Lunar logger

For a given URL, crawler is extracting famous people and storing them in remote repository.

logger REST API provides write-ahead-log functionality for the crawler.

Running app

Pre-requisites:

• JDK8
• docker 1.12.0+
• docker-compose 1.6.0+
• for IDE: lombok plugin and enabled annotation-processors

$ ./gradlew build
$ docker-compose up --build

After startup, the following are accessible:

• Logger API docs: http://localhost:8080/swagger-ui.html
• Logger API: http://localhost:8080/api
• Logger health: http://localhost:8080/health
• Logger metrics: http://localhost:8080/metrics

Add more crawler instances:

$ docker-compose scale crawler=5

Design notes

• To avoid handcrafting requests in tests, logger-api has been extracted, which also serves as a client-side SDK (for Java based implementation of crawlers). In the real world, this module should be versioned separately and tests executed against specific versions independently (similar to Consumer Driven Contracts)
• Emphasis on package design with clear dependencies and no cycles:

url -> celebrities
url -> remotekey
registrar -> *

• Some basic hypermedia. It should be possible to navigate from the API index (/api)

Acknowledgments

To minimize the scope, the following were not implemented:

• Crawler exercising Hypermedia links to navigate API
• Crawler with different strategies: randomly crashing, completing incomplete URLs, etc.
• Paging
• Security
• Query optimizations
• Proper immutability on representations, etc.
• Document locking/versioning
• Metrics exporter to console (they are available via endpoint)
• Additional layer of separation between entities and resources, but given the size of the app, it is absolutely not needed at the moment