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Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
…w of 32 The Velo response sender called `register_peer` and `wait_for_handler(peer, "_stream_stop")` for every request. In the pinned velo, `wait_for_handler` refreshes the handler list with a `_hello` round trip through the frontend's messenger. That put a control-plane round trip through the frontend in front of every request's first token. The service now keeps the set of frontends it has prepared and does both steps once per frontend. An instance id names one process, so a restarted frontend is prepared again. Response streams now use a per-stream credit window of 32, set explicitly. When the frontend is the bottleneck, every stream runs at its window, and a larger window fills the shared path from a worker to the frontend, so a new stream's first token waits behind all of it. On the mocker rig with a saturated 24-core frontend, a window of 256 put TTFT p50 at 135 to 355 ms, and 32 put it at 88 to 102 ms. Throughput was within noise, and ITL p99 was no higher. Signed-off-by: Ryan Olson <rolson@nvidia.com>
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. WalkthroughThe response service now enables the messenger mux with an initial credit of 32. It tracks peers after successful preparation and skips registration and handshake on later sender calls for those peers. ChangesVelo response streams
Priority: ➖ Normal Estimated code review effort: 2 (Simple) | ~10 minutes Merge Risk: 🔵 Low · up to Concurrent first requests to a Velo frontend can briefly duplicate setup work; later requests use the prepared-peer cache. This is a bounded performance concern, so the remaining merge risk is low. 🚥 Pre-merge checks | ✅ 3 | ❌ 2❌ Failed checks (2 warnings)
✅ Passed checks (3 passed)
Full details: Description checkExplanation The description provides extensive technical details, validation results, release status, and performance data. However, it does not follow the required template and omits the required Related Issues section, including confirmation of no related issue or an issue-closing reference. Resolution Add the required Overview, Details, Where should the reviewer start?, and Related Issues sections. In Related Issues, either provide the applicable issue reference, such as "Closes
✨ Finishing Touches 💡 1⚔️ Resolve merge conflicts 💡
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- 🪄 Fix CodeRabbit comments on this PR
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only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
Review comments at @lib/runtime/src/pipeline/network/velo_response.rs:
- Around line 358-370: Make peer preparation in the sender flow single-flight
per peer: coordinate concurrent calls so only one runs register_peer and
wait_for_handler for a given peer_id, and other calls wait for its result.
Remove the in-flight guard if preparation fails so a later call can retry; do
not evict prepared peer IDs on disconnect.
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lib/runtime/src/pipeline/network/velo_response.rs
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| Ucx, | ||
| } | ||
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| /// Per-stream credit window for response streams. |
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The opening summary only restates RESPONSE_CREDIT_WINDOW; the following lines already record the non-obvious rationale for the explicit value. Remove the redundant summary and separator while retaining that rationale.
🤖 AI Fix
Remove the redundant opening doc-comment sentence and blank separator.
| self.velo.wait_for_handler(peer_id, "_stream_stop"), | ||
| ) | ||
| .await??; | ||
| if !self.prepared_peers.contains(&peer_id) { |
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The contains check and insertion are separated by an awaited handshake, so concurrent first requests to the same frontend all observe it as unprepared and each performs register_peer plus the _hello round trip. This is the high-concurrency path the change intends to remove, leaving the initial burst with the prior frontend bottleneck behavior.
🤖 AI Fix
Coordinate preparation with a per-peer singleflight mechanism so concurrent senders await one successful registration and handshake before opening their streams.
| self.velo.wait_for_handler(peer_id, "_stream_stop"), | ||
| ) | ||
| .await??; | ||
| if !self.prepared_peers.contains(&peer_id) { |
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The contains/prepare/insert sequence is not atomic. When a worker receives multiple concurrent first requests from the same frontend, every sender can observe the set as empty and independently run register_peer plus the _hello-triggering wait_for_handler. This recreates the control-plane burst and frontend CPU/TTFT regression this change is intended to remove. Store per-peer initialization state that concurrent senders await, and mark it ready only after registration and the handshake succeed.
