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There's a fine print that says: > ¹Basic Tier instances experience a downtime and a full cache flush during scaling. Standard Tier instance experience very min
by dudus 8y ago
There's a fine print that says:
> ¹Basic Tier instances experience a downtime and a full cache flush during scaling. Standard Tier instance experience very minimal downtime and loss of some unreplicated data during scaling operation. ²Applicable for GA release only.
Does that mean that right now there are no persistance options with this Managed Redis cluster? I have never tried to use Redis but I've been eyeing it for a while and the most confusing part is how it handles persistence.
Apparently there are ways to have Redis configured to be pretty durable as outlined here:
https://redis.io/topics/persistence https://redis.io/topics/persistence
But it doesn't look like Google is supporting either RDB nor AOF with this managed service, they say RDB is coming though.
Doesn't it heavily limits the use cases for this product and relegate it to a cooler memcache?
This is not criticism, it's just curiosity on good use cases for this product.
- ihsw2 8y agoOn the surface it looks like this isn't a true-blue Redis server (or even a fork of Redis) but support for the Redis protocol bolted onto an in-house memory-based caching product.
- panarky 8y agoTheir post isn't very clear on persistence, here's how I read it. 1) Yes, they're using Redis persistence (RDB, AOF, or a Google-written persistence layer, it's not specified). 2) Basic Tier scales by tearing down the smaller Redis instance and migrating the data (???) to a larger instance. This causes downtime, but not lost data. 3) Standard Tier migrates using replication during scaling, so there's little downtime but if data is in flight at cutover, it could be lost. 4) And "coming soon" you can migrate data in and out of Cloud Memorystore by importing and exporting RDB files.
- dudus 8y agoWhy do you think they are using persistence at all, and why do you think Basic Tier doesn't have data loss on scaling? I read it differently. When they say full cache flush doesn't that imply full database flush, I was thinking all data gets wiped on scaling operation.
- nodesocket 8y agoAgree I don't think it is persistent. "a full cache flush" represents all data loss to me.
- gopalashok 8y agoFull disclosure, I'm the product manager for Cloud Memorystore 1) We are not using persistence at all in beta, this is something we are working towards 2) Scaling of basic tier will result in a full cache flush and will cause downtime during the scaling process. 3) That's correct 4) Yes we will be making Import-Export of RDB very soon
- sitkack 8y ago> 1) We are not using persistence at all in beta, this is something we are working towards Persistence is a key feature of Redis, it isn't just a fancy memcached. This severely limits the applicability of this offering.
- jkaplowitz 8y agoSo does the beta label. :) Both will change in time, from what the PM said.
- dannyw 8y agoIt’s like releasing a beta for DNS that doesn’t support IPv6 or CNAMES.
- hamandcheese 8y ago> We are not using persistence at all in beta Maybe don’t advertise it as a “data store” then.
- mrkurt 8y agoIt sounds like they're scaling by adding larger instances, replicating, and then failing over. So they'll lose any data that hasn't been synced to the new instance when the failover occurs. I'd bet it's rare, but they're being explicit about it. The Basic Tier probably only uses one instance, so they just replace it in place.
- trhway 8y agoWhat would be the point of downtime they mention other than doing the sync?
- hinkley 8y agoFrom the docs: Basic Tier: Provides a standalone Redis instance. Use this tier for applications that require a simple Redis cache. If you were only reallocating replicas you'd expect no downtime. But turning on replication isn't seamless.
- deleted 8y ago[deleted]
- antirez 8y agoMaybe this is just for the initial period. Redis has orchestration commands that allow to stop the clients in one side, migrate, shutdown the first instance, and resume the other, without the possibility of getting writes in the middle of the transition. Other providers do that to ensure safety of operations.
- dudus 8y agoThanks for chiming in. I'm a big fan of your work. Did Google consult you on this product before launch?
- antirez 8y agoNope, no vendor does (fortunately). AFAIK people get the "Redis way": grab the source and do whatever you want with such code, in the limits of the license / law. Also I get near no contacts from big corps using Redis at scale. This is a sane model otherwise my work would be dealing with communications instead of writing code :-) However when technical people from big companies ping me about bugs / issues / improvements ... then it's great feedback, but is rare.
- bradhe 8y ago> Does that mean that right now there are no persistance options with this Managed Redis cluster? It's a memory store.
- amazingman 8y agoThat's not really an answer to the question. You may not agree with it, but there are many orgs out there using Redis as a persistent datastore. If Google wants their money, they're going to need persistence options.
- bradhe 8y agoIt doesn’t guarantee it’s redis. It guarantee’s it’s redis compatible. The use case they’re (rather obviously) optimizing for is an in-memory cache.
- tgtweak 8y agoRedis persistance is not built or intended to be a write guarantee, but more of a safeguard against cold cache after a restart or failure. It looks as if free tier has persistence turned off by default and that standard tier uses snapshotting/rdb to replicate.
- zodvik 8y agoWould AOF persistence as 'everysec' not imply a write guarantee of max 1 second data loss for restart?
- tgtweak 8y agoNo, this is not a write guarantee. You can still lose an acknowledged write.
- manigandham 8y agoThat's exactly what it's built for, to save data. It's just configurable in terms of how and when its persisted.