Cassandra config change to use hostnames after ip's changed - cassandra

Question

Initial installation of Cassandra was done using IP addresses and it has been working for 6+ months. This past weekend DevOps changed security to not allow IP addresses and also reassigned new IP addresses. I modified the required files (cassandra.yaml, cassandra-rackdc.properties, etc) to contain hostnames. The issue is nodetool status gives the error, Failed to connect to '127.0.0.1:7199, and I do have JVM_OPTS="$JVM_OPTS -Djava.rmi.server.hostname=blah" in cassandra-env.sh. Any ideas how to proceed to the environment back up? Should I go through the same files and replace hostnames with the new IP addresses? Thanks.

Answer 1

There are two options to provide listen address in Cassandra.yaml.
listen_address
listen_interface
To be completely agnostic of the IP address or hostname, use the option of listen_interface and comment the listen_address. Here is the Cassandra.yaml change required
# Address or interface to bind to and tell other Cassandra nodes to connect to.
#
#listen_address: xx.xxx.xx.xxx
# Set listen_address OR listen_interface, not both. Interfaces must correspond
# to a single address, IP aliasing is not supported.
listen_interface: eth0
To figure out the actual listen_interface, issue the command
ifconfig -a
Pick the interface that shows, "UP BROADCAST RUNNING". (eth0 in mycase)
The output should look like
root#ip-xx-xxx-x-xxx:~# ifconfig -a
docker0 Link encap:Ethernet HWaddr xx:xx:xx:xx:xx:xx
inet addr:xxx.xx.x.x Bcast:0.0.0.0 Mask:255.255.0.0
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:2 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:152 (152.0 B) TX bytes:0 (0.0 B)
eth0 Link encap:Ethernet HWaddr xx:xx:xx:xx:xx:xx
inet addr:xx.xxx.xx.xx Bcast:xx.xxx.xx.xx Mask:255.255.0.0
UP BROADCAST RUNNING MULTICAST MTU:9001 Metric:1
RX packets:169552382 errors:0 dropped:0 overruns:0 frame:0
TX packets:185182015 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:88406501352 (88.4 GB) TX bytes:126516101404 (126.5 GB)
lo Link encap:Local Loopback
inet addr:xx.xxx.xx.xx Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:38490371 errors:0 dropped:0 overruns:0 frame:0
TX packets:38490371 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1
RX bytes:41155731774 (41.1 GB) TX bytes:41155731774 (41.1 GB)
Restart Cassandra and you should be good to go. Another advantage is that Cassandra.yaml no longer has to be different across your nodes (assuming all have the same network interface).