feat(boot): background the loading of DB data into Kubernetes

This uses backgrounding of the management command and uses nohup to manage the running of the task.
Logs (that are not part of the normal Django log loop) will go into /app/data/logs/load_db_state_to_k8s.log

By doing this the Controller can go into a ready state a lot earlier than otherwise when there are a lot of resources (specficially apps)

Readiness and Liveness both have 30 second delay and in that timeframe the initial set of Model save() operations will be able to take place to create the appropriate Namespaces and Services

Generally the slowest part is the Deploy but other Kubernetes resource manipulations can be a tad bit slow.

Closes #746

Author: helgi

rootfs/bin/boot

@@ -23,19 +23,28 @@ chgrp deis /var/run/docker.sock
 groupadd -g "$(stat -c "%g" /var/run/docker.sock)" docker || true
 usermod -a -G docker deis || true
 
+echo ""
 echo "Django checks:"
 python /app/manage.py check --deploy api
 
+echo ""
 echo "Health Checks:"
 python /app/manage.py healthchecks
 
+echo ""
 echo "Database Migrations:"
 sudo -E -u deis python /app/manage.py migrate --noinput
 
 # spawn a gunicorn server in the background
+echo ""
+echo "Starting up Gunicorn"
 sudo -E -u deis gunicorn -c /app/deis/gunicorn/config.py api.wsgi &
 
-python /app/manage.py load_db_state_to_k8s
+echo ""
+echo "Loading database information to Kubernetes in the background"
+echo "Log of the run can be found in /app/data/logs/load_db_state_to_k8s.log"
+# python -u avoids output buffering
+nohup python -u /app/manage.py load_db_state_to_k8s > /app/data/logs/load_db_state_to_k8s.log &
 
 # smart shutdown on SIGTERM (SIGINT is handled by gunicorn)
 function on_exit() {
@@ -46,6 +55,7 @@ function on_exit() {
 }
 trap on_exit TERM
 
+echo ""
 echo deis-controller running...
 
 wait