Introduction to Metis

Development Status

Metis is under active development. The docs may lag behind the current implementation.

What is Metis?

Metis is a GA4GH WES 1.1.0 compliant Workflow Execution Service written in Rust. It provides a standardised HTTP API for submitting, monitoring, and cancelling workflow runs across any engine.

Design Principles

• Decoupled API and engine — the HTTP layer never executes workflows. Submission and execution are separated by NATS.
• Pluggable via trait — adding a new engine requires implementing a single Rust trait, nothing in the core API changes.
• Config-driven — engine behaviour (command template, parameter validation, denied flags, workdir layout) is entirely controlled by engine.yaml. No code changes required for a new engine variant.
• Spec compliant — follows GA4GH WES 1.1.0 with extensions for SSE streaming and log pagination.

Architecture Overview

Three decoupled layers:

Layer	Component	Role
HTTP	metis-api	Validates requests, serves status/logs, handles cancellation
Messaging	NATS	Async job queue — decouples submission from execution
Execution	Engine Runtime	Builds CLI, spawns process, captures output, tracks state

Supported Workflow Engines

Engine	Workflow Type	Versions
Nextflow	NFL	DSL2
(extensible)	any	via trait

Any binary that can be invoked as a subprocess can be wrapped as a Metis engine — configure commandTemplate in engine.yaml and start metis-engine-generic.

Run States

Runs follow the WES state machine:

QUEUED → INITIALIZING → RUNNING → COMPLETE
                              ↘ EXECUTOR_ERROR
                              ↘ CANCELED
                              ↘ SYSTEM_ERROR

Next Steps

• Quick Start — run Metis locally in minutes
• Engine Configuration — full engine.yaml reference
• API Reference — all endpoints
• Architecture — deep dive into components and message flow