ben.stull
9462423642
Forward-only, fail-stop, advisory-lock-guarded psycopg runner; migration 0001 lays the account/auth_code/storefront/membership schema. Tests prove migrate-from-empty and idempotent re-migrate (INV-1 partial) and the INV-4 many-capable shape. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
88 lines
3.4 KiB
Python
88 lines
3.4 KiB
Python
"""PostgreSQL access (psycopg 3) + a forward-only migration runner.
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Standard wiggleverse stack ported to Postgres (SD-0001 D-7): a connection pool and
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numbered forward-only `.sql` migrations applied in filename order, recorded in
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`schema_migrations`. No ORM. The runner is fail-stop (a failing migration aborts and
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records nothing, so it retries next boot) and guarded by a session advisory lock so
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two booting processes never double-apply (INV-7).
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"""
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from __future__ import annotations
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from pathlib import Path
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import psycopg
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from psycopg_pool import ConnectionPool
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from . import config
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# app/platform/db.py -> parents[2] is backend/, where migrations/ lives.
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MIGRATIONS_DIR = Path(__file__).resolve().parents[2] / "migrations"
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# Arbitrary fixed key for the migration advisory lock (INV-7 concurrency guard).
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_MIGRATION_LOCK_KEY = 0x6563_6F6D_6D31 # "ecomm1"
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def open_pool(dsn: str | None = None, *, min_size: int = 1, max_size: int = 5) -> ConnectionPool:
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"""Open a small connection pool against the configured database."""
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pool = ConnectionPool(dsn or config.database_url(), min_size=min_size, max_size=max_size, open=False)
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pool.open()
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pool.wait()
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return pool
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def _migration_files(migrations_dir: Path) -> list[Path]:
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return sorted(migrations_dir.glob("*.sql"))
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def migrate(conn: psycopg.Connection, migrations_dir: Path = MIGRATIONS_DIR) -> list[str]:
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"""Apply unapplied migrations in filename order; return the names applied.
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Forward-only and fail-stop: each migration runs with its `schema_migrations`
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insert in one transaction, so a failure records nothing and is retried next time.
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A session advisory lock serializes concurrent migrators (INV-7).
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"""
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conn.execute("SELECT pg_advisory_lock(%s)", (_MIGRATION_LOCK_KEY,))
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try:
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conn.execute(
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"CREATE TABLE IF NOT EXISTS schema_migrations ("
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" filename TEXT PRIMARY KEY,"
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" applied_at TIMESTAMPTZ NOT NULL DEFAULT now())"
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)
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conn.commit()
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applied = {
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r[0] for r in conn.execute("SELECT filename FROM schema_migrations").fetchall()
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}
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ran: list[str] = []
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for path in _migration_files(migrations_dir):
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if path.name in applied:
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continue
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try:
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conn.execute(path.read_text()) # whole file; no params -> multi-statement
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conn.execute(
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"INSERT INTO schema_migrations (filename) VALUES (%s)", (path.name,)
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)
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conn.commit()
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except Exception:
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conn.rollback()
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raise
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ran.append(path.name)
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return ran
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finally:
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conn.execute("SELECT pg_advisory_unlock(%s)", (_MIGRATION_LOCK_KEY,))
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conn.commit()
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def pending_migrations(conn: psycopg.Connection, migrations_dir: Path = MIGRATIONS_DIR) -> list[str]:
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"""Migration filenames present on disk but not yet recorded as applied.
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Used by /healthz to report migration currency (§6.4). Returns all on-disk
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migrations if the tracking table does not exist yet.
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"""
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exists = conn.execute("SELECT to_regclass('public.schema_migrations')").fetchone()[0]
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if exists is None:
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return [p.name for p in _migration_files(migrations_dir)]
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applied = {
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r[0] for r in conn.execute("SELECT filename FROM schema_migrations").fetchall()
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}
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return [p.name for p in _migration_files(migrations_dir) if p.name not in applied]
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