bitronix.tm.journal.TransactionLogRecord Maven / Gradle / Ivy
package bitronix.tm.journal;
import bitronix.tm.utils.Encoder;
import bitronix.tm.utils.UidGenerator;
import bitronix.tm.utils.*;
import org.slf4j.LoggerFactory;
import org.slf4j.Logger;
import java.io.UnsupportedEncodingException;
import java.util.*;
import java.util.zip.CRC32;
/**
* Representation of a transaction log record on disk.
* On-disk format has been implemented following Mike Spille's recommendations. Quoting him:
*
* [RECORD_TYPE :4] [RECORD_LEN :4] [HEADER_LEN :4] [System.currentTimeMillis :8] [Sequence number :4]
* [Checksum :4] [Payload :X] [END_RECORD_INDICATOR :4]
* Where [RECORD_TYPE] is a passed-in record type from the TM. [RECORD_LEN] is the overall record length
* (sans [RECORD_TYPE and [RECORD_LEN]). [HEADER_LEN] is the length of the remainder of the header - important if you
* want to support easy upgrades of your format. The remaining pieces are the rest of the header, and the payload. The
* header at least should have [System.currentTimeMillis] and [Sequence number], with the [sequence number] coming from
* some monotically increasing sequence generator unique to the process. The [checksum] is optional for the paranoid
* among us. The time information can be very useful for profiling and tracking down problems in production, and in
* conjunction with the sequence number it can give you precise ordering. This doesn't give you much in this solution,
* but can be priceless if you ever move to a system with multiple dual log file pairs to lessen single-threading on a
* single log file pair. Finally, I like having an [END_RECORD_INDICATOR] as an extra corruption detector device - I'm
* a suspenders and belt kind of guy. Actually, the END_RECORD_INDICATOR and [RECORD_LEN] in conjunction are very
* useful in development, as well, to catch programming mistakes in the log system early.
*
* Payload contains [GTRID LENGTH :1] [GTRID :A] [UNIQUE NAMES COUNT :4] ([UNIQUE NAME LENGTH :2] [UNIQUE NAME :Y] ...)
* which makes a major difference with Mike's proposed format because here a record can vary in length: the GTRID size
* is A bytes long (A being the GTRID length) and there can be X unique names that are Y characters long, Y being eventually
* different for each name.
*
*
* @see XA Exposed, Part III: The Implementor's Notebook
* @author lorban
*/
public class TransactionLogRecord {
private final static Logger log = LoggerFactory.getLogger(TransactionLogRecord.class);
private int status;
private int recordLength;
private int headerLength;
private long time;
private int sequenceNumber;
private int crc32;
private Uid gtrid;
private SortedSet uniqueNames;
private int endRecord;
/**
* Use this constructor when restoring a log from the disk.
* @param status record type
* @param recordLength record length excluding status and recordLength
* @param headerLength length of all fields except gtrid, uniqueNames and endRecord
* @param time current time in milliseconds
* @param sequenceNumber atomically generated sequence number during a JVM's lifespan
* @param crc32 checksum of the full record
* @param gtrid global transaction id
* @param uniqueNames unique names of XA data sources used in this transaction
* @param endRecord end of record marker
*/
public TransactionLogRecord(int status, int recordLength, int headerLength, long time, int sequenceNumber, int crc32, Uid gtrid, Set uniqueNames, int endRecord) {
this.status = status;
this.recordLength = recordLength;
this.headerLength = headerLength;
this.time = time;
this.sequenceNumber = sequenceNumber;
this.crc32 = crc32;
this.gtrid = gtrid;
this.uniqueNames = new TreeSet(uniqueNames);
this.endRecord = endRecord;
}
/**
* Create a new transaction log ready to be stored.
