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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: What happened if one server involved in the process of data reading fail?
Date Fri, 21 May 2010 14:20:59 GMT
http://wiki.apache.org/cassandra/ArchitectureInternals

2010/5/20 史英杰 <shiyingjie1983@gmail.com>:
> What inner mechanism does Cassandra adopt to get this kind of fault
> tolerance?
>
> 2010/5/20 Simon Smith <simongsmith@gmail.com>
>>
>> On Thu, May 20, 2010 at 8:08 AM, 史英杰 <shiyingjie1983@gmail.com> wrote:
>> > Hi, All,
>> >     I am now learning the mechanism Cassandra adopts to get high
>> > availability and fault tolerance.  As I know, we should connect to one
>> > server of Cassandra first, then we can read or write data  through it,
>> > so if
>> > the server which we connect to get down, what will happen? Should we
>> > have to
>> > reconnect another server or will Cassandra control this situation?
>>
>>
>> The approach we're taking is to put the software load-balancer haproxy
>> in front of our cassandra cluster.  Use "mode tcp" within haproxy's
>> config.  I notice that Tragedy (http://github.com/enki/tragedy/) also
>> lets you put a list of servers into the connection call (we're going
>> to put the list of haproxy load balancers here).
>>
>>
>>
>> > Another sutiation, if the server which is involved in the process of
>> > data reading
>> > fail, what will Cassandra do?
>>
>>
>> If you're using Thrift to connect, catch the exceptions that library
>> throws if unable to connect and then try to connect again.   This is
>> going to happen - if/when a node goes down it causes the entire
>> cluster to hiccup a little, so if it is critical that any particular
>> read transaction succeeds, you may need to sleep as much as 5 seconds
>> (this is just my experience).
>>
>>
>> >     Thanks a lot!
>> >
>> > Yingjie
>
>



-- 
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of Riptano, the source for professional Cassandra support
http://riptano.com

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