# RESUME POINT — cubefs FUSE <-> cube-server daemon durability wiring

Saved: 2026-08-13 (user paused session; pick up from here).

## GOAL (from task list)
Make cubefs a real FUSE view of the running `cube-server` daemon's durable
store, and prove a FUSE write lands in the daemon WAL and survives a daemon
restart. (Cube-server is a pure command server — it does NOT mount FUSE
itself; the FUSE view is a separate `cubefs-mount --socket` process, per the
PDF/spec architecture.)

## WHAT IS DONE (compiles + tests green)
1. Raw-coordinate command family added to `cubesys/src/commands.rs` dispatch:
   `rawget <c> <z> <y> <x>`, `rawput <c> <z> <y> <x> <hex>`,
   `rawdel <c> <z> <y> <x>`, `rawkeys`, `rawscan <c> [z] [y]`.
   Helpers added: `parse_u8`, `hex_encode`, `hex_decode`.
   (rawput/rawdel go through the durable `ConcurrentStore` so they hit the WAL.)
2. `cubefs/src/backend.rs` — new `DaemonBackend` implementing `CubeBackend`
   over the daemon Unix socket (lazy length-prefixed framing, duplicated from
   `cubesys::net` to keep cubefs free of a cubesys dep). Registered in
   `cubefs/src/lib.rs` (`pub mod backend; pub use backend::DaemonBackend;`).
   `DaemonBackend` is Clone (clones share socket path, reconnect lazily).
3. `cubefs/src/bin/cubefs_mount.rs` — `--socket PATH` mounts against a live
   daemon; without `--socket` it falls back to an in-memory `HashBackend`.
4. `cargo build --workspace` GREEN. `cargo test --workspace` GREEN.
   (Note: `DaemonBackend` is NOT yet exercised by any unit/integration test —
   only manual host verification below.)

## WHAT IS PROVEN (host-level, same kernel/code path as the VM)
A. Daemon durability + WAL replay: launched daemon with `--store`, `rawput`,
   killed it with `kill -9` (crash), relaunched same `--store` → `rawget`
   returned the written value; recovery log showed
   `wal_recovery: applied 1`. So the DAEMON half of the durability story works.
B. Direct `rawput` from a Python client checkpoints to `store.json` (4-byte
   record appeared after the checkpoint interval). Confirmed daemon is alive,
   reachable, and durable on the host.

## WHAT IS BROKEN (the open bug) — RESOLVED 2026-08-13
FUSE write did NOT reach the daemon. Root cause was NOT a connection-caching bug
(the earlier `RefCell` cache was already removed in favour of fresh-per-call
sockets). The real blocker: `cubefs-mount` requires `--features mount` to build,
and at that point it did NOT compile (E0308: `CubeFs<DaemonBackend>` vs
`CubeFs<HashBackend>` are different types in the `match &socket`). The build was
silently failing, so the running binary was the IN-MEMORY build and `--socket`
was ignored. Fixed by type-erasing the backend (`Box<dyn CubeBackend + Send +
Sync>` + a forwarding impl in cubestore). Now compiles and the FUSE mount reaches
the daemon; durability across a daemon `kill -9` is proven (see
VERIFICATION-cubefs-daemon.md, REVISED).

## NEXT STEPS (current)
1. Repeat the single-daemon + single-mount e2e INSIDE the VM to confirm the
   deployed artifact behaves identically (host proof is on the shared code path).
   NOTE: the VM's `cubefs.service` currently launches `cubefs-mount /cubefs
   --seed` WITHOUT `--socket`, so it is in-memory there too — update the unit to
   `cubefs-mount /cubefs --socket /run/cube/cube.sock --seed` (and ensure the
   daemon is ordered Before= cubefs.service) so the VM FUSE is durable.
2. Add a `--features mount` build to the VM image's build step and to `./check`
   so the durable mount can't silently regress to in-memory again.
3. Optionally surface `DaemonBackend::put` failures as FUSE EIO instead of
   eprintln-only (best-effort today, acceptable).

## KEY FILES
- /home/CUBELinux/CUBELinux-2/cubesys/src/commands.rs  (raw* commands + helpers)
- /home/CUBELinux/CUBELinux-2/cubefs/src/backend.rs     (DaemonBackend — FIX HERE)
- /home/CUBELinux/CUBELinux-2/cubefs/src/lib.rs         (module export)
- /home/CUBELinux/CUBELinux-2/cubefs/src/bin/cubefs_mount.rs (--socket wiring)
- /home/CUBELinux/CUBELinux-2/cubestore/src/lib.rs      (CubeStore::put_raw L358)
- /home/CUBELinux/CUBELinux-2/cubefs/src/vfs.rs         (CubeFs::write L392)

## TEST HARNESS NOTES
- Launch daemon/mount as `terminal(background=true)` so Hermes tracks them.
- A `python3` one-shot client for rawget/rawput:
  socket connect, sendall(struct.pack('<I',len(payload))+payload),
  read 4-byte len then body.
- Daemon flags used:
  `--socket S --store STORE.json --recovery-log REC.ndjson --allow-anonymous
   --checkpoint-ms 400 --wal-fsync-ms 30`