Core Concepts

Phrase

A Phrase is a lazy task node that can represent:

• A single task call
• A linear chain via .then(...)
• A DAG when phrases are nested as arguments to other phrases

Important fields used by runtime internals:

• task_name
• args, kwargs
• chain
• local-placement flag via .local(force=True|False)

Language and CeleryLanguage

Language defines the abstract orchestration contract. CeleryLanguage implements it with Celery and supports:

• @lang.verb task registration
• lang.grammar(...) task signature declarations
• say, attempt_cancel, resubmit
• execution modes: local, distributed, auto
• orchestration modes: simple, compiled

Journal

Journal stores and serves job execution state. MongoJournal adds:

• timeline events (JobEvent)
• derived progress views (JobProgressView, subjobs, retries)
• optional DAG capture for visual/operational analysis
• worker capability registration for local placement routing

Corpus and Reference

• Corpus: transportable data payload (bytes/object/path/url)
• Reference: write target pointer for outputs

These enable moving larger artifacts without embedding all content in task arguments.

RestartPolicy

Defines retry semantics:

• max_retries
• backoff_seconds
• exponential_backoff
• jitter_seconds
• retry_exceptions

Profile presets are provided (none, standard, aggressive) and can be overridden field-by-field.