mlcache Prefix Purging

# mlcache Prefix Purging

# Overview

The mlcache prefix purging feature allows you to asynchronously clean cached resources in a specific name mlcache based on a designated prefix. Here, asynchronous means: the system doesn’t execute the purging operation immediately; instead, it performs the actual cleaning of eligible old cached resources only when an mlcache get operation occurs. It’s worth noting that cache resources created after the purging operation will not be cleaned again.

You can find the mlcache Purge Jobs entry in the Global Configuration page.

# Adding a New Purge Job

# Purge Job Validity Period

To prevent the accumulation of too many purge jobs, each job has a validity period. Once this period expires, the purge job will automatically become invalid. It is recommended to set the validity period to the maximum validity period of the cache resources themselves, ensuring that the purging operation covers all resources that need to be cleaned.

# Example

Suppose we have the following Lua code that uses mlcache to cache user information:

local mlcache = require "resty.mlcache"

local _M = {}

local function value_cb(username)
    return "user:" .. tostring(username)
end

function _M.go()
    local name = "foo"
    local sd_name = "ml_cache_shared_dict"
    local cache_key_prefix = "prefix-foo:"

    local cache, err = mlcache.new(name, sd_name, { lru_size = 1000})

    local args = ngx.req.get_uri_args()
    local username = args.username
    local cache_key = cache_key_prefix .. username
    local ttl, err, value = cache:peek(cache_key)
    if err then
        ngx.say("could not peek cache: ", err)
        return
    end

    ngx.say("cache key: ", cache_key, ", value: ", value, ", ttl: ", ttl)

    if not value then
        local value, err = cache:get(cache_key, { ttl = 86400 }, value_cb, username)
        if err then
            ngx.say("could not get cache: ", err)
            return
        end

        ngx.say("cache key: ", cache_key, ", value: ", value, ", err: ", err)
    end
end

return _M

# Creating a Purge Job

To create a new purge job, simply fill in the relevant information and click the create button:

# Viewing Purge Jobs

You can view all currently active purge jobs in the purge job list. The system will automatically clean up expired purge jobs periodically.