arrakis-schema 0.4.0

Schemas for the Arrakis API

Arrakis Schema Specification

This repository defines the schema for all data, metadata and API requests for the arrakis LIGO data distribution system.

Schemas are defined in one of two places:

• endpoints/: Endpoints served from Arrakis server
• publication/: Data published into Kafka

Endpoints

The Arrakis server responds to API requests corresponding to the four main actions exposed by the client API:

• stream: endpoints/stream
• describe: endpoints/describe
• find: endpoints/find
• count: endpoints/count

as well as two actions which aid in publication:

• partition: endpoints/partition
• publish: endpoints/publish

All API requests are done in a two-stage approach by first sending an Arrow Flight descriptor to the server, returning back a Flight info object which contains the request and the server to contact, contained within a Flight ticket. This ticket is then sent to receive back the expected payload with a specific Arrow flight schema dependent on the request, serialized in the Arrow .

The Flight descriptors sent to the server in the first stage are all specified here as JSON packets which are UTF-8-encoded, using the command variant of the Flight descriptor, which can be used to specify any application-specific command.

The Flight descriptor schemas are described within each endpoint in descriptor.json, while the payload schemas are described via schema.txt. In addition, a generic descriptor specification for all endpoints is described in endpoints/descriptor.json.

Publication

Publication is done by first registering a publisher via the publish endpoint with a publisher ID. If authorized to do so, the server will send a response with connection details to connect via Kafka to publish data.

The data is published via Kafka with the schema described in publication/schema.txt.

Usage

Python

The generic Flight descriptor schema is described within each endpoint in {endpoint}.json. In addition, a generic descriptor specification for all endpoints is described in descriptor.json.

from arrakis_schema import load_schema

schema = load_schema("count.json")