); } @Override public int pendingTasks() { // As we use a MpscQueue we need to ensure pendingTasks() is only executed from within the EventLoop as // otherwise we may see unexpected behavior (as size() is only allowed to be called by a single consumer). // See https://github.com/netty/netty/issues/5297 if (inEventLoop()) { return super.pendingTasks(); } else { return submit(pendingTasksCallable).syncUninterruptibly().getNow(); } } /** * Registers an arbitrary {@link SelectableChannel}, not necessarily created by Netty, to the {@link Selector} * of this event loop. Once the specified {@link SelectableChannel} is registered, the specified {@code task} will * be executed by this event loop when the {@link SelectableChannel} is ready. */ public void register(final SelectableChannel ch, final int interestOps, final NioTask<?> task) { if (ch == null) { throw new NullPointerException("ch"); } if (interestOps == 0) { throw new IllegalArgumentException("interestOps must be non-zero."); } if ((interestOps & ~ch.validOps()) != 0) { throw new IllegalArgumentException( "invalid interestOps: " + interestOps + "(validOps: " + ch.validOps() + ')'); } if (task == null) { throw new NullPointerException("task"); } if (isShutdown()) { throw new IllegalStateException("event loop shut down"); } try { ch.register(selector, interestOps, task); } catch (Exception e) { throw new EventLoopException("failed to register a channel", e); } } /** * 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; } /** * Replaces the current {@link Selector} of this event loop with newly created {@link Selector}s to work * around the infamous epoll 100% CPU bug. */ public void rebuildSelector() { if (!inEventLoop()) { execute(new Runnable() { @Override public void run() { rebuildSelector0(); } }); return; } rebuildSelector0(); } private void rebuildSelector0() { final Selector oldSelector = selector; final SelectorTuple newSelectorTuple; if (oldSelector == null) { return; } try { newSelectorTuple = openSelector(); } catch (Exception e) { logger.warn("Failed to create a new Selector.", e); return; } // Register all channels to the new Selector. int nChannels = 0; for (SelectionKey key: oldSelector.keys()) { Object a = key.attachment(); try { if (!key.isValid() || key.channel().keyFor(newSelectorTuple.unwrappedSelector) != null) { continue; } int interestOps = key.interestOps(); key.cancel(); SelectionKey newKey = key.channel().register(newSelectorTuple.unwrappedSelector, interestOps, a); if (a instanceof AbstractNioChannel) { // Update SelectionKey ((AbstractNioChannel) a).selectionKey = newKey; } nChannels ++; } catch (Exception e) { logger.warn("Failed to re-register a Channel to the new Selector.", e); if (a instanceof AbstractNioChannel) { AbstractNioChannel ch = (AbstractNioChannel) a; ch.unsafe().close(ch.unsafe().voidPromise()); } else { @SuppressWarnings("unchecked") NioTask<SelectableChannel> task = (NioTask<SelectableChannel>) a; invokeChannelUnregistered(task, key, e); } } } selector = newSelectorTuple.selector; unwrappedSelector = newSelectorTuple.unwrappedSelector; try { // time to close the old selector as everything else is registered to the new one oldSelector.close(); } catch (Throwable t) { if (logger.isWarnEnabled()) { logger.warn("Failed to close the old Selector.", t); } } logger.info("Migrated " + nChannels + " channel(s) to the new Selector."); } @Override protected void run() { for (;;) { try { switch (selectStrategy.calculateStrategy(selectNowSupplier, hasTasks())) { case SelectStrategy.CONTINUE: continue; case SelectStrategy.SELECT: select(wakenUp.getAndSet(false)); // 'wakenUp.compareAndSet(false, true)' is always evaluated // before calling 'selector.wakeup()' to reduce the wake-up // overhead. (Selector.wakeup() is an expensive operation.) // // However, there is a race condition in this approach. // The race condition is triggered when 'wakenUp' is set to // true too early. // // 'wakenUp' is set to true too early if: // 1) Selector is waken up between 'wakenUp.set(false)' and // 'selector.select(...)'. (BAD) // 2) Selector is waken up between 'selector.select(...)' and // 'if (wakenUp.get()) { ... }'. (OK) // // In the first case, 'wakenUp' is set to true and the // following 'selector.select(...)' will wake up immediately. // Until 'wakenUp' is set to false again in the next round, // 'wakenUp.compareAndSet(false, true)' will fail, and therefore // any attempt to wake up the Selector will fail, too, causing // the following 'selector.select(...)' call to block // unnecessarily. // // To fix this problem, we wake up the selector again if wakenUp // is true immediately after selector.select(...). // It is inefficient in that it wakes up the selector for both // the first case (BAD - wake-up required) and the second case // (OK - no wake-up required). if (wakenUp.get()) { selector.wakeup(); } default: // fallthrough } cancelledKeys = 0; needsToSelectAgain = false; final int ioRatio = this.ioRatio; if (ioRatio == 100) { try { processSelectedKeys(); } finally { // Ensure we always run tasks. runAllTasks(); } } else { final long ioStartTime = System.nanoTime(); try { processSelectedKeys(); } finally { // Ensure we always run tasks. final long ioTime = System.nanoTime() - ioStartTime; runAllTasks(ioTime * (100 - ioRatio) / ioRatio); } } } catch (Throwable t) { handleLoopException(t); } // Always handle shutdown even if the loop processing threw an exception. try { if (isShuttingDown()) { closeAll(); if (confirmShutdown()) { return; } } } catch (Throwable t) { handleLoopException(t); } } } private static 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 processSelectedKeys() { if (selectedKeys != null) { processSelectedKeysOptimized(); } else { processSelectedKeysPlain(selector.selectedKeys()); } } @Override protected void cleanup() { try { selector.close(); } catch (IOException e) { logger.warn("Failed to close a selector.", e); } } void cancel(SelectionKey key) { key.cancel(); cancelledKeys ++; if (cancelledKeys >= CLEANUP_INTERVAL) { cancelledKeys = 0; needsToSelectAgain = true; } } @Override protected Runnable pollTask() { Runnable task = super.pollTask(); if (needsToSelectAgain) { selectAgain(); } return task; } private void processSelectedKeysPlain(Set<SelectionKey> selectedKeys) { // check if the set is empty and if so just return to not create garbage by // creating a new Iterator every time even if there is nothing to process. // See https://github.com/netty/netty/issues/597 if (selectedKeys.isEmpty()) { return; } Iterator<SelectionKey> i = selectedKeys.iterator(); for (;;) { final SelectionKey k = i.next(); final Object a = k.attachment(); i.remove(); if (a instanceof AbstractNioChannel) { processSelectedKey(k, (AbstractNioChannel) a); } else { @SuppressWarnings("unchecked") NioTask<SelectableChannel> task = (NioTask<SelectableChannel>) a; processSelectedKey(k, task); } if (!i.hasNext()) { break; } if (needsToSelectAgain) { selectAgain(); selectedKeys = selector.selectedKeys(); // Create the iterator again to avoid ConcurrentModificationException if (selectedKeys.isEmpty()) { break; } else { i = selectedKeys.iterator(); } } } } private void processSelectedKeysOptimized() { for (int i = 0; i < selectedKeys.size; ++i) { final SelectionKey k = selectedKeys.keys[i]; // null out entry in the array to allow to have it GC'ed once the Channel close // See https://github.com/netty/netty/issues/2363 selectedKeys.keys[i] = null; final Object a = k.attachment(); if (a instanceof AbstractNioChannel) { processSelectedKey(k, (AbstractNioChannel) a); } else { @SuppressWarnings("unchecked") NioTask<SelectableChannel> task = (NioTask<SelectableChannel>) a; processSelectedKey(k, task); } if (needsToSelectAgain) { // null out entries in the array to allow to have it GC'ed once the Channel close // See https://github.com/netty/netty/issues/2363 selectedKeys.reset(i + 1); selectAgain(); i = -1; } } } private void processSelectedKey(SelectionKey k, AbstractNioChannel ch) { final AbstractNioChannel.NioUnsafe unsafe = ch.unsafe(); if (!k.isValid()) { final EventLoop eventLoop; try { eventLoop = ch.eventLoop(); } catch (Throwable ignored) { // If the channel implementation throws an exception because there is no event loop, we ignore this // because we are only trying to determine if ch is registered to this event loop and thus has authority // to close ch. return; } // Only close ch if ch is still registered to this EventLoop. ch could have deregistered from the event loop // and thus the SelectionKey could be cancelled as part of the deregistration process, but the channel is // still healthy and should not be closed. // See https://github.com/netty/netty/issues/5125 if (eventLoop != this || eventLoop == null) { return; } // close the channel if the key is not valid anymore unsafe.close(unsafe.voidPromise()); return; } try { int readyOps = k.readyOps(); // We first need to call finishConnect() before try to trigger a read(...) or write(...) as otherwise // the NIO JDK channel implementation may throw a NotYetConnectedException. if ((readyOps & SelectionKey.OP_CONNECT) != 0) { // remove OP_CONNECT as otherwise Selector.select(..) will always return without blocking // See https://github.com/netty/netty/issues/924 int ops = k.interestOps(); ops &= ~SelectionKey.OP_CONNECT; k.interestOps(ops); unsafe.finishConnect(); } // Process OP_WRITE first as we may be able to write some queued buffers and so free memory. if ((readyOps & SelectionKey.OP_WRITE) != 0) { // Call forceFlush which will also take care of clear the OP_WRITE once there is nothing left to write ch.unsafe().forceFlush(); } // Also check for readOps of 0 to