FIX Entrypoint and _CMD config variables (#8705)

The entrypoint manages the two variables AIRFLOW__CORE__SQL_ALCHEMY_CONN and AIRFLOW__CELERY__BROKER_URL but does not take into account the fact that those configurations can be overriden by AIRFLOW__CORE__SQL_ALCHEMY_CONN_CMD and AIRFLOW__CELERY__BROKER_URL_CMD which is very useful when providing the connections to those endpoints using Swarm/Kubernetes secrets.

The Dockerfile and its entrypoint come from the 2.0 refactoring (master branch) and have been backported to the 1.10 branch. Since the _CMD behaviour is present in the 1.10 stable branch the fix should be done there.

entrypoint.sh

@@ -90,16 +90,28 @@ function verify_db_connection {
     fi
 }
 
-# if no DB configured - use sqlite db by default
-AIRFLOW__CORE__SQL_ALCHEMY_CONN="${AIRFLOW__CORE__SQL_ALCHEMY_CONN:="sqlite:///${AIRFLOW_HOME}/airflow.db"}"
-
-verify_db_connection "${AIRFLOW__CORE__SQL_ALCHEMY_CONN}"
-
-AIRFLOW__CELERY__BROKER_URL=${AIRFLOW__CELERY__BROKER_URL:=}
+# Warning: command environnement variables (*_CMD) have priority over usual configuration variables
+# for configuration parameters that require sensitive information. This is the case for the SQL database
+# and the broker backend in this entrypoint script.
+
+if [[ -n "$AIRFLOW__CORE__SQL_ALCHEMY_CONN_CMD" ]]; then
+    verify_db_connection "$(eval "$AIRFLOW__CORE__SQL_ALCHEMY_CONN_CMD")"
+else
+    # if no DB configured - use sqlite db by default
+    AIRFLOW__CORE__SQL_ALCHEMY_CONN="${AIRFLOW__CORE__SQL_ALCHEMY_CONN:="sqlite:///${AIRFLOW_HOME}/airflow.db"}"
+    verify_db_connection "${AIRFLOW__CORE__SQL_ALCHEMY_CONN}"
+fi
 
-if [[ -n ${AIRFLOW__CELERY__BROKER_URL} ]] && \
-        [[ ${AIRFLOW_COMMAND} =~ ^(scheduler|worker|flower)$ ]]; then
-    verify_db_connection "${AIRFLOW__CELERY__BROKER_URL}"
+# Note: the broker backend configuration concerns only a subset of Airflow components
+if [[ "${AIRFLOW_COMMAND}" =~ ^(scheduler|worker|flower)$ ]]; then
+    if [[ -n "$AIRFLOW__CELERY__BROKER_URL_CMD" ]]; then
+        verify_db_connection "$(eval "$AIRFLOW__CELERY__BROKER_URL_CMD")"
+    else
+        AIRFLOW__CELERY__BROKER_URL=${AIRFLOW__CELERY__BROKER_URL:=}
+        if [[ -n "${AIRFLOW__CELERY__BROKER_URL}" ]]; then
+            verify_db_connection "${AIRFLOW__CELERY__BROKER_URL}"
+        fi
+    fi
 fi
 
 if [[ ${AIRFLOW_COMMAND} == "" ]]; then