class RollingCounter

Public Class Methods

new(redis_client, max_window) → counter click to toggle source

Create a new counter instance, that will store/retrieve counts with redis_client and return counts within the last max_window seconds.

Do not attempt to use counters with different max_window to access the same keys, as results will not be consistent. Instead set max_window to the max window needed, then pass the window required to get.

# File lib/rolling_counter.rb, line 15
def initialize(redis, max_window)
  @redis      = redis
  @max_window = max_window
end

Public Instance Methods

get(key) → count click to toggle source

get(key, window) → count

Returns the count for key within window seconds.

# File lib/rolling_counter.rb, line 43
def get(key, window=@max_window)
  @redis.multi { do_get(key.to_s, Time.now.to_f, window) }.last
end

inc(key, window=@max_window)

Alias for: incr

incr(key, window) -> count click to toggle source

Increment the counter for key by 1. Returns the updated count within window, or the max_window if window is not supplied.

# File lib/rolling_counter.rb, line 26
def incr(key, window=@max_window)
  key = key.to_s
  now = Time.now.to_f
  @redis.multi do
    @redis.zadd(key, now, SecureRandom.uuid)
    @redis.expire(key, @max_window.ceil)
    do_get(key, now, window)
  end.last
end

Also aliased as: increment, inc

increment(key, window=@max_window)

Alias for: incr

mget(key, [windows]) → {window:count} click to toggle source

Returns a hash of each windows count for key.

# File lib/rolling_counter.rb, line 51
def mget(key, windows)
  now = Time.now.to_f
  results = @redis.multi do
    windows.each { |window| do_get(key.to_s, now, window) }
  end.each_slice(2).map(&:last)
  Hash[windows.zip(results)]
end

Private Instance Methods

do_get(key, now, window) click to toggle source

# File lib/rolling_counter.rb, line 61
def do_get(key, now, window)
  @redis.zremrangebyscore(key, 0, now - @max_window)
  @redis.zcount(key, now - window, now)
end