Database information

Schema

habitat stores information in a CouchDB database. At present five types of document are stored, identified by a type key:

• Flight documents detailing a balloon flight (type: "flight")
• Payload Configuration documents containing settings for one payload, such as radio transmission data and format (type: "payload_configuration").
• Payload Telemetry documents containing parsed information from a telemetry message transmitted by a payload and associated with a Flight (type: "payload_telemetry")
• Listener telemetry documents containing position data on someone listening to a payload (type: "listener_telemetry")
• Listener information documents containing metadata on a listener such as name and radio (type: "listener_information")

The schema are described using JSON Schema and the latest version may be browsed online via jsonschema explorer.

Database documents are typically managed through the various web interfaces and are uploaded and retrieved using the CouchDB API.

Views, Filters & Validation Functions

Documents in the habitat CouchDB are indexed and accessed using CouchDB views, which are pre-calculated sets of results that are updated automatically and may be paged and searched through.

A selection of generic views are provided, but it’s entirely likely that a custom view would be required for a given application.

Three types of function may be defined in a CouchDB design document. Views consist of a map and optionally a reduce and are typically used to query stored data. Filters selectively include certain documents in a stream from the database, for example to the parser. Validation functions check all new incoming documents to ensure they meet whatever requirements are imposed, making sure that only valid documents are stored in the database.

For more comprehensive information, please refer to the CouchDB documentation.

Included Views

For documentation on the views currently included with habitat, please refer to the source documentation for each: habitat.views.

Using Views: Example

Simple Example

In this simple example we just fetch the list of payload_configuration documents and print out payload names. The full configuration document is available as payload[“doc”].

Python

import couchdbkit
db = couchdbkit.Server("http://habitat.habhub.org")["habitat"]
payloads = db.view("payload_configuration/name_time_created", include_docs=True)
for payload in payloads:
    print "Payload: {0}".format(payload["key"][0])

Javascript

<script src="jquery.couch.js"></script>

db = $.couch.db("habitat")
db.view("payload_configuration/name_time_created", {include_docs: true, success: function(data) {
    for(payload in data.rows) {
        console.log("Payload: " + data.rows[payload].key[0]);
    }
}});

View Collation

A more complicated example, which demonstrates view collation. The flight/launch_time_including_payloads view returns both flight documents and the associated payload_configuration documents, indicated by the second item in the key (0 for flight, 1 for payload_configuration). This code snippet fetches all the flights and prints their name and launch time and the name of each payload in them.

Python

import couchdbkit
db = couchdbkit.Server("http://habitat.habhub.org")["habitat"]
flights = db.view("flight/launch_time_including_payloads", include_docs=True)
for flight in flights:
    if flight["key"][1] == 0:
        print "Flight {0} launches at {1}!".format(
            flight["doc"]["name"], flight["doc"]["launch"]["time"])
        print "  Payloads:"
    else:
        print "    {0}".format(flight["doc"]["name"])