setting up cassandra multi node cluster on a single ubuntu server

Question

I have a Cassandra Service running on my Ubuntu Server with a single node now. I want to make it into a ring cluster with 3 nodes to get a feel of multinode cluster all being on the same server. By following the steps in this link https://www.youtube.com/watch?v=oHMJrhMtv3c, I tried to create a fresh cluster without stopping the already running cassandra service. But it has thrown address Caused by: java.net.BindException: Address already in use. So i tried changing the seeds ip to already running cassandra ip address and tried to run a second cassandra service in the foreground. This time it has thrown java.lang.RuntimeException: Unable to create thrift socket to ip port. Please let me know how to add nodes to a already running single node cluster on the same server.

Answer 1

It is very easy to run multiple Cassandra instances on the same Ubuntu machine as long as they have different IP addresses that all resolve to the local host. The entire 127.0.0.0/8 address block is reserved for loopback purposes so any packet sent to addresses (127.0.0.1 through 127.255.255.254) will be looped back.

• Use ping to check if the addresses resolve properly.
• Place two (or more) Cassandra instances into different folders.

Edit cassandra.yaml and replace

• Various file locations to the locations unique to the given instance of Cassandra.
• localhost to the IP address we give to that instance (like 127.0.0.2).
• Use SimpleSeedProvider and put addresses of all other Cassandra instances to the seed list to make a cluster (like - seeds: "127.0.0.2","127.0.0.3"
• Do not alter any port numbers, not helpful and not required.

Edit cassandra-env.sh, find where the JMX_PORT property is set and give it a different value (different port) for every instance of Cassandra. Otherwise instances cannot run together because of the conflicts on this port.

• start the instances one by one using ./cassandra startup script (you can write simple bash script for this later).

• Verify your topology with ./nodetool status . For the two nodes, for instance, the output must look like

  Datacenter: datacenter1
  =======================
  Status=Up/Down
  |/ State=Normal/Leaving/Joining/Moving
  --  Address    Load       Tokens  Owns (effective)  Host ID                               Rack
  UN  127.0.0.1  61.97 KB   256     100.0%            6c04e202-8f24-4f17-b430-0154c1512316  rack1
  UN  127.0.0.2  105.68 KB  256     100.0%            ca3073ee-451c-4cef-97ee-d312784648bb  rack1