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Ports the router-hint contract to the SGLang backend so a worker running the KVCR HiCache storage backend can act as both a hint target and a hint source, matching what the vLLM backend already does. Registration advertises the three runtime keys the router requires: the router_hint capability, the worker_type role, and a per-global-DP-rank map of KVCR peer control endpoints. All three go out together -- router_hint_metadata_ for_dp_rank returns None without worker_type, and router_hint_for_selection matches a hint source to its target on that role, so publishing a subset registers a worker the router silently never hints to. Endpoints come from the KVCR backend's --hicache-storage-backend-extra-config rather than vLLM's secondary_tiers. SGLang builds a storage backend in every attention rank's scheduler process, so one DP rank owns a block of control ports and the map strides by tp_size // dp_size; this must stay in step with _rank_port_offset on the SGLang side. Configured-for-hints but unadvertisable raises at registration instead of leaving a worker whose every peer fetch fails. On the request path, a hint arriving under extra_args.kv_transfer_params is forwarded to async_generate as kv_router_hint. An SGLang install without that kwarg warns once and recomputes the prefix, so a missing hint degrades rather than failing the request. Validation: unit tests cover the three published keys, the disaggregation-mode to worker_type mapping, DP-rank port striding (single-node and multinode), advertise-host handling, the no-op and raising paths, and hint extraction on both a current and a legacy engine. Signed-off-by: Lin Hu <linhu@nvidia.com>
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WalkthroughChangesSGLang router hint support
Estimated code review effort: 3 (Moderate) | ~30 minutes Merge Risk: 🔵 Low · up to The change can advertise KVCR control endpoints above TCP port 65535 after DP-rank offsetting, so affected workers may register successfully while peers cannot connect for hint fetches. This is localized and mergeable with owner follow-up to validate the final port and add boundary coverage. 🚥 Pre-merge checks | ✅ 3 | ❌ 2❌ Failed checks (2 warnings)
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In `@components/src/dynamo/sglang/router_hints.py`:
- Around line 50-80: Update _source_control_endpoint to reject any computed
control port above 65535 after applying port_offset, while preserving valid
boundary values; add tests covering the upper limit and overflow case. If the
helper is only used by LLM registration, type runtime_config as
ModelRuntimeConfig and server_args as ServerArgs, retaining getattr for optional
fields across supported configurations.
Apply the same fix in `@components/src/dynamo/sglang/router_hints.py` around lines
99 - 110: Covered by the consolidated final-port upper-bound validation and
multi-rank boundary test request.
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| # SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved. | ||
| # SPDX-License-Identifier: Apache-2.0 | ||
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| """Router-hint capability advertisement for the SGLang backend. | ||
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| Mirrors ``dynamo/vllm/router_hints.py``: a worker must advertise the | ||
| ``router_hint`` runtime capability, its topology role, and a per-DP-rank map of | ||
| KV source control endpoints, or the router treats it as hint-incapable and | ||
| silently emits no hints. | ||
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| The only difference from the vLLM version is where the endpoints come from. | ||
| vLLM reads ``kv_transfer_config.kv_connector_extra_config.secondary_tiers[]``; | ||
| SGLang has no secondary tiers, so the equivalent values live in the KVCR | ||
| HiCache storage backend's extra-config JSON | ||
| (``--hicache-storage-backend-extra-config``), whose ``control_host`` / | ||
| ``control_port`` / ``control_advertise_host`` fields are what the KVCR store | ||
| binds its ZMQ peer control channel to. | ||
| """ |
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would it make sense to combine this file with existing on vllm side and put them into some common repo?
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Yeah, worth doing. The shareable half is host normalization, port validation, the worker_type vocabulary, and writing the three runtime keys together — that's most of the file. What can't merge is where the endpoints come from (secondary_tiers[] vs the HiCache extra-config) and the rank layout.
Two things I'd want your call on: does dynamo/common/ work as the home, next to the constants? And would you rather do it as a follow-up? It touches the vLLM file, so it'd widen this PR beyond SGLang — happy either way, just don't want to refactor your file under you.
| host = extra_config.get("control_advertise_host") or extra_config.get( | ||
| "control_host" | ||
| ) |
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I've changes this a bit:
dynamo/components/src/dynamo/vllm/router_hints.py
Lines 106 to 109 in f313f68
I think the one we want to use for external access is control_advertise_host, and the other one is for kvcr internal things
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Fixed in 629bd08 — _source_control_endpoint now reads control_advertise_host only, matching your vLLM version.
The fallback to control_host was the bug: it's the bind address and is legitimately a wildcard, so a worker with only that set would advertise an endpoint no peer can dial — a silent P2P failure instead of a config error. Docstring and error message updated to match, and SGLang's config validation is being changed the same way so the two sides don't disagree.
- Read hicache_storage_backend_extra_config defensively. The attribute is evaluated before enable_router_hint_support can short-circuit on a non-KVCR backend, so a server_args without the field aborted registration entirely. Matches how _get_mooncake_runtime_data reads the same field. - Range-check the control port after the DP-rank offset. A base port near the top of the range carries the last rank past 65535, which registers a worker the router selects as a hint source but no peer can dial. - Advertise control_advertise_host only. control_host is the bind address and is legitimately a wildcard, so falling back to it publishes whichever of the two happens to be set. SGLang's own config validation is being changed to match; leaving them out of step would have dynamo reject a config the backend accepts, with no diagnostic tying the two together. Signed-off-by: linhu-nv <linhu@nvidia.com>
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SGLang renamed the request field to kv_hints and now parses it as a KV-hint envelope, so the old kwarg name is silently dropped by the supported-kwarg filter and every hint is lost with only a warning. Forward the router's hint under the new name. The value still passes through untouched: SGLang reads the envelope and picks out the actions it implements, so this adapter needs no further change once the router wraps its hint in one.
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Ports the router-hint contract to the SGLang backend so a worker running the KVCR HiCache storage backend can act as both a hint target and a hint source, matching what the vLLM backend already does.
Registration advertises the three runtime keys the router requires: the router_hint capability, the worker_type role, and a per-global-DP-rank map of KVCR peer control endpoints. All three go out together -- router_hint_metadata_ for_dp_rank returns None without worker_type, and router_hint_for_selection matches a hint source to its target on that role, so publishing a subset registers a worker the router silently never hints to.
Endpoints come from the KVCR backend's --hicache-storage-backend-extra-config rather than vLLM's secondary_tiers. SGLang builds a storage backend in every attention rank's scheduler process, so one DP rank owns a block of control ports and the map strides by tp_size // dp_size; this must stay in step with _rank_port_offset on the SGLang side. Configured-for-hints but unadvertisable raises at registration instead of leaving a worker whose every peer fetch fails.
On the request path, a hint arriving under extra_args.kv_transfer_params is forwarded to async_generate as kv_router_hint. An SGLang install without that kwarg warns once and recomputes the prefix, so a missing hint degrades rather than failing the request.
Validation: unit tests cover the three published keys, the disaggregation-mode to worker_type mapping, DP-rank port striding (single-node and multinode), advertise-host handling, the no-op and raising paths, and hint extraction on both a current and a legacy engine.
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Summary by CodeRabbit
New Features
Bug Fixes
Tests