聊聊artemis的lastValueProperty
CoreMessage
activemq-artemis-2.11.0/artemis-core-client/src/main/java/org/apache/activemq/artemis/core/message/impl/CoreMessage.java
public class CoreMessage extends RefCountMessage implements ICoreMessage { //......
public SimpleString getLastValueProperty() {
return getSimpleStringProperty(Message.HDR_LAST_VALUE_NAME);
}
@Override
public Message setLastValueProperty(SimpleString lastValueName) {
return putStringProperty(Message.HDR_LAST_VALUE_NAME, lastValueName);
}
//......
}
- CoreMessage提供了getLastValueProperty、setLastValueProperty方法,设置的是message的Message.HDR_LAST_VALUE_NAME(
_AMQ_LVQ_NAME
)属性
MessageReferenceImpl
activemq-artemis-2.11.0/artemis-server/src/main/java/org/apache/activemq/artemis/core/server/impl/MessageReferenceImpl.java
public class MessageReferenceImpl extends LinkedListImpl.Node<MessageReferenceImpl> implements MessageReference, Runnable { //......
public SimpleString getLastValueProperty() {
SimpleString lastValue = message.getSimpleStringProperty(queue.getLastValueKey());
if (lastValue == null) {
lastValue = message.getLastValueProperty();
}
return lastValue;
}
//......
}
- MessageReferenceImpl提供了getLastValueProperty方法,它先从message获取queue.getLastValueKey()的属性值,如果为null再读取message.getLastValueProperty()
LastValueQueue
activemq-artemis-2.11.0/artemis-server/src/main/java/org/apache/activemq/artemis/core/server/impl/LastValueQueue.java
public class LastValueQueue extends QueueImpl { private final Map<SimpleString, HolderReference> map = new ConcurrentHashMap<>();
private final SimpleString lastValueKey;
//......
@Override
public synchronized void addTail(final MessageReference ref, final boolean direct) {
if (scheduleIfPossible(ref)) {
return;
}
final SimpleString prop = ref.getLastValueProperty();
if (prop != null) {
HolderReference hr = map.get(prop);
if (hr != null) {
// We need to overwrite the old ref with the new one and ack the old one
replaceLVQMessage(ref, hr);
} else {
hr = new HolderReference(prop, ref);
map.put(prop, hr);
super.addTail(hr, direct);
}
} else {
super.addTail(ref, direct);
}
}
@Override
public synchronized void addHead(final MessageReference ref, boolean scheduling) {
// we first need to check redelivery-delay, as we can"t put anything on headers if redelivery-delay
if (!scheduling && scheduledDeliveryHandler.checkAndSchedule(ref, false)) {
return;
}
SimpleString lastValueProp = ref.getLastValueProperty();
if (lastValueProp != null) {
HolderReference hr = map.get(lastValueProp);
if (hr != null) {
if (scheduling) {
// We need to overwrite the old ref with the new one and ack the old one
replaceLVQMessage(ref, hr);
} else {
// We keep the current ref and ack the one we are returning
super.referenceHandled(ref);
try {
super.acknowledge(ref);
} catch (Exception e) {
ActiveMQServerLogger.LOGGER.errorAckingOldReference(e);
}
}
} else {
hr = new HolderReference(lastValueProp, ref);
map.put(lastValueProp, hr);
super.addHead(hr, scheduling);
}
} else {
super.addHead(ref, scheduling);
}
}
private void replaceLVQMessage(MessageReference ref, HolderReference hr) {
MessageReference oldRef = hr.getReference();
referenceHandled(oldRef);
super.refRemoved(oldRef);
try {
oldRef.acknowledge(null, AckReason.REPLACED, null);
} catch (Exception e) {
ActiveMQServerLogger.LOGGER.errorAckingOldReference(e);
}
hr.setReference(ref);
addRefSize(ref);
refAdded(ref);
}
//......
}
- LastValueQueue继承了QueueImpl,其addTail或addHead方法先通过ref.getLastValueProperty()找到lastValueProp,在从map获取HolderReference,对于HolderReference不为null的,执行replaceLVQMessage方法;该方法会替换到oldRef并对oldRef进行ack
小结
CoreMessage提供了getLastValueProperty、setLastValueProperty方法,设置的是message的Message.HDR_LAST_VALUE_NAME(_AMQ_LVQ_NAME
)属性;MessageReferenceImpl提供了getLastValueProperty方法,它先从message获取queue.getLastValueKey()的属性值,如果为null再读取message.getLastValueProperty();LastValueQueue继承了QueueImpl,其addTail或addHead方法先通过ref.getLastValueProperty()找到lastValueProp,在从map获取HolderReference,对于HolderReference不为null的,执行replaceLVQMessage方法;该方法会替换到oldRef并对oldRef进行ack
doc
- LastValueQueue
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