Remove Firecracker-specific MMDS metadata fetching and metrics host
module. CH communicates with the guest purely over TAP networking,
so MMDS (Firecracker's metadata service via MMDS address) is no longer
needed.
- Remove src/host/ module (mmds.rs, metrics.rs)
- Remove reqwest dependency (was only used for MMDS HTTP calls)
- Remove --isnotfc CLI flag (no longer dual-mode)
- Simplify health endpoint and init handler
- Update state management for CH snapshot lifecycle
- Bump version to 0.3.0
The /init handler's default_user mutation cloned the Defaults struct,
mutated the clone, then dropped it — the actual state was never updated.
This caused processes to always run as "root" regardless of the user
set via POST /init. Additionally, default_workdir was accepted in the
init request but never applied.
Wrap user and workdir fields in RwLock with accessor methods so mutations
propagate correctly through the shared AppState.
Three issues fixed:
1. Memory metrics read host-side VmRSS of the Firecracker process,
which includes guest page cache and never decreases. Replaced
readMemRSS(fcPID) with readEnvdMemUsed(client) that queries
envd's /metrics endpoint for guest-side total - MemAvailable.
This matches neofetch and reflects actual process memory.
2. Added Firecracker balloon device (deflate_on_oom, 5s stats) and
envd-side periodic page cache reclaimer (drop_caches when >80%
used). Reclaimer is gated by snapshot_in_progress flag with
sync() before freeze to prevent memory corruption during pause.
3. Sampling interval 500ms → 1s, ring buffer capacities adjusted
to maintain same time windows. Reduces per-host HTTP load from
240 calls/sec to 120 calls/sec at 120 capsules.
Also: maxDiffGenerations 8 → 1 (merge every re-pause since UFFD
lazy-loads anyway), envd mem_used formula uses total - available.