workaround possible JDK bug which may otherwise lead // to a spin loop if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) { unsafe.read(); } } catch (CancelledKeyException ignored) { unsafe.close(unsafe.voidPromise()); } } private static void processSelectedKey(SelectionKey k, NioTask<SelectableChannel> task) { int state = 0; try { task.channelReady(k.channel(), k); state = 1; } catch (Exception e) { k.cancel(); invokeChannelUnregistered(task, k, e); state = 2; } finally { switch (state) { case 0: k.cancel(); invokeChannelUnregistered(task, k, null); break; case 1: if (!k.isValid()) { // Cancelled by channelReady() invokeChannelUnregistered(task, k, null); } break; } } } private void closeAll() { selectAgain(); Set<SelectionKey> keys = selector.keys(); Collection<AbstractNioChannel> channels = new ArrayList<AbstractNioChannel>(keys.size()); for (SelectionKey k: keys) { Object a = k.attachment(); if (a instanceof AbstractNioChannel) { channels.add((AbstractNioChannel) a); } else { k.cancel(); @SuppressWarnings("unchecked") NioTask<SelectableChannel> task = (NioTask<SelectableChannel>) a; invokeChannelUnregistered(task, k, null); } } for (AbstractNioChannel ch: channels) { ch.unsafe().close(ch.unsafe().voidPromise()); } } private static void invokeChannelUnregistered(NioTask<SelectableChannel> task, SelectionKey k, Throwable cause) { try { task.channelUnregistered(k.channel(), cause); } catch (Exception e) { logger.warn("Unexpected exception while running NioTask.channelUnregistered()", e); } } @Override protected void wakeup(boolean inEventLoop) { if (!inEventLoop && wakenUp.compareAndSet(false, true)) { selector.wakeup(); } } Selector unwrappedSelector() { return unwrappedSelector; } int selectNow() throws IOException { try { return selector.selectNow(); } finally { // restore wakeup state if needed if (wakenUp.get()) { selector.wakeup(); } } } private void select(boolean oldWakenUp) throws IOException { Selector selector = this.selector; try { int selectCnt = 0; long currentTimeNanos = System.nanoTime(); long selectDeadLineNanos = currentTimeNanos + delayNanos(currentTimeNanos); for (;;) { long timeoutMillis = (selectDeadLineNanos - currentTimeNanos + 500000L) / 1000000L; if (timeoutMillis <= 0) { if (selectCnt == 0) { selector.selectNow(); selectCnt = 1; } break; } // If a task was submitted when wakenUp value was true, the task didn't get a chance to call // Selector#wakeup. So we need to check task queue again before executing select operation. // If we don't, the task might be pended until select operation was timed out. // It might be pended until idle timeout if IdleStateHandler existed in pipeline. if (hasTasks() && wakenUp.compareAndSet(false, true)) { selector.selectNow(); selectCnt = 1; break; } int selectedKeys = selector.select(timeoutMillis); selectCnt ++; if (selectedKeys != 0 || oldWakenUp || wakenUp.get() || hasTasks() || hasScheduledTasks()) { // - Selected something, // - waken up by user, or // - the task queue has a pending task. // - a scheduled task is ready for processing break; } if (Thread.interrupted()) { // Thread was interrupted so reset selected keys and break so we not run into a busy loop. // As this is most likely a bug in the handler of the user or it's client library we will // also log it. // // See https://github.com/netty/netty/issues/2426 if (logger.isDebugEnabled()) { logger.debug("Selector.select() returned prematurely because " + "Thread.currentThread().interrupt() was called. Use " + "NioEventLoop.shutdownGracefully() to shutdown the NioEventLoop."); } selectCnt = 1; break; } long time = System.nanoTime(); if (time - TimeUnit.MILLISECONDS.toNanos(timeoutMillis) >= currentTimeNanos) { // timeoutMillis elapsed without anything selected. selectCnt = 1; } else if (SELECTOR_AUTO_REBUILD_THRESHOLD > 0 && selectCnt >= SELECTOR_AUTO_REBUILD_THRESHOLD) { // The selector returned prematurely many times in a row. // Rebuild the selector to work around the problem. logger.warn( "Selector.select() returned prematurely {} times in a row; rebuilding Selector {}.", selectCnt, selector); rebuildSelector(); selector = this.selector; // Select again to populate selectedKeys. selector.selectNow(); selectCnt = 1; break; } currentTimeNanos = time; } if (selectCnt > MIN_PREMATURE_SELECTOR_RETURNS) { if (logger.isDebugEnabled()) { logger.debug("Selector.select() returned prematurely {} times in a row for Selector {}.", selectCnt - 1, selector); } } } catch (CancelledKeyException e) { if (logger.isDebugEnabled()) { logger.debug(CancelledKeyException.class.getSimpleName() + " raised by a Selector {} - JDK bug?", selector, e); } // Harmless exception - log anyway } } private void selectAgain() { needsToSelectAgain = false; try { selector.selectNow(); } catch (Throwable t) { logger.warn("Failed to update SelectionKeys.", t); } } }