Allow environment variables for sqlalchemy uri

Is your feature request related to a problem? Please describe. When deploying to multiple environments we’ll like to be able to switch database connection. Currently we have one script fixing database sqlalchemy uri

Describe the solution you’d like Allow the use of environment variables as the value of sqlalchemy_uri property of Database

Describe alternatives you’ve considered None yet

Additional context We deploy using docker

Proposal

class Database(Model, AuditMixinNullable, ImportMixin):
....
allow_env_for_uri = Column(Boolean, default=False)
....
@property
def expanded_sqlalchemy_uri(self):
    if self.allow_env_for_uri:
        return os.path.expandvars(self.sqlalchemy_uri)
    return self.sqlalchemy_uri

@property
def sqlalchemy_uri_decrypted(self):
    conn = sqla.engine.url.make_url(self.expanded_sqlalchemy_uri)
    if custom_password_store:
        conn.password = custom_password_store(conn)
    else:
        conn.password = self.password
    return str(conn)

[mistercrunch]

@willbarrett, @gbrian is not referring to SQLALCHEMY_DATABASE_URI, but to the ones ones that we encrypt and store in the database.

I’m not sure how well that is documented, but with DB_CONNECTION_MUTATOR (a configuration hook) you can intercept the Database at runtime and do whatever, meaning you can put in bogus username/password in the database, and your DB_CONNECTION_MUTATOR function can read an env var and replace the proper value.

# in your superset_config.py
def DB_CONNECTION_MUTATOR(sqlalchemy_url, params, effective_username, security_manager, source):
    # Assuming that by convention your `sqlalchemy_url` references the env var you want to use
    sqlalchemy_url = os.environ.get(sqlalchemy_url)
    return sqlalchemy_url, params

[gbrian]

Thanks @willbarrett , @mistercrunch. I implemented differently as wanted to have a flag on database connection to set if ENV replacement should apply but reconsidering in favor of: DB_CONNECTION_MUTATOR and SQL_QUERY_MUTATOR