Operate a host-local Docker container registry for kubeadm-dind clusters.

registry.sh

#!/bin/bash
# TheDiveO

function log {
    local OPTS=""
    if [[ "$1" = "-n" ]]; then
        shift; OPTS+="-n"
    fi
    MSG="$1"
    shift
    if [[ -t 2 ]]; then
        # colorful output to terminal
        echo -e ${OPTS} "\x1B[97m* \x1B[92m${MSG}\x1B[39m $*" 1>&2
    else
        # output to pipe
        echo ${OPTS} "* ${MSG} $*" 1>&2
    fi
}

function green {
    local OPTS=""
    if [[ "$1" = "-n" ]]; then
        shift; OPTS+="-n"
    fi
    if [[ -t 2 ]]; then
        echo -e ${OPTS} "\x1B[92m$1\x1B[39m" 1>&2
    else
        echo ${OPTS} "$1" 1>&2
    fi
}

function red {
    local OPTS=""
    if [[ "$1" = "-n" ]]; then
        shift; OPTS+="-n"
    fi
    if [[ -t 2 ]]; then
        echo -e ${OPTS} "\x1B[91m$1\x1B[39m" 1>&2
    else
        echo ${OPTS} "$1" 1>&2
    fi
}

CMD="${1:-}"
case ${CMD} in
    up)
        # Start local Docker registry, if it's not running already. Contrary
        # what the above link suggests, we don't enable the registry to
        # *automatically* restart. Instead, we check if the registry is not
        # already up and running, and only then start it (again). And we make
        # sure to remove a stopped (exited) registry container in case we find
        # one, before (re)starting the registry. See also:
        # https://stackoverflow.com/a/38576401
        log "starting local Docker image registry"
        if [[ ! "$(docker ps -q -f name=registry)" ]]; then
            # Remove in case the container still exists, but has exited.
            if [[ "$(docker ps -aq -f status=exited -f name=registry)" ]]; then
                docker rm registry
            fi
            docker run -d -p 5000:5000 --name registry registry:2
        fi
        # Taken from
        # https://github.com/kubernetes-sigs/kubeadm-dind-cluster/issues/56#issuecomment-387463386.
        # Run registry proxies on all Docker "Kubernetes nodes", forwarding
        # their local port 5000 to our host's port 5000. The forwarder used
        # here is the "Stupid TCP proxy", which can be found here:
        # https://hub.docker.com/r/tecnativa/tcp-proxy/
        log "starting registry forwarders on Kubernetes \"nodes\"..."
        docker ps -a -q --filter=label=mirantis.kubeadm_dind_cluster | while read CID; do
            NAME=$(docker inspect --format='{{.Name}}' $CID)
            NAME=${NAME:1}
            echo -n "Docker Kubernetes node $CID \"$NAME\": (re)starting registry forwarder "
            docker exec ${CID} /bin/bash -c "docker rm -fv registry-proxy || true"
            # run registry proxy: forward from localhost:5000 on each node to host:5000
            docker exec ${CID} /bin/bash -c \
                "docker run --name registry-proxy -d -e LISTEN=':5000'\
                -e TALK=\"\$(/sbin/ip route|awk '/default/ { print \$3 }'):5000\"\
                -p 5000:5000 tecnativa/tcp-proxy"
        done
        ;;

    down)
        # Nuke the registry container
        log "stopping local Docker image registry"
        docker rm -fv registry
        # Nuke all registry forwarders (TCP forwarders) inside the Kubernetes
        # "node" docker containers.
        log "stopping registry forwarders on Kubernetes \"nodes\"..."
        docker ps -a -q --filter=label=mirantis.kubeadm_dind_cluster \
        | while read CID; do
            NAME=$(docker inspect --format='{{.Name}}' $CID)
            NAME=${NAME:1}
            echo -n "Docker Kubernetes node $CID \"$NAME\": stopping registry forwarder "
            docker exec ${CID} /bin/bash -c \
            "docker rm -fv registry-proxy || true"
        done
        ;;

    status)
        # Try to discover the status of the local registry and the registry
        # forwarders... 
        echo -n "local docker registry: "
        if [[ "$(docker ps -q -f name=registry)" ]]; then
            green "[running]"
        else
            red "[unavailable]"
        fi
        docker ps -a -q --filter=label=mirantis.kubeadm_dind_cluster \
        | while read CID; do
            NAME=$(docker inspect --format='{{.Name}}' $CID)
            NAME=${NAME:1}
            echo -n "Docker Kubernetes node $CID \"$NAME\": registry forwarder "
            if [[ $(docker exec ${CID} /bin/bash -c \
                    "docker ps -q -f name=registry-proxy") ]]; then
                green "[running]"
            else
                red "[unavailable]"
            fi
        done
        ;;

    *)
        PROG=$(basename "$0")
        echo "usage:" >&2
        echo "  $PROG up" >&2
        echo "  $PROG down" >&2
        echo "  $PROG status" >&2
        exit 1
        ;;
esac