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com.bigdata.bfs.AtomicBlockAppendProc 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.bfs;
import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.nio.ByteBuffer;
import java.util.Arrays;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import com.bigdata.btree.AbstractBTree;
import com.bigdata.btree.BTree;
import com.bigdata.btree.IIndex;
import com.bigdata.btree.ILinearList;
import com.bigdata.btree.IRangeQuery;
import com.bigdata.btree.ITupleIterator;
import com.bigdata.btree.keys.IKeyBuilder;
import com.bigdata.btree.keys.KeyBuilder;
import com.bigdata.btree.proc.IResultHandler;
import com.bigdata.btree.proc.ISimpleIndexProcedure;
import com.bigdata.btree.view.FusedView;
import com.bigdata.io.DataOutputBuffer;
import com.bigdata.journal.AbstractJournal;
import com.bigdata.journal.Journal;
import com.bigdata.util.Bytes;
import com.bigdata.util.BytesUtil;
/**
* Atomic append of a single block to a file version.
*
* @author Bryan Thompson
*/
public class AtomicBlockAppendProc implements ISimpleIndexProcedure,
Externalizable {
private static final long serialVersionUID = 1441331704737671258L;
protected static transient Logger log = Logger
.getLogger(AtomicBlockAppendProc.class);
/**
* True iff the {@link #log} level is INFO or less.
*/
final protected static transient boolean INFO = log.getEffectiveLevel()
.toInt() <= Level.INFO.toInt();
/**
* True iff the {@link #log} level is DEBUG or less.
*/
final protected static transient boolean DEBUG = log.getEffectiveLevel()
.toInt() <= Level.DEBUG.toInt();
private String id;
private int version;
private int off;
private int len;
private byte[] b;
@Override
public final boolean isReadOnly() {
return false;
}
/**
*
* @param id
* The file identifier.
* @param version
* The file version.
* @param b
* The buffer containing the data to be written.
* @param off
* The offset in the buffer of the first byte to be written.
* @param len
* The #of bytes to be written.
*/
public AtomicBlockAppendProc(BigdataFileSystem repo, String id,
int version, byte[] b, int off, int len) {
assert id != null && id.length() > 0;
assert version >= 0;
assert b != null;
assert off >= 0 : "off="+off;
assert len >= 0 && off + len <= b.length;
assert len <= repo.getBlockSize(): "len="+len+" exceeds blockSize="+repo.getBlockSize();
this.id = id;
this.version = version;
this.off = off;
this.len = len;
this.b = b;
}
/**
* This procedure runs on the unisolated index. The block identifier is
* computed as a one up long integer for that file version using locally
* available state. The raw data for the block is written directly onto
* the {@link Journal} and an index entry is added for the file,
* version, and block whose value is the address of the block's data on
* the {@link Journal}.
*
* Note: The caller MUST have correctly identified the data service on
* which the tail of the file exists (or on which the head of the file
* will be written).
*
* The block identifier is computed by reading and decoding the key for
* the last block written for this file version (if any). Special cases
* exist when the file version spans more than one index partition, when
* the block would be the first block (in key order) for the index
* partition, and when the block would be the last block (in key order)
* for the index partition.
*
* @return true iff the block was overwritten.
*/
@Override
public Object apply(final IIndex ndx) {
// tunnel through to the backing journal.
final AbstractJournal journal = (AbstractJournal)((AbstractBTree)ndx).getStore();
// obtain the thread-local key builder for that journal.
final IKeyBuilder keyBuilder = ndx.getIndexMetadata().getKeyBuilder();
/*
* The next block identifier to be assigned.
*/
final long block = getNextBlockIdentifierInFileVersion(ndx, keyBuilder);
if (log.isInfoEnabled())
log.info("Will write " + len + " bytes on id=" + id + ", version="
+ version + ", block#=" + block);
{
/*
* write the block on the journal obtaining the address at which
* it was written - use 0L for the address of an empty block.
*/
final long addr = len == 0 ? 0L : journal.write(ByteBuffer
.wrap(b, off, len));
// form the key for the index entry for this block.
final byte[] key = keyBuilder.reset().appendText(id,
true/* unicode */, false/* successor */).append(
version).append(block).getKey();
// record the address of the block in the index.
{
final DataOutputBuffer out = new DataOutputBuffer(
Bytes.SIZEOF_LONG);
// encode the value for the entry.
out.reset().putLong(addr);
final byte[] val = out.toByteArray();
// insert the entry into the index.
ndx.insert(key, val);
}
if (log.isInfoEnabled())
log.info("Wrote " + len + " bytes : id=" + id + ", version="
+ version + ", block#=" + block + " @ addr"
+ journal.toString(addr));
}
// the block identifier.
return block;
}
/**
* Find the key for the last block written for this file version. We do this
* by forming a probe key from the file, version, and the maximum allowed
* block identifier. This is guarenteed to be after any existing block for
* that file and version.
