Changelog

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7.5.0 - 2026-09-02

  • Fix race in Atomic TokenBucket and LeakyBucket where a newly created bucket was published in ETS before its atomic was initialized, so a concurrent hit could read an uninitialized bucket. With refill_rate: 0 this lost a hit. The atomic is now initialized before it is inserted. (#202)
  • Fix TokenBucket ETS backend discarding the sub-token refill remainder on every allowed hit. Callers hitting faster than one token period never refilled, and callers paced at exactly the refill rate slowly starved. The stored clock now advances only by the time whose tokens were credited, so the remainder carries into the next hit. (#197)
  • Fix TokenBucket ETS backend returning a flat {:deny, 1000}; it now returns the real time in milliseconds until the bucket holds enough tokens to pay the cost, consistent with the other algorithms. Behaviour change: denied callers that sleep on this value will now retry much sooner (e.g. 19ms at refill_rate: 55 instead of 1000ms). Code that converts it to a retry-after header should round up and floor at 1 second; the tutorial examples were updated accordingly. (#198)
  • Add mix hammer.install Igniter task (mix igniter.install hammer) that generates a MyApp.RateLimit module and adds it to the supervision tree. Supports --backend ets|atomic|redis; redis also adds the hammer_backend_redis dependency. Igniter is an optional dependency. (#157)

7.4.1 - 2026-08-28

  • Fix TokenBucket ETS backend refill using whole-second resolution, which capped sustained throughput at capacity tokens/sec when refill_rate > capacity. Refill now uses millisecond resolution. (#192)

7.4.0 - 2026-05-19

  • Add :fix_window_per_key algorithm for ETS and Atomic backends — a fixed-window variant whose window is anchored to first hit per key instead of a globally-aligned wall-clock epoch. Same one-entry-per-key memory profile as :fix_window. The 2x boundary burst is still possible per key, but boundaries are no longer globally synchronized. (#181)

7.3.0 - 2026-03-31

  • Add expires_at/2 API for fix_window algorithm (#178)
  • Add before_clean callback on bucket expiry (#177)
  • Fix timestamp unit mismatch in TokenBucket and LeakyBucket clean/1 (#176)
  • Fix race condition between insert_new and lookup in ETS hit/5 (#175)

7.2.0 - 2026-02-03

  • Fix race condition in TokenBucket and LeakyBucket atomics backends by using compare-and-swap (CAS) with packed 64-bit values (#169)
  • Drop Elixir 1.14 support (#169)
  • Add Elixir 1.19 / OTP 28 support (#169)
  • Rename internal :algorithm option to :algorithm_module in Atomic backend for clarity (#170)

7.1.0 - 2025-07-18

  • Fix key type inconsistency in backend implementations - all backends now accept term() keys instead of String.t() (#143)
  • Add comprehensive test coverage for various key types (atoms, tuples, integers, lists, maps)
  • Fix race conditions in atomic backend tests (FixWindow, LeakyBucket, TokenBucket)
  • Replace timing-dependent tests with polling-based eventually helper for better CI reliability
  • Add documentation warning about Redis backend string key requirement
  • Fix typo in inc/3 optional callback documentation (#142)

7.0.1 - 2025-03-04

  • Fix race condition in Atomic backends during creation of key.

7.0.0 - 2025-02-06

  • Release candidate for 7.0.0. See [./guides/upgrade-v7.md] for upgrade instructions.

7.0.0-rc.4 - 2025-01-06

  • Fix Token bucket to respect custom cost

7.0.0-rc.3 - 2024-12-18

  • Fix regression to support other backends

7.0.0-rc.2 - 2024-12-17

  • Fix type specs for ETS backends
  • Adds Atomic backends and possible algorithms
  • Added :algorithm option to the Atomic backend with support for:
    • :fix_window (default) - Fixed time window rate limiting
    • :leaky_bucket - Constant rate limiting with burst capacity
    • :token_bucket - Token-based rate limiting with burst capacity
  • Add benchmarks file and run them with bench

7.0.0-rc.1 - 2024-12-13

  • Improved API a little more. Should be compatibe with previous RC
    • Made ETS backend more flexible with :algorithm option
    • Added :key_older_than option to the ETS backend
  • Added :algorithm option to the ETS backend with support for:
    • :fix_window (default) - Fixed time window rate limiting
    • :sliding_window - Sliding time window for smoother rate limiting
    • :leaky_bucket - Constant rate limiting with burst capacity
    • :token_bucket - Token-based rate limiting with burst capacity

7.0.0-rc.0 - 2024-12-13

  • Breaking change. Completely new API. Consider upgrading if you are experiencing performance or usability problems with Hammer v6. See [./guides/upgrade-v7.md] for upgrade instructions. https://github.com/ExHammer/hammer/pull/104
  • Hammer.Plug has been removed. See documentation for using Hammer as a plug in Phoenix.

6.2.1 - 2024-02-23

  • Fix issue in OTP 26 and Elixir 1.15 by not using to_existing_atom in configuration

Changed

6.2.0 - 2024-01-31

6.1.0 - 2022-06-13

Changed

6.0.0 - 2018-10-12

Changed

  • Change the ETS backend to throw an error if either expiry_ms or cleanup_interval_ms config values are missing. This should have been fixed ages ago.
  • Default :pool_max_overflow changed to 0. It's a better default, given that some users have seen weird errors when using a higher overflow. In general, capacity should be increased by using a higher :pool_size instead
  • Changed how the ETS backend does cleanups of data, should be more performant.

5.0.0 - 2018-05-18

Added

  • A new check_rate_inc function, which allows the caller to specify the integer with which to increment the bucket by. This is useful for limiting APIs which have some notion of "cost" per call.

4.0.0 - 2018-04-23

Changed

  • Use a worker-pool for the backend (via poolboy), this avoids bottle-necking all traffic through a single hammer process, thus improving throughput for the system overall

Added

  • New configuration options for backends:
    • :pool_size, determines the number of workers in the pool (default 4)
    • :pool_max_overflow, maximum extra workers to be spawned when the system is under pressure (default 4)
  • Multiple instances of the same backend! You can now have two ETS backends, fifteen Redis's, whatever you want

3.0.0 - 2018-02-20

Changed

  • Require elixir >= 1.6
  • Use a more sane supervision tree structure

2.1.0 2017-11-25

Changed

  • Add option to use more than one backend
  • Add option to suppress all logging

2.0.0 - 2017-09-24

Changed

  • New, simpler API
    • No longer need to start backend processes manually
    • Call Hammer.check_rate directly, rather than useing a macro
  • Hammer is now an OTP application, configured via Mix.Config

1.0.0 - 2017-08-22

Added

  • Formalise backend API in Hammer.Backend behaviour

0.2.1 - 2017-08-10

Changed

  • Minor fixes