/*
 * JBoss, Home of Professional Open Source.
 * See the COPYRIGHT.txt file distributed with this work for information
 * regarding copyright ownership.  Some portions may be licensed
 * to Red Hat, Inc. under one or more contributor license agreements.
 * 
 * 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 library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA.
 */

package org.teiid.common.buffer.impl;

import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.Serializable;
import java.lang.ref.PhantomReference;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

import org.teiid.client.BatchSerializer;
import org.teiid.client.ResizingArrayList;
import org.teiid.client.util.ExceptionUtil;
import org.teiid.common.buffer.*;
import org.teiid.common.buffer.AutoCleanupUtil.Removable;
import org.teiid.common.buffer.LobManager.ReferenceMode;
import org.teiid.core.TeiidComponentException;
import org.teiid.core.TeiidRuntimeException;
import org.teiid.core.types.DataTypeManager;
import org.teiid.core.types.DataTypeManager.WeakReferenceHashedValueCache;
import org.teiid.core.types.Streamable;
import org.teiid.core.util.Assertion;
import org.teiid.dqp.internal.process.DQPConfiguration;
import org.teiid.dqp.internal.process.RequestWorkItem;
import org.teiid.logging.LogConstants;
import org.teiid.logging.LogManager;
import org.teiid.logging.MessageLevel;
import org.teiid.query.QueryPlugin;
import org.teiid.query.ReplicatedObject;
import org.teiid.query.processor.relational.ListNestedSortComparator;
import org.teiid.query.sql.symbol.ElementSymbol;
import org.teiid.query.sql.symbol.Expression;
import org.teiid.query.util.CommandContext;


/**
 * <p>Default implementation of BufferManager.</p>
 * Responsible for creating/tracking TupleBuffers and providing access to the StorageManager.
 * </p>
 * 
 * TODO: add detection of pinned batches to prevent unnecessary purging of non-persistent batches
 *       - this is not necessary for already persistent batches, since we hold a weak reference
 *       
 * TODO: add a pre-fetch for tuplebuffers or some built-in correlation logic with the queue.      
 */
public class BufferManagerImpl implements BufferManager, ReplicatedObject<String> {

	private static final int SYSTEM_OVERHEAD_MEGS = 150;

	/**
	 * Asynch cleaner attempts to age out old entries and to reduce the memory size when 
	 * little is reserved.
	 */
	private static final int MAX_READ_AGE = 1<<17;
	private static final class Cleaner extends TimerTask {
		WeakReference<BufferManagerImpl> bufferRef;
		
		public Cleaner(BufferManagerImpl bufferManagerImpl) {
			this.bufferRef = new WeakReference<BufferManagerImpl>(bufferManagerImpl);
		}
		
		@Override
		public void run() {
			while (true) {
				BufferManagerImpl impl = this.bufferRef.get();
				if (impl == null) {
					this.cancel();
					return;
				}
				impl.cleaning.set(true);
				try {
					long evicted = impl.doEvictions(impl.maxProcessingBytes, false, impl.initialEvictionQueue);
					if (evicted != 0) {
						if (LogManager.isMessageToBeRecorded(LogConstants.CTX_BUFFER_MGR, MessageLevel.TRACE)) {
							LogManager.logTrace(LogConstants.CTX_BUFFER_MGR, "Asynch eviction run", evicted, impl.reserveBatchBytes.get(), impl.maxReserveBytes, impl.activeBatchBytes.get()); //$NON-NLS-1$
						}
						continue;
					}
				} catch (Throwable t) {
					LogManager.logDetail(LogConstants.CTX_BUFFER_MGR, t, "Exception during cleaning run"); //$NON-NLS-1$
				}
				synchronized (this) {
					impl.cleaning.set(false);
					try {
						this.wait(100);
					} catch (InterruptedException e) {
						break;
					}
				}
			}
		}
	}
	
	private final class Remover implements Removable {
		private Long id;
		private AtomicBoolean prefersMemory;
		
		public Remover(Long id, AtomicBoolean prefersMemory) {
			this.id = id;
			this.prefersMemory = prefersMemory;
		}

		@Override
		public void remove() {
			removeCacheGroup(id, prefersMemory.get());
		}
	}

	/**
	 * This estimate is based upon adding the value to 2/3 maps and having CacheEntry/PhysicalInfo keys
	 */
	private static final long BATCH_OVERHEAD = 128;
	
	final class BatchManagerImpl implements BatchManager, Serializer<List<? extends List<?>>> {
		final Long id;
		SizeUtility sizeUtility;
		private WeakReference<BatchManagerImpl> ref = new WeakReference<BatchManagerImpl>(this);
		private PhantomReference<Object> cleanup;
		AtomicBoolean prefersMemory = new AtomicBoolean();
		String[] types;
		private LobManager lobManager;
		private long totalSize;
		private long rowsSampled;

		private BatchManagerImpl(Long newID, Class<?>[] types) {
			this.id = newID;
			this.sizeUtility = new SizeUtility(types);
			this.types = new String[types.length];
			for (int i = 0; i < types.length; i++) {
				this.types[i] = DataTypeManager.getDataTypeName(types[i]);
			}
		}
		
		@Override
		public Long getId() {
			return id;
		}
		
		public void setLobManager(LobManager lobManager) {
			this.lobManager = lobManager;
		}
		
		@Override
		public String[] getTypes() {
			return types;
		}
		
		@Override
		public boolean prefersMemory() {
			return prefersMemory.get();
		}
		
		@Override
		public void setPrefersMemory(boolean prefers) {
			//TODO: it's only expected to move from not preferring to preferring
			this.prefersMemory.set(prefers);
		}
		
		@Override
		public boolean useSoftCache() {
			return prefersMemory.get();
		}
		
		@Override
		public Reference<? extends BatchManager> getBatchManagerReference() {
			return ref;
		}
		
