entrypoint.sh

#!/bin/bash

#  ============================================================================
#  entrypoint.sh
#
#  An entrypoint that blocks until one or more TCP hosts become availabile
#  ============================================================================

set -e

trap '{ echo "Aborting due to interrupt" ; exit 1; }' INT

timeout=${WAIT_HOSTS_TIMEOUT:-30}
waitAfterHosts=${WAIT_AFTER_HOSTS:-0}
waitBeforeHosts=${WAIT_BEFORE_HOSTS:-0}

function try() {
    if type gtimeout > /dev/null 2>&1; then
        gtimeout 1 bash -c "$1"
    elif type timeout > /dev/null 2>&1; then
        timeout 1 bash -c "$1"
    else
        echo >&2 "Couldn't find timeout or gtimeout executables in path";
        exit 1;
    fi
}

echo "Waiting for ${waitBeforeHosts} seconds."
sleep $waitBeforeHosts

# comma separated pairs of the form "[host]:[ip]"
if [ -n "$WAIT_HOSTS" ]; then
    uris=$(echo $WAIT_HOSTS | sed -e 's/,/ /g' -e 's/\s+/\n/g' | uniq)
fi

# wait for each target
if [ -z "$uris" ];
then
    echo "No wait targets found." >&2;

else
    for uri in $uris
    do
        host=$(echo $uri | cut -d: -f1)
        port=$(echo $uri | cut -d: -f2)
        [ -n "${host}" ]
        [ -n "${port}" ]
        echo "Waiting for ${uri}."
        seconds=0
        while [ "$seconds" -lt "$timeout" ] && ! try "> /dev/tcp/$host/$port 2> /dev/null"
        do
            echo -n .
            seconds=$((seconds + 1))
            sleep 1
        done

        if [ "$seconds" -lt "$timeout" ]; then
            echo "${uri} is up!"
        else
            echo "  ERROR: unable to connect to ${uri}" >&2
            exit 1
        fi
    done
    echo "All hosts are up"
fi

echo "Waiting for ${waitAfterHosts} seconds."
sleep $waitAfterHosts

# Execute the Docker container's CMD
exec "$@"