Overview

Overview of Elodin DB

Elodin DB is a time-series database purpose built for flight computers. It is designed as a central telemetry store and message bus. Flight software publish and subscribes to telemetry data and messages from Elodin DB.

Elodin DB is based on the same ECS system as Elodin Sim (and the rest of the Elodin ecosystem). Elodin DB sorts data into "entities" and "components". Entities are best thought as objects that emit telemetry. For instance an individual sensor would be an entity. A component is a piece of telemetry data that is associated with an entity. For example an accelerator's acceleration reading would be a component. Entities can have multiple components, and each component can be associated with multiple entities.

Elodin DB chiefly communicates over impeller -- Elodin's lightweight message protocol designed for flight software. In addition to impeller, Elodin DB can be queries via SQL and results are returned in the Arrow IPC format.

Quick Start

You can install Elodin DB using the following command:

curl -LsSf https://storage.googleapis.com/elodin-releases/install-db.sh | sh

Alternatively, you can download the latest portable binary for your platform:

To start a new instance of Elodin DB, use the following command:

elodin-db run

Lua REPL

The easiest way to interact with Elodin DB is through its Lua REPL. To start the REPL, run the following command:

elodin-db lua

You can connect to the database by running:

client = connect("localhost:2240")

SQL

You can query Elodin DB via SQL. The easiest way to access this interface is through the REPL where you can run the following command to connect to the database using SQL

:sql [::]:2240

This will connect to your local instance of Elodin DB, and drop you into a SQL REPL.

To list the available tables, run:

show tables;

We use Datafusion to power the SQL interface. Their docs are the best place for details on the dialect.