		@Override
		public Long createManagedBatch(List<? extends List<?>> batch,
				Long previous, boolean removeOld)
				throws TeiidComponentException {
			if (cleanup == null) {
				cache.createCacheGroup(id);
				cleanup = AutoCleanupUtil.setCleanupReference(this, new Remover(id, prefersMemory));
			}
			int sizeEstimate = getSizeEstimate(batch);
			Long oid = batchAdded.getAndIncrement();
			CacheEntry old = null;
			if (previous != null) {
				if (removeOld) {
					old = BufferManagerImpl.this.remove(id, previous, prefersMemory.get());
				} else {
					old = fastGet(previous, prefersMemory.get(), true);
				}
			} else {
				totalSize += sizeEstimate;
				rowsSampled += batch.size();
			}
			CacheKey key = new CacheKey(oid, (int)readAttempts.get(), old!=null?old.getKey().getOrderingValue():0);
			CacheEntry ce = new CacheEntry(key, sizeEstimate, batch, this.ref, false);
			if (!cache.addToCacheGroup(id, ce.getId())) {
				this.remove();
				throw new TeiidComponentException(QueryPlugin.Event.TEIID31138, QueryPlugin.Util.gs(QueryPlugin.Event.TEIID31138, id));
			}
			overheadBytes.addAndGet(BATCH_OVERHEAD);
			if (LogManager.isMessageToBeRecorded(LogConstants.CTX_BUFFER_MGR, MessageLevel.TRACE)) {
				LogManager.logTrace(LogConstants.CTX_BUFFER_MGR, "Add batch to BufferManager", this.id, ce.getId(), "with size estimate", ce.getSizeEstimate()); //$NON-NLS-1$ //$NON-NLS-2$
			}
			addMemoryEntry(ce, true);
			return oid;
		}

		@Override
		public List<? extends List<?>> deserialize(ObjectInput ois)
				throws IOException, ClassNotFoundException {
			List<? extends List<?>> batch = BatchSerializer.readBatch(ois, types);
			if (lobManager != null) {
				for (int i = batch.size() - 1; i >= 0; i--) {
					try {
						lobManager.updateReferences(batch.get(i), ReferenceMode.ATTACH);
					} catch (TeiidComponentException e) {
						 throw new TeiidRuntimeException(QueryPlugin.Event.TEIID30052, e);
					}
				}
			}
			return batch;
		}
		
		@Override
		public void serialize(List<? extends List<?>> obj,
				ObjectOutput oos) throws IOException {
			ResizingArrayList<?> list = null;
			if (obj instanceof ResizingArrayList<?>) {
				list = (ResizingArrayList<?>)obj;
			}
			try {
				//it's expected that the containing structure has updated the lob manager
				BatchSerializer.writeBatch(oos, types, obj);
			} catch (RuntimeException e) {
				if (ExceptionUtil.getExceptionOfType(e, ClassCastException.class) != null) {
					throw e;
				}
				//there is a chance of a concurrent persist while modifying 
				//in which case we want to swallow this exception
				if (list == null) {
					throw e;
				}
				LogManager.logDetail(LogConstants.CTX_BUFFER_MGR, e, "Possible Concurrent Modification", id); //$NON-NLS-1$
			}
		}
		
		public int getSizeEstimate(List<? extends List<?>> obj) {
			return (int) Math.max(1, sizeUtility.getBatchSize(DataTypeManager.isValueCacheEnabled(), obj));
		}
		
		@SuppressWarnings("unchecked")
		@Override
		public List<List<?>> getBatch(Long batch, boolean retain)
				throws TeiidComponentException {
			cleanSoftReferences();
			long reads = readAttempts.incrementAndGet();
			if (LogManager.isMessageToBeRecorded(LogConstants.CTX_BUFFER_MGR, MessageLevel.TRACE)) {
				LogManager.logTrace(LogConstants.CTX_BUFFER_MGR, id, "getting batch", batch, "total reads", reads, "reference hits", referenceHit.get()); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
			}
			CacheEntry ce = fastGet(batch, prefersMemory.get(), retain);
			if (ce != null) {
				return (List<List<?>>)(!retain?ce.nullOut():ce.getObject());
			}
			//obtain a granular lock to prevent double memory loading
			Object o = cache.lockForLoad(batch, this);
			try {
				ce = fastGet(batch, prefersMemory.get(), retain);
				if (ce != null) {
					return (List<List<?>>)(!retain?ce.nullOut():ce.getObject());
				}
				long count = readCount.incrementAndGet();
				if (LogManager.isMessageToBeRecorded(LogConstants.CTX_BUFFER_MGR, MessageLevel.DETAIL)) {
					LogManager.logDetail(LogConstants.CTX_BUFFER_MGR, id, "reading batch", batch, "from storage, total reads:", count); //$NON-NLS-1$ //$NON-NLS-2$
				}
				ce = cache.get(o, batch, this.ref);
				if (ce == null) {
					throw new AssertionError("Batch not found in storage " + batch); //$NON-NLS-1$
				}
				if (!retain) {
					removeFromCache(this.id, batch);
					persistBatchReferences(ce.getSizeEstimate());
				} else {
					addMemoryEntry(ce, false);
				}
			} finally {
				cache.unlockForLoad(o);
			}
			return (List<List<?>>)ce.getObject();
		}

		@Override
		public void remove(Long batch) {
			BufferManagerImpl.this.remove(id, batch, prefersMemory.get());
		}

		@Override
		public void remove() {
			if (cleanup != null) {
				removeCacheGroup(id, prefersMemory.get());
				AutoCleanupUtil.removeCleanupReference(cleanup);
				cleanup = null;
			}
		}

