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package org.glassfish.api.admin;
import java.util.Date;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.Semaphore;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ArrayBlockingQueue;
import org.jvnet.hk2.annotations.Service;
import javax.inject.Singleton;
import javax.inject.Inject;
/**
* The implementation of the admin command lock.
*
* @author Bill Shannon
* @author Chris Kasso
*/
@Service
@Singleton
public class AdminCommandLock {
@Inject
Logger logger;
/**
* The read/write lock. We depend on this class being a singleton
* and thus there being exactly one such lock object, shared by all
* users of this class.
*/
private static ReentrantReadWriteLock rwlock = new ReentrantReadWriteLock();
/**
* A thread which can hold a Read/Write lock across command invocations.
* Once the lock is released the thread will exit.
*/
private SuspendCommandsLockThread suspendCommandsLockThread = null;
private String lockOwner = null;
private String lockMessage = null;
private Date lockTimeOfAcquisition = null;
/**
* The status of a suspend command attempt.
*/
public enum SuspendStatus { SUCCESS, // Suspend succeeded
TIMEOUT, // Failed - suspend timed out
ILLEGALSTATE, // Failed - already suspended
ERROR // Failed - other error
};
/**
* Return the appropriate Lock object for the specified LockType.
* The returned lock has not been locked. If the LockType is
* not SHARED or EXCLUSIVE null is returned.
*
* @param type the LockType
* @return the Lock object to use, or null
*/
public Lock getLock(CommandLock.LockType type) {
if (type == CommandLock.LockType.SHARED)
return rwlock.readLock();
if (type == CommandLock.LockType.EXCLUSIVE)
return rwlock.writeLock();
return null; // no lock
}
public void dumpState(Logger logger, Level level) {
if (logger.isLoggable(level)) {
logger.log(level, "Current locking conditions are " + rwlock.getReadLockCount()
+ "/"+ rwlock.getReadHoldCount() + " shared locks"
+ "and " + rwlock.getWriteHoldCount() + " write lock");
}
}
/**
* Return the appropriate Lock object for the specified command.
* The returned lock has not been locked. If this command needs
* no lock, null is returned.
*
* @param command the AdminCommand object
* @return the Lock object to use, or null if no lock needed
*/
public Lock getLock(AdminCommand command) {
CommandLock alock = command.getClass().getAnnotation(CommandLock.class);
if (alock == null || alock.value() == CommandLock.LockType.SHARED)
return rwlock.readLock();
if (alock.value() == CommandLock.LockType.EXCLUSIVE)
return rwlock.writeLock();
return null; // no lock
}
/**
* Return the appropriate Lock object for the specified command.
* The returned lock has been locked. If this command needs
* no lock, null is returned.
*
* @param command the AdminCommand object
* @param owner the authority who requested the lock
* @return the Lock object to use, or null if no lock needed
*/
public Lock getLock(AdminCommand command, String owner) throws
AdminCommandLockTimeoutException,
AdminCommandLockException {
Lock lock = null;
boolean exclusive = false;
int timeout = 30;
CommandLock alock = command.getClass().getAnnotation(CommandLock.class);
if (alock == null || alock.value() == CommandLock.LockType.SHARED)
lock = rwlock.readLock();
else if (alock.value() == CommandLock.LockType.EXCLUSIVE) {
lock = rwlock.writeLock();
exclusive = true;
}
if (lock == null)
return null; // no lock
/*
* If the suspendCommandsLockThread is alive then we were
* suspended manually (via suspendCommands()) otherwise we
* may have been locked by a command requiring the EXCLUSIVE
* lock.
* If we were suspended via suspendCommands() we don't block
* waiting for the lock (but we try to acquire the lock just to be
* safe) - otherwise we set the timeout and try to get the lock.
*/
if (suspendCommandsLockThread != null &&
suspendCommandsLockThread.isAlive()) {
timeout = -1;
} else {
boolean badTimeOutValue = false;
String timeout_s = System.getProperty(
"com.sun.aas.commandLockTimeOut", "30");
try {
timeout = Integer.parseInt(timeout_s);
if (timeout < 0)
badTimeOutValue = true;
} catch (NumberFormatException e) {
badTimeOutValue = true;
}
if (badTimeOutValue) {
//XXX: Deal with logger injection attack.
logger.log(Level.INFO,
"Bad value com.sun.aas.commandLockTimeOut: "
+ timeout_s + ". Using 30 seconds.");
timeout = 30;
}
}
boolean lockAcquired = false;
while (!lockAcquired) {
try {
if (lock.tryLock(timeout, TimeUnit.SECONDS)) {
lockAcquired = true;
} else {
/*
* A timeout < 0 indicates the domain was likely already
* locked manually but we tried to acquire the lock
* anyway - just in case.
