scripts/lua/policies/rateLimit.lua

-- Copyright (c) 2016 IBM. All rights reserved.
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--- @module rateLimit
-- Process a rateLimit object, setting the rate and interval to the request
-- @author David Green (greend), Alex Song (songs)

local REDIS_HOST = os.getenv("REDIS_HOST")
local REDIS_PORT = os.getenv("REDIS_PORT")
local REDIS_PASS = os.getenv("REDIS_PASS")
local req = require "lib/resty/limit/req"
local utils = require "lib/utils"
local logger = require "lib/logger"
local request = require "lib/request"
local redis = require "lib/redis"

local _M = {}

--- Limit a resource/api/tenant, based on the passed in rateLimit object
-- @param obj rateLimit object containing interval, rate, scope, subscription fields
-- @param apiKey optional api key to use if subscription set to true
function limit(obj, apiKey)
  local i = 60 / obj.interval
  local r = i * obj.rate
  r = utils.concatStrings({tostring(r), 'r/m'})
  local tenantId = ngx.var.tenant
  local gatewayPath = ngx.var.gatewayPath
  local k
  -- Check scope
  if obj.scope == 'tenant' then
    k = utils.concatStrings({"tenant:", tenantId})
  elseif obj.scope == 'api' then
    local red = redis.init(REDIS_HOST, REDIS_PORT, REDIS_PASS, 10000)
    local apiId = redis.resourceToApi(red, utils.concatStrings({'resources:', tenantId, ':', gatewayPath}))
    k = utils.concatStrings({"tenant:", tenantId, ":api:", apiId})
    redis.close(red)
  elseif obj.scope == 'resource' then
    k = utils.concatStrings({"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
  -- Perform rate limiting
  local config = {
    key = k,
    zone = 'rateLimiting',
    rate = r,
    interval = obj.interval,
    log_level = ngx.NOTICE,
    rds = {host = REDIS_HOST, port = REDIS_PORT, pass = REDIS_PASS}
  }
  local ok = req.limit(config)
  if not ok then
    logger.err('Rate limit exceeded. Sending 429')
    request.err(429, 'Rate limit exceeded.')
  end
end

_M.limit = limit

return _M