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/*
* Copyright 2014-2017 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.logbuffer.*;
import org.agrona.*;
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)} method, and messages are sent via one of the
* {@link #offer(DirectBuffer)} methods, or a {@link #tryClaim(int, BufferClaim)} and {@link BufferClaim#commit()}
* method combination.
*
* The APIs used try claim and offer are non-blocking and thread safe.
*
* Note: Publication instances are threadsafe and can be shared between publishing threads.
*
* @see Aeron#addPublication(String, int)
* @see BufferClaim
*/
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.
* 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 happen 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;
private final long originalRegistrationId;
private final long registrationId;
private final long maxPossiblePosition;
private int refCount = 0;
private final int streamId;
private final int sessionId;
private final int initialTermId;
private final int maxMessageLength;
private final int maxPayloadLength;
private final int positionBitsToShift;
private volatile boolean isClosed = false;
private final TermAppender[] termAppenders = new TermAppender[PARTITION_COUNT];
private final ReadablePosition positionLimit;
private final UnsafeBuffer logMetaDataBuffer;
private final HeaderWriter headerWriter;
private final LogBuffers logBuffers;
private final ClientConductor conductor;
private final String channel;
Publication(
final ClientConductor clientConductor,
final String channel,
final int streamId,
final int sessionId,
final ReadablePosition positionLimit,
final LogBuffers logBuffers,
final long originalRegistrationId,
final long registrationId)
{
final UnsafeBuffer[] buffers = logBuffers.termBuffers();
final UnsafeBuffer logMetaDataBuffer = logBuffers.metaDataBuffer();
for (int i = 0; i < PARTITION_COUNT; i++)
{
termAppenders[i] = new TermAppender(buffers[i], logMetaDataBuffer, i);
}
final int termLength = logBuffers.termLength();
this.maxPayloadLength = LogBufferDescriptor.mtuLength(logMetaDataBuffer) - HEADER_LENGTH;
this.maxMessageLength = FrameDescriptor.computeMaxMessageLength(termLength);
this.maxPossiblePosition = termLength * (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.logBuffers = logBuffers;
this.positionBitsToShift = Integer.numberOfTrailingZeros(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();
}
/**
* 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.
*
* @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 original 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 another client has previously added
* this Publication.
*
* @return registration id
*/
public long registrationId()
{
return registrationId;
}
/**
* 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 && conductor.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()
{
conductor.clientLock().lock();
try
{
if (!isClosed && --refCount == 0)
{
isClosed = true;
conductor.releasePublication(this);
}
}
finally
{
conductor.clientLock().unlock();
}
}
/**
* 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;
}
/**
* Forcibly close the Publication and release resources
*/
void forceClose()
{
if (!isClosed)
{
isClosed = true;
conductor.asyncReleasePublication(registrationId);
conductor.lingerResource(managedResource());
}
}
/**
* 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 = rawTailVolatile(logMetaDataBuffer);
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 a negative error value of {@link #NOT_CONNECTED},
* {@link #BACK_PRESSURED}, {@link #ADMIN_ACTION}, {@link #CLOSED}, or {@link #MAX_POSITION_EXCEEDED}.
*/
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 of {@link #NOT_CONNECTED},
* {@link #BACK_PRESSURED}, {@link #ADMIN_ACTION}, {@link #CLOSED}, or {@link #MAX_POSITION_EXCEEDED}.
*/
public 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 long offer(
final DirectBuffer buffer,
final int offset,
final int length,
final ReservedValueSupplier reservedValueSupplier)
{
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, reservedValueSupplier);
}
else
{
checkForMaxMessageLength(length);
result = termAppender.appendFragmentedMessage(
headerWriter, buffer, offset, length, maxPayloadLength, reservedValueSupplier);
}
newPosition = newPosition(partitionIndex, (int)termOffset, position, result);
}
else
{
newPosition = backPressureStatus(position, length);
}
}
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.
* 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.
*
{@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 long tryClaim(final int length, final BufferClaim bufferClaim)
{
checkForMaxPayloadLength(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 = termAppender.claim(headerWriter, length, bufferClaim);
newPosition = newPosition(partitionIndex, (int)termOffset, position, result);
}
else
{
newPosition = backPressureStatus(position, length);
}
}
return newPosition;
}
/**
* Add a destination manually to a multi-destination-cast Publication.
*
* @param endpointChannel for the destination to add
*/
public void addDestination(final String endpointChannel)
{
conductor.clientLock().lock();
try
{
conductor.addDestination(registrationId, endpointChannel);
}
finally
{
conductor.clientLock().unlock();
}
}
/**
* 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)
{
conductor.clientLock().lock();
try
{
conductor.removeDestination(registrationId, endpointChannel);
}
finally
{
conductor.clientLock().unlock();
}
}
/**
* @see Publication#close()
*/
void incRef()
{
++refCount;
}
private long newPosition(final int index, final int currentTail, final long position, final long result)
{
long newPosition = ADMIN_ACTION;
final int termOffset = termOffset(result);
if (termOffset > 0)
{
newPosition = (position - currentTail) + termOffset;
}
else if ((position + currentTail) > maxPossiblePosition)
{
newPosition = MAX_POSITION_EXCEEDED;
}
else if (termOffset == TermAppender.TRIPPED)
{
final int nextIndex = nextPartitionIndex(index);
initialiseTailWithTermId(logMetaDataBuffer, nextIndex, termId(result) + 1);
activePartitionIndexOrdered(logMetaDataBuffer, nextIndex);
}
return newPosition;
}
private long backPressureStatus(final long currentPosition, final int messageLength)
{
long status = NOT_CONNECTED;
if ((currentPosition + messageLength) >= maxPossiblePosition)
{
status = MAX_POSITION_EXCEEDED;
}
else if (conductor.isPublicationConnected(timeOfLastStatusMessage(logMetaDataBuffer)))
{
status = BACK_PRESSURED;
}
return status;
}
private void checkForMaxPayloadLength(final int length)
{
if (length > maxPayloadLength)
{
throw new IllegalArgumentException(
"Claim exceeds maxPayloadLength of " + maxPayloadLength + ", length=" + length);
}
}
private void checkForMaxMessageLength(final int length)
{
if (length > maxMessageLength)
{
throw new IllegalArgumentException(
"Message exceeds maxMessageLength of " + maxMessageLength + ", length=" + 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();
}
}
}