🤖 AI Fix
Replace the check-then-insert DashSet flow with per-peer async initialization state so concurrent senders await one successful registration and handshake.
| use crate::engine::AsyncEngineContextProvider; | ||
| use crate::pipeline::Context as EngineContext; | ||
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| #[test] |
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This helper-only test remains green if VeloResponseService::new stops passing response_mux_config() into messenger_mux, so it cannot distinguish the claimed regression that response streams actually use a credit window of 32. The supported behavior should be checked at the service/mux boundary, or this tautological case should be removed.
🤖 AI Fix
Replace this helper-only test with an assertion that the constructed response service or opened response stream is configured with initial credit 32.
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This mutant passes, but at bee8b8e it changes nothing. With new() back on the inline MuxConfig { enabled: true, ..Default::default() }, all 12 tests pass. At this pin, velo's MuxConfig::default().initial_credit is already 32. With the constant at 256, this test fails with left: 256. I do not count this against the PR.
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| async fn completion_and_failure_keep_distinct_results(transport: ResponseTransport) { | ||
| let (consumer, producer) = pair(transport).await; | ||
| // Two streams to one frontend below: it is registered and handshaken |
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This narrates the setup and assertion immediately below without recording a non-obvious test constraint.
🤖 AI Fix
Remove the redundant test comment.
| } | ||
| assert!(receiver.rx.next().await.is_none()); | ||
| } | ||
| assert_eq!(producer.prepared_peers.len(), prepared_before + 1); |
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The added prepared_peers.len() assertion only proves the peer ID was inserted once; it still passes if sender registers and handshakes on every stream before reinserting the same peer. The existing completion/abort checks remain protected by this lifecycle helper, but this added check cannot distinguish the prepare-once regression it claims to cover.
🤖 AI Fix
Remove this length assertion or replace it with an observable check that the second stream does not call the peer registration/handshake path.
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[P3] Mutation confirms this. If the worker prepares on every request, the new length assertion still passes. velo_response.rs:628. It catches a missing insert but not a missing contains guard. Please count entries into the prepare branch instead. A test-only counter there reads 1 for 8 sequential streams on the head and 8 with the guard removed.
Mutants of the head, each built and run with velo_response push_handler on the GPU box.
| Mutant | Change | Result |
|---|---|---|
| none | head as pushed | 12 passed |
| M1 | if !self.prepared_peers.contains(&peer_id) { becomes if true { |
12 passed |
| M2 | self.prepared_peers.insert(peer_id); removed |
tcp_lifecycle failed at this line, left: 0 |
Each mutant changed the SHA-256 of the file, and each restore gave back the original SHA-256.
Takes the velo pin at c5b6fb3. Conflict in VeloResponseService::sender: keeps the prepare-once check, with the base branch's comment wording. Signed-off-by: Ryan Olson <rolson@nvidia.com>
velo main at bee8b8e (0.17.0, velo-ext 0.5.3) carries the stream lifecycle work this branch was pinned to (c5b6fb3), its review fixes, and the response-plane changes on top: the mux consumer reads its slot buffer directly, the default credit window is 32, the mux is on by default, and wait_for_handler answers from its cache for a known handler. The adapter still sets the window to 32 and enables the mux explicitly. Only the velo and velo-ext entries change in the lock files. cargo test -p dynamo-runtime --lib -- velo_response push_handler passes (12 tests), and clippy is clean. Signed-off-by: Ryan Olson <rolson@nvidia.com>
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Approved. The prepare-once change, the credit window of 32 and the velo pin passed every test that I ran. Only P3 items are open.
Read at d19f072712f115fdd48455ca0ac72a4fb19beb2a.
