/*
* JBoss, Home of Professional Open Source
* Copyright 2009 Red Hat Inc. and/or its affiliates and other
* contributors as indicated by the @author tags. All rights reserved.
* See the copyright.txt in the distribution for a full listing of
* individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.infinispan.loaders.decorators;
import org.infinispan.Cache;
import org.infinispan.container.DataContainer;
import org.infinispan.container.entries.InternalCacheEntry;
import org.infinispan.loaders.CacheLoaderException;
import org.infinispan.loaders.CacheStore;
import org.infinispan.loaders.modifications.Modification;
import org.infinispan.manager.EmbeddedCacheManager;
import org.infinispan.notifications.Listener;
import org.infinispan.notifications.cachemanagerlistener.annotation.CacheStarted;
import org.infinispan.notifications.cachemanagerlistener.annotation.ViewChanged;
import org.infinispan.notifications.cachemanagerlistener.event.Event;
import org.infinispan.notifications.cachemanagerlistener.event.ViewChangedEvent;
import org.infinispan.remoting.transport.Address;
import org.infinispan.transaction.xa.GlobalTransaction;
import org.infinispan.util.logging.Log;
import org.infinispan.util.logging.LogFactory;
import java.io.ObjectInput;
import java.util.List;
import java.util.Set;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
/**
* SingletonStore is a delegating cache store used for situations when only one instance should interact with the
* underlying store. The coordinator of the cluster will be responsible for the underlying CacheStore.
* <p/>
* SingletonStore is a simply facade to a real CacheStore implementation. It always delegates reads to the real
* CacheStore.
* <p/>
* Writes are delegated <i>only if</i> this SingletonStore is currently the coordinator. This avoids having all stores in
* a cluster writing the same data to the same underlying store. Although not incorrect (e.g. a DB will just discard
* additional INSERTs for the same key, and throw an exception), this will avoid a lot of redundant work.
* <p/>
* Whenever the current coordinator dies (or leaves), the second in line will take over. That SingletonStore will then
* pass writes through to its underlying CacheStore. Optionally, when a new coordinator takes over the Singleton, it can
* push the in-memory state to the cache cacheStore, within a time constraint.
*
* @author Bela Ban
* @author <a href="mailto:galder.zamarreno@jboss.com">Galder Zamarreno</a>
* @author Manik Surtani
* @since 4.0
*/
public class SingletonStore extends AbstractDelegatingStore {
private static final Log log = LogFactory.getLog(SingletonStore.class);
private static final boolean trace = log.isTraceEnabled();
EmbeddedCacheManager cacheManager;
Cache<Object, Object> cache;
SingletonStoreConfig config;
/**
* Name of thread that should pushing in-memory state to cache loader.
*/
private static final String THREAD_NAME = "SingletonStorePusherThread";
/**
* Executor service used to submit tasks to push in-memory state.
*/
private final ExecutorService executor;
/**
* Future result of the in-memory push state task. This allows SingletonStore to check whether there's any push taks
* on going.
*/
Future<?> pushStateFuture; /* FutureTask guarantess a safe publication of the result */
/**
* Address instance that allows SingletonStore to find out whether it became the coordinator of the cluster, or
* whether it stopped being it. This dictates whether the SingletonStore is active or not.
*/
private Address localAddress;
/**
* Whether the the current cache is the coordinator and therefore SingletonStore is active. Being active means
* delegating calls to the underlying cache loader.
