/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF 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 org.apache.coyote;
import java.security.AccessController;
import java.security.PrivilegedAction;
import org.apache.tomcat.util.net.AbstractEndpoint.Handler.SocketState;
import org.apache.tomcat.util.res.StringManager;
import org.apache.tomcat.util.security.PrivilegedGetTccl;
import org.apache.tomcat.util.security.PrivilegedSetTccl;
/**
* Manages the state transitions for async requests.
*
*
* The internal states that are used are:
* DISPATCHED - Standard request. Not in Async mode.
* STARTING - ServletRequest.startAsync() has been called but the
* request in which that call was made has not finished
* processing.
* STARTED - ServletRequest.startAsync() has been called and the
* request in which that call was made has finished
* processing.
* READ_WRITE_OP - Performing an asynchronous read or write.
* MUST_COMPLETE - complete() has been called before the request in which
* ServletRequest.startAsync() has finished. As soon as that
* request finishes, the complete() will be processed.
* COMPLETING - The call to complete() was made once the request was in
* the STARTED state. May or may not be triggered by a
* container thread - depends if start(Runnable) was used
* TIMING_OUT - The async request has timed out and is waiting for a call
* to complete(). If that isn't made, the error state will
* entered.
* MUST_DISPATCH - dispatch() has been called before the request in which
* ServletRequest.startAsync() has finished. As soon as that
* request finishes, the dispatch() will be processed.
* DISPATCHING - The dispatch is being processed.
* ERROR - Something went wrong.
*
* |-----------------»------|
* | \|/
* | |----------«-------ERROR-----------------------------------«-------------------------------|
* | | complete() /|\/|\\ |
* | | | | \ |
* | | |-----»-------| | \-----------»----------| |
* | | | | |dispatch() |
* | | | | \|/ |
* | | | | |--|timeout() | |
* | | | post() | | \|/ | post() |
* | | | |---------- | --»DISPATCHED«---------- | --------------COMPLETING«-----| |
* | | | | | /|\ | | | /|\ | |
* | | | | |---»- | ---| | | |--| | |
* | | ^ ^ | | |startAsync() | timeout() | |
* | | | | | \ | | | |
* | | | | | \ | | | |
* | | | | | \ | | | |
* | | | | | \ | | | |
* | \|/ | | | \ \|/ post() | | |
* | MUST_COMPLETE-«- | ----«------STARTING--»--------- | -------------| ^ |
* | /|\ /|\ | complete() | | | complete() | |
* | | | | | | post() | /----------| |
* | | | ^ |dispatch() | |-----| | / |
* | | | | | | | | | / |
* | | | | \|/ | | \|/ \|/ / post() |
* | | | | MUST_DISPATCH-----«-----| |--«--STARTED«---------«---------| |
* | | | | /|\ | / | | | |
* | | | | | |post() / | | ^ |
* ^ | ^ | | |dispatched() / | |asyncOperation() | |
* | | | ^ | | / | | | |
* | | | | | | |-------------/ | |»-READ_WRITE_OP--»---| |
* | | | | | | | dispatch() | | | | |
* | | | |post() | | | timeout()| | | | error()|
* | | | |dispatched() | \|/ \|/ | dispatch()| | |-»--------|
* | | | |---«---------- | ---DISPATCHING«-----«------ | ------«----| |
* | | | | | ^ | |
* | | | | |----| | |
* | | | | timeout() | |
* | | | | | |
* | | | | dispatch() \|/ |
* | | | |-----------«-----------TIMING_OUT |
* | | | | | |
* | | |-------«----------------------------------«------| | |
* | | complete() | |
* | | | |
* |«- | ----«-------------------«-------------------------------«--| |
* | error() |
* | complete() |
* |----------------------------------------------------------------------------|
*
*/
public class AsyncStateMachine {
/**
* The string manager for this package.
