Check connections before launching

* qc_app/__init__.py (refactor): Check connection before launching the
  application
* qc_app/check_connections.py (new file): Add code to check
  connections
* qc_app/db_utils.py (refactor): enable passing the database uri as an
  argument to the connection creation function.
* scripts/worker.py (refactor): Use new code to check for redis
  connection.

1 files changed, 28 insertions, 0 deletions

diff --git a/qc_app/check_connections.py b/qc_app/check_connections.py
new file mode 100644
index 0000000..ceccc32
--- /dev/null
+++ b/qc_app/check_connections.py
@@ -0,0 +1,28 @@
+"""Check the various connection used in the application"""
+import sys
+import traceback
+
+import redis
+import MySQLdb
+
+from qc_app.db_utils import database_connection
+
+def check_redis(uri: str):
+    "Check the redis connection"
+    try:
+        with redis.Redis.from_url(uri) as rconn:
+            rconn.ping()
+    except redis.exceptions.ConnectionError as conn_err:
+        print(conn_err, file=sys.stderr)
+        print(traceback.format_exc(), file=sys.stderr)
+        sys.exit(1)
+
+def check_db(uri: str):
+    "Check the mysql connection"
+    try:
+        with database_connection(uri) as dbconn: # pylint: disable=[unused-variable]
+            pass
+    except MySQLdb.OperationalError as op_err:
+        print(op_err, file=sys.stderr)
+        print(traceback.format_exc(), file=sys.stderr)
+        sys.exit(1)