*
* Note: This implementation uses an {@link IRangeQuery#REVERSE} iterator to
* locate the last block in the file and is capable of scale-out.
*
* @todo This implies that the leftSeparator for the index partition MUST
* NOT split the blocks for a file unless there is at least one block
* in the index partition. In practice this guarentee is easy to
* maintain. By default we choose to split an index partition on a
* file boundary. If that would result in an uneven split (or an empty
* split in the case of very large files) then we choose a split point
* that lies within the file's data - leaving at least one block for
* the file (probably many) in both partitions created by the split.
*
* @param ndx
* @param keyBuilder
* @return
*/
protected long getNextBlockIdentifierInFileVersion2(IIndex ndx,
IKeyBuilder keyBuilder) {
final byte[] fromKey = keyBuilder.reset().appendText(id,
true/* unicode */, false/* successor */).append(
version).append(0/*first valid block*/).getKey();
final byte[] toKey = keyBuilder.reset().appendText(id,
true/* unicode */, false/* successor */).append(
version).append(Long.MAX_VALUE/*max block*/).getKey();
ITupleIterator itr = ndx
.rangeIterator(fromKey, toKey, 1/* capacity */,
IRangeQuery.KEYS | IRangeQuery.REVERSE, null/*filter*/);
if(!itr.hasNext()) {
// There are no blocks for this file version.
return 0L;
}
final byte[] key = itr.next().getKey();
return getNextBlockFromPriorKey(keyBuilder, key);
}
/**
* Find the key for the last block written for this file version. We do this
* by forming a probe key from the file, version, and the maximum allowed
* block identifier. This is guarenteed to be after any existing block for
* that file and version.
*
* Note: This implementation uses the {@link ILinearList} API to locate the
* last block in the file and is NOT capable of scale-out since that API is
* NOT available for an index partition view (a {@link FusedView}).
*
* @todo This implies that the leftSeparator for the index partition MUST
* NOT split the blocks for a file unless there is at least one block
* in the index partition. In practice this guarentee is easy to
* maintain. By default we choose to split an index partition on a
* file boundary. If that would result in an uneven split (or an empty
* split in the case of very large files) then we choose a split point
* that lies within the file's data - leaving at least one block for
* the file (probably many) in both partitions created by the split.
*/
protected long getNextBlockIdentifierInFileVersion(IIndex ndx,
IKeyBuilder keyBuilder) {
final byte[] toKey = keyBuilder.reset().appendText(id,
true/* unicode */, false/* successor */).append(
version).append(Long.MAX_VALUE).getKey();
// Note: uses the ILinearList API.
final ILinearList tmp = (ILinearList) ndx;
/*
* Index of the first key after this file version.
*
* Note: This will always be an insertion point (a negative
* value) since the toKey only encodes the successor of the file
* identifier.
*
* We convert the insertion point to an index.
*
* If the index is zero (0) then there are no blocks for this
* file and the file will be the first file in the index order
* on this index partition (there may or may not be other files
* already on the index partition).
*
* Else fetch the key at that index. If that key encodes the
* same id as this file then we are appending to a file with
* existing block(s) and we decode the block identifier from the
* key. Otherwise this will be the first block written for that
* file.
*/
long toIndex = tmp.indexOf(toKey);
assert toIndex < 0 : "Expecting insertion point: id=" + id
+ ", version=" + version + ", toIndex=" + toIndex;
if (log.isDebugEnabled())
log.debug("insertionPoint=" + toIndex);
toIndex = -(toIndex + 1); // convert to an index.
// #of entries in the index.
final long entryCount = ((AbstractBTree) ndx).getEntryCount();
if (log.isDebugEnabled())
log.debug("toIndex=" + toIndex + ", entryCount=" + entryCount);
final long block;
if (toIndex == 0) {
/*
* Insertion point is before all other entries in the index.
*
* Note: In this case we need to examine the leftSeparator
* key for the index partition. If that key is for the same
* file version then we use the successor of the block
* identifier found in that key.
*
* Note: when it is not for the same file version it MAY be
* that the leftSeparator does not include the block
* identifier - the block identifier is only required in the
* leftSeparator when the a file version spans both the
* prior index partition and this index partition.
*/
if(log.isDebugEnabled())
log.debug("Insertion point is before all entries in the index partition: id="
+ id + ", version=" + version);
final byte[] leftSeparator = ((BTree) ndx)
.getIndexMetadata().getPartitionMetadata()
.getLeftSeparatorKey();
block = getNextBlockFromPriorKey(keyBuilder, leftSeparator);
} else {
if (toIndex == entryCount) {
/*
* Insertion point is after all entries in the index.
*
* Note: In this case we consider the prior key in the
* index partition. If that key is for the same file
* version then we use the successor of the block
* identifier found in that key.
*/
if (log.isDebugEnabled())
log.debug("Insertion point is after all entries in the index partition: id="
+ id + ", version=" + version);
} else {
/*
* Insertion point is at the toKey.
