The diagram above depicts a high level architecture of the WSO2 Cloud Controller. The Cloud Controller is a WSO2 Carbon based server that has several architectural components, that are namely,
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The Axiom Xpath based parser is responsible for parsing all kinds of *.xml configuration files of the Cloud Controller.
Topology publisher
We use a central location such as the Cloud Controller to maintain the topology configuration. The topology configuration refers to the information on the various service clusters present in the Cloud environment.
To view a sample file see Sample Topology Configuration
Keeping this information in the Cloud Controller alone is not sufficient as this configuration is needed in other locations as well, such as the Elastic Load Balancer (ELB), Artifact Distribution Coordinator (ADC) and other locations. As a result, the Cloud Controller syncs the topology with the other components. The following image explains how the topology synchronization takes place:
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Topology synchronization
- The Cloud controller keeps building the topology configuration and publishes it in a periodical manner to a topic created in WSO2 Message Broker (MB) that is embedded into the Cloud Controller (CC). Changing the topology configuration can be done dynamically as well as publishing can be done when configuration changes arise.
- Any subscriber who needs this topology configuration can subscribe to the relevant topic and get synced.
- Subscribers should ideally generate the difference between the configuration (such as, the difference between what it received and what it has) and if a difference is present, act upon the change in the topology.
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