feat,fix(ct-base): add extension point for background script IQSS#8932

By moving from tini to dumb-init, we can offer a new extension point:
if an application image extending this base image provides an executable
script at ${SCRIPT_DIR}/startInBackground.sh, it will be executed
after the init scripts and in parallel to the application server.

By adding ${SCRIPT_DIR} to $PATH, we can now also skip variable expansion,
fixing a bug: formerly, the "exec" in entrypoint.sh and startInForeground.sh
where not replacing the shell properly.

The switch to dumb-init makes sure signals will be transferred also to any
background processes!

modules/container-base/src/main/docker/Dockerfile

@@ -46,7 +46,7 @@ ENV PAYARA_DIR="${HOME_DIR}/appserver" \
  ADMIN_PASSWORD="admin" \
  DOMAIN_NAME="domain1" \
  PAYARA_ARGS=""
-ENV PATH="${PATH}:${PAYARA_DIR}/bin" \
+ENV PATH="${PATH}:${PAYARA_DIR}/bin:${SCRIPT_DIR}" \
  DOMAIN_DIR="${PAYARA_DIR}/glassfish/domains/${DOMAIN_NAME}" \
  DEPLOY_PROPS="" \
  PREBOOT_COMMANDS="${CONFIG_DIR}/pre-boot-commands.asadmin" \
@@ -88,7 +88,7 @@ EOF
 
 ARG JATTACH_VERSION="v2.1"
 ARG JATTACH_CHECKSUM="07885fdc782e02e7302c6d190f54c3930afa10a38140365adf54076ec1086a8e"
-ARG PKGS="jq imagemagick curl unzip wget acl dirmngr gpg lsof procps netcat tini"
+ARG PKGS="jq imagemagick curl unzip wget acl dirmngr gpg lsof procps netcat dumb-init"
 
 # Installing the packages in an extra container layer for better caching
 RUN <<EOF
@@ -214,9 +214,9 @@ RUN <<EOF
 EOF
 
 # Set the entrypoint to tini (as a process supervisor)
-ENTRYPOINT ["/usr/bin/tini", "--"]
-# JSON syntax should be used, but bypassed shell. Thus re-add expansion via shell exec.
-CMD ["sh", "-c", "${SCRIPT_DIR}/entrypoint.sh"]
+ENTRYPOINT ["/usr/bin/dumb-init", "--"]
+# This works because we add ${SCRIPT_DIR} to $PATH above!
+CMD ["entrypoint.sh"]
 
 LABEL org.opencontainers.image.created="@git.build.time@" \
  org.opencontainers.image.authors="Research Data Management at FZJ <forschungsdaten@fz-juelich.de>" \

modules/container-base/src/main/docker/scripts/entrypoint.sh

@@ -1,11 +1,17 @@
-#!/bin/bash
+#!/usr/bin/dumb-init /bin/bash
 ##########################################################################################################
 #
 # This script is a fork of https://github.com/payara/Payara/blob/master/appserver/extras/docker-images/
 # server-full/src/main/docker/bin/entrypoint.sh and licensed under CDDL 1.1 by the Payara Foundation.
 #
 ##########################################################################################################
 
+# This shellscript is supposed to be executed by https://github.com/Yelp/dumb-init to keep subprocesses
+# and zombies under control. If the ENTRYPOINT command is changed, it will still use dumb-init because shebang.
+# dumb-init takes care to send any signals to subshells, too! (Which might run in the background...)
+
+
+# Execute any scripts BEFORE the appserver starts
 for f in "${SCRIPT_DIR}"/init_* "${SCRIPT_DIR}"/init.d/*; do
  # shellcheck disable=SC1090
  case "$f" in
@@ -15,4 +21,13 @@ for f in "${SCRIPT_DIR}"/init_* "${SCRIPT_DIR}"/init.d/*; do
  echo
 done
 
+# If present, run a startInBackground.sh in the background (e.g. to run tasks AFTER the application server starts)
+if [ -x "${SCRIPT_DIR}/startInBackground.sh" ]; then
+ echo "[Entrypoint] running ${SCRIPT_DIR}/startInBackground.sh in background"
+ "${SCRIPT_DIR}"/startInBackground.sh &
+fi
+
+# Start the application server and make it REPLACE this shell, so init system and Java directly interact
+# Remember - this means no code below this statement will be run!
+echo "[Entrypoint] running ${SCRIPT_DIR}/startInForeground.sh in foreground"
 exec "${SCRIPT_DIR}"/startInForeground.sh "${PAYARA_ARGS}"