		@Override
		public String toString() {
			return id.toString();
		}
		
		@Override
		public int getRowSizeEstimate() {
			if (rowsSampled == 0) {
				return 0;
			}
			return (int)(totalSize/rowsSampled);
		}
	}
	
	private static class BatchSoftReference extends SoftReference<CacheEntry> {

		private int sizeEstimate;
		private Long key;
		
		public BatchSoftReference(CacheEntry referent,
				ReferenceQueue<? super CacheEntry> q, int sizeEstimate) {
			super(referent, q);
			this.sizeEstimate = sizeEstimate;
			this.key = referent.getId();
		}
	}

	static final int CONCURRENCY_LEVEL = 32; //TODO: make this configurable since it is roughly the same as max active plans
	private static final int TARGET_BYTES_PER_ROW = 1 << 11; //2k bytes per row
	private static ReferenceQueue<CacheEntry> SOFT_QUEUE = new ReferenceQueue<CacheEntry>();
	
	// Configuration 
    private int processorBatchSize = BufferManager.DEFAULT_PROCESSOR_BATCH_SIZE;
    //set to acceptable defaults for testing
    private int maxProcessingBytes = 1 << 21; 
    private Integer maxProcessingBytesOrig;
    long maxReserveBytes = 1 << 28;;
    AtomicLong reserveBatchBytes = new AtomicLong();
    AtomicLong overheadBytes = new AtomicLong();
    private int maxActivePlans = DQPConfiguration.DEFAULT_MAX_ACTIVE_PLANS; //used as a hint to set the reserveBatchKB
    private boolean useWeakReferences = true;
    private boolean inlineLobs = true;
    private int targetBytesPerRow = TARGET_BYTES_PER_ROW;
    private int maxSoftReferences;
    private int nominalProcessingMemoryMax = maxProcessingBytes;

    private ReentrantLock lock = new ReentrantLock();
    private Condition batchesFreed = lock.newCondition();
    
    AtomicLong activeBatchBytes = new AtomicLong();
    
    private AtomicLong readAttempts = new AtomicLong();
    //TODO: consider the size estimate in the weighting function
    LrfuEvictionQueue<CacheEntry> evictionQueue = new LrfuEvictionQueue<CacheEntry>(readAttempts);
    LrfuEvictionQueue<CacheEntry> initialEvictionQueue = new LrfuEvictionQueue<CacheEntry>(readAttempts);
    ConcurrentHashMap<Long, CacheEntry> memoryEntries = new ConcurrentHashMap<Long, CacheEntry>(16, .75f, CONCURRENCY_LEVEL);
    
    //limited size reference caches based upon the memory settings
    private WeakReferenceHashedValueCache<CacheEntry> weakReferenceCache; 
    private Map<Long, BatchSoftReference> softCache = Collections.synchronizedMap(new LinkedHashMap<Long, BatchSoftReference>(16, .75f, false) {
		private static final long serialVersionUID = 1L;

		protected boolean removeEldestEntry(Map.Entry<Long,BatchSoftReference> eldest) {
    		if (size() > maxSoftReferences) {
    			BatchSoftReference bsr = eldest.getValue();
    			clearSoftReference(bsr);
    			return true;
    		}
    		return false;
    	}

    });
    
    private Cache cache;
    
	private Map<String, TupleReference> tupleBufferMap = new ConcurrentHashMap<String, TupleReference>();
	private ReferenceQueue<TupleBuffer> tupleBufferQueue = new ReferenceQueue<TupleBuffer>();
    
    private AtomicLong tsId = new AtomicLong();
    private AtomicLong batchAdded = new AtomicLong();
    private AtomicLong readCount = new AtomicLong();
	private AtomicLong writeCount = new AtomicLong();
	private AtomicLong referenceHit = new AtomicLong();
	
	//TODO: this does not scale well with multiple embedded instances
	private static final Timer timer = new Timer("BufferManager Cleaner", true); //$NON-NLS-1$
	private Cleaner cleaner;
	private AtomicBoolean cleaning = new AtomicBoolean();
	
	public BufferManagerImpl() {
		this.cleaner = new Cleaner(this);
		timer.schedule(cleaner, 100);
	}
	
	void clearSoftReference(BatchSoftReference bsr) {
		synchronized (bsr) {
			overheadBytes.addAndGet(-bsr.sizeEstimate);
			bsr.sizeEstimate = 0;
		}
		bsr.clear();
	}
	
	void removeFromCache(Long gid, Long batch) {
		if (cache.remove(gid, batch)) {
			overheadBytes.addAndGet(-BATCH_OVERHEAD);
		}
	}
	
	public long getBatchesAdded() {
		return batchAdded.get();
	}
	
	public long getReadCount() {
		return readCount.get();
	}
	
	public long getWriteCount() {
		return writeCount.get();
	}
	
	public long getReadAttempts() {
		return readAttempts.get();
	}
	
	@Override
	public int getMaxProcessingSize() {
		return maxProcessingBytes;
	}
	
	public long getReserveBatchBytes() {
		return reserveBatchBytes.get();
	}
    
    /**
     * Get processor batch size
     * @return Number of rows in a processor batch
     */
    @Override
    public int getProcessorBatchSize() {        
        return this.processorBatchSize;
    }

    public void setTargetBytesPerRow(int targetBytesPerRow) {
		this.targetBytesPerRow = targetBytesPerRow;
	}

    public void setProcessorBatchSize(int processorBatchSize) {
        this.processorBatchSize = processorBatchSize;
    } 

