On-Prem and Azure extension with only 2 Nodes Possible?

Google Cloud Apigee
1

We have client with 2 node installation one on premise environment (DC-1), and they are asking to expand it to new Azure cloud environment (DC-2). We tried to do this Apigee expansion installation multiple data centers DC only with 2 Node virtual server installation but Cassandra was failing with the error below. We believe that Cassandra needs to be in increment of +3 Node virtual servers? So my question is can we do a multi DC installation only with 2 Nodes virtual servers? i am not able to find any documentation around this and if you can provide some incite here that would be greatly appreciated.

NFO [SSTableBatchOpen:1] 2019-04-07 21:17:56,578 SSTableReader.java:475 - Opening /opt/apigee/data/apigee-cassandra/data/system/schema_keyspaces-b0f2235744583cdb9631c43e59ce3676/system-schema_keyspaces-ka-1 (214 bytes)
ERROR [main] 2019-04-07 21:17:56,823 CassandraDaemon.java:296 - Fatal exception during initialization
org.apache.cassandra.exceptions.ConfigurationException: Cannot start node if snitch’s data center (dc-2) differs from previous data center (default). Please fix the snitch configuration, decommission and rebootstrap this node or use the flag -Dcassandra.ignore_dc=true.
at org.apache.cassandra.db.SystemKeyspace.checkHealth(SystemKeyspace.java:629) ~[apache-cassandra-2.1.16.jar:2.1.16]
at org.apache.cassandra.service.CassandraDaemon.setup(CassandraDaemon.java:292) [apache-cassandra-2.1.16.jar:2.1.16]
at org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:566) [apache-cassandra-2.1.16.jar:2.1.16]
at org.apache.cassandra.service.CassandraDaemon.main(CassandraDaemon.java:655) [apache-cassandra-2.1.16.jar:2.1.16]

2

The recommended two datacenter deployment topology is as follows:

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https://docs.apigee.com/private-cloud/v4.19.01/installation-topologies#12hostclusteredinstallation

In this Cassandra and Zookeeper would need to have a minimum of 3 nodes in each data center, 2 Qpid Server nodes in each data center, Postgres Master in one data center and the slave in the other. Routers and Message Processors could either be installed in the same node as RMP nodes or if the throughput required is considerably high those could be installed on separate nodes. Moreover, Routers and Message Processors could be scaled up dynamically if needed. In addition, OpenLDAP, Management Server and Edge UI can either be installed as shown above or on a separate node in each data center.

3

The only officially supported multi-DC topology requires 6 nodes in each DC: https://docs.apigee.com/private-cloud/v4.19.01/installation-topologies?hl=en#12hostclusteredinstallation

Even if you were willing to use an unsupported topology though, you’d need minimum 3 cassandra nodes in Azure to ensure you had a full copy of all data if your primary datacentre went offline.