Do you want to put it on a jira?
We were having some problem with the site building pipeline, I need to check if it is fixed. -Flavio On Tuesday, October 7, 2014 4:57 PM, Ivan Kelly <[email protected]> wrote: > > >Hi folks, > >I've just looked at the frontpage (zookeeper.apache.org/bookkeeper), and >it says pretty much nothing about what bookkeeper is and what it's good >for. There's even a header "What is the BookKeeper?". The? This isn't >even good english. > >Anyhow, I propose we add some text to make what bookkeeper does more >understandable, especially for people who are unfamiliar with >distributed systems. > >I've just knocked out some text, which I'll add to the frontpage >tomorrow if there are no strong objections. Suggestions are welcome of >course. > >-Ivan > ><snip> >h2. What is Bookkeeper? > >Bookkeeper is a log replication service which can be used to build >replicated state machines. A log contains a sequence of events which can >be applied to a state machine. Bookkeeper guarantees that each replica >state machine will see all the same entries, in the same order. > >h2. Eh? What good is that to me? > >Imagine for example that you have a database that you want to be able >access even if the database server goes down. You'll need to replicate >it to multiple servers. You need to ensure that if one database sees an >update, all databases see the update. But what happens if one database >server is cut off from the network for a time? Or if two clients try to >update the same field at exactly the same instance? This is where log >replication comes in. > >A database can be seen as a state machine. It is the sum of all the >updates which is has applied since its initial state. Therefore, if you >consider your replicated database as a replicated statemachine, you can >do the replication using log replication service. If all updates are >written to the log replication service before being applied to the >database, then the database will continue to be available and consistent >even if some of the replicas fail. > >This approach can be applied to many types of distributed systems, such >as messaging systems, coordination systems, filesystems, etc. > >h2. What bookkeeper is not? > >Bookkeeper has nothing to do with application/error/trace logging. There >are already many projects (link to log4j, slf4j, logback) dedicated to >that problem. > >h2. How about Hedwig? > >Hedwig is a distributed publish and subscribe system, which uses >bookkeeper to replicate its messages. ></snip> > > >
