A clustered configuration has the following minimum requirements:
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Two or more copies of the CloudBees Flow server. Clustering is supported starting with CloudBees Flow 5.0.
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Two or more CloudBees Flow agents.
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At least one CloudBees Flow web server on its own machine, or two or more servers if you are using clustering for reliability improvements.
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An enterprise license. The license is required by CloudBees Flow to connect to an external database.
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Apache ZooKeeper as the centralized service for maintaining configuration information.
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ZooKeeper should be installed on a machine without a CloudBees Flow server or load balancer. This separation of services is advised to optimize the performance and reliability of your configuration.
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ZooKeeper must be installed on an odd number of machines. For example, you may need 1, 3, 5, or more instances of the software depending on your environment.
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The CloudBees Flow servers must be configured to appear as a single instance in ZooKeeper.
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A hardware load balancer or load-balancing software installed on one machine.
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The web servers, agents, and CloudBees Flow servers should share a common file system for plugin information.
CloudBees recommends at least one CloudBees Flow web server on its own machine or two or more servers if you are using clustering for reliability improvements.
Multiple CloudBees Flow clusters can use the same database server, but not the same database schema instance.