User Management backend - Base - DB migrations

.gitignore

@@ -16,3 +16,6 @@ _pycache_/
 
 # Python
 *.pyc
+*.orig
+*.pyc.*
+/.cache

Vagrantfile

@@ -1,21 +1,4 @@
-db_file_exists    = "test -f /vagrant/edison/db.sql"
-restore_db        = "sudo -u postgres psql edison < /vagrant/edison/db.sql"
-db_restored_msg   = "echo \"Database restored.\""
-db_not_exists_msg = "echo \"db.sql not exists.\""
-try_restore_db    = "bash -c '#{db_file_exists} && #{restore_db} && #{db_restored_msg} || #{db_not_exists_msg}'"
-save_db_data      = "sudo -u postgres pg_dump edison > /vagrant/edison/db.sql"
-
 Vagrant.configure("2") do |config|
-  config.trigger.before :destroy do |trigger|
-    trigger.info = "Saving database data inside synced folder..."
-    trigger.run_remote = {inline: "#{save_db_data}"}
-  end
-
-  config.trigger.after :up do |trigger|
-    trigger.info = "Trying to restore database from /vagrant/edison/db.sql..."
-    trigger.run_remote = {inline: "#{try_restore_db}"}
-  end
-
   config.vm.box = "ubuntu/bionic64"
   config.vm.provision :shell, path: "setup.sh"
   config.vm.network "private_network", type: "dhcp"

edison/app.py

@@ -2,10 +2,12 @@
 import edison.models
 
 from flask import render_template
+from flask_migrate import Migrate
 
 
 app = edison.app
 db = edison.db
+migrate = Migrate(app, db)
 
 # Creates all tables defined in the database models and the only ones that are not created yet.
 # If there's any change in the database models you should perform a migration to apply this change in the database itself.

edison/migrations/README

@@ -0,0 +1,43 @@
+This information and more can be found at - https://flask-migrate.readthedocs.io/
+
+The content of edison/migrations folder is auto-created by Flask-Migrate extension.
+Flask-Migrate is an extension that configures Alembic in the proper way to work with Flask and Flask-SQLAlchemy application.
+In terms of the actual database migrations, everything is handled by Alembic so you get exactly the same functionality.
+
+FAQ
+
+1.  Why to use database migrations ?
+
+    Database migrations basically track granular changes to our database schema.
+    These granular changes are typically reflected as separate scripted files.
+    Every time we make a change to our database schema we should perform a migration.
+    This migration creates a new file that describes our current database schema inside edison/migrations/versions.
+    That way we could downgrade or upgrade our database schema to different versions if needed.
+
+2.  When to use database migration ?
+
+    You should perform a database migration on any change you make to the database models.
+    When a migration is performed it applies those changes to the database itself.
+
+3.  How to perform a database migration ?
+
+    -   First, we need to initialize our migrations folder (If it's not already created).
+        To do so you should first make sure to define the Flask app path inside FLASK_APP environment variable,
+        and then execute the following command:
+            flask db init
+        Executing this command will create the migrations folder inside /home/vagrant/migrations,
+        which is not good for us because we want it to be created in our project directory.
+        So we simply need to add the directory flag:
+            flask db init --directory /vagrant/edison/migrations
+
+    -   Then, we should perform the migration as follow:
+            flask db migrate -m "<migration message>" --directory /vagrant/edison/migrations
+        It will create a new version file of the database schema inside edison/migrations/versions.
+
+    -   Last, we need to apply this migration on the database itself by executing:
+            flask db upgrade --directory /vagrant/edison/migrations.
+
+4.  How to downgrade the database schema ?
+
+    Simply execute the following command:
+        flask db downgrade --directory /vagrant/edison/migrations.

edison/migrations/alembic.ini

@@ -0,0 +1,45 @@
+# A generic, single database configuration.
+
+[alembic]
+# template used to generate migration files
+# file_template = %%(rev)s_%%(slug)s
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S

edison/migrations/env.py

@@ -0,0 +1,96 @@
+from __future__ import with_statement
+
+import logging
+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+fileConfig(config.config_file_name)
+logger = logging.getLogger('alembic.env')
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+from flask import current_app
+config.set_main_option(
+    'sqlalchemy.url',
+    str(current_app.extensions['migrate'].db.engine.url).replace('%', '%%'))
+target_metadata = current_app.extensions['migrate'].db.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline():
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url, target_metadata=target_metadata, literal_binds=True
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online():
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+
+    # this callback is used to prevent an auto-migration from being generated
+    # when there are no changes to the schema
+    # reference: http://alembic.zzzcomputing.com/en/latest/cookbook.html
+    def process_revision_directives(context, revision, directives):
+        if getattr(config.cmd_opts, 'autogenerate', False):
+            script = directives[0]
+            if script.upgrade_ops.is_empty():
+                directives[:] = []
+                logger.info('No changes in schema detected.')
+
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section),
+        prefix='sqlalchemy.',
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+            process_revision_directives=process_revision_directives,
+            **current_app.extensions['migrate'].configure_args
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

edison/migrations/script.py.mako

@@ -0,0 +1,24 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+branch_labels = ${repr(branch_labels)}
+depends_on = ${repr(depends_on)}
+
+
+def upgrade():
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade():
+    ${downgrades if downgrades else "pass"}

requirements.txt

@@ -1,3 +1,5 @@
 Flask==1.1.1
 flask-sqlalchemy==2.4.1
 psycopg2-binary==2.8.5
+Flask-Migrate==2.5.3
+pytest==3.3.2

tests/conftest.py

@@ -0,0 +1,33 @@
+import pytest
+import psycopg2
+
+
+@pytest.fixture
+def db_connection():
+    connection = psycopg2.connect(
+        host="localhost",
+        database="edison",
+        user="postgres",
+        password="edison")
+
+    yield connection
+    connection.close()
+
+@pytest.fixture
+def cursor(db_connection):
+    cursor = db_connection.cursor()
+    yield cursor
+    db_connection.rollback()
+
+@pytest.fixture
+def build_users_table(cursor):
+    cursor.execute("""
+    INSERT INTO users (username) VALUES (%s);
+    """,
+    ("ahinoam",))
+
+@pytest.fixture
+def reset_users_primary_key(cursor):
+    cursor.execute("""
+    ALTER SEQUENCE users_id_seq RESTART;
+    """)

tests/db_test.py

@@ -0,0 +1,17 @@
+import pytest
+import psycopg2
+
+
+def test_users_table_rows_count(cursor, build_users_table):
+    cursor.execute("""
+    SELECT * FROM users;
+    """)
+    result = cursor.fetchall()
+    assert len(result) == 1
+
+def test_username(cursor, build_users_table):
+    cursor.execute("""
+    SELECT username FROM users;
+    """)
+    result = cursor.fetchone()
+    assert result[0] == "ahinoam"