ratelimit

A high-performance rate limiter written in C++ that speaks Redis protocol. See our blog post to learn more.

Building from source

• Ensure Bazel is installed
• Check out the smyte-db repo
• Ensure your submodules are up-to-date: git submodule update
• Build the project: bazel build -c opt ratelimit

Running it

Once compiled (as above), the binary lives at ./bazel-bin/ratelimit/ratelimit.

It takes a few options:

• --port: the TCP port to listen on (default 9049)
• --rocksdb_db_path: path where ratelimit should persist its state
• --rocksdb_create_if_missing: pass this flag to create the database if it does not exist

Example: ./bazel-bin/ratelimit/ratelimit --rocksdb_db_path ratelimit-data --rocksdb_create_if_missing

You can also run it inside docker: docker run -p 9049:9049 smyte/ratelimit

Supported commands

• RL.REDUCE key max refilltime [REFILL refillamount] [TAKE tokens] [AT timestamp]: create a bucket identified by key if it does not exist that can hold up to max tokens and return the number of tokens remaining. Every refilltime seconds refillamount tokens will be added to the bucket up to max. If refillamount is not provided it defaults to max. If there are at least tokens remaining in the bucket it will return true and reduce the amount by tokens. If tokens is not provided it defaults to 1. If you want to provide your own current timestamp for refills rather than use the server's clock you can pass a timestamp.
• RL.GET key max refilltime [REFILL refillamount] [AT timestamp]: same as RL.REDUCE, except RL.GET does not reduce the number of tokens in the bucket.
• RL.PREDUCE: same as RL.REDUCE, but uses milliseconds instead of seconds.
• RL.PGET: same as RL.GET, but uses milliseconds instead of seconds.

Example

Start the compiled server (see section on running it)

Send it some traffic:

$ redis-cli -p 9049 RL.REDUCE twoPerMin 2 60
(integer) 2
$ redis-cli -p 9049 RL.REDUCE twoPerMin 2 60
(integer) 1
$ redis-cli -p 9049 RL.REDUCE twoPerMin 2 60
(integer) 0