    @Override
    public TupleBuffer createTupleBuffer(final List elements, String groupName,
    		TupleSourceType tupleSourceType) {
    	final Long newID = this.tsId.getAndIncrement();
    	int[] lobIndexes = LobManager.getLobIndexes(elements);
    	Class<?>[] types = getTypeClasses(elements);
    	BatchManagerImpl batchManager = createBatchManager(newID, types);
    	LobManager lobManager = null;
		if (lobIndexes != null) {
			FileStore lobStore = createFileStore(newID + "_lobs"); //$NON-NLS-1$
			lobManager = new LobManager(lobIndexes, lobStore);
			batchManager.setLobManager(lobManager);
		}
    	TupleBuffer tupleBuffer = new TupleBuffer(batchManager, String.valueOf(newID), elements, lobManager, getProcessorBatchSize(elements));
        if (LogManager.isMessageToBeRecorded(LogConstants.CTX_BUFFER_MGR, MessageLevel.DETAIL)) {
        	LogManager.logDetail(LogConstants.CTX_BUFFER_MGR, "Creating TupleBuffer:", newID, elements, Arrays.toString(types), "batch size", tupleBuffer.getBatchSize(), "of type", tupleSourceType); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
        }
    	tupleBuffer.setInlineLobs(inlineLobs);
        return tupleBuffer;
    }
    
    public STree createSTree(final List<? extends Expression> elements, String groupName, int keyLength) {
    	Long newID = this.tsId.getAndIncrement();
    	int[] lobIndexes = LobManager.getLobIndexes(elements);
    	Class<?>[] types = getTypeClasses(elements);
    	BatchManagerImpl bm = createBatchManager(newID, types);
    	LobManager lobManager = null;
    	if (lobIndexes != null) {
			lobManager = new LobManager(lobIndexes, null); //persistence is not expected yet - later we might utilize storage for out-of-line lob values
			bm.setLobManager(lobManager);
		}
    	BatchManager keyManager = createBatchManager(this.tsId.getAndIncrement(), Arrays.copyOf(types, keyLength));
    	int[] compareIndexes = new int[keyLength];
    	for (int i = 1; i < compareIndexes.length; i++) {
			compareIndexes[i] = i;
		}
    	if (LogManager.isMessageToBeRecorded(LogConstants.CTX_BUFFER_MGR, MessageLevel.DETAIL)) {
    		LogManager.logDetail(LogConstants.CTX_BUFFER_MGR, "Creating STree:", newID); //$NON-NLS-1$
    	}
    	return new STree(keyManager, bm, new ListNestedSortComparator(compareIndexes), getProcessorBatchSize(elements.subList(0, keyLength)), getProcessorBatchSize(elements), keyLength, lobManager);
    }

	private static Class<?>[] getTypeClasses(final List<? extends Expression> elements) {
		Class<?>[] types = new Class[elements.size()];
        for (ListIterator<? extends Expression> i = elements.listIterator(); i.hasNext();) {
            Expression expr = i.next();
            Class<?> type = expr.getType();
            Assertion.isNotNull(type);
			types[i.previousIndex()] = type;
        }
		return types;
	}

	private BatchManagerImpl createBatchManager(final Long newID, Class<?>[] types) {
		return new BatchManagerImpl(newID, types);
	}

    @Override
    public FileStore createFileStore(String name) {
    	if (LogManager.isMessageToBeRecorded(LogConstants.CTX_BUFFER_MGR, MessageLevel.DETAIL)) {
    		LogManager.logDetail(LogConstants.CTX_BUFFER_MGR, "Creating FileStore:", name); //$NON-NLS-1$
    	}
    	return this.cache.createFileStore(name);
    }
    
    public Cache getCache() {
		return cache;
	}
        
    public void setMaxActivePlans(int maxActivePlans) {
		this.maxActivePlans = maxActivePlans;
	}
    
    public void setMaxProcessingKB(int maxProcessingKB) {
    	if (maxProcessingKB > -1) {
    		this.maxProcessingBytes = maxProcessingKB<<10;
    	} else {
    		this.maxProcessingBytes = -1;
    	}
	}
    
    public void setMaxReserveKB(int maxReserveBatchKB) {
		if (maxReserveBatchKB > -1) {
			int maxReserve = maxReserveBatchKB<<10;
			this.maxReserveBytes = maxReserve;
			this.reserveBatchBytes.set(maxReserve);
		} else {
			this.maxReserveBytes = -1;
		}
	}
    
	@Override
	public void initialize() throws TeiidComponentException {
		long maxMemory = Runtime.getRuntime().maxMemory();
		maxMemory = Math.max(0, maxMemory - (SYSTEM_OVERHEAD_MEGS << 20)); //assume an overhead for the AS/system stuff
		if (getMaxReserveKB() < 0) {
			this.maxReserveBytes = 0;
			int one_gig = 1 << 30;
			if (maxMemory > one_gig) {
				//assume 70% of the memory over the first gig
				this.maxReserveBytes = (long)Math.max(0, (maxMemory - one_gig) * .7);
			}
			this.maxReserveBytes += Math.max(0, Math.min(one_gig, maxMemory) >> 1);
    	}
		this.reserveBatchBytes.set(maxReserveBytes);
		if (this.maxProcessingBytesOrig == null) {
			//store the config value so that we can be reinitialized (this is not a clean approach)
			this.maxProcessingBytesOrig = this.maxProcessingBytes;
		}
		if (this.maxProcessingBytesOrig < 0) {
			this.maxProcessingBytes = (int)Math.min(Math.max(processorBatchSize * targetBytesPerRow * 16l, (.2 * maxMemory)/maxActivePlans),  Integer.MAX_VALUE);
		} 
		//make a guess at the max number of batches
		long memoryBatches = maxMemory / (processorBatchSize * targetBytesPerRow);
		//memoryBatches represents a full batch, so assume that most will be smaller
		int logSize = 67 - Long.numberOfLeadingZeros(memoryBatches);
		if (useWeakReferences) {
			weakReferenceCache = new WeakReferenceHashedValueCache<CacheEntry>(Math.min(30, logSize));
		}
		this.maxSoftReferences = 1 << Math.min(30, logSize);
		this.nominalProcessingMemoryMax = (int)Math.max(Math.min(this.maxReserveBytes, 2*this.maxProcessingBytes), Math.min(Integer.MAX_VALUE, 2*this.maxReserveBytes/maxActivePlans));
	}
	
	void setNominalProcessingMemoryMax(int nominalProcessingMemoryMax) {
		this.nominalProcessingMemoryMax = nominalProcessingMemoryMax;
	}

