[franklee26]

        sender side                          receiver side
       ─────────────                        ───────────────
       OPEN                                  OPEN
         │  user calls close()                │
         │  ───── flush() ──────────────►     │
         │  ───── Fin(pn=N) ─────────────►    │  (recv_bytes drains buffer)
         │                                    │  recv → Ok(0)  (EOF surfaced)
       FIN_SENT                                │
         │                                  FIN_OBSERVED
         │  ◄──── FinAck(pn=N) ──────────     │  (conn_reader auto-emits)
         │                                    │
         │  remove from ConnectionManager   remove from ConnectionManager
       CLOSED                                CLOSED

                          ┌──────────────────────────────┐
 user code  ──send()────► │ writer queue (flume bounded) │ ──► WriterHandler
 user code  ──close() ─┐  └──────────────────────────────┘         │
                       │                                            │ send_fin(pn)
                       │  flush() → reserve_close_pn → ─────────────┤
                       │                                            ▼
                       │                                       UDP socket
                       │                                            │
                       │     ┌────────────────────────────┐         │  (peer)
                       │     │ await_fin_ack(pn, 200ms)   │ ◄───────┤
                       │     └────────────────────────────┘         │
                       │             ▲                              │
                       │             │ peer's FinAck sets            │
                       │             │ local_fin_acked = true        │
                       │             │                               │
                       │     ┌──────────────────┐  fin_ack_tx        │
                       │     │  CloseBuffer     │ ◄────────────┐     │
                       │     │  - peer_fin_obs  │              │     │
                       │     │  - pending_fa_pn │              │     │
                       │     │  - local_fin_pn  │              │     │
                       │     │  - local_fin_acked│             │     │
                       │     └──────────────────┘              │     │
                       │             ▲                          │     │
                       │             │                          │     │
                       │   ┌─────────────────────────┐          │     │
                       │   │ buffer_in_close_packets │ ─────────┘     │
                       │   │ (in conn_reader)        │ ◄──────────────┤
                       │   └─────────────────────────┘ Fin/FinAck     │
                       │             │                                │
                       │             │ wake recv() if Fin              
                       │             ▼                                
                       └──► recv_bytes() returns Ok(0) when            
                            peer_fin_observed && data_buf empty       

[codecov]

Codecov Report

❌ Patch coverage is 71.13095% with 194 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.13%. Comparing base (80c8310) to head (0ec514b).

Files with missing lines	Patch %	Lines
bluefintool/src/main.rs	53.33%	63 Missing ⚠️
bluefin/src/bin/client.rs	0.00%	37 Missing ⚠️
bluefin/src/net/close_handler.rs	78.23%	32 Missing ⚠️
bluefin/src/bin/server.rs	0.00%	24 Missing ⚠️
bluefin/src/net/connection.rs	76.27%	14 Missing ⚠️
bluefin/src/worker/reader.rs	60.00%	10 Missing ⚠️
bluefin/src/worker/writer.rs	81.81%	10 Missing ⚠️
bluefin/src/worker/conn_reader.rs	97.10%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #46      +/-   ##
==========================================
+ Coverage   63.74%   69.13%   +5.39%     
==========================================
  Files          23       24       +1     
  Lines        3194     3833     +639     
==========================================
+ Hits         2036     2650     +614     
- Misses       1158     1183      +25     

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[github-actions]

Bluefin throughput bench (macOS) ✅ PASS

Config: 5 run(s) × 2 conn(s) on Darwin arm64

Client throttle: 25 µs sleep every 3000 sends

Retries: 4 of 5 run(s) needed retry (+6 extra attempt(s)). See per-run table.

why retries vary across runs

Hosted CI runners occasionally land on a deeply contended host where both bench peers get starved and a run produces 0 GOOD conns despite no actual code regression. To absorb this without weakening the gate, this job uses an asymmetric retry policy (current values: ON_ZERO=2, ON_PARTIAL=0, backoff 5s):

attempt outcome	extra retries granted
all 2 conns good	0 (accept)
1..1 conns good (partial)	up to ON_PARTIAL=0
0 conns good (catastrophic)	up to ON_ZERO=2

The retry budget is per-run and only shrinks across attempts: once a partial-good attempt has been observed in a run, that run is locked to the partial budget for the rest of its attempts -- it can never be promoted to the larger 0-good budget by a later attempt happening to collapse to 0. Only the final attempt's data is committed to the aggregate stats; earlier attempts' logs are still on disk under the run's attempt_* directory but are not parsed.

So the same code can show 0, 1, or 2 retries on different CI runs purely from runner-allocation luck. The attempts column in the per-run table below shows how many attempts each run took (bold = needed at least one retry).

Aggregate

metric	observed	floor	result
mean avg gb/s (good only)	0.475	0.40	✅
raw mean avg gb/s	0.229	—	—
min avg gb/s	0.039	—	—
mean peak gb/s	0.917	—	—
max peak gb/s (good only)	1.830	1.30	✅
good conns	3 / 10	3	✅

Per-run

run	attempts	good/N	mean avg gb/s (good)	max peak gb/s (good)	raw max peak gb/s
1	3	0/2	—	—	0.08
2	2	1/2	0.50	1.83	1.83
3	3	0/2	—	—	1.11
4	2	1/2	0.46	1.40	1.40
5	1	1/2	0.47	1.53	1.53

_{A "good conn" delivered ≥ 700 MB before idle timeout.
"max peak (good only)" filters out kernel-buffer-drain artifacts
that appear as huge inst-throughput readings on starved conns under
runner CPU contention. Floors are env-var overridable:
BLUEFIN_BENCH_FLOOR_MEAN_AVG_GBPS, BLUEFIN_BENCH_FLOOR_MAX_PEAK_GBPS,
BLUEFIN_BENCH_FLOOR_GOOD_CONNS, BLUEFIN_BENCH_GOOD_CONN_MIN_BYTES.
Ratchet up after stable runs land. Script: bench_ci.sh.}