skip to Main Content

I’m running a cassandra container with the the help of docker. For the below set of configuration I’m trying to run the script.sh script which should run after cassandra is up and running. However, the below script keeps logging ConnectionRefusedError(111) error:

dd_cassandra  | Connection error: ('Unable to connect to any servers', {'127.0.0.1:9042': ConnectionRefusedError(111, "Tried connecting to [('127.0.0.1', 9042)]. Last error: Connection refused")})
dd_cassandra  | Waiting for cassandra-node-1...

I used the solution described in this SO Post to check further execute the script only if cassandra is ready but it runs into an infinite wait.

docker-compose.yml

version: '3'

services:
  dd_cassandra:
    container_name: dd_cassandra
    build:
      context: ./cassandra
      dockerfile: Dockerfile
      args:
        BASE_IMAGE: cassandra:latest
    ports:
      - "9042:9042"

cassandra/Dockerfile

ARG BASE_IMAGE
FROM ${BASE_IMAGE}

COPY script.sh /
RUN chmod +x /script.sh
EXPOSE 9042
CMD ["/script.sh"]

cassandra/script.sh

#!/bin/bash

while ! cqlsh -e 'describe cluster' ; do
  echo "Waiting for cassandra-node-1...";
  sleep 10
done

# some other piece of code that adds runs `cqlsh` command 
# in the cassandra database

2

Answers


  1. I dont have much exp with yaml (currently learning myself), but looking at your yaml file seems port numbers don’t need to be in "" as it then appears as a string

    Login or Signup to reply.
  2. Quick fix

    What you are doing is not exactly correct how containers should be used, but to just fix it you need to add USER cassandra to Dockerfile

    ARG BASE_IMAGE
    FROM ${BASE_IMAGE}
    
    COPY script.sh /
    RUN chmod +x /script.sh
    USER cassandra
    EXPOSE 9042
    CMD ["/script.sh"]
    

    Second change is to add cassandra to script.sh before while (it’s needed because when you added your script cassandra service wasn’t starting because you have overrided CMD click here and scroll to ‘CMD ["cassandra" "-f"]’)

    #!/bin/bash
    
    cassandra
    while ! cqlsh -e 'describe cluster' ; do
      echo "Waiting for cassandra-node-1...";
      sleep 2
    done
    

    This works as I tested.


    More appropriate approach

    I suggest you doing it a little bit differently. Looking into How to check that a Cassandra node is ready? someone started cassandra container without creating new Dockerfile and he just wanted to access it from localhost, probably it was something like this using docker-compose.yaml

    version: '3'
    
    services:
      dd_cassandra:
        container_name: dd_cassandra
        image: cassandra:latest
        ports:
        - "9042:9042"
    

    Then from localhost(not any container) you can access it using cqlsh localhost 9042 -e 'describe cluster' if you don’t have cqlsh installed you can spin-up another container using docker run -it --rm --network host cassandra:latest bash and inside type that command

    To achieve what you want you can add something like this

    version: '3'
    
    services:
      dd_cassandra:
        container_name: dd_cassandra
        image: cassandra:latest
        ports:
          - "9042:9042"
    
      cassandra_script:
        build:
          context: ./cassandra
          dockerfile: Dockerfile
          args:
            BASE_IMAGE: cassandra:latest
    

    And one more change to script.sh we need add host dd_cassandra(name of the service/container) instead of using localhost

    #!/bin/bash
    
    while ! cqlsh dd_cassandra -e 'describe cluster' ; do
      echo "Waiting for cassandra-node-1...";
      sleep 10
    done
    

    After running docker-compose up and waiting around an half minute I got:

    cassandra-cassandra_script-1  | 
    cassandra-cassandra_script-1  | 
    cassandra-cassandra_script-1  | Cluster: Test Cluster
    cassandra-cassandra_script-1  | Partitioner: Murmur3Partitioner
    cassandra-cassandra_script-1  | Snitch: DynamicEndpointSnitch
    cassandra-cassandra_script-1  | 
    cassandra-cassandra_script-1 exited with code
    

    First container dd_cassandra is just cassandara service, second container cassandra_script has your script.sh in CMD so it runs your script, the limitation here is that Dockerfile can contain only one CMD so if it’s used more then once only last occurrence will be invoked.

    Login or Signup to reply.
Please signup or login to give your own answer.
Back To Top
Search