Remotely check status of cassandra using nodetool. Error: Connection refused - docker

Question

I am trying create a docker compose setup which will wait until the Cassandra container has started before running the JanusGraph container which requires Cassandra to be running before starting.
The nodetool command seems to be the standard way to check the status of Cassandra. Here is what I get running nodetool first on the cassandra container:
docker exec -it ns-orchestration_data_storage_1 nodetool status
Datacenter: datacenter1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns (effective) Host ID Rack
UN 172.31.0.2 235.53 KiB 256 100.0% eea17329-6274-45a7-a9fb-a749588b733a rack1
The first "UN" on the last stdout line means Up/Normal which I intend to use in my wait-for-cassandra-and-elasticsearch.sh script. But now when I try to run it on the janusgraph container (remote) I am getting this:
docker exec -it ns-orchestration_data_janusgraph_1 bin/nodetool -h 172.31.0.2 -u cassandra -pw <my-password-here> status
docker exec -it ns-orchestration_data_janusgraph_1 bin/nodetool -h
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/app/janusgraph-0.3.0-hadoop2/lib/slf4j-log4j12-1.7.12.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/app/janusgraph-0.3.0-hadoop2/lib/logback-classic-1.1.2.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.Log4jLoggerFactory]
nodetool: Failed to connect to '172.31.0.2:7199' - ConnectException: 'Connection refused (Connection refused)'.
I have exposed all Cassandra ports as you can see in the docker-compose file below.
I also saw this post which I am not sure is related. I tried following the instructions but I am still getting the same error.
I would appreciate any suggestions.
File: docker-compose.yml
version: '3'
services:
data_janusgraph:
build:
context: ../ns-compute-store/db-janusgraph
dockerfile: Dockerfile.janusgraph
ports:
- "8182:8182"
depends_on:
- data_storage
- data_index
networks:
- ns-net
data_storage:
build:
context: ../ns-compute-store/db-janusgraph
dockerfile: Dockerfile.cassandra
environment:
- CASSANDRA_START_RPC=true
ports:
- "9160:9160"
- "9042:9042"
- "7199:7199"
- "7001:7001"
- "7000:7000"
volumes:
- data-volume:/var/lib/cassandra
networks:
- ns-net
data_index:
image: elasticsearch:5.6
ports:
- "9200:9200"
- "9300:9300"
networks:
- ns-net
networks:
ns-net:
driver: bridge
volumes:
data-volume:
File: Dockerfile.cassandra
FROM cassandra:3.11
COPY conf/jmxremote.password /etc/cassandra/jmxremote.password
RUN chown cassandra:cassandra /etc/cassandra/jmxremote.password
RUN chmod 400 /etc/cassandra/jmxremote.password
COPY conf/jmxremote.access /usr/lib/jvm/java-8-openjdk-amd64/jre/lib/management/jmxremote.access
RUN chown cassandra:cassandra /usr/lib/jvm/java-8-openjdk-amd64/jre/lib/management/jmxremote.access
RUN chmod 400 /usr/lib/jvm/java-8-openjdk-amd64/jre/lib/management/jmxremote.access
COPY conf/cassandra.yaml /etc/cassandra/cassandra.yaml
File: Dockerfile.janusgraph
FROM openjdk:8-jre-alpine
RUN mkdir /app
WORKDIR /app
RUN apk update \
&& apk upgrade \
&& apk --no-cache add unzip
RUN wget https://github.com/JanusGraph/janusgraph/releases/download/v0.3.0/janusgraph-0.3.0-hadoop2.zip
RUN unzip janusgraph-0.3.0-hadoop2.zip
RUN apk --no-cache add bash coreutils nmap
RUN apk del unzip
ENV JVM_OPTS="$JVM_OPTS -Djava.rmi.server.hostname=data_storage"
WORKDIR /app/janusgraph-0.3.0-hadoop2
COPY wait-for-cassandra-and-elasticsearch.sh ./
COPY conf/janusgraph-cql-es.properties ./
CMD ["./wait-for-cassandra-and-elasticsearch.sh", "data_storage:9160", "data_index:9200", "./bin/gremlin-server.sh", "./conf/gremlin-server/gremlin-server-berkeleyje.yaml"]
See full code in Github Repository:
https://github.com/nvizo/janusgraph-cluster-example

Answer 1

I believe you should refer to your cassandra container name as hostname when running nodetool from your janusgraph container. Something along the lines of:
docker exec -it ns-orchestration_data_janusgraph_1 bin/nodetool -h data_storage -u cassandra -pw <my-password-here> status
Give it a try and let me know if it helps.