Current File : //opt/imunify360-webshield/lualib/resty/limit/req.lua
-- Copyright (C) Yichun Zhang (agentzh)
--
-- This library is an approximate Lua port of the standard ngx_limit_req
-- module.
local ffi = require "ffi"
local math = require "math"
local ngx_shared = ngx.shared
local ngx_now = ngx.now
local setmetatable = setmetatable
local ffi_cast = ffi.cast
local ffi_str = ffi.string
local abs = math.abs
local tonumber = tonumber
local type = type
local assert = assert
local max = math.max
-- TODO: we could avoid the tricky FFI cdata when lua_shared_dict supports
-- hash-typed values as in redis.
ffi.cdef[[
struct lua_resty_limit_req_rec {
unsigned long excess;
uint64_t last; /* time in milliseconds */
/* integer value, 1 corresponds to 0.001 r/s */
};
]]
local const_rec_ptr_type = ffi.typeof("const struct lua_resty_limit_req_rec*")
local rec_size = ffi.sizeof("struct lua_resty_limit_req_rec")
-- we can share the cdata here since we only need it temporarily for
-- serialization inside the shared dict:
local rec_cdata = ffi.new("struct lua_resty_limit_req_rec")
local _M = {
_VERSION = '0.08'
}
local mt = {
__index = _M
}
function _M.new(dict_name, rate, burst)
local dict = ngx_shared[dict_name]
if not dict then
return nil, "shared dict not found"
end
assert(rate > 0 and burst >= 0)
local self = {
dict = dict,
rate = rate * 1000,
burst = burst * 1000,
}
return setmetatable(self, mt)
end
-- sees an new incoming event
-- the "commit" argument controls whether should we record the event in shm.
-- FIXME we have a (small) race-condition window between dict:get() and
-- dict:set() across multiple nginx worker processes. The size of the
-- window is proportional to the number of workers.
function _M.incoming(self, key, commit)
local dict = self.dict
local rate = self.rate
local now = ngx_now() * 1000
local excess
-- it's important to anchor the string value for the read-only pointer
-- cdata:
local v = dict:get(key)
if v then
if type(v) ~= "string" or #v ~= rec_size then
return nil, "shdict abused by other users"
end
local rec = ffi_cast(const_rec_ptr_type, v)
local elapsed = now - tonumber(rec.last)
-- print("elapsed: ", elapsed, "ms")
-- we do not handle changing rate values specifically. the excess value
-- can get automatically adjusted by the following formula with new rate
-- values rather quickly anyway.
excess = max(tonumber(rec.excess) - rate * abs(elapsed) / 1000 + 1000,
0)
-- print("excess: ", excess)
if excess > self.burst then
return nil, "rejected"
end
else
excess = 0
end
if commit then
rec_cdata.excess = excess
rec_cdata.last = now
dict:set(key, ffi_str(rec_cdata, rec_size))
end
-- return the delay in seconds, as well as excess
return excess / rate, excess / 1000
end
function _M.uncommit(self, key)
assert(key)
local dict = self.dict
local v = dict:get(key)
if not v then
return nil, "not found"
end
if type(v) ~= "string" or #v ~= rec_size then
return nil, "shdict abused by other users"
end
local rec = ffi_cast(const_rec_ptr_type, v)
local excess = max(tonumber(rec.excess) - 1000, 0)
rec_cdata.excess = excess
rec_cdata.last = rec.last
dict:set(key, ffi_str(rec_cdata, rec_size))
return true
end
function _M.set_rate(self, rate)
self.rate = rate * 1000
end
function _M.set_burst(self, burst)
self.burst = burst * 1000
end
return _M
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