- [P3] Two new comments describe older velo pins. Inline at
velo_response.rs:126. - [P3] velo 0.17.0 on crates.io is the pinned commit, and the git source stops
cargo package. Inline atCargo.toml:96. - [P3] The prepare-once assertion passes with the
containsguard removed. Reply on the thread atvelo_response.rs:628. - [P3] Concurrent first requests to a frontend all run the prepare step. Reply on the thread at
velo_response.rs:358. - This PR merges into the branch of #15231, which is still a draft.
- Not from this PR: since #15231,
lib/runtime/examples/Cargo.lockhas no velo entry.cargo metadata --lockedfails there on the base, on the head and on the merge withmain(run 36600540764, jobrust-clippy (lib/runtime/examples)). A relock fixes it.
What I ran on the GPU box, and what I did not run.
| Tree | velo_response push_handler |
--locked: root, python, kvbm |
--locked: lib/runtime/examples |
|---|---|---|---|
base 0548303 |
11 passed | pass | fail |
head code on the old pin, 2d3e2a3 |
12 passed | pass | fail |
head d19f072 |
12 passed | pass | fail |
head merged with main, c2ebd82 |
12 passed | pass | fail |
main 8e41fd8, the control |
not run | pass | pass |
On the head, clippy with -D warnings is clean for dynamo-runtime, kvbm-engine, kvbm-config and kvbm-physical. CI rust-tests (.) on c2ebd82 passed 827 dynamo_runtime tests and the tests of the three kvbm crates.
I did not run the UCX path. No CI job enables velo-ucx, and the GPU box has no rdma-core headers, so ucx_lifecycle ran neither in CI nor in this review. The pull-request/15320 workflows did not run. copy-pr-bot waits for a vetter, and all three commits are unsigned. I did not reproduce the TTFT numbers from the mocker rig.
| /// Frontends this worker has already registered and handshaken. Both are | ||
| /// per peer, not per request. Done per request, they put a messenger round | ||
| /// trip through the frontend in front of every request's first token. |
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[P3] Two new comments describe older velo pins. velo_response.rs:126. At bee8b8e, a repeated wait_for_handler returns from its cache without a round trip, so this set now saves only the repeated register_peer. Line 65 says 32 is "not velo's larger default", but the default is 32 at this pin. Please reword both comments.
Probe at bee8b8e, with the frontend shut down after its first stream.
| Call | Result |
|---|---|
wait_for_handler(frontend, "_stream_stop"), cached by the first stream |
ok in 0.000 s |
wait_for_handler(frontend, "_probe_not_registered"), the control |
Handshake failed: Connection closed |
MuxConfig::default().initial_credit |
32 |
The cached call returned ok although the frontend was down, so it made no network call. The early return is if self.client.has_cached_handler(instance_id, handler_name) in lib/velo/src/messenger/messenger.rs. It is not in da848eb, the pin that the first commit of this PR used.
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| # velo | ||
| velo = { git = "https://github.com/ai-dynamo/velo", rev = "c5b6fb33df125fe18f0b5b74fc49faef734b766c", default-features = false } | ||
| velo = { git = "https://github.com/ai-dynamo/velo", rev = "bee8b8e9e22e4a3bbaa133b2a785254f6fdf2a48", default-features = false } |
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[P3] This line pins velo by git revision, but crates.io now has velo 0.17.0 and velo-ext 0.5.3, built from this same commit. Cargo.toml:96. With the git source, cargo package -p dynamo-runtime stops because velo has no version. Please use velo = { version = "0.17.0", default-features = false }, as main does for 0.12.0, and relock.
Measured on the GPU box, with main as the control.
