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From Jonathan Shook <jsh...@gmail.com>
Subject Re: Can't get data after building cluster
Date Tue, 01 Jun 2010 19:52:03 GMT
Depending on the key, the request would have been proxied to the first
or second node.
The CLI uses a consistency level of "ONE", meaning that only a single
node's data would have been considered when you get().
Also, the responsible nodes for a given key are mapped accordingly at
request time, and proxy requests are made internally on your behalf.
This allows the R+W>N to hold, where N is the replication factor. It
closes the subset of active nodes responsible for a key in a
deterministic way.

See http://www.slideshare.net/benjaminblack/introduction-to-cassandra-replication-and-consistency
for more information.


On Tue, Jun 1, 2010 at 1:43 AM, David Boxenhorn <david@lookin2.com> wrote:
> I don't think it can be the case that "at most data in the token range
> assigned to that node will be affected" - the new node had no knowledge of
> any of our data. Any fake "data" that it might have had through some error
> on my part could not have been within the range of real data. I had 4.25 G
> of data on the 1st server, and as far as I could tell I couldn't access any
> of it.
>
>
> On Tue, Jun 1, 2010 at 9:10 AM, Jonathan Ellis <jbellis@gmail.com> wrote:
>>
>> To elaborate:
>>
>> If you manage to screw things up to where it thinks a node has data,
>> but it does not (adding a node without bootstrap would do this, for
>> instance, which is probably what you did), at most data in the token
>> range assigned to that node will be affected.
>>
>> On Tue, Jun 1, 2010 at 12:45 AM, David Boxenhorn <david@lookin2.com>
>> wrote:
>> > You say "no", but that is exactly what I just observed. Can I have some
>> > more
>> > explanation?
>> >
>> > To recap: I added a server to my cluster. It had some junk in the
>> > system/LocationInfo files from previous, unsuccessful attempts to add
>> > the
>> > server to the cluster. (They were unsuccessful because I hadn't opened
>> > the
>> > port on that computer.) When I finally succeeded in adding the 2nd
>> > server,
>> > the 1st server started returning null when I tried to get data using the
>> > CLI. I stopped the 2nd server, deleted the files in system, restarted,
>> > and
>> > everything worked.
>> >
>> > I'm afraid that this, or some similar scenario will do the same, after I
>> > go
>> > live. How can I protect myself?
>> >
>> > On Mon, May 31, 2010 at 10:10 PM, Jonathan Ellis <jbellis@gmail.com>
>> > wrote:
>> >>
>> >> No.
>> >>
>> >> On Mon, May 31, 2010 at 10:47 AM, David Boxenhorn <david@lookin2.com>
>> >> wrote:
>> >> > So.... this means that I can take my entire cluster off line if I
>> >> > make a
>> >> > mistake adding a new server??? Yikes!
>> >> >
>> >> > On Mon, May 31, 2010 at 6:41 PM, David Boxenhorn <david@lookin2.com>
>> >> > wrote:
>> >> >>
>> >> >> OK. Got it working.
>> >> >>
>> >> >> I had some data in the 2nd server from previous failed attempts
at
>> >> >> hooking
>> >> >> up to the cluster. When I deleted that data and tried again, it
said
>> >> >> "bootstrapping" and my 1st server started working again.
>> >> >>
>> >> >> On Mon, May 31, 2010 at 4:50 PM, David Boxenhorn <david@lookin2.com>
>> >> >> wrote:
>> >> >>>
>> >> >>> I am trying to get a cluster up and working for the first time.
>> >> >>>
>> >> >>> I got one server up and running, with lots of data on it, which
I
>> >> >>> can
>> >> >>> see
>> >> >>> with the CLI.
>> >> >>>
>> >> >>> I added my 2nd server, they seem to recognize each other.
>> >> >>>
>> >> >>> Now I can't see my data with the CLI. I do a get and it returns
>> >> >>> null.
>> >> >>> The
>> >> >>> data files seem to be intact.
>> >> >>>
>> >> >>> What happened??? How can I fix it?
>> >> >>>
>> >> >>
>> >> >
>> >> >
>> >>
>> >>
>> >>
>> >> --
>> >> Jonathan Ellis
>> >> Project Chair, Apache Cassandra
>> >> co-founder of Riptano, the source for professional Cassandra support
>> >> http://riptano.com
>> >
>> >
>>
>>
>>
>> --
>> Jonathan Ellis
>> Project Chair, Apache Cassandra
>> co-founder of Riptano, the source for professional Cassandra support
>> http://riptano.com
>
>

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