The Instances File

The Instances File

The instances file (instances.json), generated by ICM during the provisioning phase, describes the set of host nodes that have been successfully provisioned. This information provides input to the deployment and management phase, and the file must therefore be available during this phase, and its path provided to ICM if it is not in the current working directory. The instances file is created in the current working directory.

While the definitions file contains only one entry for each node type, including a Count value to specify the number of nodes of that type, the instances file contains an entry for reach node actually provisioned. For example, the sample definitions file provided earlier contains three entries — one for three application servers, one for two data servers, and one for an arbiter — but the resulting instances file would contain six objects, one for each provisioned node.

All of the parameters making up each node’s definition — including those in the definitions and defaults file, those not specified in the configuration files that have default values, and internal ICM parameters — appear in its entry, along with the node’s machine name constructed from the Label, Role, and Tag fields), its IP address, and its DNS name. The location of the subdirectory for that node in the deployment’s state directory is also included.