git clone git@github.com:couetilc/take-home-interview_Jan-2023_apple.git
cd take-home-interview_Jan-2023_apple
./cli previewThe prompt is clear, the app must use Ruby on Rails and return weather forecast data for an address. Caching is on the zip code level, and there are bonus points for displaying high/low temps and extended forecasts. I'm going to prompt users to use city name or zip code. I'm assuming the creators of this take home meant to limit this to weather within the USA. They used the term "zip code" in the prompt, an american creation only used within the United States and associated territories.
I found a good open weather API, open-meteo.com. I can requests for weather based on the latitude and longitude using the following format:
curl "https://api.open-meteo.com/v1/forecast"\
"?latitude=$LAT"\
"&longitude=$LON"\
"¤t_weather=true"
# See Appendix, Response AMy other problem is that I need to translate an address into a latitude and longitude. This is called geocoding. I haven't been able to find any freely available geocoding APIs online, but after exploring open-meteo.com with the console open, I noticed they have an unadvertised geocoding api I can use that accepts a name parameter which can be a city name or a zip code:
curl "https://geocoding-api.open-meteo.com/v1/search"\
"?name=$ZIP_OR_CITY"
# See Appendix, Response BTo fulfill the bonus requirements of high/low temp, I can provide a "daily" parameter and specify it to return min and max temperatures for the next week. It requires me to specify a timezone though, which I'll get from the geocoding API. Caching the API response by zipcode shouldn't be affected by this timezone parameter, I believe it's a safe assumption for this project that every zip code will have the same timezone.
curl "https://api.open-meteo.com/v1/forecast"\
"?latitude=$LAT"\
"&longitude=$LON"\
"&timezone=$TIMEZONE"\
"¤t_weather=true"\
"&daily=temperature_2m_min"\
"&daily=temperature_2m_max"To fullfill the other bonus requirements of a temperature forecast, I can provide an "hourly" parameter, and specify it to return surface temperatures for every hour in the next week.
curl "https://api.open-meteo.com/v1/forecast"\
"?latitude=$LAT"\
"&longitude=$LON"\
"&timezone=$TIMEZONE"\
"¤t_weather=true"\
"&daily=temperature_2m_min"\
"&daily=temperature_2m_max"\
"&hourly=temperature_2m"I'm thankful I found these two open APIs, otherwise I would need an API key from a paid service. I would not like to manage secrets tied to my credit card for what is a small take-home interview that will be perused by strangers. To run the project, they would need access to the secrets 😱, which means encrypting them with SOPS and providing a shared key, or deploying, both too much trouble right now.
We should have all the API data we need to fulfill the requirements of the project. Now we just need to understand what the request flow will look like, where caching fits into that, and what data model we may need, if any. Then we can put the final UI together and make things as pretty as needed.
I'm going to limit user input to zip codes only right now, it creates the simplest request flow and is a quick path to an MVP. To allow a user to put in city names means creating separate cache keys for cities vs zips, as cities are composites of multiple zip codes with a different latitude and longitude. The website would also need to provide an autocomplete form or some other type of UI pattern to let the user specify which city name they mean so I can resolve their input text to a single entity. With a zip code it's easy, they type in five numbers and it's already resolved to a single cacheable entity while meeting the requirements of the prompt.
From the users perspective, the request flow will look like:
sequenceDiagram
User->>Rails: GET /
Rails->>User: Return address input page
User->>Rails: GET /forecast/$ZIP_CODE
Rails->>Redis: Check cache
Redis->>Rails: Cached content
Rails-->>User: Maybe return forecast using cached content
Rails->>Geocoding API: GET /v1/search?name=$ZIP_CODE
Geocoding API->>Rails: Latitude and Longitude
Rails->>Weather API: GET /v1/forecast?latitude&longitude
Weather API->>Rails: current weather, hourly forecast, daily highs + lows
Rails->>Redis: Cache response with 30min TTL
Rails->>User: Return forecast page
The user will see two pages: the address input page, containing a form with a text input and submit button, and the forecast page, summarizing the weather information in a simple stacked layout that provides a link back to the address input page and indicates whether the forecast is cached.
We'll put our infrastructure together using Docker, for ease of use and so our interviewers can quickly get it running locally. We will use a Rails app, a PostgreSQL database, and Redis instance. I'll proxy requests with Caddy. I will store commands for project development and maintenance in an executable file "cli" at the root of the repo.
- Allow user to specify timezone for forecast
- Error flow when zip code is not found by open meteo.
- Widen input range from just zip code to city names. Autocomplete user input and require selecting one option so search text is resolved to one entity.
- Put API scraping on workers so user is not left hanging until all requests resolve, can poll or do websockets until data is available.
- Load test open-meteo to see if there are any limits to request frequency, respect that in rails app
Error Message:
#0 8.460 Fetching redis-client 0.12.0
#0 8.569 Installing redis-client 0.12.0
#0 52.58 Downloading debug-1.7.1 revealed dependencies not in the API or the lockfile
#0 52.58 (irb (>= 1.5.0), reline (>= 0.3.1)).
#0 52.58 Either installing with `--full-index` or running `bundle update debug` should
#0 52.58 fix the problem.
