Publish-only delta sync, re-derived on the disk-delta base#6
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nanjiangwill wants to merge 9 commits into
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Publish-only delta sync, re-derived on the disk-delta base#6nanjiangwill wants to merge 9 commits into
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Ship only the changed bytes between weight syncs as a canonical HF delta checkpoint; rollout hosts apply it into a host-local checkpoint and reload via the vanilla update_weights_from_disk path. Replaces the NCCL delta transport from THUDM#1806 with a disk-only path that needs no engine-side delta support.
sync_local_checkpoint (was sync_weights) materializes the base lazily via the idempotent init_local_checkpoint instead of a background thread; record per-sync update time in update_weight_metrics; state the pre-read/pre-push hooks' purpose (non-POSIX filesystem coherence).
The actor's update_weights is already @timer-wrapped (perf/update_weights_time), so the per-sync total/publish/reload breakdown was duplicate instrumentation. Keep only the delta-specific metrics (density, wire bytes).
The delta scaffold reworked the update-weight args: delta requires --update-weight-transport=disk (was nccl-or-disk), needs --update-weight-local-checkpoint-dir, and the --update-weight-delta-dir compatibility alias is gone (the directory belongs to the transport, not the encoding). Drop the alias resolve/backfill/conflict tests, point the transport and colocate tests at the disk path, and cover the local-checkpoint requirement.
With the delta-dir alias gone, _resolve_update_weight_disk_dir no longer normalizes anything — it's a single transport-level check, so fold it into _validate_update_weight_args.
slime_validate_args validates everything else inline; the extracted _validate_update_weight_args was the lone exception. Fold it in and test it the same way as the other slime_validate_args checks (make_slime_validate_args).
Materialize the host-local checkpoint in a daemon thread at engine init so the one-time base copy overlaps sglang launch and the first rollout (which serves from init-loaded weights) instead of blocking the first delta reload. The first sync_local_checkpoint's init_local_checkpoint is idempotent and flock-guarded, so it either finds the copy done or blocks on the same lock — no join needed.
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Add --rollout-endpoint-url to train against an elastic rollout fleet behind a single opaque HTTP endpoint (no per-engine handles). Generation routes to the URL; the disk-delta updater publishes each version to the shared disk dir and advances a `latest` pointer for the fleet to pull, instead of pushing via per-engine RPCs. Add-only: managed and external-addressed paths are unchanged. Requires delta mode + disk transport (the only cross-cluster channel) and is non-colocate. - abort: the endpoint cancels surplus when discarding; with --partial-rollout it drains so streaming tasks return their partials (closing each stream disconnects, which aborts the fleet-side request). Endpoint + --partial-rollout requires the streaming rollout, the only path that captures partials client-side. - streaming: record the weight version on an aborted partial so off-policy correction can weight it (update_from_meta_info is skipped without a finish_reason).
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Closing: jvmncs/rollout-endpoint is deprecated. The publish-only work now stacks on the disk-delta branch via #5 (disaggregated-rollout -> disk-delta-weight-sync). |
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Clean re-derivation of this branch's publish-only weight sync, rebuilt on top of the disk-level delta weight sync (PR to THUDM THUDM#2089) instead of the old
update_weight_from_distributed_delta.pythat THUDM#2089 removes.The large diff vs this branch is the base difference: it carries all of THUDM#2089's delta rewrite plus the disaggregated-rollout feature. The publish-only logic itself is ~90 lines (see #5) — on THUDM#2089's clean disk-delta, "publish" is just write the version + advance a
latestpointer, skip the engine RPCs.Dropped relative to this branch:
--update-weight-delta-publish-waitnext-sync/sync dual mode (publish is synchronous: write + announce, no in-flight drain).--update-weight-delta-root(unused).meta_info["weight_version"](captured intoSample.weight_versions), and routing/affinity belong to the fleet's router.Generation routing, placement, and abort follow the existing external-engine pattern (
ExternalRolloutServer). Intended to supersede the publish-only approach here once THUDM#2089 lands.