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/*
* Copyright 2014-2019 Real Logic Ltd.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.aeron;
import io.aeron.exceptions.AeronException;
import io.aeron.logbuffer.*;
import io.aeron.status.ChannelEndpointStatus;
import org.agrona.DirectBuffer;
import org.agrona.concurrent.UnsafeBuffer;
import org.agrona.concurrent.status.ReadablePosition;
import static io.aeron.logbuffer.LogBufferDescriptor.*;
import static io.aeron.protocol.DataHeaderFlyweight.HEADER_LENGTH;
/**
* Aeron publisher API for sending messages to subscribers of a given channel and streamId pair. {@link Publication}s
* are created via the {@link Aeron#addPublication(String, int)} {@link Aeron#addExclusivePublication(String, int)}
* methods, and messages are sent via one of the {@link #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
* {@link ExclusivePublication}. In the case of {@link ConcurrentPublication} all methods are threadsafe.
*
* @see ConcurrentPublication
* @see ExclusivePublication
* @see Aeron#addPublication(String, int)
* @see Aeron#addExclusivePublication(String, int)
*/
public abstract class Publication implements AutoCloseable
{
/**
* The publication is not yet connected to a subscriber.
*/
public static final long NOT_CONNECTED = -1;
/**
* The offer failed due to back pressure from the subscribers preventing further transmission.
*/
public static final long BACK_PRESSURED = -2;
/**
* 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.
*/
public static final long ADMIN_ACTION = -3;
/**
* The {@link Publication} has been closed and should no longer be used.
*/
public static final long CLOSED = -4;
/**
* 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.
*/
public static final long MAX_POSITION_EXCEEDED = -5;
protected final long originalRegistrationId;
protected final long registrationId;
protected final long maxPossiblePosition;
protected final int channelStatusId;
protected final int streamId;
protected final int sessionId;
protected final int maxMessageLength;
protected final int initialTermId;
protected final int maxPayloadLength;
protected final int positionBitsToShift;
protected final int termBufferLength;
protected volatile boolean isClosed = false;
protected final ReadablePosition positionLimit;
protected final UnsafeBuffer logMetaDataBuffer;
protected final HeaderWriter headerWriter;
protected final LogBuffers logBuffers;
protected final ClientConductor conductor;
protected final String channel;
protected Publication(
final ClientConductor clientConductor,
final String channel,
final int streamId,
final int sessionId,
final ReadablePosition positionLimit,
final int channelStatusId,
final LogBuffers logBuffers,
final long originalRegistrationId,
final long registrationId)
{
final UnsafeBuffer logMetaDataBuffer = logBuffers.metaDataBuffer();
this.termBufferLength = logBuffers.termLength();
this.maxMessageLength = FrameDescriptor.computeMaxMessageLength(termBufferLength);
this.maxPayloadLength = LogBufferDescriptor.mtuLength(logMetaDataBuffer) - HEADER_LENGTH;
this.maxPossiblePosition = termBufferLength * (1L << 31L);
this.conductor = clientConductor;
this.channel = channel;
this.streamId = streamId;
this.sessionId = sessionId;
this.initialTermId = LogBufferDescriptor.initialTermId(logMetaDataBuffer);
this.logMetaDataBuffer = logMetaDataBuffer;
this.originalRegistrationId = originalRegistrationId;
this.registrationId = registrationId;
this.positionLimit = positionLimit;
this.channelStatusId = channelStatusId;
this.logBuffers = logBuffers;
this.positionBitsToShift = LogBufferDescriptor.positionBitsToShift(termBufferLength);
this.headerWriter = HeaderWriter.newInstance(defaultFrameHeader(logMetaDataBuffer));
}
/**
* Number of bits to right shift a position to get a term count for how far the stream has progressed.
*
* @return of bits to right shift a position to get a term count for how far the stream has progressed.
*/
public int positionBitsToShift()
{
return positionBitsToShift;
}
/**
* Get the length in bytes for each term partition in the log buffer.
*
* @return the length in bytes for each term partition in the log buffer.
*/
public int termBufferLength()
{
return termBufferLength;
}
/**
* 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.
