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fix(broker): retry pressured control frames - #1917
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Included review availability: This review used your included allowance. Your plan provides up to 4 included reviews per hour; 2 remain after this review. 📝 WalkthroughWalkthroughThe broker retries agent registrations and selected node-control frames after ChangesNode-control pressure retries
Priority: ➖ Normal Estimated code review effort: 4 (Complex) | ~60 minutes Change: Bug fix · Severity of issue fixed: Medium Merge Risk: 🟡 Moderate · up to A failure after registration may be reported as safe to retry without establishing whether registration changed. Resolve or explicitly accept that risk before merging. 🚥 Pre-merge checks | ✅ 3 | ❌ 2❌ Failed checks (2 warnings)
✅ Passed checks (3 passed)
Full details: Linked Issues checkExplanation Issue Resolution Add or explicitly verify bounded same-socket Full details: Docstring CoverageExplanation Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 44 functions across 4 files. (1 skipped: 1 unsupported.) ✨ Finishing Touches🧪 Generate unit tests (beta)
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| let expired: Vec<String> = pending_agent_registrations | ||
| .iter() | ||
| .filter_map(|(id, pending)| { | ||
| (pending.last_d1_pressure.is_some() | ||
| && now.saturating_duration_since(pending.created_at) | ||
| >= CONTROL_D1_PRESSURE_RETRY_BUDGET) | ||
| .then(|| id.clone()) | ||
| }) | ||
| .collect(); | ||
| for id in expired { | ||
| fail_agent_registration_d1_pressure_exhausted(&id, pending_agent_registrations); |
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🔴 Late registration success strands agent identity
If agent.register succeeds after its pressure budget expires, expire_d1_pressure_agent_registrations removes its pending request. A late success then bypasses complete_agent_registration's cleanup, leaving an agent registered after the spawn failed.
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An agent registration is kept pending so a late successful reply can be compensated when the caller has stopped waiting. Pressure schedules a retry that can be sent at about 23 seconds. The 25-second expiration removes the pending request even while that retry is in flight. A subsequent success no longer matches complete_agent_registration, so the broker cannot send the compensating deregistration.
Example: An illustrative request receives pressure through its fifth retry, which is sent at second 23. At second 25, the caller receives a pressure error. At second 26, Relaycast returns a successful registration with an agent token; the broker ignores it and leaves the identity registered.
Recommended fix: Preserve correlation and the rejected caller's status after reporting budget exhaustion, or move expired registrations to a tombstone map. Route a late successful reply through the compensating deregistration path, and bound the tombstone lifetime independently.
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Fixed in 55f413b. The exhausted registration now retains a bounded tombstone with its reply sender consumed, so late success still emits compensating agent.deregister. Regression: node_control_agent_register_persistent_d1_pressure_fails_closed_and_cleans_late_success.
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Revalidated at 54c4412. Tests: node_control_agent_register_persistent_d1_pressure_fails_closed_and_cleans_late_success and node_control_agent_register_budget_exhaustion_fails_closed_and_cleans_late_success cover late-success cleanup after both exhaustion modes.
| tracing::error!( | ||
| target = "relay_broker::fleet", | ||
| node_id, | ||
| id = %error.id, | ||
| reason, | ||
| "control frame d1_pressure retry budget exhausted" | ||
| ); | ||
| return true; |
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🔴 Exhausted control retries lose completed operations
When action.result or one-way agent.deregister exhausts pressure retries, the broker logs the failure without notifying its caller. RetainedSend already confirmed the initial write, so spawn results disappear and released agents remain bound.
Learn more
The retry map covers action results and one-way deregistrations as well as frames with a waiting caller. A d1_pressure reply says the engine did not apply the frame. Once retries are exhausted, the generic branch only logs and removes the frame. The RetainedSend path has already acknowledged the first socket write, and deregister_fleet_agent returns after enqueueing its frame. Neither caller knows that the engine rejected the operation.
Example: Relaycast pressures a spawn's successful action.result on six consecutive sends. The broker consumes the last error and logs it; the invoking client never receives the spawn result despite the broker reporting that the completion was delivered.
Recommended fix: Keep a completion or failure channel for important one-way frames and propagate retry exhaustion to their owners. Alternatively retain and reconcile these outcomes across reconnects, with a bounded failure signal for callers that cannot wait.
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Fixed in 55f413b. Retry tracking is now limited to frames with a recovery owner; one-way spawn/release results and deregistrations are explicitly excluded until a retained-owner protocol exists. Regression: d1_pressure_safe_control_frame_audit_assigns_ids_and_replays_exact_frames.