*/
private static final StringManager sm = StringManager.getManager(AsyncStateMachine.class);
private static enum AsyncState {
DISPATCHED (false, false, false, false, false),
STARTING (true, true, false, false, true),
STARTED (true, true, false, false, false),
MUST_COMPLETE(true, true, true, false, false),
COMPLETING (true, false, true, false, false),
TIMING_OUT (true, true, false, false, false),
MUST_DISPATCH(true, true, false, true, true),
DISPATCHING (true, false, false, true, false),
READ_WRITE_OP(true, true, false, false, true),
ERROR (true, true, false, false, false);
private final boolean isAsync;
private final boolean isStarted;
private final boolean isCompleting;
private final boolean isDispatching;
private final boolean pauseNonContainerThread;
private AsyncState(boolean isAsync, boolean isStarted, boolean isCompleting,
boolean isDispatching, boolean pauseNonContainerThread) {
this.isAsync = isAsync;
this.isStarted = isStarted;
this.isCompleting = isCompleting;
this.isDispatching = isDispatching;
this.pauseNonContainerThread = pauseNonContainerThread;
}
public boolean isAsync() {
return isAsync;
}
public boolean isStarted() {
return isStarted;
}
public boolean isDispatching() {
return isDispatching;
}
public boolean isCompleting() {
return isCompleting;
}
public boolean getPauseNonContainerThread() {
return pauseNonContainerThread;
}
}
private volatile AsyncState state = AsyncState.DISPATCHED;
private volatile long lastAsyncStart = 0;
// Need this to fire listener on complete
private AsyncContextCallback asyncCtxt = null;
private final AbstractProcessor processor;
public AsyncStateMachine(AbstractProcessor processor) {
this.processor = processor;
}
public boolean isAsync() {
return state.isAsync();
}
public boolean isAsyncDispatching() {
return state.isDispatching();
}
public boolean isAsyncStarted() {
return state.isStarted();
}
public boolean isAsyncTimingOut() {
return state == AsyncState.TIMING_OUT;
}
public boolean isAsyncError() {
return state == AsyncState.ERROR;
}
public boolean isCompleting() {
return state.isCompleting();
}
/**
* Obtain the time that this connection last transitioned to async
* processing.
*
* @return The time (as returned by {@link System#currentTimeMillis()}) that
* this connection last transitioned to async
*/
public long getLastAsyncStart() {
return lastAsyncStart;
}
public synchronized void asyncStart(AsyncContextCallback asyncCtxt) {
if (state == AsyncState.DISPATCHED) {
state = AsyncState.STARTING;
this.asyncCtxt = asyncCtxt;
lastAsyncStart = System.currentTimeMillis();
} else {
throw new IllegalStateException(
sm.getString("asyncStateMachine.invalidAsyncState",
"asyncStart()", state));
}
}
public synchronized void asyncOperation() {
if (state==AsyncState.STARTED) {
state = AsyncState.READ_WRITE_OP;
} else {
throw new IllegalStateException(
sm.getString("asyncStateMachine.invalidAsyncState",
"asyncOperation()", state));
}
}
/*
* Async has been processed. Whether or not to enter a long poll depends on
* current state. For example, as per SRV.2.3.3.3 can now process calls to
* complete() or dispatch().
*/
public synchronized SocketState asyncPostProcess() {
// Unpause any non-container threads that may be waiting for this
// container thread to complete this method. Note because of the syncs
// those non-container threads won't start back up until until this
// method exits.
notifyAll();
if (state == AsyncState.STARTING || state == AsyncState.READ_WRITE_OP) {
state = AsyncState.STARTED;
return SocketState.LONG;
} else if (state == AsyncState.MUST_COMPLETE) {
asyncCtxt.fireOnComplete();
state = AsyncState.DISPATCHED;
return SocketState.ASYNC_END;
} else if (state == AsyncState.COMPLETING) {
asyncCtxt.fireOnComplete();
state = AsyncState.DISPATCHED;
return SocketState.ASYNC_END;
} else if (state == AsyncState.MUST_DISPATCH) {
state = AsyncState.DISPATCHING;
return SocketState.ASYNC_END;
} else if (state == AsyncState.DISPATCHING) {
state = AsyncState.DISPATCHED;
return SocketState.ASYNC_END;
} else if (state == AsyncState.STARTED) {
// This can occur if an async listener does a dispatch to an async
// servlet during onTimeout
return SocketState.LONG;
} else {
throw new IllegalStateException(
sm.getString("asyncStateMachine.invalidAsyncState",
"asyncPostProcess()", state));
}
}
public synchronized boolean asyncComplete() {
pauseNonContainerThread();
clearNonBlockingListeners();
boolean doComplete = false;
if (state == AsyncState.STARTING) {
state = AsyncState.MUST_COMPLETE;
} else if (state == AsyncState.STARTED) {
state = AsyncState.COMPLETING;
doComplete = true;
} else if (state == AsyncState.TIMING_OUT ||
state == AsyncState.ERROR) {
state = AsyncState.MUST_COMPLETE;
} else if (state == AsyncState.READ_WRITE_OP) {
state = AsyncState.MUST_COMPLETE;
} else {
throw new IllegalStateException(
sm.getString("asyncStateMachine.invalidAsyncState",
"asyncComplete()", state));
}
return doComplete;
}
public synchronized boolean asyncTimeout() {
if (state == AsyncState.STARTED) {
state = AsyncState.TIMING_OUT;
return true;
} else if (state == AsyncState.COMPLETING ||
state == AsyncState.DISPATCHING ||
state == AsyncState.DISPATCHED) {
// NOOP - App called complete() or dispatch() between the the
// timeout firing and execution reaching this point
return false;
} else {
throw new IllegalStateException(
sm.getString("asyncStateMachine.invalidAsyncState",
"asyncTimeout()", state));
}
}
public synchronized boolean asyncDispatch() {
pauseNonContainerThread();
boolean doDispatch = false;
if (state == AsyncState.STARTING ||
state == AsyncState.TIMING_OUT ||
state == AsyncState.ERROR) {
// In these three cases processing is on a container thread so no
// need to transfer processing to a new container thread
state = AsyncState.MUST_DISPATCH;
} else if (state == AsyncState.STARTED) {
state = AsyncState.DISPATCHING;
// A dispatch is always required.
