/*
* 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.exoplatform.services.jcr.impl.core.query.lucene;
import org.apache.lucene.store.Directory;
import org.exoplatform.services.jcr.impl.core.query.lucene.directory.IndexInputStream;
import org.exoplatform.services.jcr.impl.core.query.lucene.directory.IndexOutputStream;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.ArrayList;
import java.util.List;
/**
* Implements a redo log for changes that have not been committed to disk. While
* nodes are added to and removed from the volatile index (held in memory) a
* redo log is written to keep track of the changes. In case the Jackrabbit
* process terminates unexpected the redo log is applied when Jackrabbit is
* restarted the next time.
* <br>
* This class is not thread-safe.
*/
class RedoLog
{
/**
* Logger instance for this class
*/
private static final Logger log = LoggerFactory.getLogger("exo.jcr.component.core.RedoLog");
/**
* Default name of the redo log file
*/
private static final String REDO_LOG = "redo.log";
/**
* Implements a {@link ActionCollector} that counts all entries and sets
* {@link #entryCount}.
*/
private final ActionCollector ENTRY_COUNTER = new ActionCollector()
{
public void collect(MultiIndex.Action a)
{
entryCount++;
}
};
/**
* The directory where the log file is stored.
*/
private final Directory dir;
/**
* The number of log entries in the log file
*/
private int entryCount = 0;
/**
* Writer to the log file
*/
private Writer out;
/**
* Creates a new <code>RedoLog</code> instance, which stores its log in the
* given directory.
*
* @param dir the directory where the redo log file is located.
* @throws IOException if an error occurs while reading the redo log.
*/
RedoLog(Directory dir) throws IOException
{
this.dir = dir;
read(ENTRY_COUNTER);
}
/**
* Returns <code>true</code> if this redo log contains any entries,
* <code>false</code> otherwise.
* @return <code>true</code> if this redo log contains any entries,
* <code>false</code> otherwise.
*/
boolean hasEntries()
{
return entryCount > 0;
}
/**
* Returns the number of entries in this redo log.
* @return the number of entries in this redo log.
*/
int getSize()
{
return entryCount;
}
/**
* Returns a List with all {@link MultiIndex.Action} instances in the
* redo log.
*
* @return an List with all {@link MultiIndex.Action} instances in the
* redo log.
* @throws IOException if an error occurs while reading from the redo log.
*/
List<MultiIndex.Action> getActions() throws IOException
{
final List<MultiIndex.Action> actions = new ArrayList<MultiIndex.Action>();
read(new ActionCollector()
{
public void collect(MultiIndex.Action a)
{
actions.add(a);
}
});
return actions;
}
/**
* Appends an action to the log.
*
* @param action the action to append.
* @throws IOException if the node cannot be written to the redo
* log.
*/
void append(final MultiIndex.Action action) throws IOException
{
initOut();
out.write(action.toString() + "\n");
entryCount++;
}
/**
* Flushes all pending writes to the underlying file.
* @throws IOException if an error occurs while writing.
*/
void flush() throws IOException
{
if (out != null)
{
out.flush();
}
}
/**
* Clears the redo log.
* @throws IOException if the redo log cannot be cleared.
*/
synchronized void clear() throws IOException
{
if (out != null)
{
out.close();
out = null;
}
try
{
if (dir.fileExists(REDO_LOG))
{
dir.deleteFile(REDO_LOG);
}
}
catch (IOException e)
{
log.error(e.getLocalizedMessage(), e);
throw e;
}
entryCount = 0;
}
/**
* Initializes the {@link #out} stream if it is not yet set.
* @throws IOException if an error occurs while creating the
* output stream.
*/
private synchronized void initOut() throws IOException
{
if (out == null)
{
OutputStream os = new IndexOutputStream(dir.createOutput(REDO_LOG));
out = new BufferedWriter(new OutputStreamWriter(os));
}
}
/**
* Reads the log file and calls back {@link RedoLog.ActionCollector}.
*
* @param collector called back for each {@link MultiIndex.Action} read.
* @throws IOException if an error occurs while reading from the
* log file.
*/
private void read(final ActionCollector collector) throws IOException
{
if (!dir.fileExists(REDO_LOG))
{
return;
}
InputStream in = new IndexInputStream(dir.openInput(REDO_LOG));
BufferedReader reader = null;
try
{
reader = new BufferedReader(new InputStreamReader(in));
String line;
while ((line = reader.readLine()) != null)
{
try
{
collector.collect(MultiIndex.Action.fromString(line));
}
catch (IllegalArgumentException e)
{
log.warn("Malformed redo entry: " + e.getMessage());
}
}
}
finally
{
if (reader != null)
{
try
{
reader.close();
}
catch (IOException e)
{
log.warn("Exception while closing redo log: " + e.toString());
}
}
if (in != null)
{
try
{
in.close();
}
catch (IOException e)
{
log.warn("Exception while closing redo log: " + e.toString());
}
}
}
}
//-----------------------< internal >---------------------------------------
/**
* Helper interface to collect Actions read from the redo log.
*/
interface ActionCollector
{
/** Called when an action is created */
void collect(MultiIndex.Action action);
}
}