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Redis 2.8.7 is out

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Re: Redis 2.8.7 is out

#21

Post by lucian1900 »

antirez wrote: post #8
leobelle wrote: post #6

Earlier quoted context omitted.

Thanks for answering questions, any comments or progress on aphyr's complaints about using proven algorithms for Redis replication? [1] [1] http://aphyr.com/posts/307-call-me-maybe-redis-redux

Given that Apyhr's investigation in the blog post you cite does not involve anything implemented or planned for Redis, I'm not able to reply to the question. Maybe you fell in the mediatic trap of considering that discussion about Redis turning into a CP system using the proposed algorithm. If you re-read the post, Aphyr itself explains that this is not Redis Cluster. If you are curious about what triggered the post,…

You answered a different question. Are you using a verified consensus algorithm? If not, why are you making a distributed database?

You're not inspiring confidence in using anything but single node Redis.

Re: Redis 2.8.7 is out

#22

Post by redbad »

lucian1900 wrote: post #21
antirez wrote: post #8

Earlier quoted context omitted.

Given that Apyhr's investigation in the blog post you cite does not involve anything implemented or planned for Redis, I'm not able to reply to the question. Maybe you fell in the mediatic trap of considering that discussion about Redis turning into a CP system using the proposed algorithm. If you re-read the post, Aphyr itself explains that this is not Redis Cluster. If you are curious about what triggered the post,…

You answered a different question. Are you using a verified consensus algorithm? If not, why are you making a distributed database? You're not inspiring confidence in using anything but single node Redis.

It seems that antirez believes he's allowing Redis to approach AP and/or CP semantics by providing primitives that users can compose in ad-hoc ways according to their requirements.

Unfortunately, that's not a valid methodology to achieve availability or (especially) consistency.

Re: Redis 2.8.7 is out

#23

Post by antirez »

lucian1900 wrote: post #21
antirez wrote: post #8

Earlier quoted context omitted.

Given that Apyhr's investigation in the blog post you cite does not involve anything implemented or planned for Redis, I'm not able to reply to the question. Maybe you fell in the mediatic trap of considering that discussion about Redis turning into a CP system using the proposed algorithm. If you re-read the post, Aphyr itself explains that this is not Redis Cluster. If you are curious about what triggered the post,…

You answered a different question. Are you using a verified consensus algorithm? If not, why are you making a distributed database? You're not inspiring confidence in using anything but single node Redis.

Actually I tried to reply to the question of the original poster. Now I'll try to reply to your question: consensus algorithms are only used to implement the strong consistency requirements of CP databases, like for example Zookeeper. Other databases that don't feature strong consistency like Riak and Cassandra don't rely on consensus algorithms. Redis also has a form of weak consistency that does not require consensus (the merging function is, in the special case of Redis, just picking the "history" that seems the most updated, plus other systems to try to bound divergence to a given fixed amount). You can read more about the exact implementation here: http://antirez.com/news/70

This is sometimes referred as "optimistic replication" in the literature AFAIK but I'm not 100% sure.

Re: Redis 2.8.7 is out

#24

Post by mrmondo »

I can't believe sentinels still re-write their own config in /etc.

There are so many issues with sentinels they really are still a hacked together afterthought just to try and tick off a few reliability boxes.

Re: Redis 2.8.7 is out

#25

Post by zerop »

For me, beauty of redis lies in being 'data structure server '. All kinds of lists/sets/hashes redis has are very powerful. But in last few releases redis has not introduced many new types. I would like to see more focus on that in future releases, please. Also improvements on memory consumption. Thanks for all work behind redis. You guys rock, take a bow!!

Re: Redis 2.8.7 is out

#26

Post by antirez »

redbad wrote: post #22
lucian1900 wrote: post #21

Earlier quoted context omitted.

You answered a different question. Are you using a verified consensus algorithm? If not, why are you making a distributed database? You're not inspiring confidence in using anything but single node Redis.

