inrun functions

Inrun’s functions are pure transformation functions available in every {{ }} expression across a Blueprint — status fields, when: conditions, resource names, onCreate, onReconcile, mutation rules, conversion paths. They are the vocabulary of declarative operator behavior. Most come from KEL, the Kubernetes Expression Library; Inrun adds a few of its own.

Contract: pure (same input → same output), safe (nil/empty input never panics), stateless (no I/O, no side effects). Use blueprint external block or hooks for anything requiring external calls.

Why functions matter

Without functions, a Blueprint can only copy field values as-is. With them, it can reason about them — fall back to a default when a field is absent, gate a deployment on a job completing, compute a name from multiple fields. Functions are what make declarative operators expressive enough to replace hand-written reconcilers for most use cases.

Two functions to know first

default — supply a fallback value

status:
  fields:
    - path: replicas
      value: "{{ default .spec.replicas 1 }}"

If spec.replicas is absent or zero, the status field shows 1. If it is set, it passes through unchanged.

jobSucceeded — gate on a completed Job

onReconcile:
  jobs:
    - name: "{{ .metadata.name }}-migration"
      image: "{{ .spec.image }}"
      command: "{{ .spec.command }}"

  deployments:
    - name: "{{ .metadata.name }}-api"
      image: "{{ .spec.image }}"
      when:
        - field: "{{ jobSucceeded .children.job }}"
          equals: "true"

The api deployment is not created or updated until status.succeeded > 0 on the migration job.

inrun functions — explore from your terminal

inrun functions is the fastest way to discover and learn about every function available in your version of Inrun.

List all functions:

inrun functions

Search by keyword:

inrun functions search job

Show full detail and an example for one function:

inrun functions show jobSucceeded

All functions by domain

Each domain has its own reference page in this folder, generated from the functions’ doc comments: Kubernetes objects, pods, replicas, jobs, services and more from KEL, and Inrun’s own. inrun functions lists every function your version of Inrun has.

Adding a function

• A question any Kubernetes project would ask belongs in KEL: see its contributing guide.
• A function only Inrun needs goes in pkg/template/funcs, with a doc comment in KEL’s format (description, Keywords:, Example:). Then run make generate-functions to update the registry and these pages.

Contract: handle nil/empty input with a safe zero value, not a panic. Return (value, error) for functions that can meaningfully fail; return just value for infallible ones.