KahaDB db.data and ActiveMQ 5.6

Question

I am looking for answers to the following questions related to KahaDB.

I have an application that uses ActiveMQ, and the application receives from 500,000 to 1 million messages that are written to the ActiveMQ queue, and users collect them.

I noticed that the size of the db.data file varies from a few kilobytes to almost 600 or 700 MB.

I noticed that when the size of the db.data file grows, the messages get stuck, forcing me to turn off my application, restart the application so that new consumers connect to the broker to merge all messages.

• Ideally, what is the size of db.data? If an application produces and consumes at the same time, regardless of the number of messages, I think the size of db.data should be small.

• Why sometimes the file size grows and what increases the size of the db.data file?

I have ActiveMQ 5.6 and I see this problem at least 2 or 3 times a month. To brokers that work smoothly, I noticed that the size of the db.data file is in KB, not 500 MB or 700 MB.

Here is an example activeemq.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:amq="http://activemq.apache.org/schema/core" 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-2.0.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>
   <broker xmlns="http://activemq.apache.org/schema/core" brokerName="localhost" dataDirectory="/foo/activemq_5.6/data">
      <destinationPolicy>
         <policyMap>
            <policyEntries>
               <policyEntry topic=">" producerFlowControl="true" memoryLimit="1mb">
                  <pendingSubscriberPolicy>
                     <vmCursor />
                  </pendingSubscriberPolicy>
               </policyEntry>
               <policyEntry queue=">" producerFlowControl="true" memoryLimit="1mb" useCache="false" />
            </policyEntries>
         </policyMap>
      </destinationPolicy>
      <managementContext>
         <managementContext createConnector="true" />
      </managementContext>
      <persistenceAdapter>
         <kahaDB directory="/foo/activemq_5.6/data/kahadb" />
      </persistenceAdapter>
      <systemUsage>
         <systemUsage>
            <memoryUsage>
               <memoryUsage limit="64 mb" />
            </memoryUsage>
            <storeUsage>
               <storeUsage limit="100 gb" />
            </storeUsage>
            <tempUsage>
               <tempUsage limit="50 gb" />
            </tempUsage>
         </systemUsage>
      </systemUsage>
      <transportConnectors>
         <transportConnector name="openwire" uri="tcp://0.0.0.0:61616" />
      </transportConnectors>
   </broker>
   <import resource="jetty.xml" />
</beans>

Answer 1

Typically, the kahadb directory has segments for messages that have not yet been used. If there is any message in the segment that has not yet been consumed, it will save the entire segment. So if you are anything in any lineup, you will usually not have anything in common in the kaha directory.

If you have the berth console turned on, you can use it to see which queues have messages in them.

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