The .cargo_vcs_info.json in velo-0.17.0.crate and in velo-ext-0.5.3.crate names bee8b8e9e22e4a3bbaa133b2a785254f6fdf2a48. ucx-rs 0.1.0+ucx.1.22.0 on crates.io comes from a15f52de. From there to bee8b8e, only README.md and one doc comment in build.rs changed in crates/ucx-rs.
| Tree | cargo package -p dynamo-runtime --no-verify --locked |
|---|---|
main, the control |
passes the manifest step, then stops because dynamo-truthy 1.6.0 is not on crates.io yet |
| head | stops at the manifest step |
head with version = "0.17.0" |
same as main |
The head error:
error: failed to verify manifest at `.../lib/runtime/Cargo.toml`
Caused by:
all dependencies must have a version requirement specified when packaging.
dependency `velo` does not specify a version
With version = "0.17.0", the relock changes only the source and checksum lines of velo, velo-ext and ucx-rs in the three lock files. After it, cargo metadata --locked passes for all four manifests, and velo_response push_handler passes (12 tests). The same relock also repairs lib/runtime/examples/Cargo.lock.
The git source came with #15231. Of the velo pins in this stack, this is the first with a crates.io release, so this PR is the cheapest place to switch.
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Previously reported defects still present:
- Original discussion: Concurrent sender calls can all pass the DashSet contains check before any handshake finishes, so each performs peer registration and the initial handler handshake. The prepare-once optimization is therefore not single-flight for a frontend's first request burst.
- Original discussion: The added prepared_peers length assertion is still present at lib/runtime/src/pipeline/network/velo_response.rs:628, and it still only proves one peer ID remains in the set after two sequential streams. It remains green if sender runs the registration and handshake path on every stream before reinserting the same peer, so it does not distinguish the prepare-once regression; replace it with an observable count of entries into the prepare branch or remove the added check.
- Original discussion: The opening doc-comment sentence and separator remain; they merely restate
RESPONSE_CREDIT_WINDOWbefore the detailed rationale. - Original discussion: The test comment still narrates the immediately following setup and assertion without recording a non-obvious constraint.
- Original discussion: The updated git-sourced velo dependency still has no version requirement, so cargo packaging of dynamo-runtime fails manifest validation.
- Original discussion: Verified still present: concurrent first streams for one frontend can all pass the DashSet contains check before any awaits complete and each run peer registration and the handler handshake. The initial high-concurrency burst therefore retains duplicated frontend control-plane work and first-token delay.
- Original discussion: Verified still present: the check at
senderline 358 and insertion at line 371 remain separated by awaited preparation, so concurrent first streams for one frontend all enter the preparation branch. The PR therefore does not provide once-per-peer preparation for an initial concurrent burst; use per-peer singleflight state and publish readiness only after successful registration and handshake. - Original discussion: Verified still present: the git-only velo dependency has no version requirement, so cargo cannot package dynamo-runtime because every packaged dependency must declare a version.
| // Velo checks cached lifecycle support for this peer instance | ||
| // first. Its initial hello also installs the reverse UCX | ||
| // address; stream slot opens do not perform that peer | ||
| // handshake, so it runs once per peer, here. |
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The prepared_peers guard already makes the once-per-peer behavior explicit. Retain the preceding explanation that stream slot opens do not perform the handshake, but remove this implementation narration.
🤖 AI Fix
Remove the phrase so it runs once per peer, here while retaining the explanation of the required handshake.
