get_stale can`t acquire expired key

[ghost]

i send an request like this : http://10.74.151.122/api/test007/v1, and i add some log in your codes like this:
local function _get(self, key)
-- always call get_stale() as it does not free element
-- like get does on each call
local data, flags, stale = self.shdict:get_stale(key)
ngx.log(ngx.ERR,"lua----------------------test0: ", data)
ngx.log(ngx.ERR,"lua----------------------test1: ", flags)
ngx.log(ngx.ERR,"lua----------------------test2: ", stale)
ngx.log(ngx.ERR,"lua----------------------test3: ", key)
if data and stale then
if DEBUG then
print("found stale data for key : ", key)
end

  self.stale_data = { data, flags }

  return nil, nil

end

return data, flags
end

at first request, it will log nil for key = A and nil for key = B, where A is a router and B is a http api。
and the second request(less than 10s, i set positive time is 10s), it will log correct infos for both A and B
but the thrid request, only A can get infos form stale memory。 but , B get nil 。 i try to change the shdict size , no results.

all my test like this。send a request , in the 10s , after 10s
2018/03/20 17:24:25 [error] 10675#10675: *7 [lua] shcache.lua:327: _get(): lua----------------------test0: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:25 [error] 10675#10675: *7 [lua] shcache.lua:328: _get(): lua----------------------test1: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:25 [error] 10675#10675: *7 [lua] shcache.lua:329: _get(): lua----------------------test2: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:25 [error] 10675#10675: *7 [lua] shcache.lua:330: _get(): lua----------------------test3: msb:routing:api:test007:v1, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:25 [error] 10675#10675: *7 [lua] shcache.lua:358: load(): lua----------------------001: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:25 [error] 10675#10675: *7 [lua] shcache.lua:327: _get(): lua----------------------test0: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:25 [error] 10675#10675: *7 [lua] shcache.lua:328: _get(): lua----------------------test1: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:25 [error] 10675#10675: *7 [lua] shcache.lua:329: _get(): lua----------------------test2: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:25 [error] 10675#10675: *7 [lua] shcache.lua:330: _get(): lua----------------------test3: msb:routing:api:test007:v1, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:25 [error] 10675#10675: *7 [lua] shcache.lua:427: load(): lua----------------------005, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:28 [error] 10675#10675: *7 [lua] shcache.lua:327: _get(): lua----------------------test0: {"enable_host_forward":false,"subdomain":"openpalette.zte.com.cn"}, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:28 [error] 10675#10675: *7 [lua] shcache.lua:328: _get(): lua----------------------test1: 1, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:28 [error] 10675#10675: *7 [lua] shcache.lua:329: _get(): lua----------------------test2: false, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:28 [error] 10675#10675: *7 [lua] shcache.lua:330: _get(): lua----------------------test3: msb:config:global:apiroute, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:28 [error] 10675#10675: *7 [lua] shcache.lua:358: load(): lua----------------------001: 1, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:28 [error] 10675#10675: *7 [lua] shcache.lua:362: load(): lua----------------------002, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:28 [error] 10675#10675: *7 [lua] shcache.lua:327: _get(): lua----------------------test0: {"kind":"route","apiVersion":"v1","status":"1","metadata":{"name":"test007","version":"v1","namespace":"","serviceName":"test007","serviceVersion":"v1","uid":"","updateTimestamp":"2018-03-20T00:39:17Z","labels":{},"annotations":null},"spec":{"visualRange":"0","url":"/api/msdiscover/v1/config/routerfloatip","publish_port":"","publish_protocol":"http","publish_iplist":"","host":"test007","subdomain":"","apijson":"/api/msdiscover/v1/config/routerfloatip/swagger.json","apijsontype":"1","metricsUrl":"/admin/metrics","lb_policy":"round-robin","consulServiceName":"test007","useOwnUpstream":"0","enable_ssl":false,"enable_http2":false,"enable_client_verify":false,"control":"0","scenario":1,"enable_refer_match":"","connect_timeout":"","send_timeout":"","read_timeout":"","rate_limiting":{"limit_req":{}},"nodes":[{"ip":"10.74.148.68","port":80,"weight":0,"appversion":""}]}}, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:28 [error] 10675#10675: *7 [lua] shcache.lua:328: _get(): lua----------------------test1: 1, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:28 [error] 10675#10675: *7 [lua] shcache.lua:329: _get(): lua----------------------test2: false, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:28 [error] 10675#10675: *7 [lua] shcache.lua:330: _get(): lua----------------------test3: msb:routing:api:test007:v1, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:28 [error] 10675#10675: *7 [lua] shcache.lua:358: load(): lua----------------------001: 1, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:24:28 [error] 10675#10675: *7 [lua] shcache.lua:362: load(): lua----------------------002, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:327: _get(): lua----------------------test0: {"enable_host_forward":false,"subdomain":"openpalette.zte.com.cn"}, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:328: _get(): lua----------------------test1: 1, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:329: _get(): lua----------------------test2: true, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:330: _get(): lua----------------------test3: msb:config:global:apiroute, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:358: load(): lua----------------------001: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:327: _get(): lua----------------------test0: {"enable_host_forward":false,"subdomain":"openpalette.zte.com.cn"}, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:328: _get(): lua----------------------test1: 1, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:329: _get(): lua----------------------test2: true, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:330: _get(): lua----------------------test3: msb:config:global:apiroute, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:427: load(): lua----------------------005, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:327: _get(): lua----------------------test0: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:328: _get(): lua----------------------test1: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:329: _get(): lua----------------------test2: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:330: _get(): lua----------------------test3: msb:routing:api:test007:v1, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:358: load(): lua----------------------001: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:327: _get(): lua----------------------test0: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:328: _get(): lua----------------------test1: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:329: _get(): lua----------------------test2: nil, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:330: _get(): lua----------------------test3: msb:routing:api:test007:v1, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"
2018/03/20 17:25:04 [error] 10675#10675: *7 [lua] shcache.lua:427: load(): lua----------------------005, client: ::ffff:10.74.57.144, server: , request: "GET /api/test007/v1 HTTP/1.1", host: "10.74.151.122"