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Ingester

An AWS Lambda function that can be subscribed to SNS topics that provide a Departures payload. The ingester uses this payload to create or update the departures cache, which can then be queried by other services.

The ingester performs a number of functions:

  • Updates the destination name to a more meaningful value from either the circular services cache or the locality names cache;
  • Sorts the departures into a sensible order;
  • Caches departures for the stop for quick access from the presenter; and
  • When the departures are for stop(s) in a stop area, combines the departures for stops and stores them in the cache, too.

Triggers

The function is intended to be triggered whenever data is published to a subscribed SNS topic.

Incoming payload

The function expects to receive a JSON payload containing a internal model.

Output

The output is stored in a Redis database with the location ATCO code as the key.

Environment

The function requires the following environment setup:

  • DEPARTURES_REDIS_HOST: The address to use to connect to the Redis departures cache; e.g. localhost:6379
  • LOCALITY_NAMES_REDIS_HOST: The address to use to connect to the Redis locality names cache; e.g. localhost:6379
  • STOPS_IN_AREA_REDIS_HOST: The address to use to connect to the Redis stops in area cache; e.g. localhost:6379
  • CIRCULAR_SERVICES_REDIS_HOST: The address to use to connect to the Redis stops in area cache; e.g. localhost:6379