# Internode gRPC Optimization — A/B Benchmark Runbook

Reproducible procedure to collect **before/after** artifacts for each internode gRPC
optimization stage (grpc-optimization P0–P3). Every stage is env-gated, so "before" and
"after" are the *same binary* with different env — no rebuild between runs.

> Live runs need a multi-node cluster (Docker or ≥2 rustfs endpoints), a load tool
> (`warp` or `s3bench`), and a Prometheus scrape of `/metrics`. They are not runnable in a
> single-process sandbox. Capture artifacts on a real cluster.

## One-click driver

`scripts/run_internode_grpc_ab_bench.sh --stage <p0|p1|p2|p3> --phase <before|after|request-only|canary|rollback> [-- <bench args>]`
wraps the env matrix below: it writes the stage/phase **server** env to
`<out-dir>/server-env.sh`, then runs the right underlying bench into
`target/bench/internode-transport/<stage>-<phase>/`.

```bash
# P1 A/B (restart the cluster with each phase's server-env.sh between the two runs):
scripts/run_internode_grpc_ab_bench.sh --stage p1 --phase before -- --access-key AK --secret-key SK --metrics-url http://node1:9000/metrics
scripts/run_internode_grpc_ab_bench.sh --stage p1 --phase after  -- --access-key AK --secret-key SK --metrics-url http://node1:9000/metrics
# P3 failover A/B (docker four-node):
scripts/run_internode_grpc_ab_bench.sh --stage p3 --phase after
# P2 rollout gates (env preview for request-only rehearsal, canary, and rollback):
scripts/run_internode_grpc_ab_bench.sh --stage p2 --phase request-only --dry-run
scripts/run_internode_grpc_ab_bench.sh --stage p2 --phase canary --dry-run
scripts/run_internode_grpc_ab_bench.sh --stage p2 --phase rollback --dry-run
```

`RUSTFS_INTERNODE_*` are **server** env: for the load-driven stages (p0/p1/p2) source the emitted `server-env.sh` on every node and restart rustfs *before* the run — the driver cannot mutate an already-running server. The P2 `canary` phase is the exception: source it only on the selected canary node after the release-window counters and fleet-support checks pass, and keep the rest of the fleet on `before` or `request-only` while observing fallback/decode-error counters. Use `--dry-run` to preview the env and command.

## Harness

- Throughput / latency: `scripts/run_internode_transport_baseline.sh` (drives
  `run_object_batch_bench.sh`; writes `target/bench/internode-transport-<ts>/`). Pass
  `--metrics-url <prometheus>` to also capture internode metric deltas.
- Failover / offline: `scripts/run_four_node_cluster_failover_bench.sh` (spins up a 4-node
  compose cluster, kills `FAILOVER_NODE`, benchmarks; writes
  `target/bench/four-node-failover-<ts>/`).

The one-click driver writes each run to `target/bench/internode-transport/<stage>-<phase>/`
(e.g. `p0-before/`, `p0-after/`, `p1-before/`, `p1-after/`, `p3-before/`, `p3-after/`), each
containing the emitted `server-env.sh` plus the underlying bench artifacts. `target/` is
gitignored — attach the paired directories to the PR / issue.

## Metrics to capture (Prometheus)

| Metric | Stage signal |
|---|---|
| `rustfs_system_network_internode_operation_duration_ms{operation,backend}` | control-plane RTT (P0), lock/bulk latency |
| `rustfs_system_network_internode_operation_payload_bytes` | payload size distribution (P0/P1 sizing) |
| `rustfs_system_network_internode_operation_large_payloads_total` | large unary RPCs sharing the channel (P1 target) |
| `rustfs_system_network_internode_dial_avg_time_nanos`, `..._dial_errors_total` | connect cost (P3 prewarm) |
| `rustfs_system_network_internode_msgpack_json_fallback_total{direction,message}` | must be **0** before enabling both msgpack-only gates (P2) |
| `rustfs_system_network_internode_msgpack_json_decode_error_total{direction,message,codec}` | must be **0** before enabling both msgpack-only gates (P2) |
| `rustfs_cluster_servers_offline_total` | offline detection correctness (P3 bypass) |
| lock p99 (lock metrics) | P1 head-of-line-blocking win |

## Per-stage env matrix

Run **before** with the stage's env at its baseline column, **after** with the enabled
column, everything else at defaults. Roll a restart between runs.

