Properly execute Lua script with node_redis client

Question

I'm trying to write an extremely simple Lua script to access the hyperloglog functionality in redis from node_redis. I have 1 key and multiple hashes as elements to pass. I can successfully do this only if I hard code the key and argument as in the following:

script: 'return redis.call("pfadd", 'testkey', 'valvalval')'

While this works perfectly, this is not very useful...

I've tried every possible way I can think of to access KEYS and ARGV arrays and this is what I currently have in my .js file:

var script = '\
local val = 0 \
for _, hash in pairs(ARGV) do \
     redis.call("pfadd", KEYS[1], hash) \
end \
return val';

And to call my script:

redisInstance.eval(script, 1, args, function (ret) {
    console.log(ret);
});

args is an array as follows:

['key','hash1','hash2','hash3', ...,'hash30']

The callback is always null and no keys are set on the server... The KEYS and ARGV arrays are not accessed... (when hardcoded as I said, it works fine..)

I need to pass all of the hashes as elements (total of about 30 each time) and receive the integer replies.

Thanks in advance for the help.

what is '1' for? in redisInstance.eval(script, 1, args, function (ret) {...} ? — zenbeni
A couple quick things that jump out: the callback takes two params, error and result, not just the result. Also, try invoking it like this: redisInstance.eval([script, 1, ['key'], ['hash1', 'hash2']], function(error, resp){ ... }) — aembke

Yuriy Yuriy · Accepted Answer · 2015-11-09T19:19:16

The previous answer was wrong, you need to concat all arguments and values to single array(sample using lodash):

var keys = _.keys(filteredData);
var values = _.values(filteredData); 
var command = ["function code",keys.length];
command = command.concat(keys,values);

Anyhow you should consider the ioredis as it supports abstraction for lua scirpts.

Properly execute Lua script with node_redis client

2 Answers