Typeahead service

Typeahead searches accross Datapunt APIs.

Run on your machine using:

$ pip install git+https://github.com/Amsterdam/typeahead
$ typeahead --config example.config.yml

Development / Local Testing

$ git clone git@github.com:Amsterdam/typeahead.git
$ cd typeahead

# create a virtualenv, then...

$ pip install -e .[dev,test]
$ typeahead --config example.config.yml

Design

Search endpoint

The root of the application, '/', is the search endpoint. It supports a q parameter only. Also see the info on our OpenAPI spec below.

Note that the order of the results reflect the order of the endpoints in the configuration. The importance of the order of the results is an artefact of a design mistake we have to live with for now.

Also note that the content type of the response bears slight resemblance to HAL JSON, but really isn't. This is again due to

Setuptools

Typeahead is an installable Python module. After installing (see example above), it provides the typeahead command, which executes the typeahead.main module. See setup.py for all settings.

Async HTTP

Typeahead uses asyncio and runs uvloop as its eventloop. We use aiohttp as both http server, to serve requests on many concurrent connections, and http client, to fetch search results from downstream endpoints in parallel.

In typeahead.application you can find our aiohttp.web.Application, including the routes. Note that we ship some CORS-related code in typeahead.application that will hopefully soon be provided externally.

In typeahead.handlers.* you find the handlers for all endpoints.

Configuration

Configuration is provided through a configuration file in YAML format. The JSON schema is provided in typeahead.config_schema.yml.

Module typeahead.config provides a load(path) mathod to load configuration. It will read the yaml, interpolate placeholders with the environment, validate the schema and then return the loaded configuration. This greatly reduces the need for validation of the provided configuration.

Docker, Jenkins, make

At Amsterdam, we run the code in a docker container. Our deployment pipeline is described in the provided Jenkinsfile. Use the Makefile for repetitive tasks, such as cleaning up and running tests.

Metrics

Typeahead publishes Prometheus metrics on the /metrics endpoint. Metrics include:

metric	type	labels
request_processing_seconds	summary
search_exceptions_total	counter	endpoint, exc_type
search_responses_total	counter	endpoint, status

Note that this endpoint will always run directly under the root, and will not keep the baseurl in mind. This allows us to publish the metrics only internally.

OpenAPI

Typeahead publishes its own API on the /openapi endpoint.