    @Override
    public void releaseOrphanedBuffers(long count) {
    	releaseBuffers(count, false);
    }
    	
    @Override
    public void releaseBuffers(int count) {
    	releaseBuffers(count, true);
    }
    
    private void releaseBuffers(long count, boolean updateContext) {
    	if (count < 1) {
    		return;
    	}
    	if (updateContext) {
        	if (LogManager.isMessageToBeRecorded(LogConstants.CTX_BUFFER_MGR, MessageLevel.TRACE)) {
        		LogManager.logTrace(LogConstants.CTX_BUFFER_MGR, "Releasing buffer space", count); //$NON-NLS-1$
        	}
	    	CommandContext context = CommandContext.getThreadLocalContext();
	    	if (context != null) {
	    		context.addAndGetReservedBuffers((int)-count);
	    	}
    	} else {
        	if (LogManager.isMessageToBeRecorded(LogConstants.CTX_BUFFER_MGR, MessageLevel.INFO)) {
        		LogManager.logTrace(LogConstants.CTX_BUFFER_MGR, "Releasing orphaned buffer space", count); //$NON-NLS-1$
        	}
    	}
    	lock.lock();
    	try {
        	this.reserveBatchBytes.addAndGet(count);
	    	batchesFreed.signalAll();
    	} finally {
    		lock.unlock();
    	}
    }
    
    @Override
    public int reserveBuffers(int count, BufferReserveMode mode) {
    	if (LogManager.isMessageToBeRecorded(LogConstants.CTX_BUFFER_MGR, MessageLevel.TRACE)) {
    		LogManager.logTrace(LogConstants.CTX_BUFFER_MGR, "Reserving buffer space", count, mode); //$NON-NLS-1$
    	}
		CommandContext context = CommandContext.getThreadLocalContext();
		int existing = 0;
		if (context != null) {
			existing = (int)Math.min(Integer.MAX_VALUE, context.addAndGetReservedBuffers(0));
		}
    	int result = count;
    	if (mode == BufferReserveMode.FORCE) {
    		reserve(count, context);
    	} else {
    		lock.lock();
    		try {
    			count = Math.min(count, nominalProcessingMemoryMax - existing);
    			result = noWaitReserve(count, false, context);
    		} finally {
    			lock.unlock();
    		}
    	}
		persistBatchReferences(result);
    	return result;
    }

	private void reserve(int count, CommandContext context) {
		this.reserveBatchBytes.addAndGet(-count);
		if (context != null) {
			context.addAndGetReservedBuffers(count);
		}
	}
    
    @Override
    public int reserveBuffersBlocking(int count, long[] val, boolean force) throws BlockedException {
    	if (LogManager.isMessageToBeRecorded(LogConstants.CTX_BUFFER_MGR, MessageLevel.TRACE)) {
    		LogManager.logTrace(LogConstants.CTX_BUFFER_MGR, "Reserving buffer space", count, force); //$NON-NLS-1$
    	}
    	assert count >= 0;
    	if (count == 0) {
    		return 0;
    	}
    	int result = 0;
		int count_orig = count;
		CommandContext context = CommandContext.getThreadLocalContext();
		long reserved = 0;
		if (context != null) {
			reserved = context.addAndGetReservedBuffers(0);
			//TODO: in theory we have to check the whole stack as we could be 
			//issuing embedded queries back to ourselves
		}
		count = Math.min(count, (int)Math.min(Integer.MAX_VALUE, nominalProcessingMemoryMax - reserved));
		if (count_orig != count && !force) {
			return 0; //is not possible to reserve the desired amount
		}
		result = noWaitReserve(count, true, context);
		if (result == 0) {
			if (val[0]++ == 0) {
				val[1] = System.currentTimeMillis();
			}
			if (val[1] > 1) {
				long last = val[1];
				val[1] = System.currentTimeMillis();
				try {
					lock.lock();
					if (val[1] - last < 10) {
						//if the time difference is too close, then wait to prevent tight spins
						//but we can't wait too long as we don't want to thread starve the system
						batchesFreed.await(20, TimeUnit.MILLISECONDS);
					}
					if ((val[0] << (force?16:18)) > count) {
						//aging out 
						//TOOD: ideally we should be using a priority queue and better scheduling
						if (!force) {
							return 0;
						}
						reserve(count_orig, context);
						result = count_orig;
					} else {
						int min = 0;
						if (force) {
							min = 2*count/3;
						} else {
							min = 4*count/5;
						}
						//if a sample looks good proceed
						if (reserveBatchBytes.get() > min){
							reserve(count_orig, context);
							result = count_orig;
						}
					}
				} catch (InterruptedException e) {
					throw new TeiidRuntimeException(e);
				} finally {
					lock.unlock();
				}
			}
			if (result == 0) {
				if (context != null) {
			    	RequestWorkItem workItem = context.getWorkItem();
			    	if (workItem != null) {
			    		//if we have a workitem (non-test scenario) then before 
			    		//throwing blocked on memory to indicate there's more work
			    		workItem.moreWork();
			    	}
				}
				throw BlockedException.BLOCKED_ON_MEMORY_EXCEPTION;
			}
		}
		if (force && result < count_orig) {
			reserve(count_orig - result, context);
			result = count_orig;
		}
		val[0] = 0;
		persistBatchReferences(result);
    	return result;
    }