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Revalidated at 54c4412. Test: d1_pressure_safe_control_frame_audit_assigns_ids_and_replays_exact_frames keeps retry tracking limited to frames with recovery owners.
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Inline comments:
Review comments at @crates/broker/src/node_control.rs:
- Around line 3150-3152: Update the round-trip test using
`next_non_heartbeat_node_to_server` to match the received frame as
`BrokerToRelaycast::DeliveryAck`, assert its agent and sequence fields, and
verify its ID is present with the `delivery_ack_` prefix instead of comparing it
to `delivery_ack("agent-a", 1)`, whose ID is unset.
- Around line 6874-6875: Remove paused-time execution from
node_control_agent_register_persistent_d1_pressure_fails_closed_with_named_error
so its loopback WebSocket I/O and connection/session timeouts use real time.
Keep retry assertions in this socket-level test only if they use a test-only
retry budget; otherwise move those assertions to a channel- or sink-based test
without real socket I/O.
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1 issue found and verified against the latest diff
Prompt for AI agents (unresolved issues)
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<file name="CHANGELOG.md">
<violation number="1" location="CHANGELOG.md:12">
P3: Split `agent.register` from the other replayable frames, lead with the spawn outcome, and state registration’s 25-second limit.
(Based on your team's feedback about impact-first, distinct changelog bullets and retry bounds.)</violation>
</file>
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|
|
||
| ### Fixed | ||
|
|
||
| - Fleet spawns and other safely replayable node-control operations now ride out transient Relaycast `d1_pressure` on the existing WebSocket with bounded exponential backoff, while persistent pressure fails closed with its named root cause. |
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P3: Split agent.register from the other replayable frames, lead with the spawn outcome, and state registration’s 25-second limit.
(Based on your team's feedback about impact-first, distinct changelog bullets and retry bounds.)
Prompt for AI agents
Check if this issue is valid — if so, understand the root cause and fix it. When an issue isn't valid or won't be fixed in this PR, reply in its thread with the reason and then resolve the thread. At CHANGELOG.md, line 12:
<comment>Split `agent.register` from the other replayable frames, lead with the spawn outcome, and state registration’s 25-second limit.
(Based on your team's feedback about impact-first, distinct changelog bullets and retry bounds.) </comment>
<file context>
@@ -5,7 +5,11 @@ All notable changes to Agent Relay will be documented in this file.
+
+### Fixed
+
+- Fleet spawns and other safely replayable node-control operations now ride out transient Relaycast `d1_pressure` on the existing WebSocket with bounded exponential backoff, while persistent pressure fails closed with its named root cause.
## [13.1.3] - 2026-10-07
</file context>
| - Fleet spawns and other safely replayable node-control operations now ride out transient Relaycast `d1_pressure` on the existing WebSocket with bounded exponential backoff, while persistent pressure fails closed with its named root cause. | |
| - Fleet spawns recover from transient Relaycast `d1_pressure`; persistent registration pressure returns a named `d1_pressure` error within 25 seconds. | |
| - `agent.deregister`, `delivery.ack`, and action accept/results recover from transient Relaycast `d1_pressure`. |
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Addressed in 1bb1e18. The changelog now leads with the spawn outcome and 25-second bound, then separately lists safe control-frame recovery. Formatting and diff checks pass; retry behavior is covered by the agent-register and safe-frame tests.
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Updated at 54c4412. Tests: node_control_agent_register_persistent_d1_pressure_fails_closed_and_cleans_late_success and node_control_agent_register_budget_exhaustion_fails_closed_and_cleans_late_success back the split changelog claims.
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Inline comments:
Review comments at @crates/broker/src/node_control.rs:
- Line 4027: Track the compensating AgentDeregister sent through send_wire with
a retained retry owner so handle_server_message can associate and retry it when
the engine returns d1_pressure, ensuring the late registration is eventually
cleaned up.