| Stage | Env | before (baseline) | after (enabled) |
|---|---|---|---|
| P0 nodelay | `RUSTFS_INTERNODE_RPC_TCP_NODELAY` | `false` | `true` (default) |
| P0 stream window | `RUSTFS_INTERNODE_RPC_HTTP2_STREAM_WINDOW_SIZE` | `0` | unset (1 MiB) |
| P0 conn window | `RUSTFS_INTERNODE_RPC_HTTP2_CONN_WINDOW_SIZE` | `0` | unset (2 MiB) |
| P0 msg limit | `RUSTFS_INTERNODE_RPC_MAX_MESSAGE_SIZE` | `4194304` | unset (100 MiB) |
| P1 isolation | `RUSTFS_INTERNODE_CHANNEL_ISOLATION` | `false` (default) | `true` |
| P1 bulk pool | `RUSTFS_INTERNODE_BULK_CHANNELS` | `1` | `2`–`4` |
| P2 msgpack-only request | `RUSTFS_INTERNODE_RPC_MSGPACK_ONLY` | `false` (default) | `true` (only after fallback counter = 0 across a window) |
| P2 fleet confirmation | `RUSTFS_INTERNODE_RPC_MSGPACK_ONLY_FLEET_CONFIRMED` | `false` (default) | `true` (only after mixed-version, fallback-zero, soak, and rollback gates pass) |
| P3 prewarm | `RUSTFS_INTERNODE_PREWARM` | `false` (default) | `true` |
| P3 offline bypass | `RUSTFS_INTERNODE_OFFLINE_BYPASS` | `false` (default) | `true` |
| P3 reprobe / threshold | `RUSTFS_INTERNODE_OFFLINE_REPROBE_SECS` / `RUSTFS_INTERNODE_OFFLINE_FAILURE_THRESHOLD` | defaults | `5` / `3` |

## Procedure per stage

1. **Baseline**: start the cluster with the stage's env at the *before* column. Run the
   relevant bench; save to `.../baseline/` (or `.../after-P{n-1}/` when chaining stages).
2. **After**: restart with the *after* column; re-run the identical bench; save to
   `.../after-P{n}/`.
3. Diff the object-bench summaries and the metric deltas.

- **P0** — `run_internode_transport_baseline.sh` with `--sizes 4KiB,1MiB,16MiB,128MiB` and
  `--concurrencies 1,16,64`. Expect: small-RPC `duration_ms` (DiskInfo/Ping) down (nodelay),
  large-metadata (ReadMultiple/BatchReadVersion) throughput up (windows). Functional: a
  `>4 MiB` multi-version `xl.meta` no longer fails `out_of_range`.
- **P1** — mixed workload (large `ReadAll` + high-frequency `Refresh`). Acceptance gate from
  the design doc: **lock p99 down ≥ 20%** with `RUSTFS_INTERNODE_CHANNEL_ISOLATION=true`.
- **P2** — observe `msgpack_json_fallback_total` and `msgpack_json_decode_error_total` across a release window; both must stay **0** before flipping both `RUSTFS_INTERNODE_RPC_MSGPACK_ONLY=true` and `RUSTFS_INTERNODE_RPC_MSGPACK_ONLY_FLEET_CONFIRMED=true` (see the msgpack convergence runbook). Codec allocation via a `dhat`/`heaptrack` micro-run.
- **P3** — cold-start: first cross-node op latency should drop ~one connect RTT with prewarm.
  Failover: `run_four_node_cluster_failover_bench.sh`, kill a node with
  `RUSTFS_INTERNODE_OFFLINE_BYPASS=true`; expect faster failover and a correct
  `rustfs_cluster_servers_offline_total` (1 while the node is down, back to 0 after recovery).

## Acceptance gates & artifact layout

Each stage's paired run must satisfy an explicit gate before its numbers are accepted. Record
the gate verdict (pass/fail + measured delta) in the paired directory's `summary` and attach it.