	private int noWaitReserve(int count, boolean allOrNothing, CommandContext context) {
		boolean success = false;
		for (int i = 0; !success && i < 2; i++) {
			long reserveBatch = this.reserveBatchBytes.get();
			long overhead = this.overheadBytes.get();
			long current = reserveBatch - overhead;
			if (allOrNothing) {
				if (count > current) {
					return 0;
				}
			} else if (count > current) {
				count = (int)Math.max(0, current);
			}
			if (count == 0) {
				return 0;
			}
			if (this.reserveBatchBytes.compareAndSet(reserveBatch, reserveBatch - count)) {
				success = true;
			}
		}
		//the value is changing rapidly, but we've already potentially adjusted the value twice, so just proceed
		if (!success) {
			this.reserveBatchBytes.addAndGet(-count);
		}
		if (context != null) {
			context.addAndGetReservedBuffers(count);
		}
		return count;
	}
    
	void persistBatchReferences(int max) {
		if (max <= 0) {
			return;
		}
		if (!cleaning.get()) {
			synchronized (cleaner) {
				cleaner.notify();
			}
		}
		long activeBatch = activeBatchBytes.get() + overheadBytes.get();
		long reserveBatch = reserveBatchBytes.get();
		long memoryCount = activeBatch + maxReserveBytes - reserveBatch;
		if (memoryCount <= maxReserveBytes) {
			if (DataTypeManager.USE_VALUE_CACHE && DataTypeManager.isValueCacheEnabled() && memoryCount < maxReserveBytes / 8) {
				DataTypeManager.setValueCacheEnabled(false);
			}
			return;
		} else if (DataTypeManager.USE_VALUE_CACHE) {
			DataTypeManager.setValueCacheEnabled(true);
		}
		//we delay work here as there should be excess vm space, we are using an overestimate, and we want the cleaner to do the work if possible
		//TODO: track sizes held by each queue independently
		long maxToFree = Math.min(max, memoryCount - maxReserveBytes);
		LrfuEvictionQueue<CacheEntry> first = initialEvictionQueue;
		LrfuEvictionQueue<CacheEntry> second = evictionQueue;
		if (evictionQueue.getSize() > 2*initialEvictionQueue.getSize()) {
			//attempt to evict from the non-initial queue first as these should essentially be cost "free" and hopefully the reference cache can mitigate
			//the cost of rereading
			first = evictionQueue;
			second = initialEvictionQueue;
		}
		maxToFree -= doEvictions(maxToFree, true, first);
		if (maxToFree > 0) {
			maxToFree = Math.min(maxToFree, activeBatchBytes.get() + overheadBytes.get() - reserveBatchBytes.get());
			if (maxToFree > 0) {
				doEvictions(maxToFree, true, second);
			}
		}
	}
	
	long doEvictions(long maxToFree, boolean checkActiveBatch, LrfuEvictionQueue<CacheEntry> queue) {
		if (queue == evictionQueue) {
			maxToFree = Math.min(maxToFree, this.maxProcessingBytes);
		}
		long freed = 0;
		while (freed <= maxToFree && (
				!checkActiveBatch //age out 
				|| (queue == evictionQueue && activeBatchBytes.get() + overheadBytes.get() + this.maxReserveBytes/2 > reserveBatchBytes.get()) //nominal cleaning criterion 
				|| (queue != evictionQueue && activeBatchBytes.get() + overheadBytes.get() + 3*this.maxReserveBytes/4 > reserveBatchBytes.get()))) { //assume that basically all initial batches will need to be written out at some point
			CacheEntry ce = queue.firstEntry(checkActiveBatch);
			if (ce == null) {
				break;
			}
			synchronized (ce) {
				if (!memoryEntries.containsKey(ce.getId())) {
					if (!checkActiveBatch) {
						queue.remove(ce);
					}
					continue; //not currently a valid eviction
				}
			}
			if (!checkActiveBatch) {
				long lastAccess = ce.getKey().getLastAccess();
				long currentTime = readAttempts.get();
				long age = currentTime - lastAccess;
				if (age < MAX_READ_AGE) {
					checkActiveBatch = true;
					continue;
				}
			}
			boolean evicted = true;
			try {
				evicted = evict(ce);
			} catch (Throwable e) {
				LogManager.logError(LogConstants.CTX_BUFFER_MGR, e, QueryPlugin.Util.gs(QueryPlugin.Event.TEIID30017, ce.getId() ));
			} finally {
				synchronized (ce) {
					if (evicted && memoryEntries.remove(ce.getId()) != null) {
						freed += ce.getSizeEstimate();
						activeBatchBytes.addAndGet(-ce.getSizeEstimate());
						queue.remove(ce); //ensures that an intervening get will still be cleaned
					}
				}
			}
		}
		return freed;
	}

	boolean evict(CacheEntry ce) throws Exception {
		Serializer<?> s = ce.getSerializer();
		if (s == null) {
			return true;
		}
		boolean persist = false;
		synchronized (ce) {
			if (!ce.isPersistent()) {
				persist = true;
				ce.setPersistent(true);
			}
		}
		if (persist) {
			long count = writeCount.incrementAndGet();
			if (LogManager.isMessageToBeRecorded(LogConstants.CTX_BUFFER_MGR, MessageLevel.DETAIL)) {
				LogManager.logDetail(LogConstants.CTX_BUFFER_MGR, s.getId(), ce.getId(), "writing batch to storage, total writes: ", count); //$NON-NLS-1$
			}
		}
		boolean result = cache.add(ce, s);
		if (s.useSoftCache()) {
			createSoftReference(ce);
		} else if (useWeakReferences) {
			weakReferenceCache.getValue(ce); //a get will set the value
		}
		return result;
	}

	private void createSoftReference(CacheEntry ce) {
		//if we don't set aside some reserve, we 
		//will push the soft ref out of memory potentially too quickly
		int sizeEstimate = ce.getSizeEstimate()/2;
		BatchSoftReference ref = new BatchSoftReference(ce, SOFT_QUEUE, sizeEstimate);
		softCache.put(ce.getId(), ref);
		overheadBytes.addAndGet(sizeEstimate);
	}
	
