uk.co.real_logic.aeron.Publication Maven / Gradle / Ivy
Show all versions of aeron-all Show documentation
/*
* Copyright 2014 - 2016 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 uk.co.real_logic.aeron;
import uk.co.real_logic.aeron.logbuffer.*;
import uk.co.real_logic.agrona.DirectBuffer;
import uk.co.real_logic.agrona.ManagedResource;
import uk.co.real_logic.agrona.concurrent.UnsafeBuffer;
import uk.co.real_logic.agrona.concurrent.status.ReadablePosition;
import static uk.co.real_logic.aeron.logbuffer.LogBufferDescriptor.*;
import static uk.co.real_logic.aeron.protocol.DataHeaderFlyweight.HEADER_LENGTH;
/**
* Aeron Publisher API for sending messages to subscribers of a given channel and streamId pair. Publishers
* are created via an {@link Aeron} object, and messages are sent via an offer method or a claim and commit
* method combination.
*
* The APIs used to send are all non-blocking.
*
* Note: Publication instances are threadsafe and can be shared between publishing threads.
* @see Aeron#addPublication(String, int)
*/
public 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.
*/
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;
private final long registrationId;
private final int streamId;
private final int sessionId;
private final int initialTermId;
private final int maxPayloadLength;
private final int positionBitsToShift;
private final ReadablePosition positionLimit;
private final TermAppender[] termAppenders = new TermAppender[PARTITION_COUNT];
private final UnsafeBuffer logMetaDataBuffer;
private final HeaderWriter headerWriter;
private final LogBuffers logBuffers;
private final ClientConductor clientConductor;
private final String channel;
private volatile boolean isClosed = false;
private int refCount = 0;
Publication(
final ClientConductor clientConductor,
final String channel,
final int streamId,
final int sessionId,
final ReadablePosition positionLimit,
final LogBuffers logBuffers,
final long registrationId)
{
final UnsafeBuffer[] buffers = logBuffers.atomicBuffers();
final UnsafeBuffer logMetaDataBuffer = buffers[LOG_META_DATA_SECTION_INDEX];
for (int i = 0; i < PARTITION_COUNT; i++)
{
termAppenders[i] = new TermAppender(buffers[i], buffers[i + PARTITION_COUNT]);
}
this.maxPayloadLength = mtuLength(logMetaDataBuffer) - HEADER_LENGTH;
this.clientConductor = clientConductor;
this.channel = channel;
this.streamId = streamId;
this.sessionId = sessionId;
this.initialTermId = LogBufferDescriptor.initialTermId(logMetaDataBuffer);
this.logMetaDataBuffer = logMetaDataBuffer;
this.registrationId = registrationId;
this.positionLimit = positionLimit;
this.logBuffers = logBuffers;
this.positionBitsToShift = Integer.numberOfTrailingZeros(logBuffers.termLength());
this.headerWriter = new HeaderWriter(defaultFrameHeader(logMetaDataBuffer));
}
/**
* 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 logBuffers.termLength();
}
/**
* 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.
*
* @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.
*
* @return maximum message length supported in bytes.
*/
public int maxMessageLength()
{
return FrameDescriptor.computeMaxMessageLength(logBuffers.termLength());
}
/**
* Has the {@link Publication} seen an active Subscriber recently?
*
* @return true if this {@link Publication} has seen an active subscriber otherwise false.
*/
public boolean isConnected()
{
return !isClosed && clientConductor.isPublicationConnected(timeOfLastStatusMessage(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()
{
synchronized (clientConductor)
{
if (--refCount == 0)
{
release();
}
}
}
/**
* 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;
}
/**
* Release resources and forcibly close the Publication regardless of reference count.
*/
void release()
{
if (!isClosed)
{
isClosed = true;
clientConductor.releasePublication(this);
}
}
/**
* 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.
* @throws IllegalStateException if the publication is closed.
*/
public long position()
{
if (isClosed)
{
return CLOSED;
}
final long rawTail = termAppenders[activePartitionIndex(logMetaDataBuffer)].rawTailVolatile();
final int termOffset = termOffset(rawTail, logBuffers.termLength());
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();
}
/**
* Non-blocking publish of a buffer containing a message.
*
* @param buffer containing message.
* @return The new stream position, otherwise {@link #NOT_CONNECTED}, {@link #BACK_PRESSURED},
* {@link #ADMIN_ACTION} or {@link #CLOSED}.
*/
public 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 {@link #NOT_CONNECTED}, {@link #BACK_PRESSURED} or
* {@link #ADMIN_ACTION}.
