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From "Kenneth Brotman" <>
Subject RE: [EXTERNAL] RE: Adding new DC?
Date Mon, 12 Mar 2018 23:24:06 GMT


Please provide the following setting from the yaml files you  are using:









Kenneth Brotman


From: Kunal Gangakhedkar [] 
Sent: Monday, March 12, 2018 4:13 PM
Cc: Nikhil Soman
Subject: Re: [EXTERNAL] RE: Adding new DC?



On 13 March 2018 at 00:06, Durity, Sean R <> wrote:

You cannot migrate and upgrade at the same time across major versions. Streaming is (usually)
not compatible between versions.


I'm not trying to upgrade as of now - first priority is the migration.

We can look at version upgrade later on.



As to the migration question, I would expect that you may need to put the external-facing
ip addresses in several places in the cassandra.yaml file. And, yes, it would require a restart.
Why is a non-restart more desirable? Most Cassandra changes require a restart, but you can
do a rolling restart and not impact your application. This is fairly normal admin work and
can/should be automated.


I just tried setting the broadcast_address in one of the instances in GCE to its public IP
and restarted the service.

However, it now shows all other nodes (in GCE) as DN in nodetool status output and the other
nodes also report this node as DN with its internal/private IP address.


I also tried setting the broadcast_rpc_address to the internal/private IP address - still
the same.



How large is the cluster to migrate (# of nodes and size of data). The preferred method might
depend on how much data needs to move. Is any application outage acceptable?


No. of nodes: 5

RF: 3

Data size (as reported by the load factor in nodetool status output): ~30GB per node





Sean Durity

lord of the (C*) rings (Staff Systems Engineer – Cassandra)

From: Kunal Gangakhedkar [] 
Sent: Sunday, March 11, 2018 10:20 PM
Subject: [EXTERNAL] RE: Adding new DC?


Hi Kenneth,


Replies inline below.


On 12-Mar-2018 3:40 AM, "Kenneth Brotman" <> wrote:

Hi Kunal,


That version of Cassandra is too far before me so I’ll let others answer.  I was wonder
why you wouldn’t want to end up on 3.0x if you’re going through all the trouble of migrating



Application side constraints - some data types are different between 2.1.x and 3.x (for example,
date vs. timestamp).


Besides, this is production setup - so, cannot take risk.

Are both data centers in the same region on AWS?  Can you provide yaml file for us to see?



No, they are in different regions - GCE setup is in us-east while AWS setup is in Asia-south




Kenneth Brotman


From: Kunal Gangakhedkar [mailto:kgangakhedkar@gmailcom <>
Sent: Sunday, March 11, 2018 2:32 PM
Subject: Adding new DC?


Hi all,


We currently have a cluster in GCE for one of the customers.

They want it to be migrated to AWS.


I have setup one node in AWS to join into the cluster by following:


Will add more nodes once the first one joins successfully.


The node in AWS has an elastic IP - which is white-listed for ports 7000-7001, 7199, 9042
in GCE firewall.


The snitch is set to GossipingPropertyFileSnitch. The GCE setup has dc=DC1, rack=RAC1 while
on AWS, I changed the DC to dc=DC2.


When I start cassandra service on the AWS instance, I see the version handshake msgs in the
logs trying to connect to the public IPs of the GCE nodes: - Handshaking version with /xx.xx.xx.xx

However, nodetool status output on both sides don't show the other side at all. That is, the
GCE setup doesn't show the new DC (dc=DC2) and the AWS setup doesn't show old DC (dc=DC1).


In cassandra.yaml file, I'm only using listen_interface and rpc_interface settings - no explicit
IP addresses used - so, ends up using the internal private IP ranges.


Do I need to explicitly add the broadcast_address? for both side?

Would that require restarting of cassandra service on GCE side? Or is it possible to change
that setting on-the-fly without a restart?


I would prefer a non-restart option.


PS: The cassandra version running in GCE is 2.1.18 while the new node setup in AWS is running
2.1.20 - just in case if that's relevant







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