/**
* Cache.java
* Copyright 2006 by Michael Peter Christen
* First released 26.10.2006 at http://yacy.net
*
* $LastChangedDate$
* $LastChangedRevision$
* $LastChangedBy$
*
* This library 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 library 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 program in the file lgpl21.txt
* If not, see <http://www.gnu.org/licenses/>.
*/
package net.yacy.kelondro.index;
import java.io.IOException;
import java.util.Collection;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import net.yacy.cora.order.CloneableIterator;
import net.yacy.cora.util.SpaceExceededException;
import net.yacy.kelondro.index.Row.Entry;
import net.yacy.kelondro.util.MemoryControl;
public final class Cache implements Index, Iterable<Row.Entry> {
// this is a combined read cache and write buffer
// we maintain four tables:
// - a read-cache
// - a miss-cache
// - a write buffer for rows that are not contained in the target index
// - a write buffer for rows that are known to be contained in target
// furthermore, if we access a kelondroFlexTable, we can use the ram index of the underlying index
// static object tracker; stores information about object cache usage
private static final TreeMap<String, Cache> objectTracker = new TreeMap<String, Cache>();
private static final long memStopGrow = 40 * 1024 * 1024; // a limit for the node cache to stop growing if less than this memory amount is available
private static final long memStartShrink = 20 * 1024 * 1024; // a limit for the node cache to start with shrinking if less than this memory amount is available
// class objects
private final Index index; // the back-end of the cache
private RowSet readHitCache; // contains a complete copy of the cached objects
private RowSet readMissCache; // contains only the keys of the objects that had been a miss
private Row keyrow;
private int readHit, readMiss, writeUnique, writeDouble, cacheDelete, cacheFlush;
private int hasnotHit, hasnotMiss, hasnotUnique, hasnotDouble, hasnotDelete;
private final int hitLimit, missLimit;
/**
* create a ObjectIndex cache. The cache may either limited by a number of entries in the hit/miss cache
* or the cache size can only be limited by the available RAM
* @param backupIndex the ObjectIndex that is cached
* @param hitLimit a limit of cache hit entries. If given as value <= 0, then only the RAM limits the size
* @param missLimit a limit of cache miss entries. If given as value <= 0, then only the RAM limits the size
*/
public Cache(final Index backupIndex, final int hitLimit, final int missLimit) {
this.index = backupIndex;
this.hitLimit = hitLimit;
this.missLimit = missLimit;
init();
objectTracker.put(backupIndex.filename(), this);
}
private void init() {
final Row row = this.index.row();
this.keyrow = new Row(new Column[]{row.column(0)}, row.objectOrder);
this.readHitCache = new RowSet(row);
this.readMissCache = new RowSet(this.keyrow);
this.readHit = 0;
this.readMiss = 0;
this.writeUnique = 0;
this.writeDouble = 0;
this.cacheDelete = 0;
this.cacheFlush = 0;
this.hasnotHit = 0;
this.hasnotMiss = 0;
this.hasnotUnique = 0;
this.hasnotDouble = 0;
this.hasnotDelete = 0;
}
@Override
public long mem() {
return this.index.mem() + this.readHitCache.mem() + this.readMissCache.mem();
}
@Override
public void optimize() {
this.index.optimize();
this.readHitCache.optimize();
this.readMissCache.optimize();
}
public final int writeBufferSize() {
return 0;
}
public final static long getMemStopGrow() {
return memStopGrow ;
}
public final static long getMemStartShrink() {
return memStartShrink ;
}
public final int getHitLimit() {
return this.hitLimit;
}
public final int getMissLimit() {
return this.missLimit;
}
@Override
public byte[] smallestKey() {
return this.index.smallestKey();
}
@Override
public byte[] largestKey() {
return this.index.largestKey();
}
public static final Iterator<String> filenames() {
// iterates string objects; all file names from record tracker
return objectTracker.keySet().iterator();
}
public enum StatKeys {
objectHitChunkSize,
objectHitCacheCount,
objectHitMem,
objectHitCacheReadHit,
objectHitCacheReadMiss,
objectHitCacheWriteUnique,
objectHitCacheWriteDouble,
objectHitCacheDeletes,
objectHitCacheFlushes,
objectMissChunkSize,
objectMissCacheCount,
objectMissMem,
objectMissCacheReadHit,
objectMissCacheReadMiss,
objectMissCacheWriteUnique,
objectMissCacheWriteDouble,
objectMissCacheDeletes,
objectMissCacheFlushes;
}
public static final Map<StatKeys, String> memoryStats(final String filename) {
// returns a map for each file in the tracker;
// the map represents properties for each record oobjects,
// i.e. for cache memory allocation
final Cache theObjectsCache = objectTracker.get(filename);
return theObjectsCache.memoryStats();
}
private final Map<StatKeys, String> memoryStats() {
// returns statistical data about this object
final HashMap<StatKeys, String> map = new HashMap<StatKeys, String>(20);
map.put(StatKeys.objectHitChunkSize, (this.readHitCache == null) ? "0" : Integer.toString(this.readHitCache.rowdef.objectsize));
