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From "Kenneth Brotman" <kenbrot...@yahoo.com.INVALID>
Subject RE: [EXTERNAL] RE: Adding new DC?
Date Mon, 12 Mar 2018 21:58:57 GMT
You can’t migrate and upgrade at the same time perhaps but you could do one and then the
other so as to end up on new version.  I’m guessing it’s an error in the yaml file or
a port not open.  Is there any good reason for a production cluster to still be on version
2.1x?

 

Kenneth Brotman

 

From: Durity, Sean R [mailto:SEAN_R_DURITY@homedepot.com] 
Sent: Monday, March 12, 2018 11:36 AM
To: user@cassandra.apache.org
Subject: RE: [EXTERNAL] RE: Adding new DC?

 

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

 

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.

 

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?

 

Sean Durity

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

From: Kunal Gangakhedkar [mailto:kgangakhedkar@gmail.com] 
Sent: Sunday, March 11, 2018 10:20 PM
To: user@cassandra.apache.org
Subject: [EXTERNAL] RE: Adding new DC?

 

Hi Kenneth,

 

Replies inline below.

 

On 12-Mar-2018 3:40 AM, "Kenneth Brotman" <kenbrotman@yahoo.com.invalid> 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
anyway?  

 

 

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
(Mumbai)

 

Thanks,

Kunal

Kenneth Brotman

 

From: Kunal Gangakhedkar [mailto:kgangakhedkar@gmail.com] 
Sent: Sunday, March 11, 2018 2:32 PM
To: user@cassandra.apache.org
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:

https://docs.datastax.com/en/cassandra/2.1/cassandra/operations/ops_add_dc_to_cluster_t.html
<https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.datastax.com_en_cassandra_2.1_cassandra_operations_ops-5Fadd-5Fdc-5Fto-5Fcluster-5Ft.html&d=DwMFaQ&c=MtgQEAMQGqekjTjiAhkudQ&r=aC_gxC6z_4f9GLlbWiKzHm1vucZTtVYWDDvyLkh8IaQ&m=4s2PNt4_Ty1RVe_0dQ4sn-jQTjmz-Wmxnf2OS4URoYo&s=pfA6Jkn2UwG7AISlAM3OJ1OzQpghd_nVJj-KnYLCvBk&e=>


 

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:

    OutboundTcpConnection.java:496 - 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

 

Thanks,


Kunal

 

 

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