OpenSlides/openslides/utils/schema_version.py
2019-09-02 08:09:28 +02:00

86 lines
2.9 KiB
Python

from typing import Optional
from django.db.models import Max
from mypy_extensions import TypedDict
from . import logging
logger = logging.getLogger(__name__)
SchemaVersion = TypedDict("SchemaVersion", {"migration": int, "config": int, "db": str})
class SchemaVersionHandler:
"""
Handler for the schema version of this running OpenSlides instance.
What is a schema version? This is an indictor of the current schema of the data
in the database, config variables, and the database itself. E.b. with a migration,
new/changed config variables or with a database change, the schema of the data changes.
To detect this is needed to reset the cache, so it does not hold any old data. This
affects the server cache, but also the client uses this technique to flush the cache.
Get the current schema with `get`. The schema version is built just once. After a change
in the schema, all workers needs a restart!
"""
def __init__(self) -> None:
self._schema_version: Optional[SchemaVersion] = None
def get(self) -> SchemaVersion:
if self._schema_version is not None:
return self._schema_version
from django.db.migrations.recorder import MigrationRecorder
migration = MigrationRecorder.Migration.objects.aggregate(Max("id"))["id__max"]
from openslides.core.config import ConfigStore
try:
config = ConfigStore.objects.get(key="config_version").value
except ConfigStore.DoesNotExist:
config = 0
try:
db = ConfigStore.objects.get(key="db_id").value
except ConfigStore.DoesNotExist:
db = ""
self._schema_version = {"migration": migration, "config": config, "db": db}
return self._schema_version
def compare(self, other: Optional[SchemaVersion]) -> bool:
current = self.get()
if not other:
logger.info("No old schema version")
return False
equal = True
if current["db"] != other["db"]:
other_db = other["db"] or "<empty>"
logger.info(f"DB changed from {other_db} to {current['db']}")
equal = False
if current["config"] != other["config"]:
other_config = other["config"] or "<empty>"
logger.info(f"Config changed from {other_config} to {current['config']}")
equal = False
if current["migration"] != other["migration"]:
logger.info(
f"Migration changed from {other['migration']} to {current['migration']}"
)
equal = False
return equal
def log_current(self) -> None:
current = self.get()
logger.info(
f"""Schema version:
DB: {current["db"]}
migration: {current["migration"]}
config: {current["config"]}"""
)
schema_version_handler = SchemaVersionHandler()