*
* @return the maximum possible position this stream can reach due to it term buffer length.
*/
public long maxPossiblePosition()
{
return maxPossiblePosition;
}
/**
* Media address for delivery to the channel.
*
* @return Media address for delivery to the channel.
*/
public String channel()
{
return channel;
}
/**
* Stream identity for scoping within the channel media address.
*
* @return Stream identity for scoping within the channel media address.
*/
public int streamId()
{
return streamId;
}
/**
* Session under which messages are published. Identifies this Publication instance. Sessions are unique across
* all active publications on a driver instance.
*
* @return the session id for this publication.
*/
public int sessionId()
{
return sessionId;
}
/**
* The initial term id assigned when this {@link Publication} was created. This can be used to determine how many
* terms have passed since creation.
*
* @return the initial term id.
*/
public int initialTermId()
{
return initialTermId;
}
/**
* Maximum message length supported in bytes. Messages may be made of multiple fragments if greater than
* MTU length.
*
* @return maximum message length supported in bytes.
*/
public int maxMessageLength()
{
return maxMessageLength;
}
/**
* Maximum length of a message payload that fits within a message fragment.
*
* This is he MTU length minus the message fragment header length.
*
* @return maximum message fragment payload length.
*/
public int maxPayloadLength()
{
return maxPayloadLength;
}
/**
* Get the registration used to register this Publication with the media driver by the first publisher.
*
* @return original registration id
*/
public long originalRegistrationId()
{
return originalRegistrationId;
}
/**
* Is this Publication the original instance added to the driver? If not then it was added after another client
* has already added the publication.
*
* @return true if this instance is the first added otherwise false.
*/
public boolean isOriginal()
{
return originalRegistrationId == registrationId;
}
/**
* Get the registration id used to register this Publication with the media driver.
*
* If this value is different from the {@link #originalRegistrationId()} then a previous active registration exists.
*
* @return registration id
*/
public long registrationId()
{
return registrationId;
}
/**
* Has the {@link Publication} seen an active Subscriber recently?
*
* @return true if this {@link Publication} has recently seen an active subscriber otherwise false.
*/
public boolean isConnected()
{
return !isClosed && LogBufferDescriptor.isConnected(logMetaDataBuffer);
}
/**
* 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.
*/
public void close()
{
if (!isClosed)
{
conductor.releasePublication(this);
}
}
/**
* Has this object been closed and should no longer be used?
*
* @return true if it has been closed otherwise false.
*/
public boolean isClosed()
{
return isClosed;
}
/**
* Get the status of the media channel for this Publication.
*
* The status will be {@link io.aeron.status.ChannelEndpointStatus#ERRORED} if a socket exception occurs on setup
* and {@link io.aeron.status.ChannelEndpointStatus#ACTIVE} if all is well.
*
* @return status for the channel as one of the constants from {@link ChannelEndpointStatus} with it being
* {@link ChannelEndpointStatus#NO_ID_ALLOCATED} if the publication is closed.
* @see io.aeron.status.ChannelEndpointStatus
*/
public long channelStatus()
{
if (isClosed)
{
return ChannelEndpointStatus.NO_ID_ALLOCATED;
}
return conductor.channelStatus(channelStatusId);
}
/**
* Get the counter used to represent the channel status for this publication.
*
* @return the counter used to represent the channel status for this publication.
*/
public int channelStatusId()
{
return channelStatusId;
}
/**
* Get the current position to which the publication has advanced for this stream.
*
* @return the current position to which the publication has advanced for this stream or {@link #CLOSED}.
*/
public long position()
{
if (isClosed)
{
return CLOSED;
}
final long rawTail = rawTailVolatile(logMetaDataBuffer);
final int termOffset = termOffset(rawTail, termBufferLength);
return computePosition(termId(rawTail), termOffset, positionBitsToShift, initialTermId);
}
/**
* Get the position limit beyond which this {@link Publication} will be back pressured.
*
* This should only be used as a guide to determine when back pressure is likely to be applied.
*
* @return the position limit beyond which this {@link Publication} will be back pressured.
*/
public long positionLimit()
{
if (isClosed)
{
return CLOSED;
}
return positionLimit.getVolatile();
}
/**
* Get the counter id for the position limit after which the publication will be back pressured.