*
* Note: Since the probe key is beyond the last block
* for the file version we adjust the toIndex so that we
* consider the prior key.
*/
if (log.isDebugEnabled())
log.debug("Insertion point is at the toKey: id=" + id
+ ", version=" + version);
}
/*
* Adjust to consider the key before the insertion point.
*/
toIndex--;
/*
* Look at the key at the computed index. If it is a key for
* this file version then we use the successor of the given
* block identifier. Otherwise we are writing a new file
* version and the block identifier will be zero (0).
*/
if (log.isDebugEnabled())
log.debug("adjusted toIndex="+toIndex+", entryCount="+entryCount);
// the key at that index.
final byte[] key = tmp.keyAt(toIndex);
assert key != null : "Expecting entry: id=" + id
+ ", version=" + version + ", toIndex=" + toIndex;
block = getNextBlockFromPriorKey(keyBuilder, key);
}
return block;
}
/**
* Decode the block identifier in the key and return the block
* identifier plus one, which is the block identifier to be used for the
* atomic append operation. If the key does NOT encode the same file +
* version then no blocks exist for that file version and the method
* returns zero (0L) as the block identifer to be used.
*
* @param keyBuilder
* The key builder.
* @param key
* The key - either from the index partition or in some cases
* from the leftSeparator of the index partition metadata.
*
* Note that the leftSeparator MAY be an empty byte[] (e.g.,
* for the 1st index partition in the key order) and MIGHT
* NOT include the block identifier (the block identifier is
* only included when it is necessary to split a file across
* index partitions). When the block identifier is omitted
* from the key and the key encodes the same file and version
* we therefore use zero (0L) as the next block identifier
* since we will be appending the first block to the file
* version.
*
* @return The block identifier that will be used by the atomic append
* operation.
*/
protected long getNextBlockFromPriorKey(IKeyBuilder keyBuilder,
byte[] key) {
// encode just the file id and the version.
final byte[] prefix = keyBuilder.reset().appendText(id,
true/* unicode */, false/* successor */).append(version)
.getKey();
if (DEBUG)
log.debug("Comparing\nkey :" + Arrays.toString(key)
+ "\nprefix:" + Arrays.toString(prefix));
/*
* Test the encoded file id and version against the encoded file id
* and version in the recovered key. If they compare equals (for the
* length of the key that we just built) then they encode the same
* file id and version.
*
* (I.e., if true, then the key is from a block entry for this
* version of this file).
*/
if (key.length >= prefix.length) {
final int cmp = BytesUtil.compareBytesWithLenAndOffset(0,
prefix.length, prefix, 0, prefix.length, key);
if(DEBUG)
log.debug("Comparing " + prefix.length + " byte prefix with "
+ key.length + " byte key: cmp=" + cmp);
if (cmp == 0) {
/*
* The key at the computed toIndex is the same file version.
*/
if (prefix.length + Bytes.SIZEOF_LONG == key.length) {
/*
* The given key includes a block identifier so we
* extract it.
*
* Note: When the given key is a leftSeparator for an
* index partition AND the file version is not split
* across the index partition then the block identifer
* MAY be omitted from the leftSeparator. In this case
* the block identifier will be zero since there are no
* blocks yet for that file version.
*/
// last block identifier assigned for this file + 1.
final long block = KeyBuilder.decodeLong(key,
key.length - Bytes.SIZEOF_LONG) + 1;
if (block > BigdataFileSystem.MAX_BLOCK) {
throw new RuntimeException(
"File version has maximum #of blocks: id="
+ id + ", version=" + version);
}
if(INFO)
log.info("Appending to existing file version: id=" + id
+ ", version=" + version + ", block=" + block);
return block;
} else {
/*
* This case arises when the leftSeparator encodes the
* file version but does not include a block identifier.
*/
if(INFO)
log.info("Key is for same file version but does not contain block identifier.");
}
} else {
/*
* Since the key does not compare as equal for the full
* length of the prefix it can not encode the same file
* version.
*/
if(DEBUG)
log.debug("Key does not compare as equal for length of prefix.");
}
} else {
/*
* Since the key is shorter than the prefix it can not be for
* the same file version.
*/
log.debug("Key is shorter than prefix.");
}
/*
* The key at computed toIndex is a different file version so we are
* starting a new file version at block := 0.
*/
if(INFO)
log.info("Appending to new file version: id=" + id + ", version="
+ version + ", block=" + 0L);
return 0L;
}
@Override
public void readExternal(final ObjectInput in) throws IOException,
ClassNotFoundException {
id = in.readUTF();
version = in.readInt();
off = 0; // Note: offset always zero when de-serialized.
len = in.readInt();
b = new byte[len];
in.readFully(b);
}
@Override
public void writeExternal(final ObjectOutput out) throws IOException {
out.writeUTF(id);
out.writeInt(version);
/*
* Note: offset not written when serialized and always zero when
* de-serialized.
*/
out.writeInt(len); /* length */
out.write(b, off, len); /* data */
}
}
