[zhongdaor-nv]

Overview

Make ZMQ the default event plane for every discovery backend. Previously the default was backend-driven — local backends (file/mem) used ZMQ while distributed backends (etcd/kubernetes) used NATS. Now ZMQ is the default everywhere; NATS remains a first-class opt-in via DYN_EVENT_PLANE=nats.

Since the request plane already defaults to TCP, a standard etcd deployment now opens no NATS connection by default — NATS is only connected when explicitly requested (DYN_EVENT_PLANE=nats, NATS_SERVER set, DYN_REQUEST_PLANE=nats, durable KV events, or the NATS audit sink).

Changes

• discovery::EventTransportKind: #[default] and from_env() / from_env_or_default() now resolve to Zmq when DYN_EVENT_PLANE is unset/empty.
• DiscoveryBackend::resolve_event_transport_kind (authoritative resolver): unset/empty/invalid → Zmq unconditionally (dropped the backend-driven branch).
• Durable KV events stay NATS-only. The subscriber still refuses to start the JetStream path under a non-NATS transport, but now with an actionable message: set DYN_EVENT_PLANE=nats or drop --durable-kv-events.
• Tests: tests/conftest.py pins DYN_EVENT_PLANE=nats when durable_kv_events=True so the durable/JetStream path keeps working under the new default.
• Docs / CLI help: event-plane design doc, router guide, CLAUDE.md, and the --event-plane help text updated to describe ZMQ-default / NATS-opt-in.

Compatibility / blast radius

• Audited every default-path NATS consumer (audit sink, trace, FPM, LoRA, worker-query recovery, runtime accessors, discovery): all either ride the transport-agnostic event plane, are explicit opt-ins, or handle an absent NATS client gracefully. Nothing in the default path crashes for lack of NATS.
• Rollback is a single env var: DYN_EVENT_PLANE=nats restores prior behavior.

Testing

• cargo test --locked -p dynamo-runtime --lib — 395 passed (incl. ZMQ transport tests)
• cargo clippy --locked --no-deps -p dynamo-runtime -p dynamo-llm — clean
• Build of dynamo-runtime + dynamo-llm — green

🤖 Generated with Claude Code

Summary by CodeRabbit

• Configuration Changes

  • Event plane now defaults to ZMQ instead of NATS across all discovery backends.
  • NATS event transport is now opt-in via configuration flag.

• Documentation & Help Text

  • Updated CLI help text and configuration documentation to reflect new event plane defaults.
  • Improved error messages to guide users on configuring NATS when needed.

[github-actions]

🌿 Fern Docs Preview: https://nvidia-preview-21679e01-e607-470f-91e6-269e3b9ff56d.docs.buildwithfern.com/dynamo/dev

[coderabbitai]

Walkthrough

Switches the default DYN_EVENT_PLANE / EventTransportKind from NATS (previously auto-selected based on discovery backend) to ZMQ universally. NATS becomes strictly opt-in via DYN_EVENT_PLANE=nats. The change propagates through the Rust runtime resolution logic, a durable-KV mismatch error message, the Python test fixture's env-var save/restore handling, CLI help strings, and documentation.

Changes

ZMQ as universal default event plane

Layer / File(s)	Summary
EventTransportKind default and resolve_event_transport_kind logic lib/runtime/src/discovery/mod.rs, lib/runtime/src/distributed.rs	#[default] variant on EventTransportKind switched from Nats to Zmq; from_env() and from_env_or_default() return Zmq for unset/empty/invalid DYN_EVENT_PLANE. resolve_event_transport_kind removes is_local() branching and uses DYN_EVENT_PLANE as the sole authoritative source with Zmq as the universal fallback; doc comments updated.
Durable-KV mismatch error and test fixture env-var lifecycle lib/llm/src/kv_router/indexer/recovery/subscriber.rs, tests/conftest.py	anyhow::bail! message in start_subscriber updated to name the ZMQ default and offer DYN_EVENT_PLANE=nats or removing --durable-kv-events. runtime_services_dynamic_ports fixture now snapshots DYN_EVENT_PLANE before the test, pins it to "nats" when durable_kv_events=True, and restores or removes it at teardown.
CLI help text and documentation components/src/dynamo/common/configuration/groups/runtime_args.py, components/src/dynamo/frontend/frontend_args.py, docs/design-docs/event-plane.md, docs/components/router/router-guide.md	--event-plane help strings in both Python arg groups drop auto-detection wording and document zmq as the fixed default. Design doc transport table, Transport Selection instructions, and Environment Variables section are rewritten for the ZMQ default / NATS opt-in model; router-guide KV event transport table updated accordingly.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description covers the overview, detailed changes, and testing validation, but the 'Related Issues' section is incomplete—it neither links to issues nor confirms no related issue exists with the required checkbox.	Complete the 'Related Issues' section by either linking to relevant issues (e.g., 'Closes #XXXX') or checking the 'Confirmed — no related issue' checkbox if the PR is not linked to any issue.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly summarizes the main change: switching the default event plane to ZMQ for all backends.

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@tests/conftest.py`:
- Line 1172: Move the function-local import os statement from line 1172 to the
top of the conftest.py file with the other imports. Then, replace all direct
os.environ mutation assignments (lines 1188-1209) with monkeypatch.setenv()
calls. Ensure the fixture receives monkeypatch as a parameter so it can call
monkeypatch.setenv(key, value) instead of os.environ[key] = value for each
environment variable being set.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

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Run ID: 2a06e340-4619-46ca-bc0a-79e6cbe8a4ee

📥 Commits

Reviewing files that changed from the base of the PR and between f9e8854 and e94f4cf.

📒 Files selected for processing (8)

• components/src/dynamo/common/configuration/groups/runtime_args.py
• components/src/dynamo/frontend/frontend_args.py
• docs/components/router/router-guide.md
• docs/design-docs/event-plane.md
• lib/llm/src/kv_router/indexer/recovery/subscriber.rs
• lib/runtime/src/discovery/mod.rs
• lib/runtime/src/distributed.rs
• tests/conftest.py

[biswapanda]

lgtm

[athreesh]

LGTM!