is it possible to call lua functions defined in other lua scripts in redis?

Question

I have tried to declare a function without the local keyword and then call that function from anther script but it gives me an error when I run the command.

test = function ()    
    return 'test'
end



# from some other script
test()

Edit:

I can't believe I still have no answer to this. I'll include more details of my setup.

I am using node with the redis-scripto package to load the scripts into redis. Here is an example.

var Scripto = require('redis-scripto');
var scriptManager = new Scripto(redis);

scriptManager.loadFromDir('./lua_scripts');

var keys    = [key1, key2];
var values  = [val];

scriptManager.run('run_function', keys, values, function(err, result) {
console.log(err, result)
})

And the lua scripts.

-- ./lua_scripts/dict_2_bulk.lua

-- turns a dictionary table into a bulk reply table
dict2bulk = function (dict)
    local result = {}
    for k, v in pairs(dict) do
        table.insert(result, k)
        table.insert(result, v)
    end
    return result
end


-- run_function.lua 

return dict2bulk({ test=1 })

Throws the following error.

[Error: ERR Error running script (call to f_d06f7fd783cc537d535ec59228a18f70fccde663): @enable_strict_lua:14: user_script:1: Script attempted to access unexisting global variable 'dict2bulk' ] undefined

I'll ask the obvious: in the second script, do you (or anywhere else) 'require' the script that specifies the function? That is, does that code actually run? — Nathan
The scripts are loaded into redis via the script load command. There is no requires from within the scripts themselves. Do I need them? — Tim Fairbrother
if I use require, it gives me an error. Script attempted to access unexisting global variable 'require'. I'm not sure require will work from within Redis. — Tim Fairbrother
Also, the script runs. I can run normal redis commands that execute successfully but it doesn't know anything about the functions that I have declared in other scripts. — Tim Fairbrother
@Nathan, can you please tell me how I am supposed to use require inside Redis when there is no filesystem? — Tim Fairbrother

Josiah Josiah · Accepted Answer · 2014-03-24T02:00:58

I'm going to be contrary to the accepted answer, because the accepted answer is wrong.

While you can't explicitly define named functions, you can call any script that you can call with EVALSHA. More specifically, all of the Lua scripts that you have explicitly defined via SCRIPT LOAD or implicitly via EVAL are available in the global Lua namespace at f_<sha1 hash> (until/unless you call SCRIPT FLUSH), which you can call any time.

The problem that you run into is that the functions are defined as taking no arguments, and the KEYS and ARGV tables are actually globals. So if you want to be able to communicate between Lua scripts, you either need to mangle your KEYS and ARGV tables, or you need to use the standard Redis keyspace for communication between your functions.

127.0.0.1:6379> script load "return {KEYS[1], ARGV[1]}"
"d006f1a90249474274c76f5be725b8f5804a346b"
127.0.0.1:6379> eval "return f_d006f1a90249474274c76f5be725b8f5804a346b()" 1 "hello" "world"
1) "hello"
2) "world"
127.0.0.1:6379> eval "KEYS[1] = 'blah!'; return f_d006f1a90249474274c76f5be725b8f5804a346b()" 1 "hello" "world"
1) "blah!"
2) "world"
127.0.0.1:6379>

All of this said, this is in complete violation of spec, and is entirely possible to stop working in strange ways if you attempt to run this in a Redis cluster scenario.

is it possible to call lua functions defined in other lua scripts in redis?

3 Answers