Eriksen is a model factory that makes it easy to write model code that retrieves or saves data to multiple, configurable places. It's main job is to Marshal reads & writes to a configurable and swappable backend, allowing for a separation that preserves an interface even when the backend data storage system changes.

npm i eriksen

Eriksen is useful when you're writing code that may change database backends, or if you're currently changing code to move from one backend to another. Since it concerns itself with only the db interactions from your code, it allows your data access code to be more modularized within a codebase. And since Eriksen acts as the coding interface, you should not need to change any other code unless expectations change as db backends switch in or out.

Because Eriksen sits between the code that accesses a backend storage system, this allows for Eriksen to log failures for a non-primary backend in the background.

This example creates two models in different databases and configures eriksen to use cassandra as the primary and dynamodb as the secondary. It calls the getAllOfTheThings method with cassandra as the primary, meaning if the getAllOfTheThings fails in dynamo, it just logs out the errors, does not fail the call. If the primary fails it will throw an error.

  // cassandra model
  const cassandraMapper = {
    getAllOfTheThings: (name) => {
      return cassandra.query("SELECT ...");
    }
  }

  // dynamo model
  const dynamoMapper = {
    getAllOfTheThings: (name) => {
      return aws.dynamodb.DocumentClient(...);
    }
  }

  const Eriksen = require('eriksen');
  const model = new Eriksen('allThings');
  model.addModel('cassandra', cassandraMapper);
  model.addModel('dynamodb', dynamoMapper);
  model.configure({
    primary: cassandraMapper,
    secondary: dynamoMapper
  });

  function retrieveAllOfTheThings(thingName) {
    return model.proxy.getAllOfTheThings(name);
  }

  // calling function that calls the eriksen instance to marshall calls
  retrieveAllOfTheThings('allMyThings')
    .then((things) => {
      console.log('list of my things', things);
    })
    .catch((err) => {
      console.log(`it failed ${err.message}`);
    });