Create keyspace automatically inside docker container with cassandra

Question

I was wondering if someone has tried to build a cassandra docker image with default keyspace, I've tried to do it on BUILD time but it doesn't work because cassandra is not running in that phase. It was something similar to this:

FROM cassandra:2.0
COPY ../somewhere/keyspace_definition.txt /src/keyspace_definition.txt
RUN /usr/bin/cqlsh -f /src/keyspace_definition.txt

My new approach will be to do it from the entrypoint script, but, I wanted to now if someone else has a better idea.

Happy shipping :D

Answer 1

Base on answers from @jan-oudrincky and @alexander-morozov, I build a new docker image which has a wrapper of original docker-entrypoint.sh to create keyspace when environment variable CASSANDRA_KEYSPACE is set. It will be useful in dev/test environment.

It doesn't modify docker-entrypoint.sh so even if cassandra base image has any modification you just need a rebuild.

Dockerfile

FROM cassandra

COPY entrypoint-wrap.sh /entrypoint-wrap.sh
ENTRYPOINT ["/entrypoint-wrap.sh"]
CMD ["cassandra", "-f"]

entrypoint-wrap.sh

#!/bin/bash

if [[ ! -z "$CASSANDRA_KEYSPACE" && $1 = 'cassandra' ]]; then
  # Create default keyspace for single node cluster
  CQL="CREATE KEYSPACE $CASSANDRA_KEYSPACE WITH REPLICATION = {'class': 'SimpleStrategy', 'replication_factor': 1};"
  until echo $CQL | cqlsh; do
    echo "cqlsh: Cassandra is unavailable - retry later"
    sleep 2
  done &
fi

exec /docker-entrypoint.sh "$@"

Answer 2

Tackled this issue today. Build image, which overwrites default Cassandra docker-entrypoint.sh with one modified, appended, right before exec "$@"

for f in docker-entrypoint-initdb.d/*; do
    case "$f" in
        *.sh)     echo "$0: running $f"; . "$f" ;;
        *.cql)    echo "$0: running $f" && until cqlsh -f "$f"; do >&2 echo "Cassandra is unavailable - sleeping"; sleep 2; done & ;;
        *)        echo "$0: ignoring $f" ;;
    esac
    echo
done

Put the desired *.cql in image in docker-entrypoint-initdb.d/.

Image will start, boot up the cassandra, and retries inserting to the database unless it succeeds. Just make sure your scripts are IF NOT EXISTS otherwise the script will run indefinitely.