Can set data in Redis server but can't get it - node.js

Question

I can set the value for a key in my Redis server (when I flushall, run this code, and then get key in redis-cli, I get back the proper values), but when I try to get key values through my NodeJs server, it never even logs out 'got data'.
I considered maybe this was because these functions were running asynchronously, and I was asking to get values that weren't yet stored in the cache, but that does not explain why it wouldn't print 'got data' ever.
My console logs-> 'start'->'data saved'->'end' (and no 'got data', ever)
In redis-cli-> flushall->get test->(nil)->run app.js(in the other terminal)->get test->"1, 2, 3, 4, 5"
I get no errors at all, the code runs, but does not do what I want it to.
Also, don't know if this is relevant, but when connecting to the Redis server, just Redis.createClient() only created a client but did not connect and when I looked it up, the general idea I got was that newer versions did not connect automatically and you had to manually redisClient.connect().
I struggled with this a bit at the start but seemed to have sorted this problem, but just thought I'd mention it, if I messed up somehow, please correct me, as I'm pretty new to NodeJs and codng in general.
My code:
const redisClient = Redis.createClient();
redisClient.connect();
const data = [1, 2, 3, 4, 5];
app.get('/', async(req, res, next) => {
console.log('start')
await redisClient.set('test', data);
console.log('data saved');
await redisClient.get('test', (error, test)=>{
console.log('got data');
console.log(test);
});
console.log('end');
});
Thanks!

Answer 1

I have seen your code. Based on my investigation you should remove the callback and keep await only while you get the data from redis.
I have investigated more this issue and have found that client.get() and client.set() function runs asynchronously. Hence it would achieve this way.
client.set('foo', 'bar', (err, reply) => {
if (err) throw err;
console.log(reply);
client.get('foo', (err, reply) => {
if (err) throw err;
console.log(reply);
});
});
But everytime is not the same use-case that we should set and get the value immediately.
To get rid of this, Following are the options.
Promises and async/await
you can promisify a subset of node_redis functions one at a time using native Node.js promises and util.promisify:
example:
const redis = require('redis');
const { promisify } = require('util');
const runApplication = async () => {
const client = redis.createClient();
const setAsync = promisify(client.set).bind(client);
const getAsync = promisify(client.get).bind(client);
await setAsync('foo', 'bar');
const fooValue = await getAsync('foo');
console.log(fooValue);
};
I have used the await here and solve an issue. In addition to that you can use redis.get().then() also to fetch the data rather than a callback.
I am also attaching the link with an example provided by redis repo
https://github.com/redis/node-redis/blob/master/examples/connect-as-acl-user.js
Following is the code, I have tested and it is working fine now.
redis.js
const redis = require("redis");
const redisClient = redis.createClient({
url: "redis://host:6379",
password: "password",
});
redisClient.connect();
// const { promisify } = require("util");
// promisify(redisClient.get).bind(redisClient);
// promisify(redisClient.set).bind(redisClient);
module.exports = redisClient;
index.js
const express = require("express");
const app = express();
const redisClient = require("./redis");
app.get("/set", async (req, res, next) => {
try {
const data = req.query.p;
await redisClient.set("test", data);
res.status(200).json({
message: "data cached",
data: data,
});
} catch (err) {
console.error(err);
res.status(500).json({
message: "Something went wrong",
});
}
});
app.get("/get", async (req, res, next) => {
try {
// const data = await redisClient.get("test");
const data = await reddisClient.get("test").then((data) => {
return data;
});
res.status(200).json({
message: "Cached data retrieved",
data,
});
} catch (err) {
console.error(err);
res.status(500).json({
message: "Something went wrong",
});
}
});
app.listen(process.env.PORT || 3000, () => {
console.log("Node server started");
});
Please find attached a screenshot of the output.
So the final thought is that, when we are using callback and wants to execute the code synchronously you should either use callback inside callback (but it is created callback hell, so it would not suggested anymore) or you should use promise/async await/native promisify library of nodejs.
Please visit below link to get the simplest understanding and example.
https://docs.redis.com/latest/rs/references/client_references/client_nodejs/
Hope my question clear your mind. I am happy to accept the relevant suggestion to improve an answer.