Publication (Aeron Message Transport)

java.lang.Object
- io.aeron.Publication

All Implemented Interfaces:

AutoCloseable

Direct Known Subclasses:

ConcurrentPublication, ExclusivePublication
```
public abstract class Publication
extends Object
implements AutoCloseable
```
Aeron publisher API for sending messages to subscribers of a given channel and streamId pair. Publications are created via the Aeron.addPublication(String, int) Aeron.addExclusivePublication(String, int) methods, and messages are sent via one of the offer(DirectBuffer) methods.
The APIs used for tryClaim and offer are non-blocking.
Note: All methods are threadsafe with the exception of offer and tryClaim for the subclass ExclusivePublication. In the case of ConcurrentPublication all methods are threadsafe.

See Also:

ConcurrentPublication, ExclusivePublication, Aeron.addPublication(String, int), Aeron.addExclusivePublication(String, int)

Field Summary

Fields
Modifier and Type	Field and Description
`static long`	`ADMIN_ACTION` The offer failed due to an administration action and should be retried.
`static long`	`BACK_PRESSURED` The offer failed due to back pressure from the subscribers preventing further transmission.
`protected String`	`channel`
`protected int`	`channelStatusId`
`static long`	`CLOSED` The `Publication` has been closed and should no longer be used.
`protected io.aeron.ClientConductor`	`conductor`
`protected HeaderWriter`	`headerWriter`
`protected int`	`initialTermId`
`protected boolean`	`isClosed`
`protected LogBuffers`	`logBuffers`
`protected UnsafeBuffer`	`logMetaDataBuffer`
`static long`	`MAX_POSITION_EXCEEDED` The offer failed due to reaching the maximum position of the stream given term buffer length times the total possible number of terms.
`protected int`	`maxMessageLength`
`protected int`	`maxPayloadLength`
`protected long`	`maxPossiblePosition`
`static long`	`NOT_CONNECTED` The publication is not connected to a subscriber, this can be an intermittent state as subscribers come and go.
`protected long`	`originalRegistrationId`
`protected int`	`positionBitsToShift`
`protected ReadablePosition`	`positionLimit`
`protected long`	`registrationId`
`protected int`	`sessionId`
`protected int`	`streamId`
`protected int`	`termBufferLength`

Constructor Summary

Constructors
Modifier	Constructor and Description
`protected`	`Publication(io.aeron.ClientConductor clientConductor, String channel, int streamId, int sessionId, ReadablePosition positionLimit, int channelStatusId, LogBuffers logBuffers, long originalRegistrationId, long registrationId)`

