I’m curious – is the scaling needed for the amount of data, the amount of user 
connections, throughput or what? I have a 200ish cluster, but it is primarily a 
disk space issue. When I can have (and administer) nodes with large disks, the 
cluster size will shrink.


Sean Durity

From: Isaac Reath (BLOOMBERG/ 919 3RD A) <ire...@bloomberg.net>
Sent: Monday, July 13, 2020 10:35 AM
To: user@cassandra.apache.org
Subject: [EXTERNAL] Re: Running Large Clusters in Production

Thanks for the info Jeff, all very helpful!
From: user@cassandra.apache.org<mailto:user@cassandra.apache.org> At: 07/11/20 
12:30:36
To: user@cassandra.apache.org<mailto:user@cassandra.apache.org>
Subject: Re: Running Large Clusters in Production

Gossip related stuff eventually becomes the issue

For example, when a new host joins the cluster (or replaces a failed host), the 
new bootstrapping tokens go into a “pending range” set. Writes then merge 
pending ranges with final ranges, and the data structures involved here weren’t 
necessarily designed for hundreds of thousands of ranges, so it’s likely they 
stop behaving at some point 
(https://issues.apache.org/jira/browse/CASSANDRA-6345 
[issues.apache.org]<https://urldefense.com/v3/__https:/issues.apache.org/jira/browse/CASSANDRA-6345__;!!M-nmYVHPHQ!cuNBkxxbXQWIlkzR4IaScJBk5m04XNEIXtp5dnuYZj5rQQjp_cM8neG6aq1fHgj60hZbg2U$>
 , https://issues.apache.org/jira/browse/CASSANDRA-6127 
[issues.apache.org]<https://urldefense.com/v3/__https:/issues.apache.org/jira/browse/CASSANDRA-6127__;!!M-nmYVHPHQ!cuNBkxxbXQWIlkzR4IaScJBk5m04XNEIXtp5dnuYZj5rQQjp_cM8neG6aq1fHgj616F6neA$>
   as an example, but there have been others)

Unrelated to vnodes, until cassandra 4.0, the internode messaging requires 
basically 6 threads per instance - 3 for ingress and 3 for egress, to every 
other host in the cluster. The full mesh gets pretty expensive, it was 
rewritten in 4.0 and that thousand number may go up quite a bit after that.


On Jul 11, 2020, at 9:16 AM, Isaac Reath (BLOOMBERG/ 919 3RD A) 
<ire...@bloomberg.net<mailto:ire...@bloomberg.net>> wrote:

Thank you John and Jeff, I was leaning towards sharding and this really helps 
support that opinion. Would you mind explaining a bit more what about vnodes 
caused those issues?
From: user@cassandra.apache.org<mailto:user@cassandra.apache.org> At: 07/10/20 
19:06:27
To: user@cassandra.apache.org<mailto:user@cassandra.apache.org>
Cc: Isaac Reath (BLOOMBERG/ 919 3RD A )
Subject: Re: Running Large Clusters in Production

I worked on a handful of large clusters (> 200 nodes) using vnodes, and there 
were some serious issues with both performance and availability.  We had to put 
in a LOT of work to fix the problems.

I agree with Jeff - it's way better to manage multiple clusters than a really 
large one.


On Fri, Jul 10, 2020 at 2:49 PM Jeff Jirsa 
<jji...@gmail.com<mailto:jji...@gmail.com>> wrote:
1000 instances are fine if you're not using vnodes.

I'm not sure what the limit is if you're using vnodes.

If you might get to 1000, shard early before you get there. Running 8x100 host 
clusters will be easier than one 800 host cluster.


On Fri, Jul 10, 2020 at 2:19 PM Isaac Reath (BLOOMBERG/ 919 3RD A) 
<ire...@bloomberg.net<mailto:ire...@bloomberg.net>> wrote:
Hi All,

I’m currently dealing with a use case that is running on around 200 nodes, due 
to growth of their product as well as onboarding additional data sources, we 
are looking at having to expand that to around 700 nodes, and potentially 
beyond to 1000+. To that end I have a couple of questions:

1) For those who have experienced managing clusters at that scale, what types 
of operational challenges have you run into that you might not see when 
operating 100 node clusters? A couple that come to mind are version (especially 
major version) upgrades become a lot more risky as it no longer becomes 
feasible to do a blue / green style deployment of the database and backup & 
restore operations seem far more error prone as well for the same reason 
(having to do an in-place restore instead of being able to spin up a new 
cluster to restore to).

2) Is there a cluster size beyond which sharding across multiple clusters 
becomes the recommended approach?

Thanks,
Isaac




________________________________

The information in this Internet Email is confidential and may be legally 
privileged. It is intended solely for the addressee. Access to this Email by 
anyone else is unauthorized. If you are not the intended recipient, any 
disclosure, copying, distribution or any action taken or omitted to be taken in 
reliance on it, is prohibited and may be unlawful. When addressed to our 
clients any opinions or advice contained in this Email are subject to the terms 
and conditions expressed in any applicable governing The Home Depot terms of 
business or client engagement letter. The Home Depot disclaims all 
responsibility and liability for the accuracy and content of this attachment 
and for any damages or losses arising from any inaccuracies, errors, viruses, 
e.g., worms, trojan horses, etc., or other items of a destructive nature, which 
may be contained in this attachment and shall not be liable for direct, 
indirect, consequential or special damages in connection with this e-mail 
message or its attachment.

Reply via email to