Stack Inheritance

Stack inheritance combines a stack version with the files and services supplied by its supported parent. StackExtensionHelper and the stack loader apply the inheritance rules; the result must be validated as an assembled stack rather than inferred from directory names.

File and Service Rules

Some stack files are inherited, some are replaced when defined by the child, and some are merged. Service definitions follow the service inheritance rules: a service can reuse a definition from common-services, while child metadata can add or override supported properties. Configuration dependencies and role command order must be checked after merging.

Merge and Deletion Behavior

The merge is property-specific. A child value generally overrides a parent value; an omitted child property is retained when the rule permits inheritance. Configuration dependencies use an all-or-nothing rule, while custom commands merge by name and child definitions override same-name parent commands. Cardinality is taken from the child when supplied, otherwise from the parent. Explicit deletion markers are honored by the stack merge implementation.

Common Services and Validation

Current BIGTOP services demonstrate reuse from common-services, including BIGTOP AMBARI-METRICS. Validate the final metainfo.xml, scripts, configuration files, package paths, alerts, metrics.json, telemetry.json, and service checks. Do not assume unsupported cross-stack extends syntax or inheritance for files that the loader treats as replacement-only.

The merge implementation is org.apache.ambari.server.api.util.StackExtensionHelper#mergeServices; inspect it when a service inheritance result is ambiguous.