This design seeks to reduce read-pressure on our DB by moving rate limit
tabulation to a key-value datastore. This PR provides the following:
- (README.md) a short guide to the schemas, formats, and concepts
introduced in this PR
- (source.go) an interface for storing, retrieving, and resetting a
subscriber bucket
- (name.go) an enumeration of all defined rate limits
- (limit.go) a schema for defining default limits and per-subscriber
overrides
- (limiter.go) a high-level API for interacting with key-value rate
limits
- (gcra.go) an implementation of the Generic Cell Rate Algorithm, a
leaky bucket-style scheduling algorithm, used to calculate the present
or future capacity of a subscriber bucket using spend and refund
operations
Note: the included source implementation is test-only and currently
accomplished using a simple in-memory map protected by a mutex,
implementations using Redis and potentially other data stores will
follow.
Part of #5545
055f620c4b