Add initial Alembic migrations.

alembic.ini

@@ -0,0 +1,59 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts
+script_location = %(here)s/mediagoblin/db/migrations
+
+# template used to generate migration files
+# file_template = %%(rev)s_%%(slug)s
+
+# max length of characters to apply to the
+# "slug" field
+#truncate_slug_length = 40
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+# set to 'true' to allow .pyc and .pyo files without
+# a source .py file to be detected as revisions in the
+# versions/ directory
+# sourceless = false
+
+sqlalchemy.url = sqlite:///mediagoblin.db
+
+
+# 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

mediagoblin/db/migration_tools.py

@@ -16,6 +16,12 @@
 
 from __future__ import unicode_literals
 
+import os
+
+from alembic import command
+from alembic.config import Config
+
+from mediagoblin.db.base import Base
 from mediagoblin.tools.common import simple_printer
 from sqlalchemy import Table
 from sqlalchemy.sql import select
@@ -24,6 +30,29 @@ class TableAlreadyExists(Exception):
     pass
 
 
+class AlembicMigrationManager(object):
+
+    def __init__(self, session):
+        root_dir = os.path.abspath(os.path.dirname(os.path.dirname(
+            os.path.dirname(__file__))))
+        alembic_cfg_path = os.path.join(root_dir, 'alembic.ini')
+        self.alembic_cfg = Config(alembic_cfg_path)
+        self.session = session
+
+    def init_tables(self):
+        Base.metadata.create_all(self.session.bind)
+        # load the Alembic configuration and generate the
+        # version table, "stamping" it with the most recent rev:
+        command.stamp(self.alembic_cfg, 'head')
+
+    def init_or_migrate(self, version='head'):
+        # TODO(berker): Check this
+        # http://alembic.readthedocs.org/en/latest/api.html#alembic.migration.MigrationContext
+        # current_rev = context.get_current_revision()
+        # Call self.init_tables() first if current_rev is None?
+        command.upgrade(self.alembic_cfg, version)
+
+
 class MigrationManager(object):
     """
     Migration handling tool.

mediagoblin/db/migrations/README

@@ -0,0 +1 @@
+Generic single-database configuration.

mediagoblin/db/migrations/env.py

@@ -0,0 +1,71 @@
+from __future__ import with_statement
+from alembic import context
+from sqlalchemy import engine_from_config, pool
+from logging.config import fileConfig
+
+# 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)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+target_metadata = None
+
+# 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)
+
+    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.
+
+    """
+    engine = engine_from_config(
+                config.get_section(config.config_ini_section),
+                prefix='sqlalchemy.',
+                poolclass=pool.NullPool)
+
+    connection = engine.connect()
+    context.configure(
+                connection=connection,
+                target_metadata=target_metadata
+                )
+
+    try:
+        with context.begin_transaction():
+            context.run_migrations()
+    finally:
+        connection.close()
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()
+

mediagoblin/db/migrations/script.py.mako

@@ -0,0 +1,22 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision}
+Create Date: ${create_date}
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+def upgrade():
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade():
+    ${downgrades if downgrades else "pass"}

mediagoblin/gmg_commands/dbupdate.py

@@ -106,6 +106,13 @@ forgotten to add it? ({1})'.format(plugin, exc))
     return managed_dbdata
 
 
+def run_alembic_migrations(db, app_config, global_config):
+    from mediagoblin.db.migration_tools import AlembicMigrationManager
+    Session = sessionmaker(bind=db.engine)
+    manager = AlembicMigrationManager(Session())
+    manager.init_or_migrate()
+
+
 def run_dbupdate(app_config, global_config):
     """
     Initialize or migrate the database as specified by the config file.
@@ -118,6 +125,7 @@ def run_dbupdate(app_config, global_config):
     db = setup_connection_and_db_from_config(app_config, migrations=True)
     # Run the migrations
     run_all_migrations(db, app_config, global_config)
+    run_alembic_migrations(db, app_config, global_config)
 
 
 def run_all_migrations(db, app_config, global_config):

setup.py

@@ -57,6 +57,7 @@ install_requires = [
     # TODO(berker): Upgrade to 19.2
     # See https://github.com/benoitc/gunicorn/issues/830
     'gunicorn==19',
+    'alembic==0.6.6',
     'python-dateutil',
     'wtforms',
     'py-bcrypt',