From: CaselIT Date: Fri, 26 Feb 2021 20:21:52 +0000 (+0100) Subject: Add async template to Alembic X-Git-Tag: rel_1_5_6~4 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8196af9a8622bc97d4c29c22f2a5b309fd9fa857;p=thirdparty%2Fsqlalchemy%2Falembic.git Add async template to Alembic Add async template to Alembic to bootstrap environments that use async DBAPI. Updated the cookbook to include a migration guide on how to adapt an existing enviroment for use with DBAPI drivers. Fixes: #805 Change-Id: I5281b95ce8d48a31591902116c746ef9ae3fd7af --- diff --git a/alembic/templates/async/README b/alembic/templates/async/README new file mode 100644 index 00000000..e0d0858f --- /dev/null +++ b/alembic/templates/async/README @@ -0,0 +1 @@ +Generic single-database configuration with an async dbapi. \ No newline at end of file diff --git a/alembic/templates/async/alembic.ini.mako b/alembic/templates/async/alembic.ini.mako new file mode 100644 index 00000000..bf7e5d1c --- /dev/null +++ b/alembic/templates/async/alembic.ini.mako @@ -0,0 +1,89 @@ +# A generic, single database configuration. + +[alembic] +# path to migration scripts +script_location = ${script_location} + +# template used to generate migration files +# file_template = %%(rev)s_%%(slug)s + +# sys.path path, will be prepended to sys.path if present. +# defaults to the current working directory. +prepend_sys_path = . + +# timezone to use when rendering the date +# within the migration file as well as the filename. +# string value is passed to dateutil.tz.gettz() +# leave blank for localtime +# timezone = + +# 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 + +# version location specification; this defaults +# to ${script_location}/versions. When using multiple version +# directories, initial revisions must be specified with --version-path +# version_locations = %(here)s/bar %(here)s/bat ${script_location}/versions + +# the output encoding used when revision files +# are written from script.py.mako +# output_encoding = utf-8 + +sqlalchemy.url = driver://user:pass@localhost/dbname + + +[post_write_hooks] +# post_write_hooks defines scripts or Python functions that are run +# on newly generated revision scripts. See the documentation for further +# detail and examples + +# format using "black" - use the console_scripts runner, against the "black" entrypoint +# hooks=black +# black.type=console_scripts +# black.entrypoint=black +# black.options=-l 79 + +# 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 diff --git a/alembic/templates/async/env.py b/alembic/templates/async/env.py new file mode 100644 index 00000000..ade3dc40 --- /dev/null +++ b/alembic/templates/async/env.py @@ -0,0 +1,84 @@ +import asyncio +from logging.config import fileConfig + +from sqlalchemy import engine_from_config +from sqlalchemy import pool +from sqlalchemy.ext.asyncio import AsyncEngine + +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) + +# 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, + literal_binds=True, + dialect_opts={"paramstyle": "named"}, + ) + + with context.begin_transaction(): + context.run_migrations() + + +def do_run_migrations(connection): + context.configure(connection=connection, target_metadata=target_metadata) + + with context.begin_transaction(): + context.run_migrations() + + +async 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. + + """ + connectable = AsyncEngine( + engine_from_config( + config.get_section(config.config_ini_section), + prefix="sqlalchemy.", + poolclass=pool.NullPool, + future=True, + ) + ) + + async with connectable.connect() as connection: + await connection.run_sync(do_run_migrations) + + +if context.is_offline_mode(): + run_migrations_offline() +else: + asyncio.run(run_migrations_online()) diff --git a/alembic/templates/async/script.py.mako b/alembic/templates/async/script.py.mako new file mode 100644 index 00000000..2c015630 --- /dev/null +++ b/alembic/templates/async/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"} diff --git a/docs/build/cookbook.rst b/docs/build/cookbook.rst index 2f409d91..d5230626 100644 --- a/docs/build/cookbook.rst +++ b/docs/build/cookbook.rst @@ -1497,3 +1497,61 @@ example of applying this to the "message" field is as follows: def downgrade(): ${downgrades if downgrades else "pass"} + +Using Asyncio with Alembic +========================== + +SQLAlchemy version 1.4 introduced experimental support for asyncio, allowing +use of most of its interface from async applications. Alembic currently does +not provide an async api directly, but it can use an use SQLAlchemy Async +engine to run the migrations and autogenerate. + +New configurations can use the template "async" to bootstrap an environment which +can be used with async DBAPI like asyncpg, running the command:: + + alembic init -t async + +Existing configurations can be updated to use an async DBAPI by updating the ``env.py`` +file that's used by Alembic to start its operations. In particular only +``run_migrations_online`` will need to be updated to be something like the example below:: + + import asyncio + + # ... no change required to the rest of the code + + + def do_run_migrations(connection): + context.configure(connection=connection, target_metadata=target_metadata) + + with context.begin_transaction(): + context.run_migrations() + + + async 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. + + """ + connectable = AsyncEngine( + engine_from_config( + config.get_section(config.config_ini_section), + prefix="sqlalchemy.", + poolclass=pool.NullPool, + future=True, + ) + ) + + async with connectable.connect() as connection: + await connection.run_sync(do_run_migrations) + + + if context.is_offline_mode(): + run_migrations_offline() + else: + asyncio.run(run_migrations_online()) + +An asnyc application can also interact with the Alembic api directly by using +the SQLAlchemy ``run_sync`` method to adapt the non-async api of Alembic to +an async consumer. diff --git a/docs/build/unreleased/805.rst b/docs/build/unreleased/805.rst new file mode 100644 index 00000000..23fc20c5 --- /dev/null +++ b/docs/build/unreleased/805.rst @@ -0,0 +1,7 @@ +.. change:: + :tags: template + :ticket: 805 + + Add async template to Alembic to bootstrap environments that use + async DBAPI. Updated the cookbook to include a migration guide + on how to adapt an existing enviroment for use with DBAPI drivers.