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`addDestination(String endpointChannel)` Add a destination manually to a multi-destination-cast Publication.
`long`	`asyncAddDestination(String endpointChannel)` Asynchronously add a destination manually to a multi-destination-cast Publication.
`long`	`asyncRemoveDestination(String endpointChannel)` Asynchronously remove a previously added destination from a multi-destination-cast Publication.
`abstract long`	`availableWindow()` Available window for offering into a publication before the `positionLimit()` is reached.
`String`	`channel()` Media address for delivery to the channel.
`long`	`channelStatus()` Get the status of the media channel for this Publication.
`int`	`channelStatusId()` Get the counter used to represent the channel status for this publication.
`void`	`close()` Release resources used by this Publication when there are no more references.
`int`	`initialTermId()` The initial term id assigned when this `Publication` was created.
`boolean`	`isClosed()` Has this object been closed and should no longer be used?
`boolean`	`isConnected()` Has the `Publication` seen an active Subscriber recently?
`boolean`	`isOriginal()` Is this Publication the original instance added to the driver? If not then it was added after another client has already added the publication.
`int`	`maxMessageLength()` Maximum message length supported in bytes.
`int`	`maxPayloadLength()` Maximum length of a message payload that fits within a message fragment.
`long`	`maxPossiblePosition()` The maximum possible position this stream can reach due to its term buffer length.
`long`	`offer(DirectBuffer buffer)` Non-blocking publish of a buffer containing a message.
`long`	`offer(DirectBuffer buffer, int offset, int length)` Non-blocking publish of a partial buffer containing a message.
`long`	`offer(DirectBuffer bufferOne, int offsetOne, int lengthOne, DirectBuffer bufferTwo, int offsetTwo, int lengthTwo)` Non-blocking publish of a message composed of two parts, e.g.
`abstract long`	`offer(DirectBuffer bufferOne, int offsetOne, int lengthOne, DirectBuffer bufferTwo, int offsetTwo, int lengthTwo, ReservedValueSupplier reservedValueSupplier)` Non-blocking publish of a message composed of two parts, e.g.
`abstract long`	`offer(DirectBuffer buffer, int offset, int length, ReservedValueSupplier reservedValueSupplier)` Non-blocking publish of a partial buffer containing a message.
`long`	`offer(DirectBufferVector[] vectors)` Non-blocking publish by gathering buffer vectors into a message.
`abstract long`	`offer(DirectBufferVector[] vectors, ReservedValueSupplier reservedValueSupplier)` Non-blocking publish by gathering buffer vectors into a message.
`long`	`originalRegistrationId()` Get the registration used to register this Publication with the media driver by the first publisher.
`long`	`position()` Get the current position to which the publication has advanced for this stream.
`int`	`positionBitsToShift()` Number of bits to right shift a position to get a term count for how far the stream has progressed.
`long`	`positionLimit()` Get the position limit beyond which this `Publication` will be back pressured.
`int`	`positionLimitId()` Get the counter id for the position limit after which the publication will be back pressured.
`long`	`registrationId()` Get the registration id used to register this Publication with the media driver.
`void`	`removeDestination(String endpointChannel)` Remove a previously added destination manually from a multi-destination-cast Publication.
`int`	`sessionId()` Session under which messages are published.
`int`	`streamId()` Stream identity for scoping within the channel media address.
`int`	`termBufferLength()` Get the length in bytes for each term partition in the log buffer.
`String`	`toString()`
`abstract long`	`tryClaim(int length, BufferClaim bufferClaim)` Try to claim a range in the publication log into which a message can be written with zero copy semantics.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - NOT_CONNECTED
```
public static final long NOT_CONNECTED
```
    The publication is not connected to a subscriber, this can be an intermittent state as subscribers come and go.
    
    See Also:
    
    Constant Field Values
  - BACK_PRESSURED
```
public static final long BACK_PRESSURED
```
    The offer failed due to back pressure from the subscribers preventing further transmission.
    
    See Also:
    
    Constant Field Values
  - ADMIN_ACTION
```
public static final long ADMIN_ACTION
```
    The offer failed due to an administration action and should be retried. The action is an operation such as log rotation which is likely to have succeeded by the next retry attempt.
    
    See Also:
    
    Constant Field Values
  - CLOSED
```
public static final long CLOSED
```
    The Publication has been closed and should no longer be used.
    
    See Also:
    
    Constant Field Values
  - MAX_POSITION_EXCEEDED
```
public static final long MAX_POSITION_EXCEEDED
```
    The offer failed due to reaching the maximum position of the stream given term buffer length times the total possible number of terms.
    If this happens then the publication should be closed and a new one added. To make it less likely to happen then increase the term buffer length.
    
    See Also:
    
    Constant Field Values
  - originalRegistrationId
```
protected final long originalRegistrationId
```
  - registrationId
```
protected final long registrationId
```
  - maxPossiblePosition
```
protected final long maxPossiblePosition
```
  - channelStatusId
```
protected final int channelStatusId
```
  - streamId
```
protected final int streamId
```
  - sessionId
```
protected final int sessionId
```
  - maxMessageLength
```
protected final int maxMessageLength
```
  - initialTermId
```
protected final int initialTermId
```
  - maxPayloadLength
```
protected final int maxPayloadLength
```
  - positionBitsToShift
```
protected final int positionBitsToShift
```
  - termBufferLength
```
protected final int termBufferLength
```
  - isClosed
```
protected volatile boolean isClosed
```
  - positionLimit
```
protected final ReadablePosition positionLimit
```
  - logMetaDataBuffer
```
protected final UnsafeBuffer logMetaDataBuffer
```
  - headerWriter
```
protected final HeaderWriter headerWriter
```
  - logBuffers
```
protected final LogBuffers logBuffers
```
  - conductor
```
protected final io.aeron.ClientConductor conductor
```
  - channel
```
protected final String channel
```
- Constructor Detail
  - Publication
```
protected Publication(io.aeron.ClientConductor clientConductor,
                      String channel,
                      int streamId,
                      int sessionId,
                      ReadablePosition positionLimit,
                      int channelStatusId,
                      LogBuffers logBuffers,
                      long originalRegistrationId,
                      long registrationId)
```
- Method Detail
  - positionBitsToShift
```
public int positionBitsToShift()
```
    Number of bits to right shift a position to get a term count for how far the stream has progressed.
    
