HelloBug0 commented on issue #3112:
URL: https://github.com/apache/apisix/issues/3112#issuecomment-751319250
I see. There is need to protect the cache when setting a stale object. In
this way, I also have two questions.
+ Why do we lock the function execution of fetch_valid_cache in line 119? Is
it OK if we call the function out of the lock?
+ I still don't clear that why we call the function of fetch_valid_cache
twice. It‘s natually to think that the code from line 100 to line 134 to be
programed like this.
```lua
local cache_obj = fetch_valid_cache(lru_obj, invalid_stale, item_ttl,
item_release, key, version)
if cache_obj then
return cache_obj.val
end
local lock, err = resty_lock:new(lock_shdict_name)
if not lock then
return nil, "failed to create lock: " .. err
end
local key_s = tostring(key)
log.info("try to lock with key ", key_s)
local elapsed, err = lock:lock(key_s)
if not elapsed then
return nil, "failed to acquire the lock: " .. err
end
local obj, err = create_obj_fun(...)
if obj ~= nil then
lru_obj:set(key, {val = obj, ver = version}, item_ttl)
end
lock:unlock()
log.info("unlock with key ", key_s)
return obj, err
```
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