Parameter merging

The Pull Server's parameter merging system enables hierarchical configuration management. You define parameter values at different scope levels, and the server merges them into a single resolved set for each node based on precedence rules.

Merge order

Parameters flow from the broadest scope to the narrowest. Narrower scopes override broader ones:

Default → Custom scope types (ordered by precedence) → Node

The Default scope provides baseline values. Custom scope types (such as Region, Environment, or Team) apply organization-specific overrides. The Node scope provides per-node customization.

Scope types and precedence

Scope types define the categories in your hierarchy. Each scope type has a precedence value that determines its position in the merge order. Higher precedence values are applied later and override lower ones.

Scope type	Precedence	Description
Default	0	Global baseline (built-in)
Region	10	Geographic grouping
Environment	20	Deployment stage
Node	∞	Per-node overrides (built-in)

Default and Node scopes are built-in. You create custom scope types for your organizational structure.

Scope values

Each scope type has one or more scope values representing specific instances. For example, the Region scope type might have US-West and EU-Central as scope values.

Node tags

Nodes are associated with scope values through tags. A node can have one tag per scope type. Tags determine which parameter files apply to a given node.

For example, a node tagged with Region: US-West and Environment: Production receives parameters merged in this order:

Default → Region/US-West → Environment/Production → Node/<fqdn>

Deep merge behavior

Parameter merging performs a deep merge of YAML/JSON objects:

• Scalar values at a narrower scope replace the broader value.
• Nested objects are merged recursively — properties from narrower scopes override matching properties, while non-conflicting properties are preserved.
• Arrays at a narrower scope replace the entire array from the broader scope.

Example

Default parameters:

logLevel: Warning
maxConnections: 100
analytics: true

Environment/Production parameters:

logLevel: Error

Merged result:

logLevel: Error          # Overridden by Environment
maxConnections: 100      # Inherited from Default
analytics: true          # Inherited from Default

Provenance tracking

The Pull Server tracks the origin of each merged value. When viewing merged parameters in the web UI, the Provenance Visualization panel shows which scope contributed each value. This makes it easy to understand why a parameter has a particular value and which scope to edit if you need to change it.

Parameter versioning

Parameter files are versioned independently from the configurations they belong to. You can update parameters without creating a new configuration version. Each parameter scope has its own version history.

Parameter validation

When a configuration defines a parameter schema, the Pull Server validates parameter files against that schema. The ParameterCompatibilityService checks for breaking changes between schema versions before activation.