fix(mysql): Add seed support in MySQL (#552)

Ref #541.
New capability of "seeding" a db container using image's support for
/docker-entrypoint-initdb.d/ folder.

Using the "transferable" system, borrowed from Kafka. 

Updates DbContainer to have a new (NOOP-default) `_transfer_seed()`
method, run after `_start()` and before `_connect()`, to allow the
folder transfer.

Currently implemented only in MySQL, but extensible to others that use
the `/docker-entrypoint-initdb.d/` system.

---------

Co-authored-by: Jb DOYON <jb@jiby.tech>

Author: OverkillGuy

core/testcontainers/core/generic.py

@@ -70,8 +70,12 @@ def _create_connection_url(
     def start(self) -> "DbContainer":
         self._configure()
         super().start()
+        self._transfer_seed()
         self._connect()
         return self
 
     def _configure(self) -> None:
         raise NotImplementedError
+
+    def _transfer_seed(self) -> None:
+        pass

modules/mysql/testcontainers/mysql/__init__.py

@@ -11,7 +11,10 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 import re
+import tarfile
+from io import BytesIO
 from os import environ
+from pathlib import Path
 from typing import Optional
 
 from testcontainers.core.generic import DbContainer
@@ -40,6 +43,22 @@ class MySqlContainer(DbContainer):
             ...     with engine.begin() as connection:
             ...         result = connection.execute(sqlalchemy.text("select version()"))
             ...         version, = result.fetchone()
+
+        The optional :code:`seed` parameter enables arbitrary SQL files to be loaded.
+        This is perfect for schema and sample data. This works by mounting the seed to
+        `/docker-entrypoint-initdb./d`, which containerized MySQL are set up to load
+        automatically.
+
+        .. doctest::
+            >>> import sqlalchemy
+            >>> from testcontainers.mysql import MySqlContainer
+            >>> with MySqlContainer(seed="../../tests/seeds/") as mysql:
+            ...     engine = sqlalchemy.create_engine(mysql.get_connection_url())
+            ...     with engine.begin() as connection:
+            ...         query = "select * from stuff"  # Can now rely on schema/data
+            ...         result = connection.execute(sqlalchemy.text(query))
+            ...         first_stuff, = result.fetchone()
+
     """
 
     def __init__(
@@ -50,6 +69,7 @@ def __init__(
         password: Optional[str] = None,
         dbname: Optional[str] = None,
         port: int = 3306,
+        seed: Optional[str] = None,
         **kwargs,
     ) -> None:
         raise_for_deprecated_parameter(kwargs, "MYSQL_USER", "username")
@@ -67,6 +87,7 @@ def __init__(
 
         if self.username == "root":
             self.root_password = self.password
+        self.seed = seed
 
     def _configure(self) -> None:
         self.with_env("MYSQL_ROOT_PASSWORD", self.root_password)
@@ -86,3 +107,14 @@ def get_connection_url(self) -> str:
         return super()._create_connection_url(
             dialect="mysql+pymysql", username=self.username, password=self.password, dbname=self.dbname, port=self.port
         )
+
+    def _transfer_seed(self) -> None:
+        if self.seed is None:
+            return
+        src_path = Path(self.seed)
+        dest_path = "/docker-entrypoint-initdb.d/"
+        with BytesIO() as archive, tarfile.TarFile(fileobj=archive, mode="w") as tar:
+            for filename in src_path.iterdir():
+                tar.add(filename.absolute(), arcname=filename.relative_to(src_path))
+            archive.seek(0)
+            self.get_wrapped_container().put_archive(dest_path, archive)

modules/mysql/tests/seeds/01-schema.sql

@@ -0,0 +1,6 @@
+-- Sample SQL schema, no data
+CREATE TABLE `stuff` (
+ `id` mediumint NOT NULL AUTO_INCREMENT,
+ `name` VARCHAR(63) NOT NULL,
+ PRIMARY KEY (`id`)
+);

modules/mysql/tests/seeds/02-seeds.sql

@@ -0,0 +1,3 @@
+-- Sample data, to be loaded after the schema
+INSERT INTO stuff (name)
+VALUES ("foo"), ("bar"), ("qux"), ("frob");

modules/mysql/tests/test_mysql.py

@@ -1,3 +1,4 @@
+from pathlib import Path
 import re
 from unittest import mock
 
@@ -29,6 +30,18 @@ def test_docker_run_legacy_mysql():
                 assert row[0].startswith("5.7.44")
 
 
+@pytest.mark.skipif(is_arm(), reason="mysql container not available for ARM")
+def test_docker_run_mysql_8_seed():
+    # Avoid pytest CWD path issues
+    SEEDS_PATH = (Path(__file__).parent / "seeds").absolute()
+    config = MySqlContainer("mysql:8", seed=SEEDS_PATH)
+    with config as mysql:
+        engine = sqlalchemy.create_engine(mysql.get_connection_url())
+        with engine.begin() as connection:
+            result = connection.execute(sqlalchemy.text("select * from stuff"))
+            assert len(list(result)) == 4, "Should have gotten all the stuff"
+
+
 @pytest.mark.parametrize("version", ["11.3.2", "10.11.7"])
 def test_docker_run_mariadb(version: str):
     with MySqlContainer(f"mariadb:{version}") as mariadb: