go-link-shortener-backend, v1.8

Back-end of the service for shorting links.

Adding transformations of values received from a distributed counter, refactoring and adding bulky testing.

adding transformations of values received from a distributed counter:
- using linear transformations:
  - multiplication;
  - shift;
removing:
- generating link codes:
  - removing using a version 4 UUID;
  - using sequential counters:
    - removing formatting a counter as an integer number in the 10 base;
refactoring:
- extracting the counters package:
  - moving the generators.chunkedCounter structure to the counters.ChunkedCounter structure;
  - extracting the counters.CounterGroup structure from the generators.DistributedGenerator structure;
- using external packages:
  - replacing Printer interfaces to the special package;
  - extracting HTTP utility functions to the single package;
testing:
- bulky testing:
  - adding a bulky test of the generators.DistributedGenerator structure;
  - adding an integration bulky test of link creating;
- Travis CI configuration:
  - using data race detection;
  - using the dep tool;
improving repository decor:
- adding the change log.

RESTful API:
- link model:
  - creating by an URL;
  - getting by a code;
- representing in a JSON:
  - payloads:
    - of requests;
    - of responses;
  - errors;
generating link codes:
- using sequential counters:
  - formatting:
    - formatting a counter as an integer number in the 62 base;
  - storing:
    - storing in a database only counters chunks;
    - storing counters themselves in memory;
  - sharding:
    - sharding counters chunks;
    - selecting a shard of a counter chunk at random;
server:
- additional routing:
  - redirecting to the link URL by its code;
  - serving static files;
- storing settings in environment variables;
- supporting graceful shutdown;
- logging:
  - logging requests;
  - logging errors;
- panics:
  - recovering on panics;
  - logging of panics;
databases:
- storing links in the MongoDB database;
- storing counters chunks in the etcd database:
  - using a record version as a counter chunk;
- caching links in the Redis database;
distributing:
- Docker image;
- Docker Compose configuration.

$ go-link-shortener

Environment variables:

SERVER_ADDRESS — server URI (default: :8080);
SERVER_STATIC_PATH — path to the project's front-end (default: ./static);
CACHE_ADDRESS — Redis connection URI (default: localhost:6379);
CACHE_TTL_CODE — time to live of links in Redis, stored by their code (e.g. 72h3m0.5s; default: 1h);
CACHE_TTL_URL — time to live of links in Redis, stored by their URL (e.g. 72h3m0.5s; default: 1h);
STORAGE_ADDRESS — MongoDB connection URI (default: mongodb://localhost:27017);
COUNTER_ADDRESS — etcd connection URI (default: localhost:2379);
COUNTER_COUNT — count of distributed counters (default: 2);
COUNTER_CHUNK — step of a distributed counter (default: 1000);
COUNTER_RANGE — range of a distributed counter (default: 1000000000).

Content: code.

License: MIT.