| Stage | Bench | Acceptance gate | Primary metric(s) |
|---|---|---|---|
| **P0** | `run_internode_transport_baseline.sh` | small-RPC `duration_ms` (DiskInfo/Ping) **down**; large-metadata (ReadMultiple/BatchReadVersion) throughput **up**; a `>4 MiB` multi-version `xl.meta` no longer fails `out_of_range` (functional). | `..._operation_duration_ms{operation}`, `..._operation_payload_bytes`, object-bench throughput |
| **P1** | `run_internode_transport_baseline.sh` (mixed: large `ReadAll` + high-frequency `Refresh`) | **lock p99 down ≥ 20%** with `RUSTFS_INTERNODE_CHANNEL_ISOLATION=true` vs baseline. | lock p99 (lock metrics), `..._operation_large_payloads_total` |
| **P3 cold-start** | `run_internode_transport_baseline.sh` (fresh cluster, first cross-node op) | first cross-node op latency **drops ~one connect RTT** with `RUSTFS_INTERNODE_PREWARM=true`. | `..._dial_avg_time_nanos`, first-op `..._operation_duration_ms` |
| **P3 offline** | dedicated *sustained-offline + survivor cross-node access* experiment (the standard four-node failover bench is **not** sensitive to the bypass — quorum holds, `recovery_seconds=0`) | with `RUSTFS_INTERNODE_OFFLINE_BYPASS=true`, survivor cross-node op latency to the downed peer **fast-fails** instead of hanging the dial timeout; `rustfs_cluster_servers_offline_total` = **1** while down, back to **0** after recovery. | `rustfs_cluster_servers_offline_total`, survivor cross-node `..._operation_duration_ms`, `..._dial_errors_total` |

> **P2 is not a throughput gate.** Its acceptance is operational: `msgpack_json_fallback_total`
> must read **0** across a full release window before both msgpack-only env gates are enabled (see
> the msgpack convergence runbook). Do not benchmark P2 as before/after throughput.

Artifact layout per stage (attach both halves + the diff):

```
target/bench/internode-transport/
  p0-before/  p0-after/     # server-env.sh + object-bench summaries + metric deltas
  p1-before/  p1-after/     # + lock p99 delta (the ≥20% gate)
  p2-before/  p2-request-only/  p2-canary/  p2-after/  p2-rollback/  # env gate artifacts + fallback/decode-error observations
  p3-before/  p3-after/     # cold-start + sustained-offline experiment + offline gauge trace
```

## Bench-host prerequisites (ansible bare-metal)

Captured while running the first real A/B on a 4-node ansible cluster; needed before any live run:

- **RPC secret is mandatory on current `main`.** Internode RPC fails closed: default creds
  (`RUSTFS_SECRET_KEY=rustfsadmin`) with no `RUSTFS_RPC_SECRET` → the node aborts startup immediately
  with `store init aborted: endpoints include remote nodes but RPC authentication secret is not
  configured` (builds before the preflight instead showed `No valid auth token` and never reached
  `storage_quorum`). Set a **non-default** `RUSTFS_RPC_SECRET`, identical on every node.
- **systemd start timeout.** The install unit is `Type=notify`; READY only fires after quorum, which on
  freshly-purged disks exceeds a 30 s `TimeoutStartSec` → crash loop. Use a drop-in `TimeoutStartSec=infinity`.
- **Server-side metrics need OTLP.** RustFS has no Prometheus pull endpoint (`/admin/v3/metrics` is NDJSON,
  not exposition); it only pushes via OTLP. To capture lock/offline/internode metrics, run an
  otel-collector (OTLP receiver → Prometheus exporter) and set `RUSTFS_OBS_ENDPOINT`,
  `RUSTFS_OBS_METRICS_EXPORT_ENABLED=true`, `RUSTFS_OBS_METER_INTERVAL=5`. For lock p99 also set
  `RUSTFS_OBJECT_LOCK_DIAG_ENABLE=true` (default off).
- **P3 offline method.** Standard failover is quorum-insensitive to the bypass. Use a *sustained-offline +
  survivor cross-node access* run instead: all nodes up → stop one node (sustained) → warm up to trip
  offline detection → drive warp on the survivors only (`--host` excludes the dead node) → compare
  survivor op p99 and `rustfs_cluster_servers_offline_total` for `RUSTFS_INTERNODE_OFFLINE_BYPASS` off/on.

## Rollback

Every stage rolls back by setting the env back to its baseline column and restarting. P2 rolls back by unsetting either msgpack-only gate, or by setting both `RUSTFS_INTERNODE_RPC_MSGPACK_ONLY=false` and `RUSTFS_INTERNODE_RPC_MSGPACK_ONLY_FLEET_CONFIRMED=false`; no wire format is broken because the JSON fields, `_bin` fields, and proto field numbers remain additive. Do not remove or reuse JSON proto fields as part of this benchmark stage.