scripts/lua/policies/rateLimit.lua

-- Copyright (c) 2016 IBM. All rights reserved.
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--   Software is furnished to do so, subject to the following conditions:
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--   The above copyright notice and this permission notice shall be included in
--   all copies or substantial portions of the Software.
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--   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
--   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
--   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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--- @module rateLimit

local utils = require "lib/utils"
local request = require "lib/request"

local _M = {}

--- Limit a resource/api/tenant, based on the passed in rateLimit object
-- @param red redis client instance
-- @param obj rateLimit object containing interval, rate, scope, subscription fields
-- @param apiKey optional api key to use if subscription is set to true
function limit(dataStore, obj, apiKey)
  local rate = obj.interval / obj.rate
  local tenantId = ngx.var.tenant
  local gatewayPath = ngx.var.gatewayPath
  local k
  -- Check scope
  if obj.scope == "tenant" then
    k = utils.concatStrings({"ratelimit:tenant:", tenantId})
  elseif obj.scope == "api" then
    local apiId = ngx.var.apiId
    k = utils.concatStrings({"ratelimit:tenant:", tenantId, ":api:", apiId})
  elseif obj.scope == "resource" then
    k = utils.concatStrings({"ratelimit:tenant:", tenantId, ":resource:", gatewayPath})
  end
  -- Check subscription
  if obj.subscription ~= nil and obj.subscription == true and apiKey ~= nil then
    k = utils.concatStrings({k, ":subscription:", apiKey})
  end

  if dataStore:getRateLimit(k) == ngx.null then
    dataStore:setRateLimit(k, "", "PX", math.floor(rate*1000))
  else
    return request.err(429, 'Rate limit exceeded')
  end
end

_M.limit = limit

return _M