Configure gunicorn errorlog

Related: alphagov/notifications-api/pull/1274

gunicorn_config.py

@@ -0,0 +1,8 @@
+import sys
+import traceback
+
+
+def worker_abort(worker):
+    worker.log.info("worker received ABORT")
+    for threadId, stack in sys._current_frames().items():
+        worker.log.info(''.join(traceback.format_stack(stack)))

manifest-base.yml

@@ -1,7 +1,7 @@
 ---
 
 buildpack: python_buildpack
-command: scripts/run_app_paas.sh gunicorn -w 5 -b 0.0.0.0:$PORT wsgi
+command: scripts/run_app_paas.sh gunicorn -c /home/vcap/app/gunicorn_config.py --error-logfile /home/vcap/logs/gunicorn_error.log -w 5 -b 0.0.0.0:$PORT wsgi
 services:
   - notify-aws
   - notify-config

scripts/run_app_paas.sh

@@ -29,6 +29,11 @@ state_file = /home/vcap/logs/awslogs-state
 file = /home/vcap/logs/app.log*
 log_group_name = paas-${CW_APP_NAME}-application
 log_stream_name = {hostname}
+
+[/home/vcap/logs/gunicorn_error.log]
+file = /home/vcap/logs/gunicorn_error.log
+log_group_name = paas-${CW_APP_NAME}-gunicorn
+log_stream_name = {hostname}
 EOF
 }