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​Concepts and ​Expressions

This section lists key concepts and templating expressions. You can treat this section as a lookup reference anytime you need more details about a specific concept or expression.

Flowable Tasks

Flowable Tasks

Flowable tasks control the orchestration logic β€” run tasks or subflows in parallel, create loops and conditional branching.

Runnable Tasks

Runnable Tasks

Runnable tasks are data processing tasks incl. file system operations, API calls, database queries, etc. These tasks can be compute-intensive and are processed by workers.

Revision

Revision

Flows are versioned by default. Whenever you make any changes to your flows, a new revision is created. This allows you to rollback to a previous version of your flow if needed.

Secret

Secret

Secret is a mechanism that allows you to securely store sensitive information, such as passwords and API keys, and retrieve them in your flows.

Pebble Templating Engine

Pebble Templating Engine

Pebble is a Java templating engine inspired by Twig and similar to the Python Jinja Template Engine syntax. Kestra uses it to dynamically render variables, inputs and outputs within the execution context.

Blueprints

Blueprints

Blueprints is a curated, organized, and searchable catalog of ready-to-use examples designed to help you kickstart your workflow.

Naming conventions

Naming conventions

To keep your flows and tasks organized, it's useful to adopt a consistent naming convention. This page describes some common conventions.

Expression

Expression

Kestra's expressions use Pebble Templating along with flow's execution context to render various flow and task properties.

Expression Types

Expression Types

There are many ways to use expressions in Kestra. This page will guide you through different types of expressions.

Expression Usage

Expression Usage

This page summarizes the main syntax of filters, functions, and control structures available in Pebble templating.

Filter

Filter

Filters can be used in expressions to perform some transformations on variables such as formatting a date, converting a string to uppercase, or joining a list of strings.

JSON Filters

JSON Filters

JSON filters are used to manipulate JSON objects, often API responses.

Numeric Filters

Numeric Filters

Numeric filters are used to format numbers or convert strings to numbers.

Object Filters (Maps, Arrays and More)

Object Filters (Maps, Arrays and More)

Object filters help you manipulate maps and arrays.

String Filters

String Filters

String filters are used to manipulate strings i.e. textual data.

Temporal Filters

Temporal Filters

Temporals filters are used to format dates and timestamps.

Function

Function

Functions can be called to generate content. Functions are called by their name followed by parentheses () and may have arguments.

Operator

Operator

Operators are used to perform logical operations within templated expressions such as comparing values and performing arithmetic operations.

Tag

Tag

Tags are used to control the flow of the template. They are enclosed in {% %}.

Test

Test

Tests are used to perform logical operations within templated expressions such as checking if a variable is defined or if a variable is empty.

Deprecated handlebars

Deprecated handlebars

Handlebars are deprecated and superseded by Pebble. These functions will be removed soon and are disabled by default.