Handle SIGTERM and shutdown gracefully.

docker/run.sh

@@ -6,6 +6,10 @@ export DISPLAY=:10.0
 Xvfb :10 -ac 1>/tmp/xvfb.log 2>/tmp/xvfb.err &
 
 # run the webapp server
-python3 /app/vasl_templates/webapp/run_server.py \
+# IMPORTANT! This script runs as PID 1, which is the only process that will receive signals,
+# so we must replace it with the Python webserver process if it is to receive e.g. SIGTERM,
+# which we must handle if "docker stop" and scaling down in Kubernetes is to work (otherwise
+# things timeout and we get SIGKILL'ed).
+exec python3 /app/vasl_templates/webapp/run_server.py \
     --addr 0.0.0.0 \
     --force-init-delay 30

vasl_templates/webapp/__init__.py

@@ -129,8 +129,8 @@ def _is_flask_child_process():
 
 # ---------------------------------------------------------------------
 
-def _on_sigint( signum, stack ): #pylint: disable=unused-argument
-    """Clean up after a SIGINT."""
+def _on_sig( signum, stack ): #pylint: disable=unused-argument
+    """Clean up after a SIGINT/SIGTERM."""
 
     # FUDGE! Since we added gRPC test control, we want to shutdown properly and clean things up (e.g. temp files
     # created by the gRPC service), but the Flask reloader complicates what we have to do here horribly :-(
@@ -258,7 +258,10 @@ import vasl_templates.webapp.downloads #pylint: disable=cyclic-import
 import vasl_templates.webapp.lfa #pylint: disable=cyclic-import
 
 # install our signal handler (must be done in the main thread)
-signal.signal( signal.SIGINT, _on_sigint )
+signal.signal( signal.SIGINT, _on_sig )
+# NOTE: We must handle SIGTERM, so that "docker stop" and scaling down in Kubernetes
+# work properly (otherwise it times out and we get SIGKILL'ed :-/).
+signal.signal( signal.SIGTERM, _on_sig )
 
 # register startup initialization
 app.before_request( _on_request )