	/**
	 * Get a CacheEntry without hitting storage
	 */
	CacheEntry fastGet(Long batch, Boolean prefersMemory, boolean retain) {
		CacheEntry ce = null;
		if (retain) {
			ce = memoryEntries.get(batch);
		} else {
			ce = memoryEntries.remove(batch);
		}
		if (ce != null) {
			synchronized (ce) {
				if (retain) {
					//there is a minute chance the batch was evicted
					//this call ensures that we won't leak
					if (memoryEntries.containsKey(batch)) {
						if (ce.isPersistent()) {
							evictionQueue.touch(ce);
						} else {
							initialEvictionQueue.touch(ce);
						}
					}
				} else {
					evictionQueue.remove(ce);
					if (!ce.isPersistent()) {
						initialEvictionQueue.remove(ce);
					}
				}
			}
			if (!retain) {
				BufferManagerImpl.this.remove(ce, true);
			}
			return ce;
		}
		if (prefersMemory == null || prefersMemory) {
			BatchSoftReference bsr = softCache.remove(batch);
			if (bsr != null) {
				ce = bsr.get();
				if (ce != null) {
					clearSoftReference(bsr);
				}
			}
		}
		if (ce == null && (prefersMemory == null || !prefersMemory) && useWeakReferences) {
			ce = weakReferenceCache.getByHash(batch);
			if (ce == null || !ce.getId().equals(batch)) {
				return null;
			}
		}
		if (ce != null && ce.getObject() != null) {
			referenceHit.getAndIncrement();
			if (retain) {
				addMemoryEntry(ce, false);
			} else {
				BufferManagerImpl.this.remove(ce, false);
			}
			return ce;
		}
		return null;
	}
	
	AtomicInteger removed = new AtomicInteger();
	
	CacheEntry remove(Long gid, Long batch, boolean prefersMemory) {
		if (LogManager.isMessageToBeRecorded(LogConstants.CTX_BUFFER_MGR, MessageLevel.TRACE)) {
			LogManager.logTrace(LogConstants.CTX_BUFFER_MGR, "Removing batch from BufferManager", gid, batch); //$NON-NLS-1$
		}
		cleanSoftReferences();
		CacheEntry ce = fastGet(batch, prefersMemory, false);
		if (ce == null) {
			removeFromCache(gid, batch);
		} else {
			ce.nullOut();
		}
		return ce;
	}

	private void remove(CacheEntry ce, boolean inMemory) {
		if (inMemory) {
			activeBatchBytes.addAndGet(-ce.getSizeEstimate());
		}
		Serializer<?> s = ce.getSerializer();
		if (s != null) {
			removeFromCache(s.getId(), ce.getId());
		}
	}
	
	void addMemoryEntry(CacheEntry ce, boolean initial) {
		persistBatchReferences(ce.getSizeEstimate());
		synchronized (ce) {
			boolean added = memoryEntries.put(ce.getId(), ce) == null;
			if (initial) {
				initialEvictionQueue.add(ce);
			} else if (added) {
				evictionQueue.recordAccess(ce);
				evictionQueue.add(ce);
			} else {
				evictionQueue.touch(ce);
			}
		}
		activeBatchBytes.getAndAdd(ce.getSizeEstimate());
	}
	
	void removeCacheGroup(Long id, Boolean prefersMemory) {
		cleanSoftReferences();
		Collection<Long> vals = cache.removeCacheGroup(id);
		long overhead = vals.size() * BATCH_OVERHEAD;
		overheadBytes.addAndGet(-overhead);
		if (!vals.isEmpty()) {
			for (Long val : vals) {
				//TODO: we will unnecessarily call remove on the cache, but that should be low cost
				fastGet(val, prefersMemory, false);
			}
		}
	}
	
	void cleanSoftReferences() {
		for (int i = 0; i < 10; i++) {
			BatchSoftReference ref = (BatchSoftReference)SOFT_QUEUE.poll();
			if (ref == null) {
				break;
			}
			softCache.remove(ref.key);
			clearSoftReference(ref);
		}
	}
	
	@Override
	public int getProcessorBatchSize(List<? extends Expression> schema) {
		return getSizeEstimates(schema)[0];
	}
	
	private int[] getSizeEstimates(List<? extends Expression> elements) {
		int total = 0;
		boolean isValueCacheEnabled = DataTypeManager.isValueCacheEnabled();
		for (int i = elements.size() - 1; i >= 0; i--) {
			Class<?> type = elements.get(i).getType();
			total += SizeUtility.getSize(isValueCacheEnabled, type);
		}
		//assume 64-bit
		total += 8*elements.size() + 36;  // column list / row overhead
		
		//nominal targetBytesPerRow but can scale up or down
		
		int totalCopy = total;
		boolean less = totalCopy < targetBytesPerRow;
		int rowCount = processorBatchSize;
		
		for (int i = 0; i < 3; i++) {
			if (less) {
				totalCopy <<= 1;
			} else {
				totalCopy >>= 2;
			}
			if (less && totalCopy > targetBytesPerRow
					|| !less && totalCopy < targetBytesPerRow) {
				break;
			}
			if (less) {
				rowCount <<= 1;
			} else {
				rowCount >>= 1;
			}
		}
		rowCount = Math.max(1, rowCount);
		total *= rowCount; 
		return new int[]{rowCount, Math.max(1, total)};
	}
	
	@Override
	public int getSchemaSize(List<? extends Expression> elements) {
		return getSizeEstimates(elements)[1];
	}

	public void shutdown() {
		this.cache.shutdown();
		this.cache = null;
		this.memoryEntries.clear();
		this.evictionQueue.getEvictionQueue().clear();
		this.initialEvictionQueue.getEvictionQueue().clear();
		this.cleaner.cancel();
	}

