discourse/lib/rate_limiter.rb

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require_dependency 'rate_limiter/limit_exceeded'
require_dependency 'rate_limiter/on_create_record'
# A redis backed rate limiter.
class RateLimiter
# We don't observe rate limits in test mode
def self.disabled?
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Rails.env.test?
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end
def initialize(user, key, max, secs)
@user = user
@key = "rate-limit:#{@user.id}:#{key}"
@max = max
@secs = secs
end
def clear!
$redis.del(@key)
end
def can_perform?
return true if RateLimiter.disabled?
return true if @user.staff?
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result = $redis.get(@key)
return true if result.blank?
return true if result.to_i < @max
false
end
def performed!
return if RateLimiter.disabled?
return if @user.staff?
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result = $redis.incr(@key).to_i
$redis.expire(@key, @secs) if result == 1
if result > @max
# In case we go over, clamp it to the maximum
$redis.decr(@key)
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raise LimitExceeded.new($redis.ttl(@key))
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end
end
def rollback!
return if RateLimiter.disabled?
$redis.decr(@key)
end
end