How to delete caching after some specified time?

Questions
1

How to delete entity caching.

token, err = singletons.cache:get(token_cache_key, nil,
            load_token_into_memory, ngx.ctx.api,
            access_token)

In above example, It cache the token data but expiration time is not fixed.
So is there any way to passed expire time in cache:get() function or you @all have any other suggestion for delete the cache after specific time?

Thanks you

2

Hi,

The second parameter (nil in your example) is an options hash. You can use the ttl option there to set a “time to leave”.

singletons.cache:get(token_cache_key, { ttl = 5 },
                     load_token_into_memory, ngx.ctx.api, access_token)

Internally this method is using ngx.shared.DICT.set, where ttl is passed as the exptime parameter there - so it is in seconds.

3

It is worth pointing out that internally, singletons.cache actually relies on lua-resty-mlcache.

(which itself relies on lua-resty-lrucache and said lua_shared_dict as pointed out by @kikito.)

4

@thibaultcha,
Hello,
kong.singletons is resurrecting a stale item from the cache from shm even there is no resurrect_ttl is specified.

How to avoid this behavior?

if I need to declare my own mlcacahe instance to avoid this ( by not specifiying resurrect_ttl), what is the best way to inject in to kong’s init so this mlcache instance is shared across all the workers.

Thank you.

5

Hi, @rsvenkatesh, next time please consider opening a new thread instead of asking a new question in an old one - it’s easier to discover for others this way.

In case you are still having that problem: the default value for resurrect_ttl can be controlled globally by changing the relevant config option in the config file:

If you want to tweak the ressurect_ttl value for an individual request, leaving the rest unaltered, you can also do that by using the options parameter, the same way as with the ttl:

singletons.cache:get(token_cache_key, { resurrect_ttl = 0 },
                     load_token_into_memory, ngx.ctx.api, access_token)
6

I have tried with resurrect_ttl = 0 already, that doesn’t seems to help. Only way is not even mentioning resurrect_ttl. After I have instance of mlcache without specifying anything to resurrect_ttl, things seems to work as expected.

Thank you.