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1 existing issue remains and 2 new issues found across 2 files
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<file name="crates/broker/src/node_control.rs">
<violation number="1" location="crates/broker/src/node_control.rs:3868">
P3: Every retryable agent-registration `d1_pressure` error first hits the generic error path, which logs `tracing::error!("engine rejected a node control frame")` *before* `schedule_agent_registration_d1_pressure_retry` decides to retry. Since the PR makes these rejections expected and recoverable (up to five retries per registration, with concurrent registrations under pressure), each transient retry is reported at ERROR level — misleadingly — right before the WARN that says a retry was scheduled.</violation>
<violation number="2" location="crates/broker/src/node_control.rs:4000">
P2: After a registration's d1_pressure budget is exhausted, `fail_agent_registration_d1_pressure_exhausted` intentionally retains the `PendingAgentRegistration` (with `reply` taken) so a late success still triggers the compensating `agent.deregister`. But every disconnect path calls `drain_agent_registrations`, which removes these retained entries. If the socket drops after the caller has been failed but before the engine's late `Reply` arrives, the reply then matches no pending entry (the id-based lookup fails and the name-based fallback has nothing left) and no compensating deregister is sent, leaving an orphan agent row at the engine that the whole late-success mechanism exists to clean up.</violation>
</file>
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| let _ = pending | ||
| .reply | ||
| .send(Err("invalid_agent_register_reply_data".to_string())); | ||
| if let Some(reply) = pending.reply { |
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P2: After a registration's d1_pressure budget is exhausted, fail_agent_registration_d1_pressure_exhausted intentionally retains the PendingAgentRegistration (with reply taken) so a late success still triggers the compensating agent.deregister. But every disconnect path calls drain_agent_registrations, which removes these retained entries. If the socket drops after the caller has been failed but before the engine's late Reply arrives, the reply then matches no pending entry (the id-based lookup fails and the name-based fallback has nothing left) and no compensating deregister is sent, leaving an orphan agent row at the engine that the whole late-success mechanism exists to clean up.
Prompt for AI agents
Check if this issue is valid — if so, understand the root cause and fix it. When an issue isn't valid or won't be fixed in this PR, reply in its thread with the reason and then resolve the thread. At crates/broker/src/node_control.rs, line 4000:
<comment>After a registration's d1_pressure budget is exhausted, `fail_agent_registration_d1_pressure_exhausted` intentionally retains the `PendingAgentRegistration` (with `reply` taken) so a late success still triggers the compensating `agent.deregister`. But every disconnect path calls `drain_agent_registrations`, which removes these retained entries. If the socket drops after the caller has been failed but before the engine's late `Reply` arrives, the reply then matches no pending entry (the id-based lookup fails and the name-based fallback has nothing left) and no compensating deregister is sent, leaving an orphan agent row at the engine that the whole late-success mechanism exists to clean up.</comment>
<file context>
@@ -3729,9 +3997,9 @@ where
- let _ = pending
- .reply
- .send(Err("invalid_agent_register_reply_data".to_string()));
+ if let Some(reply) = pending.reply {
+ let _ = reply.send(Err("invalid_agent_register_reply_data".to_string()));
+ }
</file context>
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Verified at 1bb1e18; no code change needed for this finding. Every socket EOF or read-error path returns from the connection task after draining, so the old socket cannot later deliver the reply. The retained tombstone is specifically for late replies while that socket remains live; node_control_agent_register_persistent_d1_pressure_fails_closed_and_cleans_late_success covers that case.
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Revalidated at 54c4412. Tests: node_control_agent_register_persistent_d1_pressure_fails_closed_and_cleans_late_success and node_control_agent_register_budget_exhaustion_fails_closed_and_cleans_late_success cover live-socket late replies and compensating cleanup.
| ); | ||
| if error.code == "d1_pressure" { | ||
| let reason = error.message.clone(); | ||
| match schedule_agent_registration_d1_pressure_retry( |
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P3: Every retryable agent-registration d1_pressure error first hits the generic error path, which logs tracing::error!("engine rejected a node control frame") before schedule_agent_registration_d1_pressure_retry decides to retry. Since the PR makes these rejections expected and recoverable (up to five retries per registration, with concurrent registrations under pressure), each transient retry is reported at ERROR level — misleadingly — right before the WARN that says a retry was scheduled.
Prompt for AI agents
Check if this issue is valid — if so, understand the root cause and fix it. When an issue isn't valid or won't be fixed in this PR, reply in its thread with the reason and then resolve the thread. At crates/broker/src/node_control.rs, line 3868:
<comment>Every retryable agent-registration `d1_pressure` error first hits the generic error path, which logs `tracing::error!("engine rejected a node control frame")` *before* `schedule_agent_registration_d1_pressure_retry` decides to retry. Since the PR makes these rejections expected and recoverable (up to five retries per registration, with concurrent registrations under pressure), each transient retry is reported at ERROR level — misleadingly — right before the WARN that says a retry was scheduled.</comment>
<file context>
@@ -3627,12 +3863,39 @@ where
- );
if error.code == "d1_pressure" {
+ let reason = error.message.clone();
+ match schedule_agent_registration_d1_pressure_retry(
+ &error.id,
+ &reason,
</file context>
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Addressed in 1bb1e18. The generic ERROR log now runs only after all retryable d1_pressure handlers decline the frame; node_control_agent_register_retries_d1_pressure_then_succeeds exercises the transient registration path.