------
failed to solve: executor failed running [/bin/sh -c bundle]: exit code: 34
This was fixed by running bundle inside the webapp container like so:
./cli webapp-run bundle update debug
Error message:
Error response from daemon: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: exec: "rails": executable file not found in $PATH: unknown
One solution is to change the docker entrypoint to explicitly target the rails executable in the folder:
CMD ["./bin/rails", "server", "-b", "0.0.0.0"]
It's easier to update the path variable to include the application's bin folder
ENV PATH="${PATH}:/usr/src/app/bin"
{
"latitude": 40.710335,
"longitude": -73.99307,
"generationtime_ms": 0.32508373260498047,
"utc_offset_seconds": 0,
"timezone": "GMT",
"timezone_abbreviation": "GMT",
"elevation": 51.0,
"current_weather": {
"temperature": 2.4,
"windspeed": 11.3,
"winddirection": 22.0,
"weathercode": 0,
"time": "2023-01-08T16:00"
}
}{
"results": [
{
"id": 5128581,
"name": "New York",
"latitude": 40.71427,
"longitude": -74.00597,
"elevation": 10.0,
"feature_code": "PPL",
"country_code": "US",
"admin1_id": 5128638,
"timezone": "America/New_York",
"population": 8175133,
"postcodes": [
"10001",
"10002",
"10003",
"10004",
"10005",
"10006",
"10007",
"10008",
"10009",
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"10171",
"10172",
"10173",
"10174",
"10175",
"10176",
"10177",
"10178",
"10179",
"10185",
"10199",
"10203",
"10211",
"10212",
"10213",
"10242",
"10249",
"10256",
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"10259",
"10260",
"10261",
"10265",
"10268",
"10269",
"10270",
"10271",
"10272",
"10273",
"10274",
"10275",
"10276",
"10277",
"10278",
"10279",
"10280",
"10281",
"10282",
"10285",
"10286"
],
"country_id": 6252001,
"country": "United States",
"admin1": "New York"
}
],
"generationtime_ms": 0.29802322
}{
"latitude": 40.710335,
"longitude": -73.99307,
"generationtime_ms": 0.40793418884277344,
"utc_offset_seconds": -18000,
"timezone": "America/New_York",
"timezone_abbreviation": "EST",
"elevation": 51.0,
"current_weather": {
"temperature": 3.0,
"windspeed": 4.4,
"winddirection": 35.0,
"weathercode": 3,
"time": "2023-01-08T12:00"
},
"hourly_units": {
"time": "iso8601",
"temperature_2m": "°C"
},
"hourly": {
"time": [
"2023-01-08T00:00",
"2023-01-08T01:00",
"2023-01-08T02:00",
"2023-01-08T03:00",
"2023-01-08T04:00",
"2023-01-08T05:00",
"2023-01-08T06:00",
"2023-01-08T07:00",
"2023-01-08T08:00",
"2023-01-08T09:00",
"2023-01-08T10:00",
"2023-01-08T11:00",
"2023-01-08T12:00",
"2023-01-08T13:00",
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"2023-01-08T15:00",
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],
"temperature_2m": [
2.0,
1.7,
1.0,
0.3,
0.1,
-0.4,
-0.4,
-0.7,
-0.7,
0.7,
2.1,
2.4,
3.0,
3.7,
4.1,
3.7,
3.2,
1.4,
0.3,
-0.2,
-0.4,
-0.3,
0.2,
-0.1,
-0.0,
0.0,
0.8,
1.2,
1.2,
0.9,
0.7,
0.8,
0.8,
1.2,
2.1,
3.3,
4.6,
5.7,
5.7,
5.2,
4.1,
2.2,
1.0,
0.3,
-0.2,
-0.2,
-0.3,
-0.3,
-0.3,
-0.2,
-0.2,
-0.1,
-0.1,
-0.2,
-0.1,
-0.2,
1.7,
2.3,
3.4,
4.6,
5.5,
6.1,
6.2,
6.3,
6.2,
5.6,
5.3,
4.9,
4.6,
4.4,
4.2,
4.0,
3.7,
3.5,
3.4,
2.9,
2.4,
2.0,
1.7,
1.4,
1.4,
2.4,
3.5,
4.4,
5.1,
5.4,
5.7,
5.8,
5.6,
5.2,
4.9,
4.6,
4.5,
4.5,
4.5,
4.5,
4.0,
3.9,
3.7,
3.7,
3.5,
3.6,
3.6,
4.0,
4.1,
4.4,
4.9,
5.4,
6.2,
6.6,
6.7,
6.6,
6.5,
6.8,
7.7,
8.4,
8.8,
9.0,
9.5,
9.8,
9.8,
10.1,
10.4,
10.8,
11.3,
11.5,
11.7,
11.8,
11.6,
11.2,
11.1,
11.8,
12.8,
13.7,
13.5,
12.9,
11.8,
10.8,
9.5,
8.0,
7.2,
6.7,
6.0,
5.5,
5.0,
4.4,
4.0,
3.8,
3.4,
3.1,
2.6,
2.3,
2.4,
2.6,
3.0,
3.3,
3.8,
4.2,
4.4,
4.5,
4.2,
3.5,
2.5,
1.4,
1.0,
0.6,
0.3,
0.1
]
},
"daily_units": {
"time": "iso8601",
"temperature_2m_max": "°C",
"temperature_2m_min": "°C"
},
"daily": {
"time": [
"2023-01-08",
"2023-01-09",
"2023-01-10",
"2023-01-11",
"2023-01-12",
"2023-01-13",
"2023-01-14"
],
"temperature_2m_max": [
4.1,
5.7,
6.3,
5.8,
9.8,
13.7,
5.0
],
"temperature_2m_min": [
-0.7,
-0.3,
-0.3,
1.4,
3.5,
5.5,
0.1
]
}
}