Home

interpose

Shared mechanism for metalayerlab interceptors — a policy-configurable async middleware pipeline, the layered settings loader, Secret values, and Prometheus text exposition.

interpose is a small Python library for metalayerlab's interceptors (mitm-proxy, sluice), which depend on a GitHub release tag. It has three components: the pipeline, settings (with secrets) and metrics.

Pipeline

One middleware loop, interpose.pipeline: the project keeps its own hooks and unit of work, and fail open or closed is policy, per project and per middleware.

• API: interpose.pipeline
• How the guard works
• Performance
• A hook "timed out" although it returned a result

Settings

interpose.settings and interpose.secret. Each setting is declared once and read from a _FILE variable, the environment, a YAML file or its default, with strict types and a record of where each value came from:

from pathlib import Path

from interpose.settings import Setting, Settings, port

SETTINGS = Settings(
    "MYAPP_",
    (Setting("listen.port", 8080, "Port.", check=port),),
    default_path=Path("/etc/myapp/config.yaml"),
)
r = SETTINGS.resolve(environ={"MYAPP_LISTEN_PORT": "9090"})
assert (r.values["listen.port"], r.sources["listen.port"]) == (9090, "MYAPP_LISTEN_PORT")

• First run
• API: interpose.settings · interpose.secret
• How a value is resolved
• Secrets
• Common problems

Metrics

Prometheus text exposition, interpose.metrics, with every label's values declared up front. The project serves the text.

• API: interpose.metrics
• How the text is rendered

Table of Contents

Getting started: Introduction · Quick Start

Using it: API Reference Help: Troubleshooting · FAQ · Security

Developers: Contributing · Architecture Internals · Testing Guide · Release Process