*
* @return the counter id for the position limit after which the publication will be back pressured.
*/
public int positionLimitId()
{
return positionLimit.id();
}
/**
* Available window for offering into a publication before the {@link #positionLimit()} is reached.
*
* @return window for offering into a publication before the {@link #positionLimit()} is reached. If
* the publication is closed then {@link #CLOSED} will be returned.
*/
public abstract long availableWindow();
/**
* Non-blocking publish of a buffer containing a message.
*
* @param buffer containing message.
* @return The new stream position, otherwise a negative error value of {@link #NOT_CONNECTED},
* {@link #BACK_PRESSURED}, {@link #ADMIN_ACTION}, {@link #CLOSED}, or {@link #MAX_POSITION_EXCEEDED}.
*/
public final long offer(final DirectBuffer buffer)
{
return offer(buffer, 0, buffer.capacity());
}
/**
* Non-blocking publish of a partial buffer containing a message.
*
* @param buffer containing message.
* @param offset offset in the buffer at which the encoded message begins.
* @param length in bytes of the encoded message.
* @return The new stream position, otherwise a negative error value of {@link #NOT_CONNECTED},
* {@link #BACK_PRESSURED}, {@link #ADMIN_ACTION}, {@link #CLOSED}, or {@link #MAX_POSITION_EXCEEDED}.
*/
public final long offer(final DirectBuffer buffer, final int offset, final int length)
{
return offer(buffer, offset, length, null);
}
/**
* Non-blocking publish of a partial buffer containing a message.
*
* @param buffer containing message.
* @param offset offset in the buffer at which the encoded message begins.
* @param length in bytes of the encoded message.
* @param reservedValueSupplier {@link ReservedValueSupplier} for the frame.
* @return The new stream position, otherwise a negative error value of {@link #NOT_CONNECTED},
* {@link #BACK_PRESSURED}, {@link #ADMIN_ACTION}, {@link #CLOSED}, or {@link #MAX_POSITION_EXCEEDED}.
*/
public abstract long offer(
DirectBuffer buffer, int offset, int length, ReservedValueSupplier reservedValueSupplier);
/**
* Non-blocking publish of a message composed of two parts, e.g. a header and encapsulated payload.
*
* @param bufferOne containing the first part of the message.
* @param offsetOne at which the first part of the message begins.
* @param lengthOne of the first part of the message.
* @param bufferTwo containing the second part of the message.
* @param offsetTwo at which the second part of the message begins.
* @param lengthTwo of the second part of the message.
* @return The new stream position, otherwise a negative error value of {@link #NOT_CONNECTED},
* {@link #BACK_PRESSURED}, {@link #ADMIN_ACTION}, {@link #CLOSED}, or {@link #MAX_POSITION_EXCEEDED}.
*/
public final long offer(
final DirectBuffer bufferOne,
final int offsetOne,
final int lengthOne,
final DirectBuffer bufferTwo,
final int offsetTwo,
final int lengthTwo)
{
return offer(bufferOne, offsetOne, lengthOne, bufferTwo, offsetTwo, lengthTwo, null);
}
/**
* Non-blocking publish of a message composed of two parts, e.g. a header and encapsulated payload.
*
* @param bufferOne containing the first part of the message.
* @param offsetOne at which the first part of the message begins.
* @param lengthOne of the first part of the message.
* @param bufferTwo containing the second part of the message.
* @param offsetTwo at which the second part of the message begins.
* @param lengthTwo of the second part of the message.
* @param reservedValueSupplier {@link ReservedValueSupplier} for the frame.
* @return The new stream position, otherwise a negative error value of {@link #NOT_CONNECTED},
* {@link #BACK_PRESSURED}, {@link #ADMIN_ACTION}, {@link #CLOSED}, or {@link #MAX_POSITION_EXCEEDED}.
*/
public abstract long offer(
DirectBuffer bufferOne,
int offsetOne,
int lengthOne,
DirectBuffer bufferTwo,
int offsetTwo,
int lengthTwo,
ReservedValueSupplier reservedValueSupplier);
/**
* Non-blocking publish by gathering buffer vectors into a message.