map.put(StatKeys.objectHitCacheCount, (this.readHitCache == null) ? "0" : Integer.toString(this.readHitCache.size()));
map.put(StatKeys.objectHitMem, (this.readHitCache == null) ? "0" : Long.toString(this.readHitCache.rowdef.objectsize * this.readHitCache.size()));
map.put(StatKeys.objectHitCacheReadHit, Integer.toString(this.readHit));
map.put(StatKeys.objectHitCacheReadMiss, Integer.toString(this.readMiss));
map.put(StatKeys.objectHitCacheWriteUnique, Integer.toString(this.writeUnique));
map.put(StatKeys.objectHitCacheWriteDouble, Integer.toString(this.writeDouble));
map.put(StatKeys.objectHitCacheDeletes, Integer.toString(this.cacheDelete));
map.put(StatKeys.objectHitCacheFlushes, Integer.toString(this.cacheFlush));
map.put(StatKeys.objectMissChunkSize, (this.readMissCache == null) ? "0" : Integer.toString(this.readMissCache.rowdef.objectsize));
map.put(StatKeys.objectMissCacheCount, (this.readMissCache == null) ? "0" : Integer.toString(this.readMissCache.size()));
map.put(StatKeys.objectMissMem, (this.readMissCache == null) ? "0" : Long.toString(this.readMissCache.rowdef.objectsize * this.readMissCache.size()));
map.put(StatKeys.objectMissCacheReadHit, Integer.toString(this.hasnotHit));
map.put(StatKeys.objectMissCacheReadMiss, Integer.toString(this.hasnotMiss));
map.put(StatKeys.objectMissCacheWriteUnique, Integer.toString(this.hasnotUnique));
map.put(StatKeys.objectMissCacheWriteDouble, Integer.toString(this.hasnotDouble));
map.put(StatKeys.objectMissCacheDeletes, Integer.toString(this.hasnotDelete));
map.put(StatKeys.objectMissCacheFlushes, "0"); // a miss cache flush can only happen if we have a deletion cache (which we dont have)
// future feature .. map.put("objectElderTimeRead", index.profile().)
return map;
}
/**
* checks for space in the miss cache
* @return true if it is allowed to write into this cache
*/
private final boolean checkMissSpace() {
// returns true if it is allowed to write into this cache
if (this.readMissCache == null) return false;
// check given limitation
if (this.missLimit > 0 && this.readMissCache.size() >= this.missLimit) return false;
// check memory
long available = MemoryControl.available();
if (MemoryControl.shortStatus() || available - 2 * 1024 * 1024 < this.readMissCache.memoryNeededForGrow()) {
this.readMissCache.clear();
}
available = MemoryControl.available();
return (available - 2 * 1024 * 1024 > this.readMissCache.memoryNeededForGrow());
}
/**
* checks for space in the hit cache
* @return true if it is allowed to write into this cache
*/
private final boolean checkHitSpace() {
// returns true if it is allowed to write into this cache
if (this.readHitCache == null) return false;
// check given limitation
if (this.hitLimit > 0 && this.readHitCache.size() >= this.hitLimit) return false;
// check memory
long available = MemoryControl.available();
if (MemoryControl.shortStatus() || available - 2 * 1024 * 1024 < this.readHitCache.memoryNeededForGrow()) {
this.readHitCache.clear();
}
available = MemoryControl.available();
return (available - 2 * 1024 * 1024 > this.readHitCache.memoryNeededForGrow());
}
public final synchronized void clearCache() {
if (this.readMissCache != null) this.readMissCache.clear();
if (this.readHitCache != null) this.readHitCache.clear();
}
@Override
public final synchronized void close() {
this.index.close();
this.readHitCache = null;
this.readMissCache = null;
}
@Override
public final synchronized boolean has(final byte[] key) {
// first look into the miss cache
if (this.readMissCache != null) {
if (this.readMissCache.has(key)) {
this.hasnotHit++;
return false;
}
this.hasnotMiss++;
}
// then try the hit cache and the buffers
if (this.readHitCache != null) {
if (this.readHitCache.has(key)) {
this.readHit++;
return true;
}
this.readMiss++;
}
// finally ask the back-end index
return this.index.has(key);
}
@Override
public final synchronized Row.Entry get(final byte[] key, final boolean cachecopy) throws IOException {
// first look into the miss cache
if (this.readMissCache != null) {
if (this.readMissCache.has(key)) {
this.hasnotHit++;
return null;
}
this.hasnotMiss++;
}
Row.Entry entry = null;
// then try the hit cache and the buffers
if (this.readHitCache != null) {
entry = this.readHitCache.get(key, cachecopy);
if (entry != null) {
this.readHit++;
return entry;
}
}
// finally ask the back-end index
this.readMiss++;
entry = this.index.get(key, cachecopy);
// learn from result
if (entry == null) {
if (checkMissSpace()) try {
final Row.Entry dummy = this.readMissCache.replace(this.readMissCache.row().newEntry(key));
if (dummy == null) this.hasnotUnique++; else this.hasnotDouble++;
} catch (final SpaceExceededException e) {
clearCache();
}
return null;
}
if (checkHitSpace()) try {
final Row.Entry dummy = this.readHitCache.replace(entry);
if (dummy == null) this.writeUnique++; else this.writeDouble++;
} catch (final SpaceExceededException e) {
clearCache();
}
return entry;
}
@Override
public Map<byte[], Row.Entry> get(final Collection<byte[]> keys, final boolean forcecopy) throws IOException, InterruptedException {
final Map<byte[], Row.Entry> map = new TreeMap<byte[], Row.Entry>(row().objectOrder);
Row.Entry entry;
for (final byte[] key: keys) {
entry = get(key, forcecopy);
if (entry != null) map.put(key, entry);
}
return map;
}
@Override
public final synchronized boolean put(final Row.Entry row) throws IOException, SpaceExceededException {
assert (row != null);
assert (row.columns() == row().columns());
//assert (!(serverLog.allZero(row.getColBytes(index.primarykey()))));
final byte[] key = row.getPrimaryKeyBytes();
checkHitSpace();
// remove entry from miss- and hit-cache
if (this.readMissCache != null) {
if (this.readMissCache.delete(key)) {
this.hasnotHit++;
}
}
// write to the back-end
boolean c;
try {
c = this.index.put(row);
} catch (final SpaceExceededException e1) {
// flush all caches to get more memory
clearCache();
c = this.index.put(row); // try again
}
if (checkHitSpace()) try {
final Row.Entry dummy = this.readHitCache.replace(row); // overwrite old entry
if (dummy == null) this.writeUnique++; else this.writeDouble++;
} catch (final SpaceExceededException e) {
clearCache();
}
return c;
}
@Override
public final synchronized Row.Entry replace(final Row.Entry row) throws IOException, SpaceExceededException {
assert (row != null);
assert (row.columns() == row().columns());
//assert (!(serverLog.allZero(row.getColBytes(index.primarykey()))));
final byte[] key = row.getPrimaryKeyBytes();
checkHitSpace();
// remove entry from miss- and hit-cache
if (this.readMissCache != null) {
if (this.readMissCache.delete(key)) {
this.hasnotHit++;
// the entry does not exist before
try {
this.index.put(row);
} catch (final SpaceExceededException e1) {
// flush all caches to get more memory
clearCache();
this.index.put(row); // try again
}
// write to backend
if (checkHitSpace()) try {
final Row.Entry dummy = this.readHitCache.replace(row); // learn that entry
if (dummy == null) this.writeUnique++; else this.writeDouble++;
} catch (final SpaceExceededException e) {
clearCache();
}
return null;
}
}
Row.Entry entry = null;
// write to the back-end
try {
entry = this.index.replace(row);
} catch (final SpaceExceededException e1) {
// flush all caches to get more memory
clearCache();
this.index.replace(row); // try again
}
if (checkHitSpace()) try {
final Row.Entry dummy = this.readHitCache.replace(row); // learn that entry
if (dummy == null) this.writeUnique++; else this.writeDouble++;
} catch (final SpaceExceededException e) {
clearCache();
}
return entry;
}
@Override
public final synchronized void addUnique(final Row.Entry row) throws IOException, SpaceExceededException {
assert (row != null);
assert (row.columns() == row().columns());
//assert (!(serverLog.allZero(row.getColBytes(index.primarykey()))));
final byte[] key = row.getPrimaryKeyBytes();
checkHitSpace();
// remove entry from miss- and hit-cache
if (this.readMissCache != null) {
this.readMissCache.delete(key);
this.hasnotDelete++;
// the entry does not exist before
}
// the worst case: we must write to the back-end directly
try {
this.index.addUnique(row);
} catch (final SpaceExceededException e1) {
// flush all caches to get more memory
clearCache();
this.index.addUnique(row); // try again
}
if (checkHitSpace()) try {
final Row.Entry dummy = this.readHitCache.replace(row); // learn that entry
if (dummy == null) this.writeUnique++; else this.writeDouble++;
} catch (final SpaceExceededException e) {
clearCache();
}
}
public final synchronized void addUnique(final Row.Entry row, final Date entryDate) throws IOException, SpaceExceededException {
if (entryDate == null) {
addUnique(row);
return;
}
assert (row != null);
assert (row.columns() == row().columns());
final byte[] key = row.getPrimaryKeyBytes();
checkHitSpace();
// remove entry from miss- and hit-cache
if (this.readMissCache != null) {
this.readMissCache.delete(key);
this.hasnotDelete++;
}
// the worst case: we must write to the backend directly
try {
this.index.addUnique(row);
} catch (final SpaceExceededException e1) {
// flush all caches to get more memory
clearCache();
this.index.addUnique(row); // try again
}
if (checkHitSpace()) try {
final Row.Entry dummy = this.readHitCache.replace(row); // learn that entry
if (dummy == null) this.writeUnique++; else this.writeDouble++;
} catch (final SpaceExceededException e) {
clearCache();
}
}
public final synchronized void addUnique(final List<Row.Entry> rows) throws IOException, SpaceExceededException {
final Iterator<Row.Entry> i = rows.iterator();
Row.Entry r;
while (i.hasNext()) {
r = i.next();
try {
addUnique(r);
} catch (final SpaceExceededException e) {
// flush all caches to get more memory
clearCache();
addUnique(r); // try again
}
}
}
@Override
public final synchronized List<RowCollection> removeDoubles() throws IOException, SpaceExceededException {
return this.index.removeDoubles();
// todo: remove reported entries from the cache!!!
}
@Override
public final synchronized boolean delete(final byte[] key) throws IOException {
checkMissSpace();
// add entry to miss-cache
if (checkMissSpace()) try {
// set the miss cache; if there was already an entry we know that the return value must be null
final Row.Entry dummy = this.readMissCache.replace(this.readMissCache.row().newEntry(key));
if (dummy == null) {
this.hasnotUnique++;
} else {
this.hasnotHit++;
this.hasnotDouble++;
}
} catch (final SpaceExceededException e) {
clearCache();
}
// remove entry from hit-cache
if (this.readHitCache != null) {
final Row.Entry entry = this.readHitCache.remove(key);
if (entry == null) {
this.readMiss++;
} else {
this.readHit++;
this.cacheDelete++;
}
}
return this.index.delete(key);
}
@Override
public final synchronized Row.Entry remove(final byte[] key) throws IOException {
checkMissSpace();
// add entry to miss-cache
if (checkMissSpace()) try {
// set the miss cache; if there was already an entry we know that the return value must be null
final Row.Entry dummy = this.readMissCache.replace(this.readMissCache.row().newEntry(key));
if (dummy == null) {
this.hasnotUnique++;
} else {
this.hasnotHit++;
this.hasnotDouble++;
}
} catch (final SpaceExceededException e) {
clearCache();
}
// remove entry from hit-cache
if (this.readHitCache != null) {
final Row.Entry entry = this.readHitCache.remove(key);
if (entry == null) {
this.readMiss++;
} else {
this.readHit++;
this.cacheDelete++;
}
}
return this.index.remove(key);
}
@Override
public final synchronized Row.Entry removeOne() throws IOException {
checkMissSpace();
final Row.Entry entry = this.index.removeOne();
if (entry == null) return null;
final byte[] key = entry.getPrimaryKeyBytes();
if (checkMissSpace()) try {
final Row.Entry dummy = this.readMissCache.replace(this.readMissCache.row().newEntry(key));
if (dummy == null) this.hasnotUnique++; else this.hasnotDouble++;
} catch (final SpaceExceededException e) {
clearCache();
}
if (this.readHitCache != null) {
if (this.readHitCache.delete(key)) this.cacheDelete++;
}
return entry;
}
@Override
public synchronized List<Row.Entry> top(final int count) throws IOException {
return this.index.top(count);
}
@Override
public synchronized List<Row.Entry> random(final int count) throws IOException {
return this.index.random(count);
}
@Override
public final synchronized Row row() {
return this.index.row();
}
@Override
public final synchronized CloneableIterator<byte[]> keys(final boolean up, final byte[] firstKey) throws IOException {
return this.index.keys(up, firstKey);
}
@Override
public final synchronized CloneableIterator<Row.Entry> rows(final boolean up, final byte[] firstKey) throws IOException {
return this.index.rows(up, firstKey);
}
@Override
public final Iterator<Entry> iterator() {
try {
return rows();
} catch (final IOException e) {
return null;
}
}
@Override
public final synchronized CloneableIterator<Row.Entry> rows() throws IOException {
return this.index.rows();
}
@Override
public final int size() {
return this.index.size();
}
@Override
public final boolean isEmpty() {
return this.index.isEmpty();
}
@Override
public final String filename() {
return this.index.filename();
}
@Override
public final void clear() throws IOException {
this.index.clear();
init();
}
@Override
public final void deleteOnExit() {
this.index.deleteOnExit();
}
}