nanoreddit

This service is to accept posts and represent them as a feed => Simplified version of the Reddit feed API that powers http://old.reddit.com.

API Reference

POST /submit

Create new posts

Request

{
	"title": "title",
	"author": "t2_abcdefg9",
	"link": "https://reddit.com",
	"subreddit": "golang",
	"score": 999,
	"promoted": false,
	"nsfw": false
}

Constraints:

• author should be a random 8 lowercase letters or numbers prefixed with t2_
• a post cannot have both a link and content simultaneously

Example:

% curl -X POST --header "Content-Type: application/json" --data-raw '{"title":"title", "author":"t2_abcdefg9", "link":"https://reddit.com", "subreddit":"golang", "score":999, "promoted":false, "nsfw":false}' http://localhost:8080/submit

GET /feed?page=0

Generate a paginated feed of posts

Response

[
  {
    "title": "title 1",
    "author": "t2_abcdefg9",
    "link": "https://reddit.com",
    "subreddit": "golang",
    "score": 999,
    "promoted": false,
    "nsfw": false
  },
  {
    "title": "enlarge something",
    "author": "t2_abcdefg9",
    "link": "https://reddit.com",
    "subreddit": "golang",
    "score": 999,
    "promoted": true,
    "nsfw": false
  },
  {
    "title": "title 2",
    "author": "t2_abcdefg9",
    "link": "https://reddit.com",
    "subreddit": "golang",
    "score": 99,
    "promoted": false,
    "nsfw": false
  }
]

Example:

% curl -X GET http://localhost:8080/feed?page=0

Constraints:

• It should be ranked by score, and the post with the highest score should show up first.
• It should be paginated, and each page should have at most 27 posts. Your API should support fetching a specific page in the feed.
• If a page has 3 posts or greater, the second post should always be a promoted post if a promoted post is available, regardless of the score.
• If a page has greater than 16 posts, the 16th post should always be a promoted post if a promoted post is available, regardless of the score.
• As an exception to rules 3 and 4, a promoted post should never be shown adjacent to an NSFW post. You can ignore rules 3 and 4 in this case.

Components

           ______________                  ____________________
          |              | dump posts     |    Redis           |
*-/submit-| HTTP-server  |--------------->|                    |
          |              | process posts  |  posts(stream)     |
          | materializer |<---------------|  feed(sorted set)  |
          | |          ^ |  update feed   |  promoted(ring)    |
          | |          | |--------------->|                    |
          | v__________| |  update promo  |                    |
          |              |--------------->|                    |
          |              |merge feed&promo|                    |
*-/feed---|              |<---------------|____________________|
          |______________|

Service nanoreddit includes several routines:

1. http-server based on chi. It accepts and validates requests. After this, all incoming posts go to the steam called posts. Of course, in production, it should be replaced something more reliable. For example, it can be Kafka.
2. The Materializer is a worker, which is processing posts from the stream posts and putting promoted and non-promoted posts into promoted and feed lists, respectively.
3. The feed is accessible by calling /feed. It reads feed from Redis, enriches with some promoted posts, and returns as a response.

How to run

% docker-compose -f docker-compose.infra.yaml -f docker-compose.service.yaml up --build
% go test -tags=integration ./test -count=1

To configure service you can use environment variables:

SERVICE_LISTEN_ADDRESS=:8080
SERVICE_SHUTDOWN_TIMEOUT=30s
SERVICE_LOGREQUESTS=true
FEED_PAGE_SIZE=25
ES_STREAM=posts
ES_FEED=feed
ES_PROMOTION=promotion
ES_GROUP=materializer
ES_CONSUMER=nanoreddit
REDIS_URL=redis://localhost:6379/0
LOGGER_LEVEL=info
LOGGER_TIMESTAMP=true
LOGGER_CALLER=true
LOGGER_PRETTY=true