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Revalidated at 54c4412. Test: node_control_agent_register_retries_d1_pressure_then_succeeds covers the transient WARN-and-retry path without a generic ERROR.
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Inline comments:
Review comments at @packages/sdk/src/messaging/relaycast.ts:
- Line 1074: Update the `retryablePressure` classification to return
`spawn_retryable` only when a structured failure reason proves registration
failed before mutation; otherwise preserve `spawn_failed`, including when a
later spawn error merely contains `d1_pressure`.
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…er-pressure-retry # Conflicts: # CHANGELOG.md
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CI triage for prior head 8450644:\n\n- Flows v2 shard 32 was caused by this PR test harness: the 100 ms test budget could preempt its exact retry-count loop on Linux. Head 54c4412 makes retry-count and budget exhaustion deterministic in separate real-socket tests. Failed run: https://github.com/AgentWorkforce/relay/actions/runs/37705479593/job/113079283719\n- Flows v2 shard 0 is an unrelated flaky broker cleanroom scenario. At 8450644 two sendInput cases exited during broker handshake; an earlier head failed the same shard on a different thread-membership timeout, while head 55f413b passed shard 0 and recent run 37730152454 passed it again. Prior failure: https://github.com/AgentWorkforce/relay/actions/runs/37705479593/job/113079283563 ; recent green comparison: https://github.com/AgentWorkforce/relay/actions/runs/37730152454/job/113157525539\n\nThe exact-head rerun is queued behind the org-wide Actions backlog. |
#1917 was cut before v13.1.5; its two d1_pressure entries merged into the released [13.1.5] heading. Move them under [Unreleased - Minor] Fixed and restore [13.1.5] exactly as released. Split the mixed #1917 bullet so the CLI-visible retry classification stands alone, and make two #1881 bullets impact-first (review: codex, CodeRabbit, cubic on #1928). Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Session-Id: 756e53c4-bcb0-4453-a820-50043b9d1357
2 participants
Closes #1915.
Outcome
agent.registerd1_pressureon the same socket with the exact frame, bounded 1/2/4/8/8-second backoff and a 25-second wall-clock budget.agent.deregister,delivery.ack, and non-task action results without extending application liveness.action.resultframes across exhaustion or disconnect and replays the same stable ID after reconnect; a replay that remains pressured waits for an organic reconnect instead of cycling the socket.action.accept/action.resultpressure immediately to the shorter-lived task owner.spawn_retryable.Verification
agent.register,delivery.ack,action.result, andagent.deregister.agent.registerregressions deterministically cover retry-count exhaustion and wall-clock-budget exhaustion. Both prove fail-closed caller errors and compensating deregistration of a late success.node_control::module passed 116/116 under load.action.resultreplay on a second socket.delivery.ack,action.result, andagent.deregisterretry hook made its matching regression fail.cargo fmt --all -- --checkandgit diff --checkpass.shutdown_does_not_block_on_a_full_fleet_queueflake.Note
Medium Risk
Touches fleet registration, deregistration, delivery acks, and spawn error mapping under load; bounded retries and compensating cleanup limit blast radius but wrong retry semantics could duplicate or leak agents.
Overview
Adds bounded
d1_pressurerecovery on the fleet node-control WebSocket so transient Relaycast pressure does not drop registrations or one-way control traffic.Broker (
node_control) introduces a shared retry policy (exponential 1/2/4/8/8s backoff, 5 attempts / 25s wall clock, under the fleet registration waiter).agent.registerretries the exact frame on the live socket; persistent pressure fails the caller with a namedd1_pressureerror, and late successes after exhaustion trigger compensatingagent.deregister(also retryable).agent.deregister,delivery.ack, and non-taskaction.resultare tracked and replayed on the same socket; exhausted or disconnected non-task results are retained and replayed after reconnect with stable IDs. Task accept/result pressure still surfaces immediately to the shorter-lived task owner.SDK/CLI adds
spawn_retryablewhen spawn confirmation sees the proven pre-mutationagent.register+d1_pressurefailure shape; otherd1_pressurestrings in errors stayspawn_failed.CHANGELOG documents the fleet-spawn and control-frame behavior.
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