com.twitter.distributedlog

Class DLSN

java.lang.Object

com.twitter.distributedlog.DLSN

All Implemented Interfaces:

Comparable<DLSN>

public class DLSN
extends Object
implements Comparable<DLSN>

DistributedLog Sequence Number (DLSN) is the system generated sequence number for log record.

DLSN is comprised with 3 components:

• LogSegment Sequence Number: the sequence number of log segment that the record is written in
• Entry Id: the entry id of the entry that the record is batched in
• Slot Id: the slot id that the record is in the entry

See Also:

LogRecordWithDLSN

Field Summary

Fields

Modifier and Type	Field and Description
static DLSN	InitialDLSN
static DLSN	InvalidDLSN
static DLSN	NonInclusiveLowerBound
static byte	VERSION0
static byte	VERSION1

Constructor Summary

Constructors

Constructor and Description
DLSN(long logSegmentSequenceNo, long entryId, long slotId)

Method Summary

Methods

Modifier and Type	Method and Description
int	compareTo(DLSN that)
static DLSN	deserialize(String dlsn) Deserialize the DLSN from base64 encoded string dlsn.
static DLSN	deserializeBytes(byte[] data) Deserialize the DLSN from bytes array.
boolean	equals(Object o)
long	getEntryId() Return the entry id of the batch that the record is written to.
long	getLogSegmentSequenceNo() Return the sequence number of the log segment that the record is written to.
DLSN	getNextDLSN() Positions to a DLSN greater than the current value - this may not correspond to an actual LogRecord, its just used by the positioning logic to position the reader
long	getSlotId() Return the slot id in the batch that the record is written to.
int	hashCode()
DLSN	positionOnTheNextLedger() Positions to a DLSN greater than the current value - this may not correspond to an actual LogRecord, its just used by the positioning logic to position the reader
String	serialize() Serialize the DLSN into base64 encoded string.
String	serialize(byte version) Serialize the DLSN into base64 encoded string with given version.
byte[]	serializeBytes() Serialize the DLSN into bytes with current version.
byte[]	serializeBytes(byte version) Serialize the DLSN into bytes with given version.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

VERSION0

public static final byte VERSION0

See Also:

Constant Field Values

VERSION1

public static final byte VERSION1

See Also:

Constant Field Values

InitialDLSN

public static final DLSN InitialDLSN

NonInclusiveLowerBound

public static final DLSN NonInclusiveLowerBound

InvalidDLSN

public static final DLSN InvalidDLSN

Constructor Detail

DLSN

public DLSN(long logSegmentSequenceNo,
    long entryId,
    long slotId)

Method Detail

getLogSegmentSequenceNo

public long getLogSegmentSequenceNo()

Return the sequence number of the log segment that the record is written to.

Returns:

sequence number of the log segment that the record is written to.

getEntryId

public long getEntryId()

Return the entry id of the batch that the record is written to.

Returns:

entry id of the batch that the record is written to.

getSlotId

public long getSlotId()

Return the slot id in the batch that the record is written to.

Returns:

slot id in the batch that the record is written to.

compareTo

public int compareTo(DLSN that)

Specified by:

compareTo in interface Comparable<DLSN>

serializeBytes

public byte[] serializeBytes()

Serialize the DLSN into bytes with current version.

Returns:

the serialized bytes

serializeBytes

public byte[] serializeBytes(byte version)

Serialize the DLSN into bytes with given version.

Parameters:

version - version to serialize the DLSN

Returns:

the serialized bytes

serialize

public String serialize()

Serialize the DLSN into base64 encoded string.

Returns:

serialized base64 string

See Also:

serializeBytes()

serialize

public String serialize(byte version)

Serialize the DLSN into base64 encoded string with given version.

Parameters:

version - version to serialize the DLSN

Returns:

the serialized base64 string

See Also:

serializeBytes(byte)

deserialize

public static DLSN deserialize(String dlsn)

Deserialize the DLSN from base64 encoded string dlsn.

Parameters:

dlsn - base64 encoded string

Returns:

dlsn

deserializeBytes

public static DLSN deserializeBytes(byte[] data)

Deserialize the DLSN from bytes array.

Parameters:

data - serialized bytes

Returns:

dlsn

toString

public String toString()

Overrides:

toString in class Object

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

getNextDLSN

public DLSN getNextDLSN()

Positions to a DLSN greater than the current value - this may not correspond to an actual LogRecord, its just used by the positioning logic to position the reader

Returns:

the next DLSN

positionOnTheNextLedger

public DLSN positionOnTheNextLedger()

Positions to a DLSN greater than the current value - this may not correspond to an actual LogRecord, its just used by the positioning logic to position the reader

Returns:

the next DLSN