activemq-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Stirling Chow (JIRA)" <j...@apache.org>
Subject [jira] [Created] (AMQ-4121) Expose Destination.setMemoryUsage so that custom policies can override default MemoryUsage
Date Fri, 19 Oct 2012 23:06:16 GMT
Stirling Chow created AMQ-4121:
----------------------------------

             Summary: Expose Destination.setMemoryUsage so that custom policies can override
default MemoryUsage
                 Key: AMQ-4121
                 URL: https://issues.apache.org/jira/browse/AMQ-4121
             Project: ActiveMQ
          Issue Type: New Feature
    Affects Versions: 5.7.0
            Reporter: Stirling Chow


Using queues as an example, but this also applies to topics...

When a queue is created, it inherits the System-wide (broker) usage manager and its limits.
 A policy can be applied to the queue in order to specify a destination-specific memory usage
limit:

{code}
<policyEntry queue=">" producerFlowControl="true" memoryLimit="1mb"> 
...
{code}

This policy entry is still dependent on the existing org.apache.activemq.usage.MemoryUsage
class:

{code:title=org.apache.activemq.broker.region.policy.PolicyEntry}
public void configure(Broker broker,Queue queue) {
    baseConfiguration(broker,queue);
    if (dispatchPolicy != null) {
        queue.setDispatchPolicy(dispatchPolicy);
    }
    queue.setDeadLetterStrategy(getDeadLetterStrategy());
    queue.setMessageGroupMapFactory(getMessageGroupMapFactory());
    if (memoryLimit > 0) {
        queue.getMemoryUsage().setLimit(memoryLimit);
    }
...
{code}

We wanted to create a usage policy that would limit the number of messages in a queue by count
(i.e., max 1000 messages) rather than by memory usage.

The existing usage strategies are memory-centric.  It would be nice if a destination had a
generic Usage property rather than a specific MemoryUsage property, but barring refactoring
the interfaces, it would be possible to achieve our goal if we could *set* the MemoryUsage
property of a queue; this is as simple as adding a Destination.setMemoryUsage(MemoryUsage)
property go with the existing Destination.getMemoryUsage(MemoryUsage) property.

The attached patch contains the trivial changes to expose Destination.setMemoryUsage.  The
patch also includes an example of an extended policy that allows a discrete (i.e., count based)
usage policy on queues.  Rather than enforcing a specific limit to the number of messages
in a queue, this policy determines the limit as a multiple of the number of consumers.  It
would be even easier to do the former, but our use case required the latter.  Also note that
this consumer-ratio policy is orthogonal to the consumer prefetch limit --- it's a policy
that we needed to prevent a distributed queue with many messages from being completely drained
to a remote broker during startup (i.e., before additional brokers had started).

{code:Example of ExtendedPolicy configuration}
<bean class="com.invoqsystems.foundation.activemq.ExtendedPolicyEntry">
    <property name="queue" value="shared.notification.*" />
    <property name="messageToConsumerRatioLimit" value="99" />
</bean>
{code}

{code:com.invoqsystems.foundation.activemq.ExtendedPolicyEntry}
public class ExtendedPolicyEntry extends PolicyEntry {
    private long messageToConsumerRatioLimit;

    /**
     * This is called by AMQ when a queue is first created. If a message-to-consumer ratio
is specified, a
     * {@link DiscreteMemoryUsage} class with a {@link ConsumerRatioUsageCapacity} limiter
replaces the queue's
     * byte-based MemoryUsage class. The original parent of the queue's byte-based MemoryUsage
becomes the parent of the
     * {@link DiscreteMemoryUsage}, so it will also receive updates and can signal when the
queue is full (e.g., because
     * of queue or system memory limits).
     */
    @Override
    public void configure(Broker broker, Queue queue) {
        super.configure(broker, queue);

        if (messageToConsumerRatioLimit > 0) {
            DiscreteMemoryUsage ratioUsage = new DiscreteMemoryUsage(queue.getMemoryUsage().getParent(),
":ratio");
            ratioUsage.setLimiter(new ConsumerRatioUsageCapacity(queue));
            ratioUsage.setLimit(messageToConsumerRatioLimit);
            ratioUsage.setParent(queue.getMemoryUsage());
            ratioUsage.setExecutor(queue.getMemoryUsage().getExecutor());
            queue.setMemoryUsage(ratioUsage);
        }
    }
...
{code}


--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira

Mime
View raw message