fix(memory): concurrent writes silently drop entries — add file locking - #1726
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Two concurrent gateway sessions calling memory add/replace/remove simultaneously could both read the old state, apply their changes independently, and write — the last writer silently drops the first writer's entry. Fix: wrap each mutation in a file lock (fcntl.flock on a .lock file). Under the lock, re-read entries from disk to get the latest state, apply the mutation, then write. This ensures concurrent writers serialize properly. The lock uses a separate .lock file since the memory file itself is atomically replaced via os.replace() (can't flock a replaced file). Readers remain lock-free since atomic rename ensures they always see a complete file.
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…l-file-locking fix(memory): concurrent writes silently drop entries — add file locking
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…l-file-locking fix(memory): concurrent writes silently drop entries — add file locking
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…l-file-locking fix(memory): concurrent writes silently drop entries — add file locking
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…l-file-locking fix(memory): concurrent writes silently drop entries — add file locking
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…data loss save_to_disk() previously wrote self._entries_for(target) without re-reading the file, so a session's stale in-memory snapshot could overwrite entries from concurrent writers (other sessions, daemons, cron jobs, scripts) — issue NousResearch#85858. The fix re-reads the file under the already-held lock and merges on-disk entries with pending entries before writing. This preserves writes from external writers that don't use the memory tool's lock (the primary gap) and adds defense-in-depth for concurrent sessions (beyond PR NousResearch#1726's file locking). Merge strategy: union-where-session-wins — all pending entries preserved, on-disk entries not in pending appended, no duplicates. Conflicts (same entry modified by both) result in both versions present — safe, no data loss. Closes NousResearch#85858 Co-Authored-By: Hermes Agent <noreply@nousresearch.com>
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…l-file-locking fix(memory): concurrent writes silently drop entries — add file locking
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Summary
Two concurrent gateway sessions calling memory
add/replace/removesimultaneously could both read the old state, apply their changes independently, and write back. The last writer'sos.replace()would silently overwrite the first writer's changes.What changed
tools/memory_tool.py: All three mutating methods (add,replace,remove) now:fcntl.flockon a.lockfile)The lock uses a separate
.lockfile since the memory file itself is atomically replaced viaos.replace()(can'tflocka file that gets replaced). Readers remain lock-free — atomic rename ensures they always see a complete file.Added helpers:
_file_lock()context manager,_path_for(),_reload_target().Test plan
python -m pytest tests/ -n0 -q -k memory→ 108 passed, 2 skipped ✔