io.aeron.logbuffer

Class TermAppender

java.lang.Object

io.aeron.logbuffer.TermAppender

public class TermAppender
extends java.lang.Object

Term buffer appender which supports many producers concurrently writing an append-only log. Note: This class is threadsafe. Messages are appended to a term using a framing protocol as described in FrameDescriptor. A default message header is applied to each message with the fields filled in for fragment flags, type, term number, as appropriate. A message of type FrameDescriptor.PADDING_FRAME_TYPE is appended at the end of the buffer if claimed space is not sufficiently large to accommodate the message about to be written.

Field Summary

Fields

Modifier and Type	Field and Description
static int	FAILED The append operation went past the end of the buffer and failed.
static int	TRIPPED The append operation tripped the end of the buffer and needs to rotate.

Constructor Summary

Constructors

Constructor and Description
TermAppender(org.agrona.concurrent.UnsafeBuffer termBuffer, org.agrona.concurrent.UnsafeBuffer metaDataBuffer, int partitionIndex) Construct a view over a term buffer and state buffer for appending frames.

Method Summary

Modifier and Type	Method and Description
long	appendFragmentedMessage(HeaderWriter header, org.agrona.DirectBuffer srcBuffer, int srcOffset, int length, int maxPayloadLength, ReservedValueSupplier reservedValueSupplier) Append a fragmented message to the the term buffer.
long	appendUnfragmentedMessage(HeaderWriter header, org.agrona.DirectBuffer srcBuffer, int srcOffset, int length, ReservedValueSupplier reservedValueSupplier) Append an unfragmented message to the the term buffer.
long	claim(HeaderWriter header, int length, BufferClaim bufferClaim) Claim length of a the term buffer for writing in the message with zero copy semantics.
static long	pack(int termId, int termOffset) Pack the values for termOffset and termId into a long for returning on the stack.
long	rawTailVolatile() Get the raw current tail value in a volatile memory ordering fashion.
void	tailTermId(int termId) Set the value for the tail counter.
static int	termId(long result) The termId in which the append operation took place.
static int	termOffset(long result) The termOffset as a result of the append

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

TRIPPED

public static final int TRIPPED

The append operation tripped the end of the buffer and needs to rotate.

See Also:

Constant Field Values

FAILED

public static final int FAILED

The append operation went past the end of the buffer and failed.

See Also:

Constant Field Values

Constructor Detail

TermAppender

public TermAppender(org.agrona.concurrent.UnsafeBuffer termBuffer,
                    org.agrona.concurrent.UnsafeBuffer metaDataBuffer,
                    int partitionIndex)

Construct a view over a term buffer and state buffer for appending frames.

Parameters:

termBuffer - for where messages are stored.

metaDataBuffer - for where the state of writers is stored manage concurrency.

partitionIndex - for this will be the active appender.

Method Detail

rawTailVolatile

public long rawTailVolatile()

Get the raw current tail value in a volatile memory ordering fashion.

Returns:

the current tail value.

tailTermId

public void tailTermId(int termId)

Set the value for the tail counter.

Parameters:

termId - for the tail counter

claim

public long claim(HeaderWriter header,
                  int length,
                  BufferClaim bufferClaim)

Claim length of a the term buffer for writing in the message with zero copy semantics.

Parameters:

header - for writing the default header.

length - of the message to be written.

bufferClaim - to be updated with the claimed region.

Returns:

the resulting offset of the term after the append on success otherwise TRIPPED or FAILED packed with the termId if a padding record was inserted at the end.

appendUnfragmentedMessage

public long appendUnfragmentedMessage(HeaderWriter header,
                                      org.agrona.DirectBuffer srcBuffer,
                                      int srcOffset,
                                      int length,
                                      ReservedValueSupplier reservedValueSupplier)

Append an unfragmented message to the the term buffer.

Parameters:

header - for writing the default header.

srcBuffer - containing the message.

srcOffset - at which the message begins.

length - of the message in the source buffer.

reservedValueSupplier - ReservedValueSupplier for the frame.

Returns:

the resulting offset of the term after the append on success otherwise TRIPPED or FAILED packed with the termId if a padding record was inserted at the end.

appendFragmentedMessage

public long appendFragmentedMessage(HeaderWriter header,
                                    org.agrona.DirectBuffer srcBuffer,
                                    int srcOffset,
                                    int length,
                                    int maxPayloadLength,
                                    ReservedValueSupplier reservedValueSupplier)

Append a fragmented message to the the term buffer. The message will be split up into fragments of MTU length minus header.

Parameters:

header - for writing the default header.

srcBuffer - containing the message.

srcOffset - at which the message begins.

length - of the message in the source buffer.

maxPayloadLength - that the message will be fragmented into.

reservedValueSupplier - ReservedValueSupplier for the frame.

Returns:

the resulting offset of the term after the append on success otherwise TRIPPED or FAILED packed with the termId if a padding record was inserted at the end.

pack

public static long pack(int termId,
                        int termOffset)

Pack the values for termOffset and termId into a long for returning on the stack.

Parameters:

termId - value to be packed.

termOffset - value to be packed.

Returns:

a long with both ints packed into it.

termOffset

public static int termOffset(long result)

The termOffset as a result of the append

Parameters:

result - into which the termOffset value has been packed.

Returns:

the termOffset after the append

termId

public static int termId(long result)

The termId in which the append operation took place.

Parameters:

result - into which the termId value has been packed.

Returns:

the termId in which the append operation took place.