/**
* 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.hedwig.server.persistence;
import java.util.LinkedList;
import java.util.Queue;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hedwig.protocol.PubSubProtocol.Message;
import org.apache.hedwig.server.common.UnexpectedError;
/**
* This class is NOT thread safe. It need not be thread-safe because our
* read-ahead cache will operate with only 1 thread
*
*/
public class CacheValue {
static Logger logger = LoggerFactory.getLogger(ReadAheadCache.class);
Queue<ScanCallbackWithContext> callbacks = new LinkedList<ScanCallbackWithContext>();
Message message;
long timeOfAddition = 0;
public CacheValue() {
}
public boolean isStub() {
return message == null;
}
public long getTimeOfAddition() {
if (message == null) {
throw new UnexpectedError("Time of add requested from a stub");
}
return timeOfAddition;
}
public void setMessageAndInvokeCallbacks(Message message, long currTime) {
if (this.message != null) {
// Duplicate read for the same message coming back
return;
}
this.message = message;
this.timeOfAddition = currTime;
ScanCallbackWithContext callbackWithCtx;
if (logger.isDebugEnabled()) {
logger.debug("Invoking " + callbacks.size() + " callbacks for " + " message added to cache");
}
while ((callbackWithCtx = callbacks.poll()) != null) {
callbackWithCtx.getScanCallback().messageScanned(callbackWithCtx.getCtx(), message);
}
}
public void addCallback(ScanCallback callback, Object ctx) {
if (!isStub()) {
// call the callback right away
callback.messageScanned(ctx, message);
return;
}
callbacks.add(new ScanCallbackWithContext(callback, ctx));
}
public Message getMessage() {
return message;
}
public void setErrorAndInvokeCallbacks(Exception exception) {
ScanCallbackWithContext callbackWithCtx;
while ((callbackWithCtx = callbacks.poll()) != null) {
callbackWithCtx.getScanCallback().scanFailed(callbackWithCtx.getCtx(), exception);
}
}
}