Pause is a flexible Redis-backed rate-limiting client. Use it to track events, with rules around how often they are allowed to occur within configured time checks.
Because Pause is Redis-based, multiple ruby processes (even distributed across multiple servers) can track and report events together, and then query whether a particular identifier should be rate limited or not.
Sample applications include IP-based blocking based on HTTP request volume (see related gem "spanx"), throttling push notifications as to not overwhelm the user with too much frequency, etc.
Add this line to your application's Gemfile:
And then execute:
Or install it yourself as:
$ gem install pause
Configure Pause. This could be in a Rails initializer.
- resolution - The time resolution (in seconds) defining the minimum period into which action counts are aggregated. This defines the size of the persistent store. The higher the number, the less data needs to be persisted in Redis.
- history - The maximum amount of time (in seconds) that data is persisted
Pause.configure do |config| config.redis_host = "127.0.0.1" config.redis_port = 6379 config.redis_db = 1 config.resolution = 600 # aggregate all events into 10 minute blocks config.history = 86400 # discard all events older than 1 day end
Define local actions for your application. Actions define a scope by
which they are identified in the persistent store (aka "namespace"), and a set of checks. Checks define various
max_allowed) against periods of time (
period_seconds). When a threshold it triggered,
the action is rate limited, and stays rate limited for the duration of
Checks are configured with the following arguments (which can be passed as an array, or a symbol hash):
period_seconds- time window this is a time period against which an action is tested
max_allowed- the maximum number of times an action can be incremented during this particular time period before rate limiting is triggered.
block_ttl- amount time (seconds) an action stays rate limited after threshold is reached.
Scope is simple string used to identify this action in the Redis store, and is appended to all keys. Therefore it is advised to keep scope as short as possible to reduce memory requirements of the store.
If you are using the same Redis store to rate limit multiple actions, you must ensure that each action has a unique scope.
Resolution is the period of aggregation. As events come in, Pause aggregates them in time blocks of this length. If you set resolution to 10 minutes, all events arriving within a 10 minute block are aggregated.
Resolution must be less than or equal to the smallest
period_seconds value in your checks.
In other words, if your shortest check is 1 minute, you could set resolution to 1 minute or smaller.
require 'pause' class FollowAction < Pause::Action scope "f" check period_seconds: 60, max_allowed: 100, block_ttl: 3600 check period_seconds: 1800, max_allowed: 2000, block_ttl: 3600 end
When an event occurs, you increment an instance of your action, optionally with a timestamp and count. This saves data into a redis store, so it can be checked later by other processes. Timestamps should be in unix epoch format.
class FollowsController < ApplicationController def create action = FollowAction.new(user.id) if action.ok? # do stuff! # and track it... action.increment! else # action is rate limited, either skip # or show error, depending on the context. end end end class OtherController < ApplicationController def index action = OtherAction.new(params[:thing]) unless action.rate_limited? # perform business logic .... # track it action.increment!(params[:count].to_i, Time.now.to_i) end end end
If more data is needed about why the action is blocked, the
analyze can be called
action = NotifyViaEmailAction.new("thing") while true action.increment! rate_limit_event = action.analyze if rate_limit_event puts rate_limit_event.identifier # which key got rate limited ("thing") puts rate_limit_event.sum # total count that triggered a rate limit puts rate_limit_event.timestamp # timestamp when rate limiting occurred puts rate_limit_event.period_check # period check object, that triggered this rate limiting event else # not rate-limited, same as action.ok? end sleep 1 end
Actions have a built-in way by which they can be disabled or enabled.
This is persisted to Redis, so state is not process-bound, but shared across all ruby run-times using this action (assuming Redis store configuration is the same).
When disabled, Pause does not check state in any of its methods, so calls to increment! or ok? still work exactly as before. This is because adding extra Redis calls can be expensive in loops. You should check whether your action is enabled or disabled if it important to support enabling and disabling of rate limiting in your context.
while true if MyAction.enabled? Thing.all.each do |thing| action = MyAction.new(thing.name) action.increment! unless action.rate_limited? end end sleep 10 end
Actions can be unblocked manually after they have been blocked.
To unblock all blocked identifiers for a single action:
To unblock a single identifier for an action:
action = MyAction.new('hello') action.ok? # => false action.unblock action.ok? # => true
Want to make it better? Cool. Here's how:
- Fork it
- Create your feature branch (
git checkout -b my-new-feature)
- Commit your changes (
git commit -am 'Add some feature')
- Push to the branch (
git push origin my-new-feature)
- Create a new pull request
This gem was written by Eric Saxby, Atasay Gokkaya and Konstantin Gredeskoul at Wanelo, Inc.
Please see the LICENSE.txt file for further details.