02e884552c
fix(database): resolve Alembic log to writable config dir, never crash on read-only FS
The default Alembic migration-log path ("alembic/alembic.log") resolved a
relative path against the installed package directory, then opened it for
writing with no error handling. On a read-only filesystem -- a standard
Kubernetes hardening posture (non-root pod / read-only root filesystem) and
the default for read-only container images -- this raised an unhandled
OSError ([Errno 30] Read-only file system) during startup, aborting the
FastAPI lifespan and putting the pod into CrashLoopBackOff.
Root cause: writing mutable runtime state into the package install location
(expected to be immutable). Every other writable Langflow artifact resolves
to config_dir/cache_dir; only the Alembic log resolved into site-packages.
Changes:
- Resolve relative alembic_log_file paths against the writable config_dir
(platformdirs user cache dir, always created on startup) instead of the
read-only package directory. Absolute paths and stdout mode are unchanged.
- Add _open_alembic_log_buffer(): create the parent dir, then fall back to
stdout (with a warning) if opening the diagnostic log raises OSError. This
is the actual crash point in _run_migrations, which runs before
initialize_alembic_log_file(), so guarding only the latter was insufficient.
- Make initialize_alembic_log_file() swallow OSError for the same reason.
The migration log is diagnostic-only and must never abort startup. Existing
deployments that set LANGFLOW_ALEMBIC_LOG_FILE or LANGFLOW_ALEMBIC_LOG_TO_STDOUT
are unaffected.
Fixes #11143
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