> The most important thing Antirez did, in my opinion, was to say "No" to things. No to new features that didn't make sense.
Redis has had tremendous mission creep over the years. It started of course mostly as a volatile cache but I've now seen it also used as a message bus (in three different ways: BLPOP, PUB/SUB and Streams), for service discovery and as a general purpose database - something that Redis Labs (in my opinion: wrongly) encourages.
Memcache existed in 2009 when Redis was first released, also as a volatile cache...and still is just a volatile cache. Memcache is what "saying no" looks like. Redis is what "saying yes" looks like - and there are a lot of gotchas.
Memcache is what saying no to changing the use-case looks like. Redis is what saying no to changing the architecture in order to implement features looks like.
Redis has stayed the same, architecturally, from the beginning: it’s a keyspace where the values are arbitrary in-memory objects owned by their keys, and where commands resolve to synchronous function-calls against the objects (or ref-cells) at those keys.
Anything that can be done without changing that architecture, is in-scope for Redis. (Though if a data structure doesn’t have wide use outside of a domain, it’s best left to a module.) Anything that cannot be done without changing the architecture, won’t be done.
Much of the “fun” I’ve personally had in watching Redis evolve, has been seeing how Antirez has managed to solve the puzzles of getting features that intuitively wouldn’t be a good fit for this architecture, to fit into it anyway: changing technologies that are implemented one way everywhere else, into something else for Redis, that still work, are still performant, and still solve isomorphic use-cases—if not with the same steps you’d use to solve them in other systems. (E.g. using Streams vs. using a regular MQ; using Redis Cluster vs. using regular RDBMS replication; etc.)
Memcache also is about saying no to changing the architecture. That chosen architecture is similar to Redis Cluster -which is a change of architecture Redis did undertake.
I personally have not enjoyed all the strange and wonderful ways people have found to use Redis. Most of them are pretty fragile and (most dangerously) they often put all Redis uses in the same instance...with eviction turned on.
Wow you totally got it. This is exactly the idea I was using, I even saw an opportunity when the Redis model was potentially able to solve a new use case.
Would you mind elaborating on some of those 'fun' items - part of the problem of being aware of certain technologies without really 'following' them is understanding why they change.
It didn't really start as a volatile cache, it started as an in memory data structures server. It's useful for all kinds of stuff memcached isn't (and has been since day 1).
This. To me, Redis was always about the rich set of operations you can atomically perform on data without going full ACID. It's very different from a pure cache (although it's probably a good choice if all you need is a cache).
Yeah. I do think that Redis has suffered from some mission creep, including a deprecated misadventure in to a mode where values could be stored on disk and only temporarily cached in memory.
Maybe that's what Cal and his colleagues were using it for at the time, but the claim that it started as a volatile cache is just not true. Interesting datastructures and the fork based persistence model were there from the start.
Lists, hashes, sets and such that you have available in your programming language, but available as a networked server so any language/app/process can access the same data using the same useful structures.
Well, kinda. Feature list does look like basically random assortment of vaguely related things (or "toolbox" if you want to be nice).
But... things that are also just useful often and for what you'd need to spin off a separate service for, or make suboptimally in whatever (No)SQL you use to store your data.
So it is perfect if you just want to prototype whether given approach is viable, and "good enough" for many apps.
Strongly, strongly, disagree that Redis works well as a message bus.
Lots of reasons why but here is just one because I'm short on time: all of these (four) ways of doing a message bus with Redis offer either a work queue mode or publish/subscribe - but not both (perhaps excepting streams which I've forgotten some of the details of). I have yet to see many real world messaging scenarios where you don't end up using both.
A "proper" message bus needs to have topics, exchanges and queues - like Rabbit. 50% of that functionality is usually not 50% of the value but 10% or less (especially when you consider all the other things about Redis you need to think about - like how eviction is configured).
This is a bit typical of Redis: for any X, you can normally do X in Redis, but is it really a good idea to do X in Redis? IMO, usually no.
There's a wide field of messaging from distributed logs to queuing systems to event sourcing to complex service buses. Kafka, Pulsar, NATS, RabbitMQ, Tibco, NServiceBus, ActiveMQ, Solace, AMPS, and dozens more. What's "proper" depends on your needs.
Redis Streams actually does exactly what you describe and is basically a single-node fast Kafka replacement with multiple independent consumer groups, per-message acknowledgements, and queue semantics. We use it successfully in many high-load scenarios.
Name of the hash is a topic. Keys are nanosecond timestamps, values are the packets. You put in the data, you send a pub notify to the listener, listener goes and drains the queue. It acts as a direct exchange queue, recovers fine from a restart and it works wonderfully. For fanout, you can simply use pub sub. For topical, you can keep a list of direct exchange queue hashes. I haven't needed it.
Redis has had tremendous mission creep over the years. It started of course mostly as a volatile cache but I've now seen it also used as a message bus (in three different ways: BLPOP, PUB/SUB and Streams), for service discovery and as a general purpose database - something that Redis Labs (in my opinion: wrongly) encourages.
Memcache existed in 2009 when Redis was first released, also as a volatile cache...and still is just a volatile cache. Memcache is what "saying no" looks like. Redis is what "saying yes" looks like - and there are a lot of gotchas.