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Posted to user@cassandra.apache.org by "Logendran, Dharsan (Dharsan)" <dh...@alcatel-lucent.com> on 2014/01/15 20:36:31 UTC
Re: Question about out of sync
Hi,
I would like to get some answer for the following scenario.
Lets say we have a two nodes cluster(node_a and node_b) with the replication factor of 2. It means both nodes(node_a and node_b) will have the same amount of data replicated. If one node(node_b) goes down and comes back. Is there any way for us to find out how the node_b is behind(out of sync) or needs to catch up. The amount could be in bytes, number of rows for each column family etc.
Thanks
Dharsan
RE: Question about out of sync
Posted by "Logendran, Dharsan (Dharsan)" <dh...@alcatel-lucent.com>.
Thanks Rob,
It was quick.
Dharsan
From: Robert Coli [mailto:rcoli@eventbrite.com]
Sent: January-15-14 2:44 PM
To: user@cassandra.apache.org
Subject: Re: Question about out of sync
On Wed, Jan 15, 2014 at 11:36 AM, Logendran, Dharsan (Dharsan) <dh...@alcatel-lucent.com>> wrote:
Lets say we have a two nodes cluster(node_a and node_b) with the replication factor of 2. It means both nodes(node_a and node_b) will have the same amount of data replicated. If one node(node_b) goes down and comes back. Is there any way for us to find out how the node_b is behind(out of sync) or needs to catch up. The amount could be in bytes, number of rows for each column family etc.
You can see how many hints node_a has stored for node_b, and look at how large that is on disk, but that's about it. If you exhaust max_hint_window_in_ms there is literally no way to know how out of sync you are until you run repair.
Other notes :
1) If you're asking this question, you probably have not internalized what the "eventual" part of eventual consistency really means to your application.
2) RF=N=2 is not a recommended production configuration. Minimal recommended is usually RF=3, N=6.
=Rob
Re: Question about out of sync
Posted by Robert Coli <rc...@eventbrite.com>.
On Wed, Jan 15, 2014 at 11:36 AM, Logendran, Dharsan (Dharsan) <
dharsan.logendran@alcatel-lucent.com> wrote:
> Lets say we have a two nodes cluster(node_a and node_b) with the
> replication factor of 2. It means both nodes(node_a and node_b) will have
> the same amount of data replicated. If one node(node_b) goes down and comes
> back. Is there any way for us to find out how the node_b is behind(out of
> sync) or needs to catch up. The amount could be in bytes, number of rows
> for each column family etc.
>
You can see how many hints node_a has stored for node_b, and look at how
large that is on disk, but that's about it. If you exhaust
max_hint_window_in_ms there is literally no way to know how out of sync you
are until you run repair.
Other notes :
1) If you're asking this question, you probably have not internalized what
the "eventual" part of eventual consistency really means to your
application.
2) RF=N=2 is not a recommended production configuration. Minimal
recommended is usually RF=3, N=6.
=Rob