    Returns:
    
    of bits to right shift a position to get a term count for how far the stream has progressed.
  - termBufferLength
```
public int termBufferLength()
```
    Get the length in bytes for each term partition in the log buffer.
    
    Returns:
    
    the length in bytes for each term partition in the log buffer.
  - maxPossiblePosition
```
public long maxPossiblePosition()
```
    The maximum possible position this stream can reach due to its term buffer length.
    Maximum possible position is term-length times 2^31 in bytes.
    
    Returns:
    
    the maximum possible position this stream can reach due to it term buffer length.
  - channel
```
public String channel()
```
    Media address for delivery to the channel.
    
    Returns:
    
    Media address for delivery to the channel.
  - streamId
```
public int streamId()
```
    Stream identity for scoping within the channel media address.
    
    Returns:
    
    Stream identity for scoping within the channel media address.
  - sessionId
```
public int sessionId()
```
    Session under which messages are published. Identifies this Publication instance. Sessions are unique across all active publications on a driver instance.
    
    Returns:
    
    the session id for this publication.
  - initialTermId
```
public int initialTermId()
```
    The initial term id assigned when this Publication was created. This can be used to determine how many terms have passed since creation.
    
    Returns:
    
    the initial term id.
  - maxMessageLength
```
public int maxMessageLength()
```
    Maximum message length supported in bytes. Messages may be made of multiple fragments if greater than MTU length.
    
    Returns:
    
    maximum message length supported in bytes.
  - maxPayloadLength
```
public int maxPayloadLength()
```
    Maximum length of a message payload that fits within a message fragment.
    This is he MTU length minus the message fragment header length.
    
    Returns:
    
    maximum message fragment payload length.
  - originalRegistrationId
```
public long originalRegistrationId()
```
    Get the registration used to register this Publication with the media driver by the first publisher.
    
    Returns:
    
    original registration id
  - isOriginal
```
public boolean isOriginal()
```
    Is this Publication the original instance added to the driver? If not then it was added after another client has already added the publication.
    
    Returns:
    
    true if this instance is the first added otherwise false.
  - registrationId
```
public long registrationId()
```
    Get the registration id used to register this Publication with the media driver.
    If this value is different from the originalRegistrationId() then a previous active registration exists.
    
    Returns:
    
    registration id
  - isConnected
```
public boolean isConnected()
```
    Has the Publication seen an active Subscriber recently?
    
    Returns:
    
    true if this Publication has recently seen an active subscriber otherwise false.
  - close
```
public void close()
```
    Release resources used by this Publication when there are no more references.
    Publications are reference counted and are only truly closed when the ref count reaches zero.
    
    Specified by:
    
    close in interface AutoCloseable
  - isClosed
```
public boolean isClosed()
```
    Has this object been closed and should no longer be used?
    
    Returns:
    
    true if it has been closed otherwise false.
  - channelStatus
```
public long channelStatus()
```
    Get the status of the media channel for this Publication.
    The status will be ChannelEndpointStatus.ERRORED if a socket exception occurs on setup and ChannelEndpointStatus.ACTIVE if all is well.
    
    Returns:
    
    status for the channel as one of the constants from ChannelEndpointStatus with it being ChannelEndpointStatus.NO_ID_ALLOCATED if the publication is closed.
    
    See Also:
    
    ChannelEndpointStatus
  - channelStatusId
```
public int channelStatusId()
```
    Get the counter used to represent the channel status for this publication.
    
    Returns:
    
    the counter used to represent the channel status for this publication.
  - position
```
public long position()
```
    Get the current position to which the publication has advanced for this stream.
    
    Returns:
    
    the current position to which the publication has advanced for this stream or CLOSED.
  - positionLimit
```
public long positionLimit()
```
    Get the position limit beyond which this Publication will be back pressured.
    This should only be used as a guide to determine when back pressure is likely to be applied.
    
    Returns:
    
    the position limit beyond which this Publication will be back pressured.
  - positionLimitId
```
public int positionLimitId()
```
    Get the counter id for the position limit after which the publication will be back pressured.
    
