Limit length of stream: Difference between maxlen and max_records?

[Dronakurl]

@broker.subscriber(
    stream=StreamSub("newimage", max_records=200, maxlen=100, group="mvp", consumer="2")
)

With this, I want to limit the size of my Stream in my RedisBroker.
Does anyone know the difference between those two max-settings? I could not find it in the documentation.
I just want to prevent, that un-acknowledged messages fill up my harddrive indefinetely.

This is how I start my redis server

docker run -d --rm -p 6379:6379 --name redis redis 

[Lancetnik]

@Dronakurl hi again! Indeed, it is a confusing question
max_records is a subscriber option and represents how many messages with can read from stream by one request
maxlen is a publisher option to remove old messages at publishing if this limit exceeded

[theobouwman]

So if I only want to keep the last 20 messages, I need to set the maxlen=20 and when the 21nd message gets added it automatically removed the oldest one?

[Lancetnik]

So if I only want to keep the last 20 messages, I need to set the maxlen=20 and when the 21nd message gets added it automatically removed the oldest one?

Yes, this is how Redis Stream works

[theobouwman]

Okay. And what if I push 200 messages with a maxlen=20. Will it first consume the 200 messages, and then keep to 20 most recent ones?

[Lancetnik]

Okay. And what if I push 200 messages with a maxlen=20. Will it first consume the 200 messages, and then keep to 20 most recent ones?

Redis will remove overflowing messages regardless of whether they are read or not

[Lancetnik]

But, you should check Redis documentation instead of asking me, I am not so huge Redis expert, sorry