ActiveMQ network of brokers messages are not balanced - jms

Question

I am using ActiveMQ 5.13.4 and I have set up a network-of-brokers with two brokers A and B that are connected via a networkConnector. Each broker has a consumer connected to it (A' and B'). A' and B' consume messages from the same distributed queue (e.g. requests-queue). Each consumer is a java application, represented by a Spring DefaultJmsListenerContainerFactory having the setting concurrency: 5-10. Basically, each consumer has max 10 threads that can consume simultaneously messages from the queue.
In broker configuration (activemq.xml) I have set the prefetch size to 1, assuming that there are not many messages and they need a lot of processing time.
<policyEntry queue=">" producerFlowControl="true" optimizedDispatch="true" queuePrefetch="1" enableAudit="false">
The desired behavior is when I send 100 messages to A it starts processing 10 messages simultaneously (one for each consumer thread) and forwards another 10 to B. When B finishes processing the first 10 messages, it would get an extra 10. This would continue until all the messages are processed.
The actual behavior is that when I send 100 messages to A, it sends 10 messages, one per each thread, to the local consumer A' and forwards the remaining 90 to B'. The consumers on A' finish processing the messages and they wait while 90 messages get processed on broker B by its consumers.
Question: How can I configure the network in order to balance messages based on consumer availability?
The full activemq.xml configuration for one of the brokers is the following. The other one has the same configuration only a different name and IP in the networkConnector.
<beans
xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://activemq.apache.org/schema/core http://activemq.apache.org/schema/core/activemq-core.xsd">
<!-- Allows us to use system properties as variables in this configuration file -->
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<value>file:${activemq.conf}/credentials.properties</value>
</property>
</bean>
<!-- Allows accessing the server log -->
<bean id="logQuery" class="io.fabric8.insight.log.log4j.Log4jLogQuery"
lazy-init="false" scope="singleton"
init-method="start" destroy-method="stop">
</bean>
<!--
The <broker> element is used to configure the ActiveMQ broker.
-->
<broker xmlns="http://activemq.apache.org/schema/core"
brokerName="broker-jms-tux-01-qa-gnd"
persistent="false"
dataDirectory="${activemq.data}"
cacheTempDestinations="false"
advisorySupport="true"
useJmx="true">
<destinationPolicy>
<policyMap>
<policyEntries>
<policyEntry topic=">" producerFlowControl="true">
<!-- The constantPendingMessageLimitStrategy is used to prevent
slow topic consumers to block producers and affect other consumers
by limiting the number of messages that are retained
For more information, see:
http://activemq.apache.org/slow-consumer-handling.html
-->
<pendingMessageLimitStrategy>
<constantPendingMessageLimitStrategy limit="1000"/>
</pendingMessageLimitStrategy>
<pendingSubscriberPolicy>
<vmCursor/>
</pendingSubscriberPolicy>
</policyEntry>
<policyEntry queue=">" producerFlowControl="true" optimizedDispatch="true" queuePrefetch="1" enableAudit="false">
<!--
Allow messages to be replayed back when the broker to which they were forwarded does not have any more consumers.
See section "Stuck Messages" from http://activemq.apache.org/networks-of-brokers.html
-->
<networkBridgeFilterFactory>
<!--
N.B.: When using replayWhenNoConsumers=true for versions < 5.9, it is necessary to also disable the cursors duplicate detection using enableAudit=false as the cursor could mark the replayed messages as duplicates (depending on the time window between playing and replaying these messages over the network bridge). The problem is fully explained here: http://tmielke.blogspot.de/2012/03/i-have-messages-on-queue-but-they-dont.html
-->
<conditionalNetworkBridgeFilterFactory replayWhenNoConsumers="true"/>
</networkBridgeFilterFactory>
<pendingQueuePolicy>
<vmQueueCursor/>
</pendingQueuePolicy>
<deadLetterStrategy>
<sharedDeadLetterStrategy expiration="300000"/>
</deadLetterStrategy>
</policyEntry>
</policyEntries>
</policyMap>
</destinationPolicy>
<!--
The managementContext is used to configure how ActiveMQ is exposed in
JMX. By default, ActiveMQ uses the MBean server that is started by
the JVM. For more information, see:
http://activemq.apache.org/jmx.html
-->
<managementContext>
<managementContext createConnector="true" connectorPort="1099"/>
</managementContext>
<!-- Network of brokers -->
<networkConnectors>
<networkConnector
name="broker-jms-tux-01-qa-gnd->broker-jms-tux-02-qa-gnd"
uri="static:(tcp://10.83.16.22:61616)"
conduitSubscriptions="false"
dynamicOnly="true"
networkTTL="2"
alwaysSyncSend="true"
decreaseNetworkConsumerPriority="true"
duplex="false"/>
</networkConnectors>
<!--
The systemUsage controls the maximum amount of space the broker will
use before disabling caching and/or slowing down producers. For more information, see:
http://activemq.apache.org/producer-flow-control.html
-->
<systemUsage>
<systemUsage>
<memoryUsage>
<memoryUsage percentOfJvmHeap="80"/>
</memoryUsage>
<storeUsage>
<storeUsage limit="10 gb"/>
</storeUsage>
<tempUsage>
<tempUsage limit="4 gb"/>
</tempUsage>
</systemUsage>
</systemUsage>
<!--
The transport connectors expose ActiveMQ over a given protocol to
clients and other brokers. For more information, see:
http://activemq.apache.org/configuring-transports.html
-->
<transportConnectors>
<!-- DOS protection, limit concurrent connections to 1000 and frame size to 400MB -->
<transportConnector name="openwire" uri="tcp://0.0.0.0:61616?maximumConnections=1000&wireFormat.maxFrameSize=3200000000"/>
</transportConnectors>
<!-- destroy the spring context on shutdown to stop jetty -->
<shutdownHooks>
<bean xmlns="http://www.springframework.org/schema/beans" class="org.apache.activemq.hooks.SpringContextHook"/>
</shutdownHooks>
</broker>
<!--
Enable web consoles, REST and Ajax APIs and demos
The web consoles requires by default login, you can disable this in the jetty.xml file
Take a look at ${ACTIVEMQ_HOME}/conf/jetty.xml for more details
-->
<import resource="jetty.xml"/>
</beans>
Thanks you in advance!
**Update 25/10/2016: **
I have come across the following statement in: http://activemq.apache.org/networks-of-brokers.html
The conditionalNetworkBridgeFilterFactory factory allows a rate limit
to be specified for a destination, such that network consumer can be
throttled. Prefetch for a network consumer is largely negated by the
fact that a network consumer relays a message typically acks very
quickly so even with a low prefetch and decreased priority a network
consumer can starve a modestly quick local consumer. Throttling
provides a remedy for this.
Question: It is still not clear for me, why when the local consumer A' finishes processing the initial 10 messages, broker A does not receive any of the 80 messages remaining on B (because 10 were dispatched to the local consumer of broker B)?
I have tried setting a higher networkTTL, but it still does not work.