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Key terms

This page defines the core terms used throughout the H2O Workflows documentation. Understanding these terms helps you navigate the system and write workflow definitions effectively.

Workflow​

A declarative YAML definition that describes a set of jobs to execute. A Workflow is the top-level resource you create and manage in H2O Workflows.

Job​

A unit of work within a workflow. Each Job runs independently (or with declared dependencies) and contains one or more steps.

Step​

An individual command or action within a job. Steps execute sequentially within their parent job.

Run​

A single execution instance of a workflow. When you trigger a workflow, a Run is created to track the execution.

RunAttempt​

An execution attempt within a run. If a run is retried, each retry creates a new RunAttempt.

Workspace​

An organizational boundary in H2O AI Cloud. Workflows are scoped to a workspace, and you must select a workspace before creating or managing workflows.

RBAC​

Role-Based Access Control. Governs who can view, create, and manage workflows within a workspace. Permissions are inherited from the workspace.

Revision​

A versioned snapshot of a workflow definition. Each time you update and activate a workflow, a new Revision is created. Runs execute against a specific revision.

Runner​

A compute resource that executes workflow jobs. The orchestrator assigns jobs to available runners based on load and availability.

Trigger​

A mechanism that starts a workflow run. Triggers can be manual (on demand), scheduled using a cron expression, or callable from another workflow.

Input​

A typed parameter (string, bool, or int) defined in a workflow and provided at trigger time. Inputs are referenced in workflow YAML using ${{ .inputs.<name> }}.

Expression​

A dynamic placeholder in a workflow YAML evaluated at runtime using Go template syntax (${{ }}). Expressions can reference inputs, secrets, environment variables, and matrix variables.

Secret​

Sensitive data stored in H2O Secure Store and referenced in a workflow using ${{ .secrets.<name> }}. Secret values are masked in logs and the UI.

Matrix​

A strategy that runs a single job across multiple variable combinations, creating one parallel job instance per combination.

Concurrency group​

An identifier shared across workflow instances that prevents simultaneous execution. When two runs share a concurrency group, only one can be active at a time.

H2O Drive​

The cloud storage service used by H2O AI Cloud. Workflow steps can upload files to and download files from H2O Drive using the drive://bucket-name/path URL format.

Resource hierarchy​

Workspaces contain Workflows, which have Revisions. Runs execute against a Revision and produce RunAttempts, which contain Jobs and Steps.

Next steps​

  • Concepts for deeper explanations of each term.
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