Retrieving messages from redis stream - node.js

Question

I have a NodeJS application that is using Redis stream (library 'ioredis') to pass information around. The problem is that when I add a message to a stream and I try to retrieve it, I have to go down a lot of Arrays level:
const message = await redis.xreadgroup('GROUP', orderGroup, orderConsumer, 'COUNT', 1, 'STREAMS', orderStream, '>');
const messageId: string = message[0][1][0][0];
const pMsg: Obj = JSON.parse(JSON.parse(message[0][1][0][1][1]));
This is how I create the stream:
await redis.xgroup('CREATE', orderStream, orderGroup, '0', 'MKSTREAM')
.catch((err) => {
console.error(`Group already exists error: ${err}`);
})
Is this normal? In the Redis doc (https://redis.io/commands/xreadgroup) it shows that the return value is an array with the id of the message at position 0 and the fields at position 1. I feel like I'm missing something...

Answer 1

Here is an example output of XREADGROUP, as you can see the values are at the nested level 5.
127.0.0.1:6379> XREADGROUP Group g1 c1 COUNT 100 STREAMS s1 >
1) 1) "s1"
2) 1) 1) "1608445334963-0"
2) 1) "f1"
2) "v1"
3) "f2"
4) "v2"
2) 1) "1608445335464-0"
2) 1) "f1"
2) "v1"
3) "f2"
4) "v2"
3) 1) "1608445335856-0"
2) 1) "f1"
2) "v1"
3) "f2"
4) "v2"
For more details see https://redis.io/commands/xread

Answer 2

It is normal and expected. XREADGROUP supports reading from multiples stream keys, multiple messages, and messages can have multiple field-value pairs.
Follow the next example:
> XGROUP CREATE mystream1 mygroup 0 MKSTREAM
OK
> XGROUP CREATE mystream2 mygroup 0 MKSTREAM
OK
> XADD mystream1 * field1 value1 field2 value2
"1608444656005-0"
> XADD mystream1 * field1 value3 field2 value4
"1608444660566-0"
> XADD mystream2 * field3 value5 field4 value6
"1608444665238-0"
> XADD mystream2 * field3 value7 field4 value8
"1608444670070-0"
> XREADGROUP GROUP mygroup yo COUNT 2 STREAMS mystream1 mystream2 > >
1) 1) "mystream1"
2) 1) 1) "1608444656005-0"
2) 1) "field1"
2) "value1"
3) "field2"
4) "value2"
2) 1) "1608444660566-0"
2) 1) "field1"
2) "value3"
3) "field2"
4) "value4"
2) 1) "mystream2"
2) 1) 1) "1608444665238-0"
2) 1) "field3"
2) "value5"
3) "field4"
4) "value6"
2) 1) "1608444670070-0"
2) 1) "field3"
2) "value7"
3) "field4"
4) "value8"
The structure you get has multiple nested arrays. Using 0-indexed as in node:
[index of the stream key]
[0: the key name or 1: an array for messages]
[index of the message]
[0: the message ID or 1: an array for fields & values]
[even for field name or odd for value]

Answer 3

Where data[0][1] is the root level array (adjust this entry point for your own use).
Variables
rd: Return Data
el: Element
sel: Sub-element
rel: Relative-element
p: Relative-Object
c: Iterate-Counter for deciding if it is a key or value.
var rd = []
for(var el of data[0][1]){
var sel = el[1]
var p = {}
var c = 0
for(var rel of sel){
if(c % 2 == 0){
// Right here is where the return object keys/values are set.
p[rel] = sel[c + 1]
}
c++
}
rd.push(p)
}
return rd