*/
if (timeout >= 0)
throw new AdminCommandLockTimeoutException(
"timeout acquiring lock",
getLockTimeOfAcquisition(),
getLockOwner());
else
throw new AdminCommandLockException(
getLockMessage(),
getLockTimeOfAcquisition(),
getLockOwner());
}
} catch (java.lang.InterruptedException e) {
logger.log(Level.FINE, "Interrupted acquiring command lock. ",
e);
}
}
if (lockAcquired && exclusive) {
setLockOwner(owner);
setLockTimeOfAcquisition(new Date());
}
return lock;
}
/**
* Sets the admin user id for the user who acquired the exclusive lock.
*
* @param user the admin user who acquired the lock.
*/
private void setLockOwner(String owner) {
lockOwner = owner;
}
/**
* Get the admin user id for the user who acquired the exclusive lock.
* This does not imply the lock is still held.
*
* @return the admin user who acquired the lock
*/
public synchronized String getLockOwner() {
return lockOwner;
}
/**
* Sets a message to be returned if the lock could not be acquired.
* This message can be displayed to the user to indicate why the
* domain is locked.
*
* @param message The message to return.
*/
private void setLockMessage(String message) {
lockMessage = message;
}
/**
* Get the message to be returned if the lock could not be acquired.
*
* @return the message indicating why the domain is locked.
*/
public synchronized String getLockMessage() {
return lockMessage;
}
/**
* Sets the time the exclusive lock was acquired.
*
* @param time the time the lock was acquired
*/
private void setLockTimeOfAcquisition(Date time) {
lockTimeOfAcquisition = time;
}
/**
* Get the time the exclusive lock was acquired. This does not
* imply the lock is still held.
*
* @return the time the lock was acquired
*/
public synchronized Date getLockTimeOfAcquisition() {
return lockTimeOfAcquisition;
}
/**
* Indicates if commands are currently suspended.
*/
public synchronized boolean isSuspended() {
/*
* If the suspendCommandsLockThread is alive then we are
* already suspended or really close to it.
*/
if (suspendCommandsLockThread != null &&
suspendCommandsLockThread.isAlive()) {
return true;
}
return false;
}
/**
* Lock the DAS from accepting any commands annotated with a SHARED
* or EXCLUSIVE CommandLock. This method will result in the acquisition
* of an EXCLUSIVE lock. This method will not return until the lock
* is acquired, it times out or an error occurs.
*
* @param timeout lock timeout in seconds
* @param lockOwner the user who acquired the lock
* @return status regarding acquisition of the lock
*/
public synchronized SuspendStatus suspendCommands(
long timeout,
String lockOwner) {
return suspendCommands(timeout, lockOwner, "");
}
/**
* Lock the DAS from accepting any commands annotated with a SHARED
* or EXCLUSIVE CommandLock. This method will result in the acquisition
* of an EXCLUSIVE lock. This method will not return until the lock
* is acquired, it times out or an error occurs.
*
* @param timeout lock timeout in seconds
* @param lockOwner the user who acquired the lock
* @param message message to return when a command is blocked
* @return status regarding acquisition of the lock
*/
public synchronized SuspendStatus suspendCommands(
long timeout,
String lockOwner,
String message) {
BlockingQueue<AdminCommandLock.SuspendStatus> suspendStatusQ =
new ArrayBlockingQueue<AdminCommandLock.SuspendStatus>(1);
/*
* If the suspendCommandsLockThread is alive then we are
* already suspended or really close to it.
*/
if (suspendCommandsLockThread != null &&
suspendCommandsLockThread.isAlive()) {
return SuspendStatus.ILLEGALSTATE;
}
/*
* Start a thread to manage the RWLock.
*/
suspendCommandsLockThread =
new SuspendCommandsLockThread(timeout, suspendStatusQ, lockOwner,
message);
try {
suspendCommandsLockThread.setName(
"DAS Suspended Command Lock Thread");
suspendCommandsLockThread.setDaemon(true);
} catch (IllegalThreadStateException e) {
return SuspendStatus.ERROR;
} catch (SecurityException e) {
return SuspendStatus.ERROR;
}
suspendCommandsLockThread.start();
/*
* Block until the commandLockThread has acquired the
* EXCLUSIVE lock or times out trying.
* We don't want the suspend command to return until we
* know the domain is suspended.
* The commandLockThread puts the timeout status on the suspendStatusQ
* once it has acquired the lock or timed out trying.
*/
SuspendStatus suspendStatus = queueTake(suspendStatusQ);
return suspendStatus;
}
/**
* Release the lock allowing the DAS to accept commands. This method
* may return before the lock is released. When the thread exits the
* lock will have been released.
*
* @return the thread maintaining the lock, null if the DAS is not
* in a suspended state. The caller may join() the thread to determine
* when the lock is released.
*/
public synchronized Thread resumeCommands() {
/*
* We can't resume if commands are not already locked.
*/
if (suspendCommandsLockThread == null ||
suspendCommandsLockThread.isAlive() == false ||
suspendCommandsLockThread.resumeCommandsSemaphore == null) {
return null;
}
/*
* This allows the suspendCommandsLockThread to continue. This
* will release the RWLock and allow commands to be processed.
*/
suspendCommandsLockThread.resumeCommandsSemaphore.release();
return suspendCommandsLockThread;
}
/**
* Convenience method that puts an object on a BlockingQueue
* as well as deals with InterruptedExceptions.
