92 lines
5.1 KiB
Markdown
92 lines
5.1 KiB
Markdown
# RESUME POINT — cubefs FUSE <-> cube-server daemon durability wiring
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Saved: 2026-08-13 (user paused session; pick up from here).
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## GOAL (from task list)
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Make cubefs a real FUSE view of the running `cube-server` daemon's durable
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store, and prove a FUSE write lands in the daemon WAL and survives a daemon
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restart. (Cube-server is a pure command server — it does NOT mount FUSE
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itself; the FUSE view is a separate `cubefs-mount --socket` process, per the
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PDF/spec architecture.)
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## WHAT IS DONE (compiles + tests green)
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1. Raw-coordinate command family added to `cubesys/src/commands.rs` dispatch:
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`rawget <c> <z> <y> <x>`, `rawput <c> <z> <y> <x> <hex>`,
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`rawdel <c> <z> <y> <x>`, `rawkeys`, `rawscan <c> [z] [y]`.
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Helpers added: `parse_u8`, `hex_encode`, `hex_decode`.
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(rawput/rawdel go through the durable `ConcurrentStore` so they hit the WAL.)
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2. `cubefs/src/backend.rs` — new `DaemonBackend` implementing `CubeBackend`
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over the daemon Unix socket (lazy length-prefixed framing, duplicated from
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`cubesys::net` to keep cubefs free of a cubesys dep). Registered in
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`cubefs/src/lib.rs` (`pub mod backend; pub use backend::DaemonBackend;`).
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`DaemonBackend` is Clone (clones share socket path, reconnect lazily).
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3. `cubefs/src/bin/cubefs_mount.rs` — `--socket PATH` mounts against a live
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daemon; without `--socket` it falls back to an in-memory `HashBackend`.
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4. `cargo build --workspace` GREEN. `cargo test --workspace` GREEN.
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(Note: `DaemonBackend` is NOT yet exercised by any unit/integration test —
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only manual host verification below.)
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## WHAT IS PROVEN (host-level, same kernel/code path as the VM)
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A. Daemon durability + WAL replay: launched daemon with `--store`, `rawput`,
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killed it with `kill -9` (crash), relaunched same `--store` → `rawget`
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returned the written value; recovery log showed
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`wal_recovery: applied 1`. So the DAEMON half of the durability story works.
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B. Direct `rawput` from a Python client checkpoints to `store.json` (4-byte
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record appeared after the checkpoint interval). Confirmed daemon is alive,
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reachable, and durable on the host.
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## WHAT IS BROKEN (the open bug) — RESOLVED 2026-08-13 (commit 0300def)
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Two separate bugs hid behind the "FUSE write didn't reach the daemon" symptom:
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1. `--features mount` did not compile (E0308: `CubeFs<DaemonBackend>` vs
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`CubeFs<HashBackend>` are distinct types in the `match &socket`). The build
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failed silently, so the running binary was the IN-MEMORY build and
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`--socket` was ignored. FIXED in 8f9e7e0 by type-erasing the backend
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(`Box<dyn CubeBackend + Send + Sync>` + a forwarding impl).
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2. Even after (1), `DaemonBackend` round-tripped the WRONG layer: `put` stripped
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the record envelope to a bare body before `rawput`, but `get` returned that
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bare body as if it were a full record — so the FUSE read-back path
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(`get_record`) could not decode it, and the socket backend diverged from the
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in-memory backend. FIXED in 0300def: `DaemonBackend::put`/`get` now round-trip
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the FULL envelope (header+body) verbatim through rawput/rawget, matching the
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in-memory `HashBackend` exactly. This is now an enforced `./check daemon`
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integration test (spins up a live cube-server, runs the two `#[ignore]`d
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daemon-backed tests via `--ignored`).
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## GATE STATUS (2026-08-13)
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- `./check` (fmt+test+clippy -D warnings) GREEN.
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- `./check daemon` GREEN — proves the socket-backed record round-trip against a
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real daemon.
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- `./check mount` (live FUSE, root) — should be run before any future
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filesystem work; it is the only stage exercising the real kernel VFS path.
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## NEXT STEPS (current)
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1. Repeat the single-daemon + single-mount e2e INSIDE the VM to confirm the
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deployed artifact behaves identically (host proof is on the shared code path).
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NOTE: the VM's `cubefs.service` currently launches `cubefs-mount /cubefs
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--seed` WITHOUT `--socket`, so it is in-memory there too — update the unit to
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`cubefs-mount /cubefs --socket /run/cube/cube.sock --seed` (and ensure the
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daemon is ordered Before= cubefs.service) so the VM FUSE is durable.
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2. Add a `--features mount` build to the VM image's build step and to `./check`
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so the durable mount can't silently regress to in-memory again.
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3. Optionally surface `DaemonBackend::put` failures as FUSE EIO instead of
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eprintln-only (best-effort today, acceptable).
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## KEY FILES
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- /home/CUBELinux/CUBELinux-2/cubesys/src/commands.rs (raw* commands + helpers)
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- /home/CUBELinux/CUBELinux-2/cubefs/src/backend.rs (DaemonBackend — FIX HERE)
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- /home/CUBELinux/CUBELinux-2/cubefs/src/lib.rs (module export)
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- /home/CUBELinux/CUBELinux-2/cubefs/src/bin/cubefs_mount.rs (--socket wiring)
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- /home/CUBELinux/CUBELinux-2/cubestore/src/lib.rs (CubeStore::put_raw L358)
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- /home/CUBELinux/CUBELinux-2/cubefs/src/vfs.rs (CubeFs::write L392)
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## TEST HARNESS NOTES
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- Launch daemon/mount as `terminal(background=true)` so Hermes tracks them.
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- A `python3` one-shot client for rawget/rawput:
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socket connect, sendall(struct.pack('<I',len(payload))+payload),
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read 4-byte len then body.
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- Daemon flags used:
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`--socket S --store STORE.json --recovery-log REC.ndjson --allow-anonymous
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--checkpoint-ms 400 --wal-fsync-ms 30`
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