*/
private volatile boolean active;
public SingletonStore(CacheStore delegate, Cache<Object, Object> cache, SingletonStoreConfig config) {
super(delegate);
this.cacheManager = cache == null ? null : cache.getCacheManager();
this.cache = cache;
this.config = config;
executor = Executors.newSingleThreadExecutor(new ThreadFactory() {
@Override
public Thread newThread(Runnable r) {
return new Thread(r, THREAD_NAME);
}
});
}
// -------------- Basic write methods
// only delegate if the current instance is active
@Override
public void store(InternalCacheEntry ed) throws CacheLoaderException {
if (active) {
if (trace) log.tracef("Storing key %s. Instance: %s", ed.getKey(), this);
super.store(ed);
} else if (trace) log.tracef("Not storing key %s. Instance: %s", ed.getKey(), this);
}
@Override
public void fromStream(ObjectInput inputStream) throws CacheLoaderException {
if (active) super.fromStream(inputStream);
}
@Override
public void clear() throws CacheLoaderException {
if (active) super.clear();
}
@Override
public boolean remove(Object key) throws CacheLoaderException {
return active && super.remove(key);
}
@Override
public void purgeExpired() throws CacheLoaderException {
if (active) super.purgeExpired();
}
@Override
public void commit(GlobalTransaction tx) throws CacheLoaderException {
if (active) super.commit(tx);
}
@Override
public void rollback(GlobalTransaction tx) {
if (active) super.rollback(tx);
}
@Override
public void prepare(List<? extends Modification> list, GlobalTransaction tx, boolean isOnePhase) throws CacheLoaderException {
if (active) super.prepare(list, tx, isOnePhase);
}
@Override
public void start() throws CacheLoaderException {
cacheManager.addListener(new SingletonStoreListener());
super.start();
}
@Override
public void stop() throws CacheLoaderException {
try {
super.stop();
} finally {
executor.shutdownNow();
}
}
/**
* Factory method for the creation of a Callable task in charge of pushing in-memory state to cache loader.
*
* @return new instance of Callable<?> whose call() method either throws an exception or returns null if the task was
* successfull.
*/
protected Callable<?> createPushStateTask() {
return new Callable() {
@Override
public Object call() throws Exception {
final boolean debugEnabled = log.isDebugEnabled();
if (debugEnabled) log.debug("start pushing in-memory state to cache cacheLoader");
pushState(cache);
if (debugEnabled) log.debug("in-memory state passed to cache cacheLoader successfully");
return null;
}
};
}
/**
* Pushes the state of a specific cache by reading the cache's data and putting in the cache store. This method is
* called recursively so that it iterates through the whole cache.
*
* @throws Exception if there's any issues reading the data from the cache or pushing data to the cache store.
*/
protected void pushState(final Cache<Object, Object> cache) throws Exception {
DataContainer dc = cache.getAdvancedCache().getDataContainer();
Set<Object> keys = dc.keySet(null);
InternalCacheEntry entry;
for (Object k : keys) if ((entry = dc.get(k, null)) != null) store(entry);
}
/**
* Method that waits for the in-memory to cache loader state to finish. This method's called in case a push state is
* already in progress and we need to wait for it to finish.
*
* @param future instance of Future representing the on going push task
* @param timeout time to wait for the push task to finish
* @param unit instance of TimeUnit representing the unit of timeout
*/
protected void awaitForPushToFinish(Future<?> future, long timeout, TimeUnit unit) {
final boolean debugEnabled = log.isDebugEnabled();
try {
if (debugEnabled) log.debug("wait for state push to cache loader to finish");
future.get(timeout, unit);
}
catch (TimeoutException e) {
if (debugEnabled) log.debug("timed out waiting for state push to cache loader to finish");
}
catch (ExecutionException e) {
if (debugEnabled) log.debug("exception reported waiting for state push to cache loader to finish");
}
catch (InterruptedException ie) {
/* Re-assert the thread's interrupted status */
Thread.currentThread().interrupt();
if (trace) log.trace("wait for state push to cache loader to finish was interrupted");
}
}
/**
* Method called when the cache either becomes the coordinator or stops being the coordinator. If it becomes the
* coordinator, it can optionally start the in-memory state transfer to the underlying cache store.
*
* @param newActiveState true if the cache just became the coordinator, false if the cache stopped being the
* coordinator.
