DB backups before migrations (#420)

* make backups before migrations

* database tests

* postgres db backup with location string

* ignore version in pg_dump and throw warning

* install latest pg_dump

* install latest

* pg update?

* remove test from github

* skip for postgres on github actions

cashu/core/migrations.py

@@ -1,8 +1,44 @@
+import os
 import re
+import time
 
 from loguru import logger
 
 from ..core.db import COCKROACH, POSTGRES, SQLITE, Database, table_with_schema
+from ..core.settings import settings
+
+
+async def backup_database(db: Database, version: int = 0) -> str:
+    # for postgres: use pg_dump
+    # for sqlite: use sqlite3
+
+    # skip backups if db_backup_path is None
+    # and if version is 0 (fresh database)
+    if not settings.db_backup_path or not version:
+        return ""
+
+    filename = f"backup_{db.name}_{int(time.time())}_v{version}"
+    try:
+        # create backup directory if it doesn't exist
+        os.makedirs(os.path.join(settings.db_backup_path), exist_ok=True)
+    except Exception as e:
+        logger.error(
+            f"Error creating backup directory: {e}. Run with BACKUP_DB_MIGRATION=False"
+            " to disable backups before database migrations."
+        )
+        raise e
+    filepath = os.path.join(settings.db_backup_path, filename)
+
+    if db.type == SQLITE:
+        filepath = f"{filepath}.sqlite3"
+        logger.info(f"Creating {db.type} backup of {db.name} db to {filepath}")
+        os.system(f"cp {db.path} {filepath}")
+    elif db.type in {POSTGRES, COCKROACH}:
+        filepath = f"{filepath}.dump"
+        logger.info(f"Creating {db.type} backup of {db.name} db to {filepath}")
+        os.system(f"pg_dump --dbname={db.db_location} --file={filepath}")
+
+    return filepath
 
 
 async def migrate_databases(db: Database, migrations_module):
@@ -19,6 +55,21 @@ async def migrate_databases(db: Database, migrations_module):
 
     async def run_migration(db, migrations_module):
         db_name = migrations_module.__name__.split(".")[-2]
+        # we first check whether any migration is needed and create a backup if so
+        migration_needed = False
+        for key, migrate in migrations_module.__dict__.items():
+            match = matcher.match(key)
+            if match:
+                version = int(match.group(1))
+                if version > current_versions.get(db_name, 0):
+                    migration_needed = True
+                    break
+        if migration_needed:
+            logger.debug(f"Creating backup of {db_name} db")
+            current_version = current_versions.get(db_name, 0)
+            await backup_database(db, current_version)
+
+        # then we run the migrations
         for key, migrate in migrations_module.__dict__.items():
             match = matcher.match(key)
             if match: