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645 lines (551 loc) · 18.5 KB
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/*
* Copyright (c) 2012 Jan Kotek
*
* Licensed 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.mapdb;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.*;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
* Naive implementation of Snapshots on top of StorageEngine.
* On update it takes old value and stores it aside.
* <p/>
* TODO merge snapshots down with Storage for best performance
*
* @author Jan Kotek
*/
public class TxEngine extends EngineWrapper {
protected static final Object TOMBSTONE = new Object();
protected final ReentrantReadWriteLock commitLock = new ReentrantReadWriteLock(CC.FAIR_LOCKS);
protected final ReentrantReadWriteLock[] locks = new ReentrantReadWriteLock[CC.CONCURRENCY];
{
for(int i=0;i<locks.length;i++) locks[i] = new ReentrantReadWriteLock(CC.FAIR_LOCKS);
}
protected volatile boolean uncommitedData = false;
protected Set<Reference<Tx>> txs = new LinkedHashSet<Reference<Tx>>();
protected ReferenceQueue<Tx> txQueue = new ReferenceQueue<Tx>();
protected final boolean fullTx;
protected final Queue<Long> preallocRecids;
protected final int PREALLOC_RECID_SIZE = 128;
protected TxEngine(Engine engine, boolean fullTx) {
super(engine);
this.fullTx = fullTx;
this.preallocRecids = fullTx ? new ArrayBlockingQueue<Long>(PREALLOC_RECID_SIZE) : null;
}
protected Long preallocRecidTake() {
assert(commitLock.isWriteLockedByCurrentThread());
Long recid = preallocRecids.poll();
if(recid!=null) return recid;
if(uncommitedData)
throw new IllegalAccessError("uncommited data");
for(int i=0;i<PREALLOC_RECID_SIZE;i++){
preallocRecids.add(super.preallocate());
}
recid = super.preallocate();
super.commit();
uncommitedData = false;
return recid;
}
public static Engine createSnapshotFor(Engine engine) {
if(engine.isReadOnly())
return engine;
if(engine instanceof TxEngine)
return ((TxEngine)engine).snapshot();
if(engine instanceof EngineWrapper)
createSnapshotFor(((EngineWrapper) engine).getWrappedEngine());
throw new UnsupportedOperationException("Snapshots are not enabled, use DBMaker.snapshotEnable()");
}
@Override
public boolean canSnapshot() {
return true;
}
@Override
public Engine snapshot() {
commitLock.writeLock().lock();
try {
cleanTxQueue();
if(uncommitedData && canRollback())
throw new IllegalAccessError("Can not create snapshot with uncommited data");
return new Tx();
} finally {
commitLock.writeLock().unlock();
}
}
protected void cleanTxQueue(){
assert(commitLock.writeLock().isHeldByCurrentThread());
for(Reference<? extends Tx> ref = txQueue.poll(); ref!=null; ref=txQueue.poll()){
txs.remove(ref);
}
}
@Override
public long preallocate() {
commitLock.writeLock().lock();
try {
uncommitedData = true;
long recid = super.preallocate();
Lock lock = locks[Store.lockPos(recid)].writeLock();
lock.lock();
try{
for(Reference<Tx> txr:txs){
Tx tx = txr.get();
if(tx==null) continue;
tx.old.putIfAbsent(recid,TOMBSTONE);
}
}finally {
lock.unlock();
}
return recid;
} finally {
commitLock.writeLock().unlock();
}
}
@Override
public void preallocate(long[] recids) {
commitLock.writeLock().lock();
try {
uncommitedData = true;
super.preallocate(recids);
for(long recid:recids){
Lock lock = locks[Store.lockPos(recid)].writeLock();
lock.lock();
try{
for(Reference<Tx> txr:txs){
Tx tx = txr.get();
if(tx==null) continue;
tx.old.putIfAbsent(recid,TOMBSTONE);
}
}finally {
lock.unlock();
}
}
} finally {
commitLock.writeLock().unlock();
}
}
@Override
public <A> long put(A value, Serializer<A> serializer) {
commitLock.readLock().lock();
try {
uncommitedData = true;
long recid = super.put(value, serializer);
Lock lock = locks[Store.lockPos(recid)].writeLock();
lock.lock();
try{
for(Reference<Tx> txr:txs){
Tx tx = txr.get();
if(tx==null) continue;
tx.old.putIfAbsent(recid,TOMBSTONE);
}
}finally {
lock.unlock();
}
return recid;
} finally {
commitLock.readLock().unlock();
}
}
@Override
public <A> A get(long recid, Serializer<A> serializer) {
commitLock.readLock().lock();
try {
return super.get(recid, serializer);
} finally {
commitLock.readLock().unlock();
}
}
@Override
public <A> void update(long recid, A value, Serializer<A> serializer) {
commitLock.readLock().lock();
try {
uncommitedData = true;