    Returns:
    
    the counter id for the position limit after which the publication will be back pressured.
  - availableWindow
```
public abstract long availableWindow()
```
    Available window for offering into a publication before the positionLimit() is reached.
    
    Returns:
    
    window for offering into a publication before the positionLimit() is reached. If the publication is closed then CLOSED will be returned.
  - offer
```
public final long offer(DirectBuffer buffer)
```
    Non-blocking publish of a buffer containing a message.
    
    Parameters:
    
    buffer - containing message.
    
    Returns:
    
    The new stream position, otherwise a negative error value of NOT_CONNECTED, BACK_PRESSURED, ADMIN_ACTION, CLOSED, or MAX_POSITION_EXCEEDED.
  - offer
```
public final long offer(DirectBuffer buffer,
                        int offset,
                        int length)
```
    Non-blocking publish of a partial buffer containing a message.
    
    Parameters:
    
    buffer - containing message.
    
    offset - offset in the buffer at which the encoded message begins.
    
    length - in bytes of the encoded message.
    
    Returns:
    
    The new stream position, otherwise a negative error value of NOT_CONNECTED, BACK_PRESSURED, ADMIN_ACTION, CLOSED, or MAX_POSITION_EXCEEDED.
  - offer
```
public abstract long offer(DirectBuffer buffer,
                           int offset,
                           int length,
                           ReservedValueSupplier reservedValueSupplier)
```
    Non-blocking publish of a partial buffer containing a message.
    
    Parameters:
    
    buffer - containing message.
    
    offset - offset in the buffer at which the encoded message begins.
    
    length - in bytes of the encoded message.
    
    reservedValueSupplier - ReservedValueSupplier for the frame.
    
    Returns:
    
    The new stream position, otherwise a negative error value of NOT_CONNECTED, BACK_PRESSURED, ADMIN_ACTION, CLOSED, or MAX_POSITION_EXCEEDED.
  - offer
```
public final long offer(DirectBuffer bufferOne,
                        int offsetOne,
                        int lengthOne,
                        DirectBuffer bufferTwo,
                        int offsetTwo,
                        int lengthTwo)
```
    Non-blocking publish of a message composed of two parts, e.g. a header and encapsulated payload.
    
    Parameters:
    
    bufferOne - containing the first part of the message.
    
    offsetOne - at which the first part of the message begins.
    
    lengthOne - of the first part of the message.
    
    bufferTwo - containing the second part of the message.
    
    offsetTwo - at which the second part of the message begins.
    
    lengthTwo - of the second part of the message.
    
    Returns:
    
    The new stream position, otherwise a negative error value of NOT_CONNECTED, BACK_PRESSURED, ADMIN_ACTION, CLOSED, or MAX_POSITION_EXCEEDED.
  - offer
```
public abstract long offer(DirectBuffer bufferOne,
                           int offsetOne,
                           int lengthOne,
                           DirectBuffer bufferTwo,
                           int offsetTwo,
                           int lengthTwo,
                           ReservedValueSupplier reservedValueSupplier)
```
    Non-blocking publish of a message composed of two parts, e.g. a header and encapsulated payload.
    
    Parameters:
    
    bufferOne - containing the first part of the message.
    
    offsetOne - at which the first part of the message begins.
    
    lengthOne - of the first part of the message.
    
    bufferTwo - containing the second part of the message.
    
    offsetTwo - at which the second part of the message begins.
    
    lengthTwo - of the second part of the message.
    
    reservedValueSupplier - ReservedValueSupplier for the frame.
    
    Returns:
    
    The new stream position, otherwise a negative error value of NOT_CONNECTED, BACK_PRESSURED, ADMIN_ACTION, CLOSED, or MAX_POSITION_EXCEEDED.
  - offer
```
public final long offer(DirectBufferVector[] vectors)
```
    Non-blocking publish by gathering buffer vectors into a message.
    
    Parameters:
    
    vectors - which make up the message.
    
    Returns:
    
    The new stream position, otherwise a negative error value of NOT_CONNECTED, BACK_PRESSURED, ADMIN_ACTION, CLOSED, or MAX_POSITION_EXCEEDED.
  - offer
```
public abstract long offer(DirectBufferVector[] vectors,
                           ReservedValueSupplier reservedValueSupplier)
```
    Non-blocking publish by gathering buffer vectors into a message.
    
