nginxredisluaopenrestyresty

pulling table with redis on lua


I'm running LUA on Nginx. I decided to fetch some variables via Redis. I am using a table on lua. It is like this;

local ip_blacklist = {
"1.1.1.1",
"1.1.1.2",
}

I'm printing on Nginx;

1.1.1.1
1.1.1.2

I want to keep the values here on Redis and not on Lua. My redis : http://prntscr.com/10sv3ln

My Lua command;

local ip = red:hmget("iplist", "ip_blacklist")

I'm printing on Nginx;

{"1.1.1.1","1.1.1.2",}

Its data does not come as a table and functions do not work. How can I call this data like local ip_blacklist?


Solution

  • https://redis.io/topics/data-types

    Redis Hashes are maps between string fields and string values

    You cannot store a Lua table as a hash value directly. As I understand, you have stored a literal string {"1.1.1.1","1.1.1.2",} using RedisInsight, but it doesn't work that way.

    You can use JSON for serialization:

    server {
        location / {
            content_by_lua_block {
                local redis = require('resty.redis')
                local json = require('cjson.safe')    
                  
                local red = redis:new()
                red:connect('127.0.0.1', 6379)
    
                -- set a string with a JSON array as a hash value; you can use RedisInsight for this step
                red:hset('iplist', 'ip_blacklist', '["1.1.1.1", "1.1.1.2"]')
                
                -- read a hash value as a string (a serialized JSON array)
                local ip_blacklist_json = red:hget('iplist', 'ip_blacklist')
                -- decode the JSON array to a Lua table
                local ip_blacklist = json.decode(ip_blacklist_json)
                
                ngx.say(type(ip_blacklist))
                for _, ip in ipairs(ip_blacklist) do
                    ngx.say(ip)
                end
            }
        }
    }
    

    Output:

    table
    1.1.1.1
    1.1.1.2