*
* @param status Object to be put on the queue
* @param itmQ The BlockingQueue
*/
private void queuePut(BlockingQueue<SuspendStatus> itmQ,
SuspendStatus status) {
boolean itemPut = false;
while (!itemPut) {
try {
itmQ.put(status);
itemPut = true;
} catch (java.lang.InterruptedException e) {
logger.log(Level.FINE,
"Interrupted putting lock status on queue", e);
}
}
}
/**
* Convenience method that takes an object from a BlockingQueue
* as well as deals with InterruptedExceptions.
*
* @param itmQ The BlockingQueue
*/
private SuspendStatus queueTake(BlockingQueue<SuspendStatus> itmQ) {
SuspendStatus status = SuspendStatus.SUCCESS;
boolean itemTake = false;
while (!itemTake) {
try {
status = itmQ.take();
itemTake = true;
} catch (java.lang.InterruptedException e) {
logger.log(Level.FINE,
"Interrupted getting status from a suspend queue", e);
}
}
return status;
}
/**
* The SuspendCommandsLockThread represents a thread which will
* hold a Read/Write lock across command invocations. Once the
* lock is released the thread will exit.
*/
private class SuspendCommandsLockThread extends Thread {
private Semaphore resumeCommandsSemaphore;
private BlockingQueue<SuspendStatus> suspendStatusQ;
private boolean suspendCommandsTimedOut;
private long timeout;
private String lockOwner;
private String message;
public SuspendCommandsLockThread(long timeout,
BlockingQueue<SuspendStatus> suspendStatusQ,
String lockOwner,
String message) {
this.suspendStatusQ = suspendStatusQ;
this.timeout = timeout;
this.lockOwner = lockOwner;
this.message = message;
resumeCommandsSemaphore = null;
suspendCommandsTimedOut = false;
}
public void run() {
/*
* The EXCLUSIVE lock/unlock must occur in the same thread.
* The lock may block if someone else currently has the
* EXCLUSIVE lock.
* This deals with both the timeout as well as the
* potential for an InterruptedException.
*/
Lock lock = getLock(CommandLock.LockType.EXCLUSIVE);
boolean lockAcquired = false;
while (!lockAcquired && !suspendCommandsTimedOut) {
try {
if (lock.tryLock(timeout, TimeUnit.SECONDS))
lockAcquired = true;
else
suspendCommandsTimedOut = true;
} catch (java.lang.InterruptedException e) {
logger.log(Level.FINE,
"Interrupted acquiring command lock. ",
e);
}
}
if (lockAcquired) {
setLockOwner(lockOwner);
setLockMessage(message);
setLockTimeOfAcquisition(new Date());
/*
* A semaphore that is triggered to signal to the thread
* to release the lock. This should only be created after
* the lock has been acquired.
*/
resumeCommandsSemaphore = new Semaphore(0, true);
}
/*
* The suspendStatusQ is used to signal that we acquired
* the lock. A blocking queue is used to indicate whether we
* timed out or ran into an error acquiring the lock.
*/
if (suspendStatusQ != null) {
if (suspendCommandsTimedOut == true) {
queuePut(suspendStatusQ, SuspendStatus.TIMEOUT);
} else {
queuePut(suspendStatusQ, SuspendStatus.SUCCESS);
}
}
/*
* If we timed out trying to get the lock then this thread
* is finished.
*/
if (suspendCommandsTimedOut)
return;
/*
* We block here waiting to be told to resume.
*/
semaphoreWait(resumeCommandsSemaphore,
"Interrupted waiting on resume semaphore");
/*
* Resume the domain by unlocking the EXCLUSIVE lock.
*/
lock.unlock();
}
/**
* Convenience method that waits on a semaphore to be
* released as well as deals with InterruptedExceptions.
*
* @param s semaphore to wait on
* @param logMsg a message to log if InterruptedException caught
*/
private void semaphoreWait(Semaphore s, String logMsg) {
boolean semaphoreReleased = false;
while (!semaphoreReleased) {
try {
s.acquire();
semaphoreReleased = true;
} catch (java.lang.InterruptedException e) {
logger.log(Level.FINE, logMsg, e);
}
}
}
}
/**
* Use this method to temporarily suspend the command lock during
* which other operations may be performed. When the method returns
* the lock will be reestablished.
* This method must be invoked from the same thread which acquired
* the original lock.
*
* @param r A Runnable which will be invoked by the method after the lock is suspended
*/
public static void runWithSuspendedLock(Runnable r) {
Lock lock = null;
try {
// We need to determine the type of lock this thread holds.
if (rwlock.isWriteLockedByCurrentThread()) {
lock = rwlock.writeLock();
} else if (rwlock.getReadHoldCount() > 0) {
lock = rwlock.readLock();
}
if (lock != null)
lock.unlock();
// Run the caller's commands without a lock in place.
r.run();
} finally {
// Relock before returning. This may block if someone else
// already grabbed the lock.
if (lock != null)
lock.lock();
}
}
}