*/
public long offer(final DirectBuffer buffer, final int offset, final int length)
{
long newPosition = CLOSED;
if (!isClosed)
{
final long limit = positionLimit.getVolatile();
final int partitionIndex = activePartitionIndex(logMetaDataBuffer);
final TermAppender termAppender = termAppenders[partitionIndex];
final long rawTail = termAppender.rawTailVolatile();
final long termOffset = rawTail & 0xFFFF_FFFFL;
final long position = computeTermBeginPosition(termId(rawTail), positionBitsToShift, initialTermId) + termOffset;
if (position < limit)
{
final long result;
if (length <= maxPayloadLength)
{
result = termAppender.appendUnfragmentedMessage(headerWriter, buffer, offset, length);
}
else
{
checkForMaxMessageLength(length);
result = termAppender.appendFragmentedMessage(headerWriter, buffer, offset, length, maxPayloadLength);
}
newPosition = newPosition(partitionIndex, (int)termOffset, position, result);
}
else if (clientConductor.isPublicationConnected(timeOfLastStatusMessage(logMetaDataBuffer)))
{
newPosition = BACK_PRESSURED;
}
else
{
newPosition = NOT_CONNECTED;
}
}
return newPosition;
}
/**
* 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.
*
*
{@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 {@link #NOT_CONNECTED}, {@link #BACK_PRESSURED},
* {@link #ADMIN_ACTION} or {@link #CLOSED}.
* @throws IllegalArgumentException if the length is greater than max payload length within an MTU.
* @see BufferClaim#commit()
* @see BufferClaim#abort()
*/
public long tryClaim(final int length, final BufferClaim bufferClaim)
{
long newPosition = CLOSED;
if (!isClosed)
{
checkForMaxPayloadLength(length);
final long limit = positionLimit.getVolatile();
final int partitionIndex = activePartitionIndex(logMetaDataBuffer);
final TermAppender termAppender = termAppenders[partitionIndex];
final long rawTail = termAppender.rawTailVolatile();
final long termOffset = rawTail & 0xFFFF_FFFFL;
final long position = computeTermBeginPosition(termId(rawTail), positionBitsToShift, initialTermId) + termOffset;
if (position < limit)
{
final long result = termAppender.claim(headerWriter, length, bufferClaim);
newPosition = newPosition(partitionIndex, (int)termOffset, position, result);
}
else if (clientConductor.isPublicationConnected(timeOfLastStatusMessage(logMetaDataBuffer)))
{
newPosition = BACK_PRESSURED;
}
else
{
newPosition = NOT_CONNECTED;
}
}
return newPosition;
}
/**
* Return the registration id used to register this Publication with the media driver.
*
* @return registration id
*/
public long registrationId()
{
return registrationId;
}
/**
* @see Publication#close()
*/
void incRef()
{
synchronized (clientConductor)
{
++refCount;
}
}
private long newPosition(final int index, final int currentTail, final long position, final long result)
{
long newPosition = ADMIN_ACTION;
final int termOffset = TermAppender.termOffset(result);
if (termOffset > 0)
{
newPosition = (position - currentTail) + termOffset;
}
else if (termOffset == TermAppender.TRIPPED)
{
final int nextIndex = nextPartitionIndex(index);
final int nextNextIndex = nextPartitionIndex(nextIndex);
termAppenders[nextIndex].tailTermId(TermAppender.termId(result) + 1);
termAppenders[nextNextIndex].statusOrdered(NEEDS_CLEANING);
LogBufferDescriptor.activePartitionIndex(logMetaDataBuffer, nextIndex);
}
return newPosition;
}
private void checkForMaxPayloadLength(final int length)
{
if (length > maxPayloadLength)
{
throw new IllegalArgumentException(String.format(
"Claim exceeds maxPayloadLength of %d, length=%d", maxPayloadLength, length));
}
}
private void checkForMaxMessageLength(final int length)
{
final int maxMessageLength = maxMessageLength();
if (length > maxMessageLength)
{
throw new IllegalArgumentException(String.format(
"Encoded message exceeds maxMessageLength of %d, length=%d", maxMessageLength, length));
}
}
ManagedResource managedResource()
{
return new PublicationManagedResource();
}
private class PublicationManagedResource implements ManagedResource
{
private long timeOfLastStateChange = 0;
public void timeOfLastStateChange(final long time)
{
this.timeOfLastStateChange = time;
}
public long timeOfLastStateChange()
{
return timeOfLastStateChange;
}
public void delete()
{
logBuffers.close();
}
}
}