// If on a non-container thread, need to get back onto a container
// thread to complete the processing.
// If on a container thread the current request/response are not the
// request/response associated with the AsyncContext so need a new
// container thread to process the different request/response.
doDispatch = true;
} else if (state == AsyncState.READ_WRITE_OP) {
state = AsyncState.DISPATCHING;
// If on a container thread then the socket will be added to the
// poller poller when the thread exits the
// AbstractConnectionHandler.process() method so don't do a dispatch
// here which would add it to the poller a second time.
if (!ContainerThreadMarker.isContainerThread()) {
doDispatch = true;
}
} else {
throw new IllegalStateException(
sm.getString("asyncStateMachine.invalidAsyncState",
"asyncDispatch()", state));
}
return doDispatch;
}
public synchronized void asyncDispatched() {
if (state == AsyncState.DISPATCHING ||
state == AsyncState.MUST_DISPATCH) {
state = AsyncState.DISPATCHED;
} else {
throw new IllegalStateException(
sm.getString("asyncStateMachine.invalidAsyncState",
"asyncDispatched()", state));
}
}
public synchronized void asyncError() {
if (state == AsyncState.STARTING ||
state == AsyncState.DISPATCHED ||
state == AsyncState.TIMING_OUT ||
state == AsyncState.MUST_COMPLETE ||
state == AsyncState.READ_WRITE_OP) {
clearNonBlockingListeners();
state = AsyncState.ERROR;
} else {
throw new IllegalStateException(
sm.getString("asyncStateMachine.invalidAsyncState",
"asyncError()", state));
}
}
public synchronized void asyncRun(Runnable runnable) {
if (state == AsyncState.STARTING || state == AsyncState.STARTED ||
state == AsyncState.READ_WRITE_OP) {
// Execute the runnable using a container thread from the
// Connector's thread pool. Use a wrapper to prevent a memory leak
ClassLoader oldCL;
if (Constants.IS_SECURITY_ENABLED) {
PrivilegedAction pa = new PrivilegedGetTccl();
oldCL = AccessController.doPrivileged(pa);
} else {
oldCL = Thread.currentThread().getContextClassLoader();
}
try {
if (Constants.IS_SECURITY_ENABLED) {
PrivilegedAction pa = new PrivilegedSetTccl(
this.getClass().getClassLoader());
AccessController.doPrivileged(pa);
} else {
Thread.currentThread().setContextClassLoader(
this.getClass().getClassLoader());
}
processor.getExecutor().execute(runnable);
} finally {
if (Constants.IS_SECURITY_ENABLED) {
PrivilegedAction pa = new PrivilegedSetTccl(
oldCL);
AccessController.doPrivileged(pa);
} else {
Thread.currentThread().setContextClassLoader(oldCL);
}
}
} else {
throw new IllegalStateException(
sm.getString("asyncStateMachine.invalidAsyncState",
"asyncRun()", state));
}
}
public synchronized void recycle() {
// Use lastAsyncStart to determine if this instance has been used since
// it was last recycled. If it hasn't there is no need to recycle again
// which saves the relatively expensive call to notifyAll()
if (lastAsyncStart == 0) {
return;
}
// Ensure in case of error that any non-container threads that have been
// paused are unpaused.
notifyAll();
asyncCtxt = null;
state = AsyncState.DISPATCHED;
lastAsyncStart = 0;
}
private void clearNonBlockingListeners() {
processor.getRequest().listener = null;
processor.getRequest().getResponse().listener = null;
}
/*
* startAsync() has been called but the container thread where this was
* called has not completed processing. To avoid various race conditions -
* including several related to error page handling - pause this
* non-container thread until the container thread has finished processing.
* The non-container thread will be paused until the container thread
* completes asyncPostProcess().
*/
private synchronized void pauseNonContainerThread() {
while (!ContainerThreadMarker.isContainerThread() &&
state.getPauseNonContainerThread()) {
try {
wait();
} catch (InterruptedException e) {
// TODO Log this?
}
}
}
}