Simple product search

The mission

You should create a new controller with a method accepting id of product as a parameter. The method should return json representation of product data.

A basic workflow for the task:

• Request with product id comes in.
• If product is cached retrieve from cache.
• If product is not cached retrieve from ElasticSearch/MySQL and add to cache.
• Increment the number of requests for given product.
• Return product data in JSON.

The solution

IProductStorage interface was created to allow uniform access to product storage. IRequestStatisticsStorage was created to allow uniform access to tracking requests for each product.

ProductController works against these interfaces, so changing implementation can be achieved by changing config file and rebuilding DI container.

FileRequestStatisticsStorage is an implementation of IRequestStatisticsStorage which uses a single file with JSON-encoded array of request counters for each product. The implementation uses file-level locking to prevent race conditions when multiple requests as processed in quick succession.

ICache interface is provided to standardize access to various caching implementation. FilesystemCache implementation uses filesystem, cached products are saved as plain files.

Caching of products can be enabled by using CachedProductStorage implementation, which is just a decorator for IProductStorage.

This layering allows us to configure the ProductController to either use direct access to product storage or plug-in a caching layer. The caching layer itself can use various implementations of ICache.