In IBM Engineering Lifecycle Management (ELM) 7.0, there are three primary reasons why IBM MessageSight, an MQTT message broker, is needed.
It is quite possible and highly likely that a client deployment will need MessageSight for one or more of the reasons stated. Note MessageSight only runs on CentOS and RHEL operating systems (see IBM MessageSight - Provisioning your operating system).
IBM recommends that MessageSight be clustered for both scalability and high availability purposes. See Clustering in IBM IoT MessageSight and IBM MessageSight - Clustering considerations. ELM provides several JMX MBeans that reporting on aspects of the MQTT MessageBroker, i.e. MessageSight, used by ELM. In particular, see the MQTT service metrics MBean in Common Managed Beans.
IBM requires that a MessageSight cluster be shared between ELM instances that are contributing to a common global configuration.
IBM recommends that ELM instances requiring MessageSight for clustering or deep skew detection have their own independent cluster (vs shared with other ELM instances).
IBM recommends that production, test, development, etc. environments have their own independent MessageSight clusters.
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