Can't launch more than 1 cassandra node - docker

Question

I launched a cassandra docker image using the following command,
docker run --name=n1 -d cassandra:3.11.4
344138bb96e5326113af6ba5c44a17d8b40ed710fe36ce063677a56ef0c0117
This works fine,
docker exec -it n1 nodetool status gives,
Datacenter: datacenter1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns (effective) Host ID Rack
UN 172.17.0.2 103.7 KiB 256 100.0% 0ca2907d-49b9-4ed4-8bf3-6db99d0c8b45 rack1
Now when I try to launch a second node, this what I get,
docker inspect -f '{{ .NetworkSettings.IPAddress}}' n1
172.17.0.2
docker run --name n2 -d cassandra:3.11.4 -seeds 172.17.0.2
1c89b67cb61b049c4a8ae0f21bd0f7cddffad02b7e7964e502cd82e0d2ff2866
docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
344138bb96e5 cassandra:3.11.4 "docker-entrypoint.s…" 2 minutes ago Up 2 minutes 7000-7001/tcp, 7199/tcp, 9042/tcp, 9160/tcp n1
docker exec -it n1 nodetool status
Still no second node
Datacenter: datacenter1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns (effective) Host ID Rack
UN 172.17.0.2 103.7 KiB 256 100.0% 0ca2907d-49b9-4ed4-8bf3-6db99d0c8b45 rack1
docker exec -it n2 nodetool status
Error response from daemon: Container 1c89b67cb61b049c4a8ae0f21bd0f7cddffad02b7e7964e502cd82e0d2ff2866 is not running
docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
1c89b67cb61b cassandra:3.11.4 "docker-entrypoint.s…" 2 minutes ago Exited (1) 2 minutes ago n2
344138bb96e5 cassandra:3.11.4 "docker-entrypoint.s…" 4 minutes ago Up 4 minutes 7000-7001/tcp, 7199/tcp, 9042/tcp, 9160/tcp n1
What am I doing wrong here?

Answer 1

I don't know where you get the information which you can use -seeds 172.17.0.2 to specify seed in this docker image, in fact check the log of n2, it said:
getopt: invalid option -- 's'
getopt: invalid option -- 'e'
getopt: invalid option -- 'e'
getopt: invalid option -- 'd'
getopt: invalid option -- 's'
Error parsing arguments! Unknown argument "172.17.0.2"
And from it's doc, CASSANDRA_SEEDS env is the correct way, like next:
docker run --name n2 -d -e CASSANDRA_SEEDS=172.17.0.2 cassandra:3.11.4
Results:
shubuntu1#shubuntu1:~$ docker run --name n1 -d cassandra:3.11.4
1d1d95f0caeff471c409cd8eda2e77aa5d9b3a60831c284937c305e823016885
shubuntu1#shubuntu1:~$ docker exec -it n1 nodetool status
Datacenter: datacenter1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns (effective) Host ID Rack
UN 172.17.0.2 112.85 KiB 256 100.0% c6117826-2fff-48a2-964b-ba403e972154 rack1
shubuntu1#shubuntu1:~$ docker run --name n2 -d -e CASSANDRA_SEEDS=172.17.0.2 cassandra:3.11.4
37e5b84ab92b8b9087e6cff37b146b1f7e337ec9499ce907408abeba11f1985c
Wait a few time, then check again, we find the cluster has 2 nodes now:
shubuntu1#shubuntu1:~$ docker exec -it n1 nodetool status
Datacenter: datacenter1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns (effective) Host ID Rack
UN 172.17.0.3 112.98 KiB 256 100.0% e61857d3-b924-4fe9-9a68-03d603de7c38 rack1
UN 172.17.0.2 108.62 KiB 256 100.0% c6117826-2fff-48a2-964b-ba403e972154 rack1