Lock lock = locks[Store.lockPos(recid)].writeLock();
lock.lock();
try{
Object old = get(recid,serializer);
for(Reference<Tx> txr:txs){
Tx tx = txr.get();
if(tx==null) continue;
tx.old.putIfAbsent(recid,old);
}
super.update(recid, value, serializer);
}finally {
lock.unlock();
}
} finally {
commitLock.readLock().unlock();
}
}
@Override
public <A> boolean compareAndSwap(long recid, A expectedOldValue, A newValue, Serializer<A> serializer) {
commitLock.readLock().lock();
try {
uncommitedData = true;
Lock lock = locks[Store.lockPos(recid)].writeLock();
lock.lock();
try{
boolean ret = super.compareAndSwap(recid, expectedOldValue, newValue, serializer);
if(ret){
for(Reference<Tx> txr:txs){
Tx tx = txr.get();
if(tx==null) continue;
tx.old.putIfAbsent(recid,expectedOldValue);
}
}
return ret;
}finally {
lock.unlock();
}
} finally {
commitLock.readLock().unlock();
}
}
@Override
public <A> void delete(long recid, Serializer<A> serializer) {
commitLock.readLock().lock();
try {
uncommitedData = true;
Lock lock = locks[Store.lockPos(recid)].writeLock();
lock.lock();
try{
Object old = get(recid,serializer);
for(Reference<Tx> txr:txs){
Tx tx = txr.get();
if(tx==null) continue;
tx.old.putIfAbsent(recid,old);
}
super.delete(recid, serializer);
}finally {
lock.unlock();
}
} finally {
commitLock.readLock().unlock();
}
}
@Override
public void close() {
commitLock.writeLock().lock();
try {
super.close();
} finally {
commitLock.writeLock().unlock();
}
}
@Override
public void commit() {
commitLock.writeLock().lock();
try {
cleanTxQueue();
super.commit();
uncommitedData = false;
} finally {
commitLock.writeLock().unlock();
}
}
@Override
public void rollback() {
commitLock.writeLock().lock();
try {
cleanTxQueue();
super.rollback();
uncommitedData = false;
} finally {
commitLock.writeLock().unlock();
}
}
protected void superCommit() {
assert(commitLock.isWriteLockedByCurrentThread());
super.commit();
}
protected <A> void superUpdate(long recid, A value, Serializer<A> serializer) {
assert(commitLock.isWriteLockedByCurrentThread());
super.update(recid,value,serializer);
}
protected <A> void superDelete(long recid, Serializer<A> serializer) {
assert(commitLock.isWriteLockedByCurrentThread());
super.delete(recid,serializer);
}
protected <A> A superGet(long recid, Serializer<A> serializer) {
assert(commitLock.isWriteLockedByCurrentThread());
return super.get(recid,serializer);
}
public class Tx implements Engine{
protected LongConcurrentHashMap old = new LongConcurrentHashMap();
protected LongConcurrentHashMap<Fun.Tuple2> mod =
fullTx ? new LongConcurrentHashMap<Fun.Tuple2>() : null;
protected Collection<Long> usedPreallocatedRecids =
fullTx ? new ArrayList<Long>() : null;
protected final Reference<Tx> ref = new WeakReference<Tx>(this,txQueue);
protected boolean closed = false;
private Store parentEngine;
public Tx(){
assert(commitLock.isWriteLockedByCurrentThread());
txs.add(ref);
}
@Override
public long preallocate() {
if(!fullTx)
throw new UnsupportedOperationException("read-only");
commitLock.writeLock().lock();
try{
Long recid = preallocRecidTake();
usedPreallocatedRecids.add(recid);
return recid;
}finally {
commitLock.writeLock().unlock();
}
}
@Override
public void preallocate(long[] recids) {
if(!fullTx)
throw new UnsupportedOperationException("read-only");
commitLock.writeLock().lock();
try{
for(int i=0;i<recids.length;i++){
Long recid = preallocRecidTake();
usedPreallocatedRecids.add(recid);
recids[i] = recid;
}
}finally {
commitLock.writeLock().unlock();
}
}
@Override
public <A> long put(A value, Serializer<A> serializer) {
if(!fullTx)
throw new UnsupportedOperationException("read-only");
commitLock.writeLock().lock();
try{
Long recid = preallocRecidTake();
usedPreallocatedRecids.add(recid);
mod.put(recid, Fun.t2(value,serializer));
return recid;
}finally {
commitLock.writeLock().unlock();
}
}
@Override
public <A> A get(long recid, Serializer<A> serializer) {
commitLock.readLock().lock();
try{
if(closed) throw new IllegalAccessError("closed");
Lock lock = locks[Store.lockPos(recid)].readLock();
lock.lock();
try{
return getNoLock(recid, serializer);
}finally {
lock.unlock();
}
}finally {
commitLock.readLock().unlock();
}
}
private <A> A getNoLock(long recid, Serializer<A> serializer) {
if(fullTx){
Fun.Tuple2 tu = mod.get(recid);
