Google Cloud Platform - Spring Boot application connection issues with MySQL on Cloud SQL

So, I have a minimal Spring Boot Application which is supposed to connect to a MySQL database on GCP-Cloud SQL.

When I run my application on Google App Engine locally, it manages to connect to the remote MySQL database hosted on GCP. When I deploy the very same application on GAE standard, the application (apparently deployed successfully on GCP) doesn't manage to connect to the MySQL database.

This is exactly what my application.properties file looks like:

Giving a look in the GCP logging section I see the following critical error:

Uncaught exception from servlet\njava.lang.RuntimeException:
org.springframework.beans.factory.BeanCreationException: Error creating bean 
with name 'userRepository' defined in com.winery.backend.services.UserRepository 
defined in @EnableJpaRepositories declared onJpaRepositoriesRegistrar.
EnableJpaRepositoriesConfiguration: Cannot resolve reference to bean 'jpaMappingContext' 
while setting bean property 'mappingContext'; nested exception is
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jpaMappingContext':

and so on for a few thousand lines. userRepository happens to be my custom @Repository annotated interface.
Again, it works like a charm from local to cloud.

I've seen there are a few similar threads, but none of them actually provided a working solution.

When you are trying to connect using Cloud SQL's public IP address, you need to determine the public IP of your application and authorize it to connect to your instance. This won't apply for App Engine since it doesn't provide static IP address.

It's best practice for you use a Cloud SQL connector and include this dependency on your pom.xml:

<dependency>
    <groupId>com.google.cloud.sql</groupId>
    <artifactId>mysql-socket-factory-connector-j-8</artifactId>
    <version>1.1.0</version>
</dependency>

Then create a JDBC URL like this:

jdbc:mysql:///<DATABASE_NAME>?cloudSqlInstance=<INSTANCE_CONNECTION_NAME>&socketFactory=com.google.cloud.sql.mysql.SocketFactory&user=<MYSQL_USER_NAME>&password=<MYSQL_USER_PASSWORD>

> See the instance connection name on Cloud SQL in GCP console. The format should be "project-id:region:instance-name".

You can also improve this by creating a connection pool:

private static final String CLOUD_SQL_CONNECTION_NAME = System.getenv("CLOUD_SQL_CONNECTION_NAME");
private static final String DB_USER = System.getenv("DB_USER");
private static final String DB_PASS = System.getenv("DB_PASS");
private static final String DB_NAME = System.getenv("DB_NAME");

private DataSource createConnectionPool() {
    HikariConfig config = new HikariConfig();

    config.setJdbcUrl(String.format("jdbc:mysql:///%s", DB_NAME));
    config.setUsername(DB_USER); // e.g. "root", "postgres"
    config.setPassword(DB_PASS); // e.g. "my-password"
    config.addDataSourceProperty("socketFactory", "com.google.cloud.sql.mysql.SocketFactory");
    config.addDataSourceProperty("cloudSqlInstance", CLOUD_SQL_CONNECTION_NAME);
    DataSource pool = new HikariDataSource(config);
    return pool;
  }

To see the full context, see this guide.

Maybe it's the scope, if both (database and app) it's in the same host, maybe cant connect via https because cant resolve the host.

is it both in the same host/public IP?

if you are using docker:

• Try to use an alternative profile application-gcp.yml () a replace public_ip for docker service name (and be sure to create a network type bridge)

if you not:

• Try to use localhost instead of public IP