#278: working nicely!

server/README.md

@@ -62,7 +62,7 @@ docker build -t absaoss/atum-service:latest --progress=plain --no-cache \
 
 # If you want to run it against AWS, you need to add AWS related credentials into the docker container, possibly via 
 # environment variables; but you can also run it against your a local Postgres DB (in host or another Docker container).
-docker run /absolute/path/resource.conf:/opt/config/resource.conf \
+docker run -v /absolute/path/resource.conf:/opt/config/resource.conf \
   -e AWS_ACCESS_KEY_ID="abc" -e AWS_SECRET_ACCESS_KEY="def" -e AWS_SESSION_TOKEN="xyz" \
   -p 8080:8080 -p 8443:8443 absaoss/atum-service:latest
 

server/docker_entrypoint.sh

@@ -4,10 +4,24 @@
 CUSTOM_CONFIG_LOCATION="/opt/config/resource.conf"
 JAR_LOCATION="/opt/app/atum-service.jar"
 
+# Why `exec` - mostly for a correct termination signal handling & finishing the application.
+#
+# Explanation: The exec command replaces the shell process with the Java process, so the Java process (our application)
+#   becomes the main process (PID 1) in the container. Docker automatically sends termination signals
+#   (SIGTERM, SIGINT, etc.) to PID 1, so the Java process will directly receive the signals and can terminate cleanly.
+#
+#   When you define ENTRYPOINT in a Dockerfile and it points to a shell script, as it is in our case, what actually
+#   happens is that the shell starts first, executes the script, and then runs whatever commands are inside that script.
+#   For example, without exec, the process flow looks like this:
+#     1. Docker starts the container, and the shell process (/bin/sh) is launched.
+#     2. The shell process begins executing this `docker_entrypoint.sh` script.
+#     3. Inside the script, if you run java, the shell spawns a child process to run the java command, while the shell
+#       process remains the parent process (still PID 1). But what we want is our Java to have PID 1 to receive
+#       termination signals.
 if [ -f "${CUSTOM_CONFIG_LOCATION}" ]; then
     echo "Running with custom config"
-    java -Dconfig.file="${CUSTOM_CONFIG_LOCATION}" -jar "${JAR_LOCATION}"
+    exec java -Dconfig.file="${CUSTOM_CONFIG_LOCATION}" -jar "${JAR_LOCATION}"
 else
     echo "Running with default config"
-    java -jar "${JAR_LOCATION}"
+    exec java -jar "${JAR_LOCATION}"
 fi