com.bigdata.resources.JournalIndex Maven / Gradle / Ivy
/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
[email protected]
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package com.bigdata.resources;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.util.UUID;
import com.bigdata.btree.BTree;
import com.bigdata.btree.Checkpoint;
import com.bigdata.btree.DefaultTupleSerializer;
import com.bigdata.btree.ITuple;
import com.bigdata.btree.IndexMetadata;
import com.bigdata.btree.keys.ASCIIKeyBuilderFactory;
import com.bigdata.btree.keys.IKeyBuilder;
import com.bigdata.btree.keys.IKeyBuilderFactory;
import com.bigdata.btree.keys.KeyBuilder;
import com.bigdata.io.SerializerUtil;
import com.bigdata.journal.ICommitRecord;
import com.bigdata.journal.IJournal;
import com.bigdata.mdi.JournalMetadata;
import com.bigdata.rawstore.IRawStore;
import com.bigdata.util.Bytes;
/**
* {@link BTree} mapping {@link IJournal} createTimes (long integers)
* to {@link JournalMetadata} records describing the {@link IJournal}.
*
* Note: Access to this object MUST be synchronized.
*
* Note: This is used as a transient data structure that is populated from the
* file system by the {@link ResourceManager}.
*/
public class JournalIndex extends BTree {
/**
* Instance used to encode the timestamp into the key.
*/
final private IKeyBuilder keyBuilder = new KeyBuilder(Bytes.SIZEOF_LONG);
/**
* Create a transient instance.
*
* @return The new instance.
*/
static public JournalIndex createTransient() {
final IndexMetadata metadata = new IndexMetadata(UUID.randomUUID());
metadata.setBTreeClassName(JournalIndex.class.getName());
metadata.setTupleSerializer(new TupleSerializer(
new ASCIIKeyBuilderFactory(Bytes.SIZEOF_LONG)));
return (JournalIndex) BTree.createTransient(/*store, */metadata);
}
/**
* Load from the store.
*
* @param store
* The backing store.
* @param checkpoint
* The {@link Checkpoint} record.
* @param metadata
* The metadata record for the index.
*/
public JournalIndex(final IRawStore store, final Checkpoint checkpoint,
final IndexMetadata metadata, final boolean readOnly) {
super(store, checkpoint, metadata, readOnly);
}
/**
* Encodes the commit time into a key.
*
* @param commitTime
* The commit time.
*
* @return The corresponding key.
*/
private byte[] getKey(final long commitTime) {
// return metadata.getTupleSerializer().serializeKey(commitTime);
return keyBuilder.reset().append(commitTime).getKey();
}
/**
* Return the {@link JournalMetadata} identifying the journal having the
* largest createTime that is less than or equal to the given timestamp.
* This is used primarily to locate the commit record that will serve as the
* ground state for a transaction having timestamp as its start
* time. In this context the LTE search identifies the most recent commit
* state that not later than the start time of the transaction.
*
* @param timestamp
* The given timestamp.
*
* @return The description of the relevant journal resource -or-
* null iff there are no journals in the index that
* satisify the probe.
*
* @throws IllegalArgumentException
* if timestamp is less than or equals to ZERO (0L).
*/
synchronized public JournalMetadata find(final long timestamp) {
if (timestamp <= 0L)
throw new IllegalArgumentException();
// find (first less than or equal to).
final long index = findIndexOf(timestamp);
if(index == -1) {
// No match.
log.warn("Not found: " + timestamp);
return null;
}
return valueAtIndex(index);
}
/**
* Retrieve the entry from the index.
*/
private JournalMetadata valueAtIndex(final long index) {
final byte[] val = super.valueAt(index);
assert val != null : "Entry has null value: index=" + index;
final JournalMetadata entry = (JournalMetadata) SerializerUtil
.deserialize(val);
return entry;
}
/**
* Find the first journal whose createTime is strictly greater
* than the timestamp.
*
* @param timestamp
* The timestamp. A value of ZERO (0) may be used to find the
* first journal.
*
* @return The commit record -or- null if there is no commit
* record whose timestamp is strictly greater than timestamp.
*/
synchronized public JournalMetadata findNext(final long timestamp) {
/*
* Note: can also be written using rangeIterator().next().
*/
if (timestamp < 0L)
throw new IllegalArgumentException();
// find first strictly greater than.
final long index = findIndexOf(Math.abs(timestamp)) + 1;
if (index == nentries) {
// No match.
return null;
}
return valueAtIndex(index);
}
/**
* Find the index of the {@link ICommitRecord} having the largest timestamp
* that is less than or equal to the given timestamp.
*
* @return The index of the {@link ICommitRecord} having the largest
* timestamp that is less than or equal to the given timestamp -or-
* -1 iff there are no {@link ICommitRecord}s
* defined.
*/
synchronized public long findIndexOf(final long timestamp) {
long pos = super.indexOf(getKey(timestamp));
if (pos < 0) {
/*
* the key lies between the entries in the index, or possible before
* the first entry in the index. [pos] represents the insert
* position. we convert it to an entry index and subtract one to get
* the index of the first commit record less than the given
* timestamp.
*/
pos = -(pos+1);
if(pos == 0) {
// No entry is less than or equal to this timestamp.
return -1;
}
pos--;
return pos;
} else {
/*
* exact hit on an entry.
*/
return pos;
}
}
/**
* Add an entry under the commitTime associated with the
* {@link JournalMetadata} record.
*
* @param resourceMetadata
* The {@link JournalMetadata} record.
*
* @exception IllegalArgumentException
* if commitTime is 0L.
* @exception IllegalArgumentException
* if resourceMetadata is null.
* @exception IllegalArgumentException
* if there is already an entry registered under for the
* given timestamp.
*/
synchronized public void add(final JournalMetadata resourceMetadata) {
if (resourceMetadata == null)
throw new IllegalArgumentException();
assert resourceMetadata.isJournal();
final long createTime = resourceMetadata.getCreateTime();
if (createTime == 0L)
throw new IllegalArgumentException();
final byte[] key = getKey(createTime);
if(super.contains(key)) {
throw new IllegalArgumentException("entry exists: timestamp="
+ createTime);
}
// add a serialized entry to the persistent index.
super.insert(key, SerializerUtil.serialize(resourceMetadata));
}
/**
* Encapsulates key and value formation.
*
* @author Bryan Thompson
* @version $Id$
*/
static protected class TupleSerializer extends
DefaultTupleSerializer {
/**
*
*/
private static final long serialVersionUID = -2851852959439807542L;
/**
* De-serialization ctor.
*/
public TupleSerializer() {
super();
}
/**
* Ctor when creating a new instance.
*
* @param keyBuilderFactory
*/
public TupleSerializer(final IKeyBuilderFactory keyBuilderFactory) {
super(keyBuilderFactory);
}
/**
* Decodes the key as a commit time.
*/
@Override
public Long deserializeKey(ITuple tuple) {
final byte[] key = tuple.getKeyBuffer().array();
final long id = KeyBuilder.decodeLong(key, 0);
return id;
}
/**
* The initial version (no additional persistent state).
*/
private final static transient byte VERSION0 = 0;
/**
* The current version.
*/
private final static transient byte VERSION = VERSION0;
public void readExternal(final ObjectInput in) throws IOException,
ClassNotFoundException {
super.readExternal(in);
final byte version = in.readByte();
switch (version) {
case VERSION0:
break;
default:
throw new UnsupportedOperationException("Unknown version: "
+ version);
}
}
public void writeExternal(final ObjectOutput out) throws IOException {
super.writeExternal(out);
out.writeByte(VERSION);
}
}
}