Function Reference

Use functions when you need to generate or retrieve a value dynamically with syntax such as {{ functionName(...) }}.

Functions are best thought of as helpers that either fetch something, compute something, or force evaluation behavior that plain variables and filters cannot provide on their own.

Function groups

  • Rendering and debugging — render(), renderOnce(), printContext(), template inheritance helpers
  • Data access — secret(), credential(), read(), fileURI(), kv(), encrypt(), decrypt()
  • Data parsing — fromJson(), fromIon(), yaml()
  • Workflow helpers — errorLogs(), currentEachOutput(), tasksWithState(), iterationOutput(), parentOutput(), appLink()
  • Utilities — now(), uuid(), randomInt(), http(), fileSize(), fileExists(), and more
  • Date and calendar — isWeekend(), isPublicHoliday(), dayOfWeek(), monthOfYear(), and more

Worked example

This flow uses several runtime functions together: now() for a timestamp, uuid() for a unique run identifier, secret() for a credential, and render() to evaluate a namespace variable containing Pebble:

id: function_reference_example
namespace: company.team


tasks:
  - id: log_context
    type: io.kestra.plugin.core.log.Log
    message:
      - "Run ID: {{ uuid() }}"
      - "Started at: {{ now() | date('yyyy-MM-dd HH:mm:ss') }}"
      - "API key: {{ secret('MY_API_KEY') }}"
      - "Config value: {{ render(namespace.my_config) }}"

Rendering Functions

Reference for Kestra's rendering and debugging functions — render(), renderOnce(), printContext(), block(), and parent() — for evaluating nested expressions and inspecting execution context.

Data Access Functions

Reference for Kestra's data access functions — secret(), credential(), read(), fileURI(), kv(), encrypt(), and decrypt() — for resolving secrets, files, and stored values at runtime.

Parsing Functions

Reference for Kestra's data parsing functions — fromJson(), fromIon(), and yaml() — for deserializing task outputs and working with structured data in expressions.

Workflow Functions

Reference for Kestra's workflow and execution helper functions — errorLogs(), currentEachOutput(), tasksWithState(), iterationOutput(), parentOutput(), and appLink().

Utility Functions

Reference for Kestra's utility functions — now(), uuid(), randomInt(), range(), http(), fileSize(), fileExists(), isFileEmpty(), and more — for generating values and inspecting files at runtime.

Date Functions

Reference for Kestra's date and calendar functions — isWeekend(), isPublicHoliday(), isDayWeekInMonth(), dayOfWeek(), dayOfMonth(), monthOfYear(), and hourOfDay() — for scheduling and routing logic.

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