Current File : //opt/imunify360-webshield/lualib/resty/lock.lua
-- Copyright (C) Yichun Zhang (agentzh)
require "resty.core.shdict" -- enforce this to avoid dead locks
local ffi = require "ffi"
local ffi_new = ffi.new
local shared = ngx.shared
local sleep = ngx.sleep
local log = ngx.log
local max = math.max
local min = math.min
local debug = ngx.config.debug
local setmetatable = setmetatable
local tonumber = tonumber
local _M = { _VERSION = '0.08' }
local mt = { __index = _M }
local ERR = ngx.ERR
local FREE_LIST_REF = 0
-- FIXME: we don't need this when we have __gc metamethod support on Lua
-- tables.
local memo = {}
if debug then _M.memo = memo end
local function ref_obj(key)
if key == nil then
return -1
end
local ref = memo[FREE_LIST_REF]
if ref and ref ~= 0 then
memo[FREE_LIST_REF] = memo[ref]
else
ref = #memo + 1
end
memo[ref] = key
-- print("ref key_id returned ", ref)
return ref
end
if debug then _M.ref_obj = ref_obj end
local function unref_obj(ref)
if ref >= 0 then
memo[ref] = memo[FREE_LIST_REF]
memo[FREE_LIST_REF] = ref
end
end
if debug then _M.unref_obj = unref_obj end
local function gc_lock(cdata)
local dict_id = tonumber(cdata.dict_id)
local key_id = tonumber(cdata.key_id)
-- print("key_id: ", key_id, ", key: ", memo[key_id], "dict: ",
-- type(memo[cdata.dict_id]))
if key_id > 0 then
local key = memo[key_id]
unref_obj(key_id)
local dict = memo[dict_id]
-- print("dict.delete type: ", type(dict.delete))
local ok, err = dict:delete(key)
if not ok then
log(ERR, 'failed to delete key "', key, '": ', err)
end
cdata.key_id = 0
end
unref_obj(dict_id)
end
local ctype = ffi.metatype("struct { int key_id; int dict_id; }",
{ __gc = gc_lock })
function _M.new(_, dict_name, opts)
local dict = shared[dict_name]
if not dict then
return nil, "dictionary not found"
end
local cdata = ffi_new(ctype)
cdata.key_id = 0
cdata.dict_id = ref_obj(dict)
local timeout, exptime, step, ratio, max_step
if opts then
timeout = opts.timeout
exptime = opts.exptime
step = opts.step
ratio = opts.ratio
max_step = opts.max_step
end
if not exptime then
exptime = 30
end
if timeout then
timeout = min(timeout, exptime)
if step then
step = min(step, timeout)
end
end
local self = {
cdata = cdata,
dict = dict,
timeout = timeout or 5,
exptime = exptime,
step = step or 0.001,
ratio = ratio or 2,
max_step = max_step or 0.5,
}
setmetatable(self, mt)
return self
end
function _M.lock(self, key)
if not key then
return nil, "nil key"
end
local dict = self.dict
local cdata = self.cdata
if cdata.key_id > 0 then
return nil, "locked"
end
local exptime = self.exptime
local ok, err = dict:add(key, true, exptime)
if ok then
cdata.key_id = ref_obj(key)
self.key = key
return 0
end
if err ~= "exists" then
return nil, err
end
-- lock held by others
local step = self.step
local ratio = self.ratio
local timeout = self.timeout
local max_step = self.max_step
local elapsed = 0
while timeout > 0 do
sleep(step)
elapsed = elapsed + step
timeout = timeout - step
local ok, err = dict:add(key, true, exptime)
if ok then
cdata.key_id = ref_obj(key)
self.key = key
return elapsed
end
if err ~= "exists" then
return nil, err
end
if timeout <= 0 then
break
end
step = min(max(0.001, step * ratio), timeout, max_step)
end
return nil, "timeout"
end
function _M.unlock(self)
local dict = self.dict
local cdata = self.cdata
local key_id = tonumber(cdata.key_id)
if key_id <= 0 then
return nil, "unlocked"
end
local key = memo[key_id]
unref_obj(key_id)
local ok, err = dict:delete(key)
if not ok then
return nil, err
end
cdata.key_id = 0
return 1
end
function _M.expire(self, time)
local dict = self.dict
local cdata = self.cdata
local key_id = tonumber(cdata.key_id)
if key_id <= 0 then
return nil, "unlocked"
end
if not time then
time = self.exptime
end
local ok, err = dict:replace(self.key, true, time)
if not ok then
return nil, err
end
return true
end
return _M
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