    Parameters:
    
    vectors - which make up the message.
    
    reservedValueSupplier - ReservedValueSupplier for the frame.
    
    Returns:
    
    The new stream position, otherwise a negative error value of NOT_CONNECTED, BACK_PRESSURED, ADMIN_ACTION, CLOSED, or MAX_POSITION_EXCEEDED.
  - tryClaim
```
public abstract long tryClaim(int length,
                              BufferClaim bufferClaim)
```
    Try to claim a range in the publication log into which a message can be written with zero copy semantics. Once the message has been written then BufferClaim.commit() should be called thus making it available. A claim length cannot be greater than maxPayloadLength().
    Note: This method can only be used for message lengths less than MTU length minus header. If the claim is held for more than the aeron.publication.unblock.timeout system property then the driver will assume the publication thread is dead and will unblock the claim thus allowing other threads to make progress for ConcurrentPublication and other claims to be sent to reach end-of-stream (EOS).
```
     final BufferClaim bufferClaim = new BufferClaim(); // Can be stored and reused to avoid allocation

     if (publication.tryClaim(messageLength, bufferClaim) > 0L)
     {
         try
         {
              final MutableDirectBuffer buffer = bufferClaim.buffer();
              final int offset = bufferClaim.offset();

              // Work with buffer directly or wrap with a flyweight
         }
         finally
         {
             bufferClaim.commit();
         }
     }
 
```
    Parameters:
    
    length - of the range to claim, in bytes..
    
    bufferClaim - to be populated if the claim succeeds.
    
    Returns:
    
    The new stream position, otherwise a negative error value of NOT_CONNECTED, BACK_PRESSURED, ADMIN_ACTION, CLOSED, or MAX_POSITION_EXCEEDED.
    
    Throws:
    
    IllegalArgumentException - if the length is greater than maxPayloadLength() within an MTU.
    
    See Also:
    
    BufferClaim.commit(), BufferClaim.abort()
  - addDestination
```
public void addDestination(String endpointChannel)
```
    Add a destination manually to a multi-destination-cast Publication.
    
    Parameters:
    
    endpointChannel - for the destination to add.
  - removeDestination
```
public void removeDestination(String endpointChannel)
```
    Remove a previously added destination manually from a multi-destination-cast Publication.
    
    Parameters:
    
    endpointChannel - for the destination to remove.
  - asyncAddDestination
```
public long asyncAddDestination(String endpointChannel)
```
    Asynchronously add a destination manually to a multi-destination-cast Publication.
    Errors will be delivered asynchronously to the Aeron.Context.errorHandler(). Completion can be tracked by passing the returned correlation id to Aeron.isCommandActive(long).
    
    Parameters:
    
    endpointChannel - for the destination to add.
    
    Returns:
    
    the correlationId for the command.
  - asyncRemoveDestination
```
public long asyncRemoveDestination(String endpointChannel)
```
    Asynchronously remove a previously added destination from a multi-destination-cast Publication.
    Errors will be delivered asynchronously to the Aeron.Context.errorHandler(). Completion can be tracked by passing the returned correlation id to Aeron.isCommandActive(long).
    
    Parameters:
    
    endpointChannel - for the destination to remove.
    
    Returns:
    
    the correlationId for the command.
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object

Class Publication

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

NOT_CONNECTED

BACK_PRESSURED

ADMIN_ACTION

CLOSED

MAX_POSITION_EXCEEDED

originalRegistrationId

registrationId

maxPossiblePosition

channelStatusId

streamId

sessionId

maxMessageLength

initialTermId

maxPayloadLength

positionBitsToShift

termBufferLength

isClosed

positionLimit

logMetaDataBuffer

headerWriter

logBuffers

conductor

channel

Constructor Detail

Publication

Method Detail

positionBitsToShift

termBufferLength

maxPossiblePosition

channel

streamId

sessionId

initialTermId

maxMessageLength

maxPayloadLength

originalRegistrationId

isOriginal

registrationId

isConnected

close

isClosed

channelStatus

channelStatusId

position

positionLimit

positionLimitId

availableWindow

offer

offer

offer

offer

offer

offer

offer

tryClaim

addDestination

removeDestination

asyncAddDestination

asyncRemoveDestination

toString