Initialising a mysql database and persist data using Docker compose - mysql

Question

I am trying to run a web application that uses two docker containers: one contains the application code and the other container is a mysql database instance.
I am trying to populate the db with an sql file and also try to persist the database data through a volume. I am encountering an issue with the sql init file being copied into the mysql container but not being executed.
This is how my docker-compose.yml looks like:
version: "3.7"
services:
db:
image: mysql:8.0.19
command: '--default-authentication-plugin=mysql_native_password'
restart: always
volumes:
- db-data:/var/lib/mysql
- ./db:/docker-entrypoint-initdb.d/:ro
environment:
- MYSQL_ROOT_PASSWORD=password
networks:
- backend
app:
build: app
restart: always
depends_on:
- db
ports:
- 5000:5000
networks:
- backend
- frontend
volumes:
- ./app/src:/code
volumes:
db-data:
networks:
backend:
frontend:
And this is the log when starting the mysql container
2021-04-17 12:34:01+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 8.0.19-1debian10 started.
2021-04-17 12:34:01+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'
2021-04-17 12:34:01+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 8.0.19-1debian10 started.
2021-04-17T12:34:01.466444Z 0 [Warning] [MY-011070] [Server] 'Disabling symbolic links using --skip-symbolic-links (or equivalent) is the default. Consider not using this option as it' is deprecated and will be removed in a future release.
2021-04-17T12:34:01.466615Z 0 [System] [MY-010116] [Server] /usr/sbin/mysqld (mysqld 8.0.19) starting as process 1
2021-04-17T12:34:01.891144Z 0 [Warning] [MY-010068] [Server] CA certificate ca.pem is self signed.
2021-04-17T12:34:01.895163Z 0 [Warning] [MY-011810] [Server] Insecure configuration for --pid-file: Location '/var/run/mysqld' in the path is accessible to all OS users. Consider choosing a different directory.
2021-04-17T12:34:01.916128Z 0 [System] [MY-010931] [Server] /usr/sbin/mysqld: ready for connections. Version: '8.0.19' socket: '/var/run/mysqld/mysqld.sock' port: 3306 MySQL Community Server - GPL.
2021-04-17T12:34:02.051164Z 0 [System] [MY-011323] [Server] X Plugin ready for connections. Socket: '/var/run/mysqld/mysqlx.sock' bind-address: '::' port: 33060
It does not look like the init.sql file is being executed. Also from the mysql container CLI I can see that the 'init.sql' file has been copied.
# cd docker-entrypoint-initdb.d
# ls
init.sql
# mysql -u root -p
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| example |
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.01 sec)
I am quite new to Docker and Docker compose but I cannot figure out how to make this work.