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Acquire exclusive lock during db migration #50

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Acquire exclusive lock during db migration #50

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22 changes: 13 additions & 9 deletions alembic/env.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@
from logging.config import fileConfig

import alembic_postgresql_enum # noqa: F401
from sqlalchemy import pool
from sqlalchemy import pool, text
from sqlalchemy.engine import Connection
from sqlalchemy.ext.asyncio import async_engine_from_config

Expand All @@ -16,6 +16,15 @@

L = logging.getLogger("alembic.env")

# server settings to reduce possible service disruptions while running the migration
SERVER_SETTINGS = {
# Abort any statement that takes more than the specified amount of time
"statement_timeout": "6000",
# Abort any statement that waits longer than the specified amount of time while
# attempting to acquire a lock on a table, index, row, or other database object
"lock_timeout": "4000",
}

# this is the Alembic Config object, which provides
# access to the values within the .ini file in use.
config = context.config
Expand Down Expand Up @@ -87,25 +96,20 @@ def do_run_migrations(connection: Connection) -> None:
)

with context.begin_transaction():
# obtain an exclusive transaction-level advisory lock, waiting if necessary
connection.execute(text("SELECT pg_advisory_xact_lock(12345)"))
context.run_migrations()


async def run_async_migrations() -> None:
"""In this scenario we need to create an Engine
and associate a connection with the context.
"""
server_settings = {
# Abort any statement that takes more than the specified amount of time
"statement_timeout": "6000",
# Abort any statement that waits longer than the specified amount of time while
# attempting to acquire a lock on a table, index, row, or other database object
"lock_timeout": "4000",
}
connectable = async_engine_from_config(
config.get_section(config.config_ini_section, {}),
prefix="sqlalchemy.",
poolclass=pool.NullPool,
connect_args={"server_settings": server_settings},
connect_args={"server_settings": SERVER_SETTINGS},
)

async with connectable.connect() as connection:
Expand Down