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Message Broker

Message Broker is an intermediary program/module that is responsible for translating and forwarding messages in specific format from sender to receiver.

By default Sabre Red 360 tries to connect to the broker located by default at tcp://localhost:61616. If the connection is refused, Sabre Red 360 will start its own embedded broker that listens for connections at tcp://localhost:61616. Remote broker is the answer for the need of integration between Sabre Red 360 and external applications in distributed environment like Terminal Services.

Sabre Red 360 can be remotely configured by Sabre Admin to be in specific mode. For Termial Services users it is highly recommended to use remote mode only.

Embedded

native api embedded

Remote

native api remote

It should be noted that ActiveMQ requries Java 8.

Remote broker configuration:

<!--
    Licensed to the Apache Software Foundation (ASF) under one or more
    contributor license agreements.  See the NOTICE file distributed with
    this work for additional information regarding copyright ownership.
    The ASF licenses this file to You 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.
-->
<!-- START SNIPPET: example -->
<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="localhost"
        dataDirectory="${activemq.data}" persistent="false">

        <destinationPolicy>
            <policyMap>
                <policyEntries>
                    <policyEntry topic=">">
                        <!-- 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="10000" />
                        </pendingMessageLimitStrategy>
                    </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="false" />
        </managementContext>

        <!--
            Configure message persistence for the broker. The default persistence
            mechanism is the KahaDB store (identified by the kahaDB tag).
            For more information, see:

            http://activemq.apache.org/persistence.html
        -->
        <persistenceAdapter>
            <kahaDB directory="${activemq.data}/kahadb" />
        </persistenceAdapter>


        <!--
            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="70" />
                </memoryUsage>
                <storeUsage>
                    <storeUsage limit="100 gb" />
                </storeUsage>
                <tempUsage>
                    <tempUsage limit="50 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 100MB -->
            <transportConnector name="openwire"
                uri="tcp://0.0.0.0:61616?maximumConnections=1000&amp;wireFormat.maxFrameSize=104857600" />
        </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"/>
    -->
    <import resource="jetty.xml" />

</beans>
<!-- END SNIPPET: example -->

The difference with default configuration is disabled persistence, in order to reduce disk usage.

<broker xmlns="http://activemq.apache.org/schema/core" brokerName="localhost" dataDirectory="${activemq.data}" persistent="false">

In ActiveMQ config file, you can modify the limit of concurrent connections for specified protocol and url, by changing the maximumConnections value, be default limit is set to 1000.

<transportConnectors>
    <!-- DOS protection, limit concurrent connections to 1000 and frame size to 100MB -->
    <transportConnector name="openwire" uri="tcp://0.0.0.0:61616?maximumConnections=1000&amp;wireFormat.maxFrameSize=104857600"/>
</transportConnectors>

Configuraton file is placed in apache-activemq-5.15.3/conf/activemq.xml