velo is a crates.io dependency again, in place of the git rev bee8b8e. 0.18.0 (velo-ext 0.5.4) adds producer backpressure at the per-slot byte cap, QUIC and TCP transport lanes, mux lanes, a fix for a connection gauge deadlock, and a TCP socket-buffer option. The adapter needs no code change. The lock files come from `cargo update -p velo -p velo-ext`. Only velo, velo-ext and ucx-rs change. The root lock also moves a few Windows-only windows-sys, heck and itertools edges of other crates to versions that are already in it. Signed-off-by: Ryan Olson <rolson@nvidia.com>
The TCP response transport is built with lanes(4). Each lane is its own TCP connection, read by its own task on the frontend, and the velo mux spreads the response streams over the lanes. One connection is limited by the task that reads it. On the two-node mocker rig (8 x 64 workers, concurrency 8,192, ISL 1,024, OSL 900), 4 lanes against 1, both on velo 0.18.0: 2,406 against 1,359 requests/s, ITL p99 4.9 against 15.0 ms, end-to-end p99 4.5 against 13.5 s, and 20.0 against 37.4 ms of frontend CPU per request. tcp_responses_use_four_lanes builds the transport and checks its lane count; it fails when the lanes() call is removed. UCX has no lanes and is unchanged. Signed-off-by: Ryan Olson <rolson@nvidia.com>
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/ok to test e55a5c5 |
@ryanolson, there was an error processing your request: See the following link for more information: https://docs.gha-runners.nvidia.com/cpr/e/2/ |
Signed-off-by: jthomson04 <jwillthomson19@gmail.com>
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Superseded by #15231 at 0a579b9. The combined branch retains Ryan Olson’s authored peer-preparation/credit and four-lane commits, shared peer initialization with retry, mux-only services, Runtime ownership and shutdown, and the actual-handshake regression test. It uses merged Velo 18f51dba95687dc5408d960f90e134b013c2fb12 and updates all four lockfiles. Benchmark files remain local. Ryan’s branch is retained. |
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Summary
Prepare each Velo response peer once, share concurrent preparation attempts, and retry failed attempts. Keep the measured four TCP lanes and credit window of 32. Add request-context diagnostics for setup, cancellation, stop, and unexpected stream termination.
Use Velo's core communication stack with
default-features = false, optionalvelo-ucx, and.mux_only(). This removes the unused fallback TCP listener while retaining large responses through chunked rendezvous. KVBM crates explicitly enableservicesbecause they use distributed events and filesystem discovery. The response runtime alone does not enable services.Tie the process-shared response service to Dynamo Runtime owners. Runtime clones share one owner. After endpoint drain, the last Runtime owner awaits full Velo shutdown before it cancels the main runtime token. Other Runtime owners keep the service active; stream handles do not prevent explicit shutdown. Retain an owned Tokio runtime until its shared service closes. A later Runtime can create a fresh service.
Release status
This PR targets the Velo 0.19.0 breaking release from compatible cleanup, optional services, and ownership/API cleanup. The two breaking PRs are independent follow-ups to the compatible baseline.
The release is not published. For reproducible validation, the manifest and all three affected lockfiles pin the combined candidate at
c271c5837b7df171aa10a72e6d1780e615a150ca. Replace the Git source/revision with the registryversion = "0.19.0"after that release is published. This PR remains a draft while that release is pending.Validation
The refreshed candidate passes 5 selected TCP tests, 6 selected UCX tests, and the Runtime graceful-shutdown regression.
UCX_TLS=tcp.cargo metadata --locked. Cargo trees confirm response-runtime Velo features are empty by default and[ucx]withvelo-ucx, while KVBM enables[services].The combined Velo candidate passes 1,744 all-feature tests, 1,126 core tests, 1,292 core+UCX tests, production library checks, Clippy, formatting, and documentation checks. Its local request/reply and streaming benchmark comparison is recorded on the Velo PRs.
No full KVBM/CUDA binding build or RDMA hardware test was run for this update. The performance campaign below used Velo 0.18.0; it has not been repeated for this 0.19.0 candidate.
Prior performance measurements (Velo 0.18.0)
The two-node mocker rig: 8 worker processes of 64 workers, concurrency 8,192, ISL 1,024, OSL 900, speedup 10, 150,000 requests per rep, 3 interleaved reps, aiperf with
--use-server-token-count. Both phases ran in one allocation on one node pair. Medians; TTFT is on the settled window (requests that started 10 s or later).bee8b8e, TCP, 1 lane (before)bee8b8e(15.0 against 10.0 ms, and 13.5 against 9.1 s). In this setup both rise with the requests in flight, and the onebee8b8erep with as many requests in flight as the 0.18.0 reps (8,094) had 13.7 ms, against 13.5 to 16.0. That is one rep, so it is evidence, not proof.