vicaya 1231 days ago link
(Reposting my blog comment here)"I mean primarily the ability to face a network partition and continue providing write service to all clients transitively connected to a majority of servers. Secondarily, I mean the ability to continue providing read only service to all clients connected to any server."A truly available system, in the sense of CAP, allows writes, not just reads, even under partition, even for clients not connected to the "majority" nodes. This leads inevitably to the need for conflict detection and resolution, and that whole "eventually consistent" thing. It's also not free, but it would probably be Grey Nike Air Max Theas suitable for some set of Heroku customers, particularly if they're already using Google App Engine.
entropy process kicks in a replicates 'bar' to the other hosts. Now a read for key A returns 'bar'. In short, when a client performs a write and gets a failure back they actually have no idea if it will update the data store or not. You cannot implement compare and set in that type of environment.
Ahh I see it's in the extra small note at the bottom"I mean primarily the ability to face a network partition and continue providing write service to all clients transitively connected to a majority of servers."Probably should be a little more prominent considering it's one of the first questions you'd want answered but I was a bit careless to miss it.
is Paxos. We have a post coming up about it.
As explained in the post, the minority side of the partition is not writable.
krarick 1232 days ago link
sigil 1232 days ago linkbmizerany 1232 days ago link
back from all nodes will return 'foo'. Time goes along and read repair or some other anti Mens Nike Air Max 2015 Black And White
benblack 1232 days ago link
besquared 1232 days ago link
"The only freely available tool that attempts to provide both of these is zookeeper, but zookeeper is specialized, focused on locking and server management. We need a general purpose tool that provides the same guarantees in a clean, well designed package."I think they dismissed Zookeeper too quickly without trying to understand it first. The zookeeper primitives (get/set nodes and their children) seems simpler and cleaner than doozer is client protocol, AFAICT. Zookeeper should scale better (especially for readers) than typical Paxos based systems as well.
Yes, it Mens Nike Air Max Tavas Black
available data store from Heroku labs
sigil 1232 days ago link
leef 1232 days ago link
That is not how paxos works. It guarantees that all hosts in the system learn the same sequence of writes. The scenario where "one host accepts the write and two fail" does not happen. Paxos provides a much stronger guarantee than simple quorums.
besquared 1232 days ago link
Great, looking forward to it.
You actually cannot implement strongly consistent compare and set on a quorum based system. You perform a write to key A with data 'bar' and one host accepts the write and two fail resulting in your client getting a failure back. Reading data Nike Air Max Tavas Red University
The problem with zookeeper is there is no safe way to dynamically change the nodes in the cluster. That's where Paxos comes in since it is provably correct even with nodes joining and leaving.
leef 1231 days ago link
What happens when you CAS the same key from two sides of a network partition and the partitions rejoin?
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