* @param status record type
* @param gtrid global transaction id
* @param uniqueNames unique names of XA data sources used in this transaction
*/
public TransactionLogRecord(int status, Uid gtrid, Set uniqueNames) {
this.status = status;
time = System.currentTimeMillis();
sequenceNumber = UidGenerator.getNextSequenceNumber();
this.gtrid = gtrid;
this.uniqueNames = new TreeSet(uniqueNames);
endRecord = TransactionLogAppender.END_RECORD;
refresh();
}
public int getStatus() {
return status;
}
public int getRecordLength() {
return recordLength;
}
public int getHeaderLength() {
return headerLength;
}
public long getTime() {
return time;
}
public int getSequenceNumber() {
return sequenceNumber;
}
public int getCrc32() {
return crc32;
}
public Uid getGtrid() {
return gtrid;
}
public Set getUniqueNames() {
return Collections.unmodifiableSortedSet(uniqueNames);
}
public int getEndRecord() {
return endRecord;
}
public void removeUniqueNames(Collection namesToRemove) {
uniqueNames.removeAll(namesToRemove);
refresh();
}
/**
* Recalculate and store the dynamic values of this record: {@link #getRecordLength()}, {@link #getRecordHeaderLength()}
* and {@link #calculateCrc32()}. This method must be called each time after the set of contained unique names is updated.
*/
private void refresh() {
recordLength = calculateRecordLength(uniqueNames);
headerLength = getRecordHeaderLength();
crc32 = calculateCrc32();
}
/**
* Recalculate the CRC32 value of this record (using {@link #calculateCrc32()}) and compare it with the stored value.
* @return true if the recalculated value equals the stored one, false otherwise.
*/
public boolean isCrc32Correct() {
return calculateCrc32() == getCrc32();
}
/**
* Calculate the CRC32 value of this record.
* @return the CRC32 value of this record.
*/
public int calculateCrc32() {
CRC32 crc32 = new CRC32();
crc32.update(Encoder.intToBytes(status));
crc32.update(Encoder.intToBytes(recordLength));
crc32.update(Encoder.intToBytes(headerLength));
crc32.update(Encoder.longToBytes(time));
crc32.update(Encoder.intToBytes(sequenceNumber));
crc32.update(gtrid.getArray());
crc32.update(Encoder.intToBytes(uniqueNames.size()));
Iterator it = uniqueNames.iterator();
while (it.hasNext()) {
String name = (String) it.next();
crc32.update(Encoder.shortToBytes((short) name.length()));
try {
crc32.update(name.getBytes("US-ASCII"));
} catch (UnsupportedEncodingException ex) {
log.error("unable to convert unique name bytes to US-ASCII", ex);
}
}
crc32.update(Encoder.intToBytes(endRecord));
return (int) crc32.getValue();
}
public String toString() {
StringBuffer sb = new StringBuffer(128);
sb.append("a Bitronix TransactionLogRecord with ");
sb.append("status="); sb.append(Decoder.decodeStatus(status)); sb.append(", ");
sb.append("recordLength="); sb.append(recordLength); sb.append(", ");
sb.append("headerLength="); sb.append(headerLength); sb.append(", ");
sb.append("time="); sb.append(time); sb.append(", ");
sb.append("sequenceNumber="); sb.append(sequenceNumber); sb.append(", ");
sb.append("crc32="); sb.append(crc32); sb.append(", ");
sb.append("gtrid="); sb.append(gtrid.toString()); sb.append(", ");
sb.append("uniqueNames=");
Iterator it = uniqueNames.iterator();
while (it.hasNext()) {
Object o = it.next();
sb.append(o);
if (it.hasNext())
sb.append(',');
}
return sb.toString();
}
/**
* this is the total size on disk of a TransactionLog.
* @return recordLength
*/
int calculateTotalRecordSize() {
return calculateRecordLength(uniqueNames) + 4 + 4; // + status + record length
}
/**
* this is the value needed by field recordLength in the TransactionLog.
* @param uniqueNames the unique names ofthe record.
* @return recordLength
*/
private int calculateRecordLength(Set uniqueNames) {
int totalSize = 0;
Iterator it = uniqueNames.iterator();
while (it.hasNext()) {
String uniqueName = (String) it.next();
totalSize += 2 + uniqueName.length(); // 2 bytes for storing the unique name length + unique name length
}
totalSize += getFixedRecordLength();
return totalSize;
}
/**
* Length of all the fixed size fields part of the record length header except status and record length.
* @return fixedRecordLength
*/
private int getFixedRecordLength() {
return 4 + 8 + 4 + 4 + 1 + gtrid.getArray().length + 4 + 4; // record header length + current time + sequence number + checksum + GTRID size + GTRID + unique names count + end record marker
}
/**
* Value needed by field headerLength in the TransactionLog.
* @return headerLength
*/
private int getRecordHeaderLength() {
return 4 + 4 + 4 + 8 + 4 + 4; // status + record length + record header length + current time + sequence number + checksum
}
}