Every RPC handler that answers a hit-or-miss question now increments
lock-free atomic counters. The GetMetrics RPC (0x13) returns a JSON
snapshot of every counter; the new claw-cargo peer-metrics CLI
prints hit rates, byte volumes, and counter uptime.
Placement engines can now poll these across the fleet to bias runner
scheduling toward whichever node has the warmest cache for a given
repo/tag combination.
## New module: cluster/metrics.rs (268 lines)
Types:
- CacheMetrics — atomic counters, all AtomicU64, Relaxed ordering
(metrics are advisory, not consistency-critical)
- MetricsReply — JSON snapshot returned by GetMetrics
Public API:
- CacheMetrics::new() — timestamped start, all counters at 0
- record_get_ref_hit / _miss
- record_get_tag_hit / _miss
- record_blob_get_bytes / record_blob_put_bytes
- record_get_chunk_hit / _miss
- record_has_chunk_hit / _miss
- snapshot() — atomic-load every field into a MetricsReply
MetricsReply derived helpers:
- get_ref_hit_rate() / get_tag_hit_rate() / has_chunk_hit_rate() —
Option<f64> so 0/0 returns None instead of NaN
## RPC method
- GetMetrics (0x13): payload = empty; reply = JSON MetricsReply
Wire-level instrumentation added to RpcRouter dispatch:
- GetRef → record_get_ref_hit / _miss
- GetTag → record_get_tag_hit / _miss
- BlobGet → record_blob_get_bytes (on hit)
- BlobPut → record_blob_put_bytes
- HasChunk → record_has_chunk_hit / _miss
- GetChunk → record_get_chunk_hit + record_blob_get_bytes on hit
/ record_get_chunk_miss
RpcRouter grows Arc<CacheMetrics> unconditionally — every router has
metrics, so a fresh node with no traffic still returns a valid
snapshot with all zeros + started_unix.
Streaming variants (BlobPutStream / BlobGetStream) don't yet track
byte counts — they'd require plumbing the count out of put_stream /
stream_to. Follow-on if it turns out to matter for placement.
## Client helper + CLI
- call_get_metrics(&conn) → Result<MetricsReply>
- claw-cargo peer-metrics [--peer ...] [--peer-addr ...] [--tls-dir ...]
Fetches + pretty-prints:
counter uptime: 42s
GetRef hits/misses: 123 / 45
hit rate: 73.21%
GetTag hits/misses: 8 / 2
hit rate: 80.00%
HasChunk hits/miss: 512 / 88
hit rate: 85.33%
GetChunk hits/miss: 47 / 12
Blob GET bytes: 1.23 GiB
Blob PUT bytes: 3.45 GiB
human_bytes() helper picks GiB / MiB / KiB / B based on magnitude.
Subcommand count now 9: build / prefetch / status / fingerprint /
pin / unpin / list-tags / prewarm / peer-metrics.
## Tests (13 new, all real filesystem / real QUIC — no mocks)
CacheMetrics (6):
- new_starts_all_counters_at_zero_except_timestamp
- recorders_increment_the_right_field (every recorder × 1-2 counts)
- hit_rates_none_when_zero_events (avoids 0/0 NaN)
- hit_rates_compute_correctly (3 hits / 1 miss → 75%)
- snapshot_round_trips_through_json
- snapshots_across_threads_are_consistent_up_to_relaxed_ordering
(8 threads × 1000 increments → exactly 8000)
RPC integration (7):
- phase_5g_method_byte_encoding
- get_metrics_returns_empty_snapshot_before_any_activity
- get_ref_records_hit_and_miss_counters (2 hits + 1 miss)
- get_tag_records_hit_and_miss_counters
- blob_get_and_blob_put_record_byte_counts
- has_chunk_and_get_chunk_record_hit_miss_counters
- **end_to_end_get_metrics_over_real_quic** — seed activity locally,
fire GetRef/GetTag/BlobGet dispatches to move the counters, then
fetch metrics through real QUIC + mTLS and verify each field
including the 0.5 hit rate calculation
238 tests pass. Pre-existing macOS-only failure unchanged.
File sizes (all under 1300-line ceiling):
- cluster/metrics.rs: 268
- cluster/rpc.rs: 818
- cluster/rpc/tests_phase5.rs: 905
- claw_cargo.rs: 894
## What this enables
Fleet-wide visibility into which peer is actually serving traffic:
# From anywhere with connectivity + fleet mTLS
claw-cargo peer-metrics --peer tank
claw-cargo peer-metrics --peer architect
claw-cargo peer-metrics --peer morpheus
Compare hit rates side by side to see which node's cache is warmest.
A placement engine can automate this — poll every 30s, feed the
scheduler.
## Follow-on
- 5h: streaming variant of prewarm (fixed-memory ceiling for many-GB
blobs)
- 5i: metrics also published via gossip so PeerView carries hit rate
without a per-peer GetMetrics roundtrip
- 5j: prometheus /metrics endpoint on the daemon for existing dash
integrations
- 6: FUSE mount for warm-tier git worktrees
Omar Sobh
d36cec11a6