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/*
* 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.
* 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 from a container thread. The
* dispatch will be processed once processing control returns to
* the container.
* DISPATCHING - dispatch() has been called from a non-container thread. The
* dispatch will be processed as soon as a container thread is
* available.
* ERROR - Something went wrong.
*
* |----------------->--------------|
* | \|/
* | |----------<---------------ERROR
* | | complete() /|\ | \
* | | | | \---------------|
* | | | | |dispatch()
* | | | |postProcess() \|/
* | | error()| | |
* | | | | |--|timeout() |
* | | postProcess() | \|/ | \|/ | auto
* | | |--------------->DISPATCHED<---------- | --------------COMPLETING<-----|
* | | | /|\ | | | /|\ |
* | | | |--->-------| | | |--| |
* | | ^ | |startAsync() | timeout() |
* | | | | | | |
* | \|/ | | complete() \|/ postProcess() | |
* | MUST_COMPLETE-<- | ----<------STARTING-->--------- | ------------| ^
* | /|\ | | | | complete() |
* | | | | | | /-----------|
* | | ^ |dispatch() | | /
* | | | | | | /
* | | | \|/ | \|/ /
* | | |----<----MUST_DISPATCH----<------| STARTED
* | | | auto \ /|
* | | | \ / |
* ^ ^ ^ \ dispatch()/ |
* | | | \ / |
* | | | |-------- \ -------------/ |auto
* | | | | \ |
* | | | | \ |
* | | | auto \|/ \ \|/
* | | |---<------DISPATCHING \---------TIMING_OUT
* | | dispatch() | |
* | | | |
* | |-------<----------------------------------<------| |
* | complete() |
* | |
* |<--------<-------------------<-------------------------------<--|
* error()
*
*/
public class AsyncStateMachine {
/**
* The string manager for this package.
*/
private static final StringManager sm =
StringManager.getManager(Constants.Package);
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, false, false, false, false),
MUST_DISPATCH(true, true, false, true, true),
DISPATCHING (true, false, false, true, false),
ERROR (true, false, 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;
// Need this to fire listener on complete
private AsyncContextCallback asyncCtxt = null;
private Processor processor;
public AsyncStateMachine(Processor 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();
}
public synchronized void asyncStart(AsyncContextCallback asyncCtxt) {
if (state == AsyncState.DISPATCHED) {
state = AsyncState.STARTING;
this.asyncCtxt = asyncCtxt;
} else {
throw new IllegalStateException(
sm.getString("asyncStateMachine.invalidAsyncState",
"asyncStart()", 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.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();
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 {
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) {
// 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.
state = AsyncState.DISPATCHING;
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 boolean asyncError() {
boolean doDispatch = false;
if (state == AsyncState.DISPATCHED ||
state == AsyncState.TIMING_OUT) {
state = AsyncState.ERROR;
} else {
throw new IllegalStateException(
sm.getString("asyncStateMachine.invalidAsyncState",
"asyncError()", state));
}
return doDispatch;
}
public synchronized void asyncRun(Runnable runnable) {
if (state == AsyncState.STARTING || state == AsyncState.STARTED) {
// 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() {
// Ensure in case of error that any non-container threads that have been
// paused are unpaused.
notifyAll();
asyncCtxt = null;
state = AsyncState.DISPATCHED;
}
/*
* 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?
}
}
}
}
