Field Values
The provisioning, deployment, and configuration work done by ICM is determined by a number of field values that you provide. For example, the Provider field specifies the provisioning platform to use; if its value is AWS, the specified nodes are provisioned on AWS.
The are two ways to specify field values:
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Some can be specified on the command line (see Command Line).
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All can be included in the two configuration files (see Configuration, State and Log Files), although some can appear only in the defaults.json file, and others intended for the definitions file only.
There are also defaults for most ICM fields. In descending order of precedence, these specifications are ranked as follows:
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Command line option
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Entry in definitions.json configuration file
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Entry in defaults.json configuration file
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ICM default value
This avoids repeating commonly used fields while allowing flexibility. The defaults file (defaults.json) can be used to provide values (when a value is required or to override the defaults) for multiple deployments in a particular category, for example those that are provisioned on the same platform. The definitions file (definitions.json) provides values for a particular deployment, such as specifying the nodes in the cluster and the labels that identify them, but can also contain fields included in the defaults file, in order to override the defaults.json value for a particular node type in a particular deployment. Specifying a field value as a command line options let you override both configuration files in the context of a particular command in a particular deployment.
The following illustration shows two deployments sharing a single defaults.json file, with different definitions.json files — the first for a distributed cache cluster, the second for a sharded cluster.
ICM Configuration Files Define Deployments
For comprehensive lists of the required and optional fields that can be specified in these files, see ICM Configuration Parameters in the “ICM Reference” chapter.
