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Comment by netgusto | Hacker News Reader

Could someone ELI5 what's a redis stream ? I thought that pub/sub mecanisms were some kind of a stream already.

Redis Pubsub is fire-and-forget, so if you aren't listening when a message is fired, you'll never receive it. Redis Streams store messages, so you can connect and read all the messages since you last checked. It's a similar model to Kafka.

I've not been following Redis a lot, so this one is new to me. I read antirez's original Streams blog post[0] but it feels like it's missing some stuff--is it known out there how this interacts with Redis Sentinel or, separately, Redis Cluster?

[0] - http://antirez.com/news/114

In the Redis sense, streams are just a new data structure (value type of a key), so there shouldn't be any special concerns with regards to Sentinel, partitioning and/or clustering in that sense.

That is my intuition, yeah, but that makes me pretty worried about hammering hot keys and the like with regards to Cluster.

I also don't mind running Kafka, though, so I may not be the target audience.

is it strictly in-mem? for instance if redis is restarted is there an option for unread streams to be saved with redis persistence

The built-in persistence mechanisms should be compatible with Streams.

This article from Brandur does a great job of explaining a use case for Redis Streams [0]. As part of that he begins by explaining what they are, how they work, and a bit about how they differ from Kafka.

[0]: https://brandur.org/redis-streams

Redis streams will allow for direct modeling of time series data. For example,

     redis-cli>XADD AAPL 1516899637000.0 open 221.25 high 222.1 low 220.90 close 221.50 volume 1121223234234

(All data is imaginary.)

Found the rationale for this: https://github.com/redis/redis-rcp/blob/master/RCP11.md#rati...

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