Monitoring & Logging

Miles emits per-rollout metrics to stdout and (optionally) Weights & Biases. SGLang and Ray write their own logs to their default directories.

What gets logged by default

Each rollout iteration emits a structured row to stdout (illustrative shape — exact fields depend on backend and config):

[trainer] iter 12/3000 | loss=0.412 reward=0.61 kl=0.018
                      | rollout=18.4s train=22.1s p2p=2.1s  (total 42.6s)
                      | grad_norm=0.93 lr=1.0e-06

When --use-wandb is set, metrics also go to wandb under the train/, rollout/, and perf/ namespaces (see miles/utils/wandb_utils.py).

Enabling wandb

ray job submit --address=auto -- \
  python3 train.py ... \
    --use-wandb \
    --wandb-project miles \
    --wandb-group qwen3-30b-grpo

Available flags: --use-wandb, --wandb-project, --wandb-group. WANDB_API_KEY should be supplied via Ray’s env_vars rather than baked into the launch script.

What to watch

Signal	Healthy pattern	Red flag
`loss`	Slow decay over hundreds of iterations	Spike → crash within an iteration
`raw_reward`	Trending up, with healthy variance	Saturates near a single value (collapse)
`kl_loss`	Bounded, drifts up over time	Sudden jump (policy diverged from ref) — only logged when `--use-kl-loss`
`train_rollout_logprob_abs_diff`	Stable and small (≪ 1.0)	Climbing without bound → train/inference precision drift
`entropy_loss`	Slowly decreasing	Falls to ~0 too fast (mode collapse)
`grad_norm`	< `clip_grad` (1.0 by default)	Repeatedly hitting clip threshold
`rollout_time` / `train_time`	Roughly balanced	One ≫ other → resource imbalance
`train/pg_clipfrac`	< 0.2	> 0.5 means policy is moving fast → drop LR

Panel names follow what loss.py and the rollout logger emit; Miles’s wandb metrics live under train/, rollout/, perf/, multi_turn/, passrate/ namespaces.

Custom loggers

Replace the default rollout logger with your own to push to internal systems:

def my_log(rollout_id, args, samples, extra, rollout_time) -> bool:
    statsd.gauge("miles.reward", mean([s.reward for s in samples]))
    return False   # also keep default logging

--custom-rollout-log-function-path my_pkg.logging.my_log

Profiling

Tool	When
`nvidia-smi dmon -s u`	Quick sanity check on GPU utilization
`nsys profile`	Deep CUDA-level profiling
`py-spy dump --pid <ray worker>`	Find Python-side stalls
`ray timeline`	Inspect Ray task scheduling

Built-in PyTorch profiler

The PyTorch profiler is wired into Miles via miles/utils/profile_utils.py. Flags differ by backend: Megatron — choose which sub-loop to profile:

--profile-target train_overall    # or train_actor, train_log_probs (multi-arg)

FSDP — additionally exposes the standard FSDPArgs window:

--use-pytorch-profiler
--profile-step-start 10
--profile-step-end 12
--memory-snapshot-path snapshot.pickle
--tensorboard-dir /data/tb-run-42

Open the trace in chrome://tracing or Perfetto.

Where the log files live

Source	Path
Trainer stdout	wherever you redirected `ray job submit` (or Ray dashboard)
Ray workers	`~/.ray/session_latest/logs/`
wandb local cache	`wandb/run-<id>/files/`
FSDP profiler / memory snapshot	`--tensorboard-dir`, `--memory-snapshot-path`

Router endpoints

The router exposes a small FastAPI surface used internally by Miles:

Endpoint	Method	What
`/add_worker`	POST	Register an SGLang engine
`/list_workers`	GET	List registered workers
any other path	GET / POST / PUT / DELETE	Proxied to a selected SGLang worker — e.g. `/generate`, `/v1/chat/completions`, `/health`.

​What gets logged by default

​Enabling wandb

​What to watch

​Custom loggers

​Profiling

​Built-in PyTorch profiler

​Where the log files live

​Router endpoints