ObjectStoreMixin.save() calls len(self) -> len(self.data) immediately.
StatsStore never set self.data in __init__, so any call to save() before
add() raised AttributeError: 'StatsStore' object has no attribute 'data',
crashing APRSDStatsStoreThread on the first tick if the path where
enable_save is True is hit.
Tests updated/added (tests/threads/test_stats.py):
- test_init: now asserts data exists and equals {} (was asserting absence)
- test_save_before_add_does_not_raise: regression guard — save() must not
raise AttributeError when called before add()
Closes#241
Add stats_store_interval config option to control how frequently
the statsstore.json file is written to disk. Default remains 10
seconds for backward compatibility.
This allows reducing disk I/O in production deployments and
can help avoid potential file corruption issues when external
processes read the stats file.
hemna