Re: Running multiple instances of Cassandra on each node in the cluster

[Eric Evans]

On Thu, May 10, 2018 at 2:25 AM  wrote:

> Dear community,
>
> Is it possible to have a cluster in Cassandra where each of the server is
> running multiple instances of Cassandra(each instance is part of the same
> cluster).
>
> I'm aware that if there's a single server in the cluster, then it's
> possible to run multiple instances of Cassandra on it
> , but is it also possible
> to have multiple such servers in the cluster. If yes, how will the
> configuration look like(listen address, ports etc)?
>
> Even if it was possible, I understand that there might not be any
> performance benefits at all, just wanted to know if it's theoretically
> possible.
>
We do this.  It's not ideal from an operational POV, but as Jeff points
out, if you have more hardware than it makes sense to give to a single
Cassandra node, it's an option.

Perhaps the biggest/most obvious thing to be aware of is that you need to
use the network-topology strategy, and you need to ensure that all of the
instances on a host are part of the same rack (otherwise you'll end up with
replicas on the same machine, which isn't very redundant).

If you are fluent in Puppet, our setup is here:
https://github.com/wikimedia/puppet (Cassandra module here:
https://github.com/wikimedia/puppet/tree/production/modules/cassandra)

One of the things that Puppet module does, is write per-instance metadata
as YAML files into /etc/cassandra-instances.d/, which we use in support of
some tooling to ease some the operation burden.  As an example, there is a
`c-foreach-nt` script that iteratively issues nodetool commands against all
configured instances (or a `c-any-nt` when you only need one, and don't
care which), and a `c-foreach-restart` that iteratively restarts.  Those
are here: https://github.com/eevans/cassandra-tools-wmf


-- 
Eric Evans
eev...@wikimedia.org

Re: Running multiple instances of Cassandra on each node in the cluster

[Jeff Jirsa]

It works fine, and there can be meaningful performance benefits if you have
a sufficiently large machine where either you have so much RAM or so much
disk that a single instance would likely underutilize those resources. You
can configure it by adding multiple IPs to the servers, and running one
instance of cassandra per IP.


On Thu, May 10, 2018 at 12:55 PM,  wrote:

> Dear community,
>
> Is it possible to have a cluster in Cassandra where each of the server is
> running multiple instances of Cassandra(each instance is part of the same
> cluster).
>
> I'm aware that if there's a single server in the cluster, then it's
> possible to run multiple instances of Cassandra on it
> , but is it also possible
> to have multiple such servers in the cluster. If yes, how will the
> configuration look like(listen address, ports etc)?
>
> Even if it was possible, I understand that there might not be any
> performance benefits at all, just wanted to know if it's theoretically
> possible.
>
>
>
> Stack Overflow Link: https://stackoverflow.com/
> questions/50267683/multiple-instances-of-cassandra-on-
> each-node-in-the-cluster
>
>
>
> Thanks and regards,
>
> Vishal Sharma
>
>
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Running multiple instances of Cassandra on each node in the cluster

[Vishal1.Sharma]

Dear community,

Is it possible to have a cluster in Cassandra where each of the server is 
running multiple instances of Cassandra(each instance is part of the same 
cluster).

I'm aware that if there's a single server in the cluster, then it's possible to 
run multiple instances of Cassandra on 
it, but is it also possible to 
have multiple such servers in the cluster. If yes, how will the configuration 
look like(listen address, ports etc)?

Even if it was possible, I understand that there might not be any performance 
benefits at all, just wanted to know if it's theoretically possible.



Stack Overflow Link: 
https://stackoverflow.com/questions/50267683/multiple-instances-of-cassandra-on-each-node-in-the-cluster



Thanks and regards,

Vishal Sharma
"Confidentiality Warning: This message and any attachments are intended only 
for the use of the intended recipient(s). 
are confidential and may be privileged. If you are not the intended recipient. 
you are hereby notified that any 
review. re-transmission. conversion to hard copy. copying. circulation or other 
use of this message and any attachments is 
strictly prohibited. If you are not the intended recipient. please notify the 
sender immediately by return email. 
and delete this message and any attachments from your system.

Virus Warning: Although the company has taken reasonable precautions to ensure 
no viruses are present in this email. 
The company cannot accept responsibility for any loss or damage arising from 
the use of this email or attachment."