if(tu!=null){
if(tu.a==TOMBSTONE)
return null;
return (A) tu.a;
}
}
Object oldVal = old.get(recid);
if(oldVal!=null){
if(oldVal==TOMBSTONE)
return null;
return (A) oldVal;
}
return TxEngine.this.get(recid, serializer);
}
@Override
public <A> void update(long recid, A value, Serializer<A> serializer) {
if(!fullTx)
throw new UnsupportedOperationException("read-only");
commitLock.readLock().lock();
try{
mod.put(recid, Fun.t2(value,serializer));
}finally {
commitLock.readLock().unlock();
}
}
@Override
public <A> boolean compareAndSwap(long recid, A expectedOldValue, A newValue, Serializer<A> serializer) {
if(!fullTx)
throw new UnsupportedOperationException("read-only");
commitLock.readLock().lock();
try{
Lock lock = locks[Store.lockPos(recid)].writeLock();
lock.lock();
try{
A oldVal = getNoLock(recid, serializer);
boolean ret = oldVal!=null && oldVal.equals(expectedOldValue);
if(ret){
mod.put(recid,Fun.t2(newValue,serializer));
}
return ret;
}finally {
lock.unlock();
}
}finally {
commitLock.readLock().unlock();
}
}
@Override
public <A> void delete(long recid, Serializer<A> serializer) {
if(!fullTx)
throw new UnsupportedOperationException("read-only");
commitLock.readLock().lock();
try{
mod.put(recid,Fun.t2(TOMBSTONE,serializer));
}finally {
commitLock.readLock().unlock();
}
}
@Override
public void close() {
closed = true;
old.clear();
ref.clear();
}
@Override
public boolean isClosed() {
return closed;
}
@Override
public void commit() {
if(!fullTx)
throw new UnsupportedOperationException("read-only");
commitLock.writeLock().lock();
try{
if(closed) return;
if(uncommitedData)
throw new IllegalAccessError("uncommitted data");
txs.remove(ref);
cleanTxQueue();
if(pojo.hasUnsavedChanges())
pojo.save(this);
//check no other TX has modified our data
LongMap.LongMapIterator oldIter = old.longMapIterator();
while(oldIter.moveToNext()){
long recid = oldIter.key();
for(Reference<Tx> ref2:txs){
Tx tx = ref2.get();
if(tx==this||tx==null) continue;
if(tx.mod.containsKey(recid)){
close();
throw new TxRollbackException();
}
}
}
LongMap.LongMapIterator<Fun.Tuple2> iter = mod.longMapIterator();
while(iter.moveToNext()){
long recid = iter.key();
if(old.containsKey(recid)){
close();
throw new TxRollbackException();
}
}
iter = mod.longMapIterator();
while(iter.moveToNext()){
long recid = iter.key();
Fun.Tuple2 val = iter.value();
Serializer ser = (Serializer) val.b;
Object old = superGet(recid,ser);
if(old==null)
old = TOMBSTONE;
for(Reference<Tx> txr:txs){
Tx tx = txr.get();
if(tx==null||tx==this) continue;
tx.old.putIfAbsent(recid,old);
}
if(val.a==TOMBSTONE){
superDelete(recid, ser);
}else {
superUpdate(recid, val.a, ser);
}
}
//there are no conflicts, so update the POJO in parent
//TODO sort of hack, is it thread safe?
getWrappedEngine().getSerializerPojo().registered = pojo.registered;
superCommit();
close();
}finally {
commitLock.writeLock().unlock();
}
}
@Override
public void rollback() throws UnsupportedOperationException {
if(!fullTx)
throw new UnsupportedOperationException("read-only");
commitLock.writeLock().lock();
try{
if(closed) return;
if(uncommitedData)
throw new IllegalAccessError("uncommitted data");
txs.remove(ref);
cleanTxQueue();
for(Long prealloc:usedPreallocatedRecids){
TxEngine.this.superDelete(prealloc,null);
}
TxEngine.this.superCommit();
close();
}finally {
commitLock.writeLock().unlock();
}
}
@Override
public boolean isReadOnly() {
return !fullTx;
}
@Override
public boolean canRollback() {
return fullTx;
}
@Override
public boolean canSnapshot() {
return false;
}
@Override
public Engine snapshot() throws UnsupportedOperationException {
throw new UnsupportedOperationException();
//TODO see Issue #281
}
@Override
public void clearCache() {
}
@Override
public void compact() {
}
SerializerPojo pojo = new SerializerPojo((CopyOnWriteArrayList<SerializerPojo.ClassInfo>) TxEngine.this.getSerializerPojo().registered.clone());
@Override
public SerializerPojo getSerializerPojo() {
return pojo;
}
@Override
public void closeListenerRegister(Runnable closeListener) {
throw new UnsupportedOperationException();
}
@Override
public void closeListenerUnregister(Runnable closeListener) {
throw new UnsupportedOperationException();
}
public Engine getWrappedEngine() {
return TxEngine.this.getWrappedEngine();
}
}
}