RL Admin Control

RL Admin Control#

SGLang-Omni exposes a small administrative API for inference-side RL workflows. The contract follows the SGLang and Miles control surface while preserving the Omni pipeline boundary:

HTTP / router -> Client -> Coordinator -> Stage -> Scheduler -> ModelWorker

The control plane carries only metadata and small result summaries. Tensor payloads and bulk checkpoint data must be moved through disk, a distributed group, or another data plane.

Authentication#

Admin endpoints are unauthenticated by default for backward compatibility. They require Authorization: Bearer <key> when either of these is set:

  • admin_api_key passed to the worker/router create_app(...)

  • SGLANG_OMNI_ADMIN_KEY in the environment

The external router also accepts --admin-api-key. The router forwards the Authorization header to workers, so a deployment can use the same key at both layers.

Worker Endpoints#

The worker server supports:

  • GET|POST /model_info

  • POST /pause_generation

  • POST /continue_generation

  • POST /update_weights_from_disk

  • POST /update_weights_from_tensor

  • POST /init_weights_update_group

  • POST /destroy_weights_update_group

  • POST /update_weights_from_distributed

  • GET|POST /weights_checker

/update_weights_from_disk is the primary implemented update path. It pauses the target scheduler, optionally aborts active requests, calls the underlying SGLang model runner update method, optionally flushes cache, and resumes unless keep_pause=true. From-disk updates run on the scheduler thread. If active requests are present, the update is rejected unless the request sets abort_all_requests=true or generation was already paused with mode=retract.

/init_weights_update_group and /destroy_weights_update_group manage the SGLang/Miles distributed update process group. /update_weights_from_distributed then sends metadata (names, dtypes, shapes, group_name, and optional load_format / weight_version) through the admin control plane while the actual tensors move over the distributed group. The distributed update path uses the same scheduler-thread lifecycle as disk updates: active requests must be aborted or safely retracted, cache is flushed by default, and the visible weight_version is updated after a successful runner update. If the distributed update fails, the scheduler remains paused because SGLang may have partially updated the model weights; recover by reloading or otherwise repairing the worker before calling continue_generation.

/update_weights_from_tensor is still reserved for a future tensor data-plane integration and returns HTTP 501 from the worker and router HTTP APIs.

Stage and TP Behavior#

The Coordinator sends one admin operation to each target stage and waits for stage results. For TP stages, rank 0 fans the operation out to follower ranks, collects one result per rank, and returns a stage-level aggregate result with rank_results.

Stages without an admin-capable scheduler return a successful skipped result so mixed pipelines can broadcast model info or pause commands without failing on pre/post-processing stages.

Router Behavior#

The external router broadcasts admin requests to every non-dead worker. Update and pause routes temporarily disable target workers from normal request routing while the broadcast is in flight, then restore each worker’s previous disabled state.

The router serializes pause, distributed group lifecycle, and weight-update broadcasts with an admin update lock. If another update holds the lock for too long, the router returns HTTP 503 instead of blocking subsequent admin callers indefinitely. If distributed group initialization fails or times out, the target worker remains disabled until an operator explicitly re-enables it after recovery.

Weight Checker#

/weights_checker supports snapshot, reset_tensors, compare, and checksum. The Omni checker computes strict SHA256 digests from each tensor’s name, dtype, shape, and raw bytes, then derives a per-rank checksum from the sorted tensor digests. Full-model SHA256 checks block inference on that worker until the digest completes.