Add known issue for setting up the database

Author: 7homasSutter

_posts/2024-07-11-Known-Issues.md

@@ -23,4 +23,44 @@ After setting the memory limit, restart the worker container to apply the change
 you might need to adjust the memory limit of the docker daemon as well.
 
 - **Workaround**: If increasing the memory limit does not solve the issue, you can try to reduce the number of workers
-or the number of elements in the queue to process.
+or the number of elements in the queue to process.
+
+
+
+### Initial setup of the database fails 
+Sometimes when you try to deploy a new instance of FMD, the initialisation of the database fails with the following error message:
+```
+....
+mongo-db-1               | {"t":{"$date":"2024-10-29T09:32:29.237+00:00"},"s":"E",  "c":"CONTROL",  "id":20557,   "ctx":"initandlisten","msg":"DBException in initAndListen, terminating","attr":{"error":"IllegalOperation: Attempted to create a lock file on a read-only directory: /data/db"}}
+...
+```
+This can happen if the `mongo-db-1` container is not able to write to the `/data/db` directory within the container.
+Usually that means that there was a problem creating the directory for the database due to permissions on the host system. 
+If that is the case, subsequent attempts to start the container will fail because the directory already exists but is not writable and
+the container will not be able to connect to the database. The following error message will be shown in the logs:
+```
+backend-worker           | pymongo.errors.ServerSelectionTimeoutError: mongo-db-1:27017: [Errno -2] Name or service not known (configured timeouts: socketTimeoutMS: 20000.0ms, connectTimeoutMS: 20000.0ms), Timeout: 30s, Topology Description: <TopologyDescription id: 6720aba298caf29a9cb0f029, topology_type: Unknown, servers: [<ServerDescription ('mongo-db-1', 27017) server_type: Unknown, rtt: None, error=AutoReconnect('mongo-db-1:27017: [Errno -2] Name or service not known (configured timeouts: socketTimeoutMS: 20000.0ms, connectTimeoutMS: 20000.0ms)')>]>
+backend-worker exited with code 0
+```
+To overcome this issue you can remove the directories (`mongo_database` and `django_database`) and manually 
+create them with the correct permissions. The environment variables `LOCAL_MONGO_DB_PATH_NODE1` and `DJANGO_SQLITE_DATABASE_MOUNT_PATH`
+should be set to the correct paths where the directories should be created on the host.
+```
+# Check if the environment variables are set correctly in the .env file:
+cat .env
+
+# Delete the mongo_database and django_database directories -> Replace <YOUR_PATH> with the correct path:
+rm -R <YOUR_PATH>/mongo_database
+rm -R <YOUR_PATH>/django_database
+
+# Creates the mongo_database directory -> Replace <LOCAL_MONGO_DB_PATH_NODE1> with the correct path:
+mkdir -p <LOCAL_MONGO_DB_PATH_NODE1>
+
+# Create the django_database directory -> Replace <DJANGO_SQLITE_DATABASE_MOUNT_PATH> with the correct path:
+mkdir -p <DJANGO_SQLITE_DATABASE_MOUNT_PATH>
+```
+After creating the directories you can restart the deployment and the containers should start successfully.
+```
+docker compose up
+```
+