Specs

check_rate(id :: String.t(), scale_ms :: integer(), limit :: integer()) ::
  {:allow, count :: integer()}
  | {:deny, limit :: integer()}
  | {:error, reason :: any()}

Check if the action you wish to perform is within the bounds of the rate-limit.

Args:

• id: String name of the bucket. Usually the bucket name is comprised of some fixed prefix, with some dynamic string appended, such as an IP address or user id.
• scale_ms: Integer indicating size of bucket in milliseconds
• limit: Integer maximum count of actions within the bucket

Returns either {:allow, count}, {:deny, limit} or {:error, reason}

Example:

user_id = 42076
case check_rate("file_upload:#{user_id}", 60_000, 5) do
  {:allow, _count} ->
    # do the file upload
  {:deny, _limit} ->
    # render an error page or something
end

Specs

check_rate(
  backend :: atom(),
  id :: String.t(),
  scale_ms :: integer(),
  limit :: integer()
) ::
  {:allow, count :: integer()}
  | {:deny, limit :: integer()}
  | {:error, reason :: any()}

Same as check_rate/3, but allows specifying a backend.

Specs

check_rate_inc(
  id :: String.t(),
  scale_ms :: integer(),
  limit :: integer(),
  increment :: integer()
) ::
  {:allow, count :: integer()}
  | {:deny, limit :: integer()}
  | {:error, reason :: any()}

Same as check_rate/3, but allows the increment number to be specified. This is useful for limiting apis which have some idea of 'cost', where the cost of each hit can be specified.

Specs

check_rate_inc(
  backend :: atom(),
  id :: String.t(),
  scale_ms :: integer(),
  limit :: integer(),
  increment :: integer()
) ::
  {:allow, count :: integer()}
  | {:deny, limit :: integer()}
  | {:error, reason :: any()}

Same as check_rate_inc/4, but allows specifying a backend.

Specs

delete_buckets(id :: String.t()) ::
  {:ok, count :: integer()} | {:error, reason :: any()}

Delete all buckets belonging to the provided id, including the current one. Effectively resets the rate-limit for the id.

Arguments:

• id: String name of the bucket

Returns either {:ok, count} where count is the number of buckets deleted, or {:error, reason}.

Example:

user_id = 2406
{:ok, _count} = delete_buckets("file_uploads:#{user_id}")

Specs

delete_buckets(backend :: atom(), id :: String.t()) ::
  {:ok, count :: integer()} | {:error, reason :: any()}

Same as delete_buckets/1, but allows specifying a backend

Specs

inspect_bucket(id :: String.t(), scale_ms :: integer(), limit :: integer()) ::
  {:ok,
   {count :: integer(), count_remaining :: integer(),
    ms_to_next_bucket :: integer(), created_at :: integer() | nil,
    updated_at :: integer() | nil}}
  | {:error, reason :: any()}

Inspect bucket to get count, count_remaining, ms_to_next_bucket, created_at, updated_at. This function is free of side-effects and should be called with the same arguments you would use for check_rate if you intended to increment and check the bucket counter.

Arguments:

• id: String name of the bucket. Usually the bucket name is comprised of some fixed prefix,with some dynamic string appended, such as an IP address or user id.
• scale_ms: Integer indicating size of bucket in milliseconds
• limit: Integer maximum count of actions within the bucket

Returns either {:ok, {count, count_remaining, ms_to_next_bucket, created_at, updated_at}, or {:error, reason}.

Example:

inspect_bucket("file_upload:2042", 60_000, 5)
{:ok, {1, 2499, 29381612, 1450281014468, 1450281014468}}

Specs

inspect_bucket(
  backend :: atom(),
  id :: String.t(),
  scale_ms :: integer(),
  limit :: integer()
) ::
  {:ok,
   {count :: integer(), count_remaining :: integer(),
    ms_to_next_bucket :: integer(), created_at :: integer() | nil,
    updated_at :: integer() | nil}}
  | {:error, reason :: any()}

Same as inspect_bucket/3, but allows specifying a backend

Specs

make_rate_checker(
  id_prefix :: String.t(),
  scale_ms :: integer(),
  limit :: integer()
) ::
  (id :: String.t() ->
     {:allow, count :: integer()}
     | {:deny, limit :: integer()}
     | {:error, reason :: any()})

Make a rate-checker function, with the given id prefix, scale_ms and limit.

Arguments:

• id_prefix: String prefix to the id
• scale_ms: Integer indicating size of bucket in milliseconds
• limit: Integer maximum count of actions within the bucket

Returns a function which accepts an id suffix, which will be combined with the id_prefix. Calling this returned function is equivalent to: Hammer.check_rate("#{id_prefix}#{id}", scale_ms, limit)

Example:

chat_rate_limiter = make_rate_checker("send_chat_message:", 60_000, 20)
user_id = 203517
case chat_rate_limiter.(user_id) do
  {:allow, _count} ->
    # allow chat message
  {:deny, _limit} ->
    # deny
end

Specs

make_rate_checker(
  backend :: atom(),
  id_prefix :: String.t(),
  scale_ms :: integer(),
  limit :: integer()
) ::
  (id :: String.t() ->
     {:allow, count :: integer()}
     | {:deny, limit :: integer()}
     | {:error, reason :: any()})