Nodejs Redis HGETALL return different values from two consecutive calls

[CHYGO1985]

Description

Hi there,

I am having a weird issue here.

The scenario is like the following (all these happen in a local environment): I am using the node-redis, and I used HSET to store the following data: {"value":"test3","isAvail":"true","refCount":"0","acctLevel":"0","username":"user3","id":"3"}

Then I read the data from redis, and change refCount from '0' to '1', and save it back to redis via using HSET again, and here is what happens using HGETALL to read from redis 3 times in a row, here is the console.log output:

after1: {"value":"test3","isAvail":"true","refCount":"0","acctLevel":"0","username":"user3","id":"3"} after2: {"value":"test3","isAvail":"true","refCount":"1","acctLevel":"0","username":"user3","id":"3"} after3: {"value":"test3","isAvail":"true","refCount":"1","acctLevel":"0","username":"user3","id":"3"}

I did nothing between the calls. My questions is why the first time it returns refCount as '0' and 2,3 time returns as '1' ?? Is there any cache mechanism in redis? (I tried the same thing via redis-cli: write -> read -> change refCount -> save back), and the first time I call hgetall it returns refCount as '1'

My redis version is : redis_version:6.2.5

Node.js Version

v18.7.0

Redis Server Version

redis_version:6.2.5

Node Redis Version

redis@4.6.4

Platform

macOS

Logs

No response

[leibale]

@CHYGO1985 I tried to reproduce it using

import { createClient } from 'redis';

const client = createClient();
client.on('error', err => console.error(err));

await client.connect();

console.log('HSET value 0', await client.hSet('key', { value: '0' }));
console.log('HGETALL', await client.hGetAll('key'));
console.log('HSET value 1', await client.hSet('key', { value: '1' }));
console.log('HGETALL', await client.hGetAll('key'));

await client.disconnect();

but this is what it printed

HSET value 0 1
HGETALL [Object: null prototype] { value: '0' }
HSET value 1 0
HGETALL [Object: null prototype] { value: '1' }

are you using replicas of any kind?

[CHYGO1985]

@CHYGO1985 I tried to reproduce it using

import { createClient } from 'redis';

const client = createClient();
client.on('error', err => console.error(err));

await client.connect();

console.log('HSET value 0', await client.hSet('key', { value: '0' }));
console.log('HGETALL', await client.hGetAll('key'));
console.log('HSET value 1', await client.hSet('key', { value: '1' }));
console.log('HGETALL', await client.hGetAll('key'));

await client.disconnect();

but this is what it printed

HSET value 0 1
HGETALL [Object: null prototype] { value: '0' }
HSET value 1 0
HGETALL [Object: null prototype] { value: '1' }

are you using replicas of any kind?

thank you for your quick reply, let me double check my code and see if I can reproduce it in a simple sample

[leibale]

@CHYGO1985 did you manage to reproduce it?

[wmantly]

I can reproduce this pretty simply. Whenever I do HGET when there is nothing to be found, I get back [Object: null prototype] {} and it's very annoying.

[leibale]

@wmantly are you talking about HGETALL? because HGET never returns an object...
In redis, an empty hash and an empty key are equivalent, so HGETALL on an empty hash will return an empty object (you'll get the same results using redis-cli).

[wmantly]

@leibale yes, its HGETALL. I just updated from from an old version of this lib. In past versions something like this worked fine:

let res = await client.HGETALL(`${this._name}_${data[this._key]}`);

// If the redis query resolved to something, prepare the data.
if(res){
   // do stuff with the data
}else{
  // throw error about res being empty
}

But now, since HGETALL returns [Object: null prototype] {}, and [Object: null prototype] {} is truthy, that code doesn't work,

[wmantly]

In past versions, im 99% sure hgetall returned null or undefined if it got nothing from redis. which is far more helpful than an empty object.

[leibale]

@wmantly that's true, v3 returned null for empty hashes, but we changed it in v4 because:

1. It'll make this code return null, which is less convenient in this situation

await client.HSET('key', 'field', 'value');
await client.HDEL('key', 'field');
await client.HGETALL('key'); // will return `null` if we'll change it

2. is misaligned with Redis.

BTW, in v5 (which I'm actively working on) you'll be able to map RESP types to JS types, so you'll be able to make HGETALL return a Map (which has the size property) or an Array (which has the length property).

edit: anyway, this is not related to this issue.. If you think this should change, feel free to open an issue.