	@Override
	public void addTupleBuffer(TupleBuffer tb) {
		cleanDefunctTupleBuffers();
		this.tupleBufferMap.put(tb.getId(), new TupleReference(tb, this.tupleBufferQueue));
	}
	
	@Override
	public void distributeTupleBuffer(String uuid, TupleBuffer tb) {
		tb.setId(uuid);
		addTupleBuffer(tb);
	}
	
	@Override
	public TupleBuffer getTupleBuffer(String id) {		
		cleanDefunctTupleBuffers();
		Reference<TupleBuffer> r = this.tupleBufferMap.get(id);
		if (r != null) {
			return r.get();
		}
		return null;
	}
	
	private void cleanDefunctTupleBuffers() {
		while (true) {
			Reference<?> r = this.tupleBufferQueue.poll();
			if (r == null) {
				break;
			}
			this.tupleBufferMap.remove(((TupleReference)r).id);
		}
	}
	
	static class TupleReference extends WeakReference<TupleBuffer>{
		String id;
		public TupleReference(TupleBuffer referent, ReferenceQueue<? super TupleBuffer> q) {
			super(referent, q);
			id = referent.getId();
		}
	}
	
	public void setUseWeakReferences(boolean useWeakReferences) {
		this.useWeakReferences = useWeakReferences;
	}	
	
	@Override
	public void getState(OutputStream ostream) {
	}
	
	@Override
	public void getState(String state_id, OutputStream ostream) {
		TupleBuffer buffer = this.getTupleBuffer(state_id);
		if (buffer != null) {
			try {
				ObjectOutputStream out = new ObjectOutputStream(ostream);
				getTupleBufferState(out, buffer);
				out.flush();
			} catch (TeiidComponentException e) {
				 throw new TeiidRuntimeException(QueryPlugin.Event.TEIID30054, e);
			} catch (IOException e) {
				 throw new TeiidRuntimeException(QueryPlugin.Event.TEIID30055, e);
			}
		}
	}

	private void getTupleBufferState(ObjectOutputStream out, TupleBuffer buffer) throws TeiidComponentException, IOException {
		out.writeInt(buffer.getRowCount());
		out.writeInt(buffer.getBatchSize());
		out.writeObject(buffer.getTypes());
		for (int row = 1; row <= buffer.getRowCount(); row+=buffer.getBatchSize()) {
			TupleBatch b = buffer.getBatch(row);
			BatchSerializer.writeBatch(out, buffer.getTypes(), b.getTuples());
		}
	}

	@Override
	public void setState(InputStream istream) {
	}	
	
	@Override
	public void setState(String state_id, InputStream istream) {
		TupleBuffer buffer = this.getTupleBuffer(state_id);
		if (buffer == null) {
			try {
				ObjectInputStream in = new ObjectInputStream(istream);
				setTupleBufferState(state_id, in);
			} catch (IOException e) {
				 throw new TeiidRuntimeException(QueryPlugin.Event.TEIID30056, e);
			} catch(ClassNotFoundException e) {
				 throw new TeiidRuntimeException(QueryPlugin.Event.TEIID30057, e);
			} catch(TeiidComponentException e) {
				 throw new TeiidRuntimeException(QueryPlugin.Event.TEIID30058, e);
			}
		}
	}

	private void setTupleBufferState(String state_id, ObjectInputStream in) throws IOException, ClassNotFoundException, TeiidComponentException {
		int rowCount = in.readInt();
		int batchSize = in.readInt();
		String[] types = (String[])in.readObject();
		
		List<ElementSymbol> schema = new ArrayList<ElementSymbol>(types.length);
		for (int i = 0; i < types.length; i++) {
			ElementSymbol es = new ElementSymbol("x"); //$NON-NLS-1$
			es.setType(DataTypeManager.getDataTypeClass(types[i]));
			schema.add(es);
		}
		TupleBuffer buffer = createTupleBuffer(schema, "cached", TupleSourceType.FINAL); //$NON-NLS-1$
		buffer.setBatchSize(batchSize);
		buffer.setId(state_id);
		
		for (int row = 1; row <= rowCount; row+=batchSize) {
			List<List<Object>> batch = BatchSerializer.readBatch(in, types);
			for (int i = 0; i < batch.size(); i++) {
				buffer.addTuple(batch.get(i));
			}
		}
		if (buffer.getRowCount() != rowCount) {					
			buffer.remove();
			throw new IOException(QueryPlugin.Util.getString("not_found_cache")); //$NON-NLS-1$
		}	
		buffer.close();
		addTupleBuffer(buffer);
	}

	@Override
	public void setAddress(Serializable address) {
	}

	@Override
	public void droppedMembers(Collection<Serializable> addresses) {
	}	

	public void setInlineLobs(boolean inlineLobs) {
		this.inlineLobs = inlineLobs;
	}

	public int getMaxReserveKB() {
		return (int)maxReserveBytes>>10;
	}
	
	public void setCache(Cache cache) {
		this.cache = cache;
	}
	
	public int getMemoryCacheEntries() {
		return memoryEntries.size();
	}
	
	public long getActiveBatchBytes() {
		return activeBatchBytes.get();
	}
	
	@Override
	public boolean hasState(String stateId) {
		return this.getTupleBuffer(stateId) != null;
	}
	
	public long getReferenceHits() {
		return referenceHit.get();
	}
	
	@Override
	public Streamable<?> persistLob(Streamable<?> lob, FileStore store,
			byte[] bytes) throws TeiidComponentException {
		return LobManager.persistLob(lob, store, bytes, inlineLobs, DataTypeManager.MAX_LOB_MEMORY_BYTES);
	}

	public void invalidCacheGroup(Long gid) {
		removeCacheGroup(gid, null);
	}
	
}
