Quick Weather Check

Contents

• Introduction
• Requirements
• Setup
• Actions
• Screenshots
• Discussion

Introduction

Quick Weather Check allows the user to enter an address and receive the current temperature, low temperature, and high temperature. The results are cached for 30 minutes by postal code (zip code in the US). Results are not cached for countries without postal codes. See Discussion for more info. All text displayed to the user is localizable.

Requirements

This coding exercise has the following requirements:

• Must be done in Ruby on Rails
• Accept an address as input
• Retrieve forecast data for the given address. This should include, at minimum, the current temperature (Bonus points - Retrieve high/low and/or extended forecast)
• Display the requested forecast details to the user
• Cache the forecast details for 30 minutes for all subsequent requests by zip codes. Display indicator if result is pulled from cache.

Setup

Install Ruby and install Rails if needed.

Ruby version: 3.3.5

Rails version: 7.2.1

Run the setup script, which runs bundle install. This app does not need a database, so it was created with rails new quick_weather --skip-active-record

bin/setup

OpenWeatherMap API key

Sign up for a free OpenWeatherMap API key, available at openweathermap.org. Note that the free subscription gives access to the 2.5 version of the API, not the 3.0 version that includes extended forecasts.

Create a .env file in the top-level directory of the project, and add

OPENWEATHERMAP_API_KEY=your_openweathermap_key

HERE API key

Sign up for a free API key for the HERE geocoding service, available at here.com. You will also receive a organization ID, which is not needed to make API calls.

Add a line to the .env file

HERE_API_KEY=your_here_key

Enable Rails cache in development

bin/rails dev:cache

Actions

Run the test suite

bundle exec rspec

Run the server

bin/rails s

Try the site

• Visit localhost:3000
• Enter an address
• Click Get Temperatures. Note "Information is current." message
• Click Get Temperatures again. Note "Information is from the last 30 minutes." message

Screenshots

Visit to localhost:3000 without params

With a valid address, fresh results

With a valid address, cached results

With an ambiguous address

Discussion

Scalability

The app is using the default Rails cache. For a production application, the cache should be upgraded to use Redis or a similar tool.

The results from the HERE geocoder service could also be cached if needed.

For high loads, Rails servers can be scaled via Kubernetes or AWS EC2 instances. Operating agreements would be needed with the external services HERE and OpenWeatherMap to agree on the scale of traffic that is supported and what happens if a service goes down or starts returning unexpected results.

A queueing service such as Sidekiq could be added to process API calls in the background.

Security

Security policies are needed in the case of API key exposure, such as accidentally committing them to GitHub. Keys should be immediately rotated in case of an incident, and rotated regularly as a precaution.

Frontend

I looked at adding Bootstrap, but it added a lot of files and code for not much benefit. For a production app, it might be a better return on investment. I used SimpleCSS instead.

Extended forecast

With an upgrade to the OpenWeatherMap 3.0 API, it would be straightforward to add the extended forecast in WeatherService by retrieving it from the results, adding it to the returned hash, and displaying it on weather_info/show.html.erb.

Countries without postal codes

A few countries do not have postal codes. I chose not to cache those countries' results. In production this would be a vulnerability to overload the OpenWeatherMap server with too many calls, which would also lead to high costs.

It would be possible to cache a result for the whole country, or use an alternate key. This change could easily be made in GeoLocation#key, with any additional fields added in GeocodeService#parse_response.

Further research would be needed to understand the correct granularity of caching for those countries. See 2024 list of countries without postal codes.

Object Decomposition and Design Patterns

WeatherInfoController inherits from ApplicationController. It has a show action and template that allow the user to enter an address and then show the results.

Two Service objects inherit (implicitly) from Object. GeocodeService calls the HERE API and parses the results. WeatherService calls the OpenWeatherMap API and parses the results.

Initially, information was passed from GeocodeService to WeatherService in a hash. When some of this information was used to create a cache key, it became clear that this could be a separate object with #key and #valid? methods. I extracted the GeoLocation object inheriting (implicitly) from Object.