*/
protected void activeStatusChanged(boolean newActiveState) throws PushStateException {
active = newActiveState;
log.debugf("changed mode %s", this);
if (active && config.isPushStateWhenCoordinator()) doPushState();
}
/**
* Indicates whether the current cache is the coordinator of the cluster. This implementation assumes that the
* coordinator is the first member in the list.
*
* @param newView View instance containing the new view of the cluster
* @return whether the current cache is the coordinator or not.
*/
private boolean isCoordinator(List<Address> newView, Address currentAddress) {
if (!currentAddress.equals(localAddress)) localAddress = currentAddress;
if (localAddress != null) {
return !newView.isEmpty() && localAddress.equals(newView.get(0));
} else {
/* Invalid new view, so previous value returned */
return active;
}
}
/**
* Called when the SingletonStore discovers that the cache has become the coordinator and push in memory state has
* been enabled. It might not actually push the state if there's an ongoing push task running, in which case will
* wait for the push task to finish.
*
* @throws PushStateException when the push state task reports an issue.
*/
private void doPushState() throws PushStateException {
if (pushStateFuture == null || pushStateFuture.isDone()) {
Callable<?> task = createPushStateTask();
pushStateFuture = executor.submit(task);
try {
waitForTaskToFinish(pushStateFuture, config.getPushStateTimeout(), TimeUnit.MILLISECONDS);
}
catch (Exception e) {
throw new PushStateException("unable to complete in memory state push to cache loader", e);
}
} else {
/* at the most, we wait for push state timeout value. if it push task finishes earlier, this call
* will stop when the push task finishes, otherwise a timeout exception will be reported */
awaitForPushToFinish(pushStateFuture, config.getPushStateTimeout(), TimeUnit.MILLISECONDS);
}
}
/**
* Waits, within a time constraint, for a task to finish.
*
* @param future represents the task waiting to finish.
* @param timeout maximum time to wait for the time to finish.
* @param unit instance of TimeUnit representing the unit of timeout
* @throws Exception if any issues are reported while waiting for the task to finish
*/
private void waitForTaskToFinish(Future<?> future, long timeout, TimeUnit unit) throws Exception {
try {
future.get(timeout, unit);
}
catch (TimeoutException e) {
throw new Exception("task timed out", e);
}
catch (InterruptedException e) {
/* Re-assert the thread's interrupted status */
Thread.currentThread().interrupt();
if (trace) log.trace("task was interrupted");
}
finally {
/* no-op if task is completed */
future.cancel(true); /* interrupt if running */
}
}
/**
* Cache listener that reacts to cluster topology changes to find out whether a new coordinator is elected.
* SingletonStore reacts to these changes in order to decide which cache should interact with the underlying cache
* store.
*/
@Listener
public class SingletonStoreListener {
/**
* Cache started, check whether the cache is the coordinator and set the singleton store's active status.
*/
@CacheStarted
public void cacheStarted(Event e) {
localAddress = cacheManager.getAddress();
active = cacheManager.isCoordinator();
}
/**
* The cluster formation changed, so determine whether the current cache stopped being the coordinator or became
* the coordinator. This method can lead to an optional in memory to cache loader state push, if the current cache
* became the coordinator. This method will report any issues that could potentially arise from this push.
*/
@ViewChanged
public void viewChange(ViewChangedEvent event) {
boolean tmp = isCoordinator(event.getNewMembers(), event.getLocalAddress());
if (active != tmp) {
try {
activeStatusChanged(tmp);
}
catch (PushStateException e) {
log.errorChangingSingletonStoreStatus(e);
}
}
}
}
/**
* Exception representing any issues that arise from pushing the in-memory state to the cache loader.
*/
public static class PushStateException extends Exception {
private static final long serialVersionUID = 5542893943730200886L;
public PushStateException(String message, Throwable cause) {
super(message, cause);
}
public PushStateException(Throwable cause) {
super(cause);
}
}
@Override
public String toString() {
return "SingletonStore: localAddress=" + localAddress + ", active=" + active;
}
}