It seems that antirez believes he's allowing Redis to approach AP and/or CP semantics by providing primitives that users can compose in ad-hoc ways according to their requirements. Unfortunately, that's not a valid methodology to achieve availability or (especially) consistency.

In Redis Cluster there is nothing you can do to tune availability or consistency. The only thing you can tune is write "safety" using WAIT, but actually most users should never use it since the system is mostly designed to be low-latency.

Redis Cluster is not AP nor CP. It resembles more AP since it has no strong consistency, however it is not able to reach "A" of AP that is very strict. Like AP systems have some form of consistency, but not "C" of CAP. Redis does this for "A" as well, it has some form of availability, but not as strict as "A" of CAP.

Why this? You'll notice that there are not AP database systems with the powerful commands of Redis, and that there are not CP systems with the latency of Redis. So it is a very opinionated trade off to get both sacrificing other stuff (especially "A").

Re: Redis 2.8.7 is out

#27

Post by antirez »

zerop wrote: post #25

For me, beauty of redis lies in being 'data structure server '. All kinds of lists/sets/hashes redis has are very powerful. But in last few releases redis has not introduced many new types. I would like to see more focus on that in future releases, please. Also improvements on memory consumption. Thanks for all work behind redis. You guys rock, take a bow!!

I totally think you are right. Redis 3.2 was already announced to be the "back to API" release where more data structures and APIs will be added.

Oh well, in the next weeks we'll get native support for bloom filters, I hope you'll like this! And even without introducing a new data structure, they'll use strings like all the current bit operations.

Re: Redis 2.8.7 is out

#28

Post by miscoowow »

antirez wrote: post #20
miscoowow wrote: post #17

Earlier quoted context omitted.

Since I switched to Redis, I had massive drop in resource requirements, saving me a lot of money. Thank you very much. The keyspace notifications are great but I use NodeJS at the moment to listen to the events. When will it be possible to run Lua to remove the current point of failure? On the topics page, it says "In the future". Are we looking at years or months?

Awesome that you improved your stack with Redis, thanks for sharing. I'm not sure about what exact feature you are referring to, please could you describe it? Thanks.

http://redis.io/topics/notifications notify-keyspace-events Kx

Currently, NodeJS subscribes to expired keys. When the key is expired it will delete the 'physical' data from the server (thumbnails, more indepth info, etc). If NodeJS fails, even for a few seconds, I will forever have the 'physical' data stored on the server (as it doesn't re-run the expired event).

Having lua scripting do what NodeJS currently does would fix the problem.

Apart from that, Redis is perfect. ;)

Re: Redis 2.8.7 is out

#29

Post by zerop »

antirez wrote: post #27
zerop wrote: post #25

For me, beauty of redis lies in being 'data structure server '. All kinds of lists/sets/hashes redis has are very powerful. But in last few releases redis has not introduced many new types. I would like to see more focus on that in future releases, please. Also improvements on memory consumption. Thanks for all work behind redis. You guys rock, take a bow!!

I totally think you are right. Redis 3.2 was already announced to be the "back to API" release where more data structures and APIs will be added. Oh well, in the next weeks we'll get native support for bloom filters, I hope you'll like this! And even without introducing a new data structure, they'll use strings like all the current bit operations.

Thanks Antirez. Looking forward for it.

Re: Redis 2.8.7 is out

#30

Post by zerop »

antirez wrote: post #27
zerop wrote: post #25

For me, beauty of redis lies in being 'data structure server '. All kinds of lists/sets/hashes redis has are very powerful. But in last few releases redis has not introduced many new types. I would like to see more focus on that in future releases, please. Also improvements on memory consumption. Thanks for all work behind redis. You guys rock, take a bow!!

I totally think you are right. Redis 3.2 was already announced to be the "back to API" release where more data structures and APIs will be added. Oh well, in the next weeks we'll get native support for bloom filters, I hope you'll like this! And even without introducing a new data structure, they'll use strings like all the current bit operations.

I also like your this post on open source http://antirez.com/news/48 I often share it with people who ask why they should write or contribute to open source.
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