*
* @param vectors which make up the message.
* @return The new stream position, otherwise a negative error value of {@link #NOT_CONNECTED},
* {@link #BACK_PRESSURED}, {@link #ADMIN_ACTION}, {@link #CLOSED}, or {@link #MAX_POSITION_EXCEEDED}.
*/
public final long offer(final DirectBufferVector[] vectors)
{
return offer(vectors, null);
}
/**
* Non-blocking publish by gathering buffer vectors into a message.
*
* @param vectors which make up the message.
* @param reservedValueSupplier {@link ReservedValueSupplier} for the frame.
* @return The new stream position, otherwise a negative error value of {@link #NOT_CONNECTED},
* {@link #BACK_PRESSURED}, {@link #ADMIN_ACTION}, {@link #CLOSED}, or {@link #MAX_POSITION_EXCEEDED}.
*/
public abstract long offer(DirectBufferVector[] vectors, ReservedValueSupplier reservedValueSupplier);
/**
* 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 {@link BufferClaim#commit()} should be called thus making it available.
*
* 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 {@link ConcurrentPublication} and other claims to be sent to reach end-of-stream (EOS).
*
{@code
* 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();
* }
* }
* }
*
* @param length of the range to claim, in bytes..
* @param bufferClaim to be populated if the claim succeeds.
* @return The new stream position, otherwise a negative error value of {@link #NOT_CONNECTED},
* {@link #BACK_PRESSURED}, {@link #ADMIN_ACTION}, {@link #CLOSED}, or {@link #MAX_POSITION_EXCEEDED}.
* @throws IllegalArgumentException if the length is greater than {@link #maxPayloadLength()} within an MTU.
* @see BufferClaim#commit()
* @see BufferClaim#abort()
*/
public abstract long tryClaim(int length, BufferClaim bufferClaim);
/**
* Add a destination manually to a multi-destination-cast Publication.
*
* @param endpointChannel for the destination to add
*/
public void addDestination(final String endpointChannel)
{
if (isClosed)
{
throw new AeronException("Publication is closed");
}
conductor.addDestination(originalRegistrationId, endpointChannel);
}
/**
* Remove a previously added destination manually from a multi-destination-cast Publication.
*
* @param endpointChannel for the destination to remove
*/
public void removeDestination(final String endpointChannel)
{
if (isClosed)
{
throw new AeronException("Publication is closed");
}
conductor.removeDestination(originalRegistrationId, endpointChannel);
}
void internalClose()
{
isClosed = true;
}
LogBuffers logBuffers()
{
return logBuffers;
}
final long backPressureStatus(final long currentPosition, final int messageLength)
{
if ((currentPosition + messageLength) >= maxPossiblePosition)
{
return MAX_POSITION_EXCEEDED;
}
if (LogBufferDescriptor.isConnected(logMetaDataBuffer))
{
return BACK_PRESSURED;
}
return NOT_CONNECTED;
}
final void checkPositiveLength(final int length)
{
if (length < 0)
{
throw new IllegalArgumentException("invalid length: " + length);
}
}
final void checkPayloadLength(final int length)
{
if (length < 0)
{
throw new IllegalArgumentException("invalid length: " + length);
}
if (length > maxPayloadLength)
{
throw new IllegalArgumentException(
"claim exceeds maxPayloadLength of " + maxPayloadLength + ", length=" + length);
}
}
final void checkMaxMessageLength(final int length)
{
if (length > maxMessageLength)
{
throw new IllegalArgumentException(
"message exceeds maxMessageLength of " + maxMessageLength + ", length=" + length);
}
}
static int validateAndComputeLength(final int lengthOne, final int lengthTwo)
{
if (lengthOne < 0)
{
throw new IllegalArgumentException("lengthOne < 0: " + lengthOne);
}
if (lengthTwo < 0)
{
throw new IllegalArgumentException("lengthTwo < 0: " + lengthTwo);
}
final int totalLength = lengthOne + lengthTwo;
if (totalLength < 0)
{
throw new IllegalArgumentException("overflow totalLength=" + totalLength);
}
return totalLength;
}
}