Search API

Tiny Search API service build on top of Fast API allowing to query data from Elastisearch with a rate-limiter

Quick start

Simply start the app via docker compose:

docker-compose up

You can go to http://localhost:8000/docs/ and try the API from there

to import the data, you have to install dependencies locally:

poetry install
python3 import.py

Design

In this section, I will outline thoughts and design decisions which were taken during implementation

Elasticsearch

Field types

I started with designing mapping, looking at the data I identified:`

1. id, username - these fields are unique identifiers, so they are likely to be selected by exact queries, do not have stemming requirements
2. post, user_bio - these fields are text fields, so we need full-text search features such as stemming, stop words filtering
3. post_like_count, post_diamond_count - integer values, so we can have range queries for them

Analysers

I decided to proceed with standard tokenizer, it's recommended one and demonstrated good results, comparing to default settings of other tokenizers.

Filters included:

• stop - removes stop words, by default uses English dictionary
• lowercase - sets all characters to be lowercase, as register doesn't matter for search
• porter_stem - English language stemmer

{
  "mappings": {
    "properties": {
      "id": {
        "type": "keyword"
      },
      "post": {
        "type": "text"
      },
      "username": {
        "type": "keyword"
      },
      "user_bio": {
        "type": "text"
      },
      "post_like_count": {
        "type": "integer"
      },
      "post_diamond_count": {
        "type": "integer"
      }
    }
  },
  "settings": {
    "analysis": {
      "analyzer": {
        "my_analyzer": {
          "tokenizer": "standard",
          "filter": [
            "stop",
            "lowercase",
            "porter_stem"
          ]
        }
      }
    }
  }
}

What does this mapping support

• Stemming in English
• Multicolumn search
• Index optimizations (do not stem id/username)
• Typo support (couldn't make it work with multicolumn queries)

Python

I have chosen FastAPI as a modern framework with async support, Swagger generation and etc.

Elasticsearch adapter

Sadly, popular Elasticsearch libraries did not support all required features (async, PIT, scroll), so I decided to write src/es_helper.py for this to save a bit of time.

Point in time API

In order to provide consistent view for API client while paginating, I decided to utilize Point in time API usage, which allows a client to scroll data in a state they were at the moment client initialized first connection, even if they were updated. It is implemented as a query parameter, and return after each request

Pydantic

In order not to have json/dict hell, all data passed within the project, are wrapped into Pydantic models, including ElasticSearch responses.

Dockerfile

Dockerfile utilizes multistage build with caching support, so final image is slimmer and recurrent builds are faster

Rate limiting

Rate limiting is implemented by slowapi library, which is based on a popular Flask implementation. It uses Redis backend in order to allow to scale python containers without loosing global rate-limiting.

Documentation

Swagger is available at http://localhost:8000/docs