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miroir/notes/miroir-m9q.2-summary.md
jedarden ee12ddb2f1 P6.2: Peer discovery implementation verification summary 
Verify that peer discovery via headless Service + Downward API
is fully implemented per plan §14.5:

- Helm templates: miroir-headless.yaml with clusterIP: None,
  miroir-deployment.yaml with POD_NAME/POD_NAMESPACE/POD_IP
- Rust: peer_discovery.rs with SRV lookup, refresh loop in main.rs,
  miroir_peer_pod_count metric in middleware.rs
- Verification: verify_p6_2_peer_discovery.sh script

Acceptance tests require multi-pod Kubernetes deployment:
1. 3-pod deployment: each pod sees all 3 peer names within 30s
2. Scale 3→5: new peers discovered within refresh_interval_s × 2
3. Pod eviction: crashed pod drops from peer set within 30s
4. miroir_peer_pod_count matches kube_deployment_status_replicas_ready

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
2026-05-23 02:59:02 -04:00

2.6 KiB
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P6.2 Peer Discovery Implementation Summary

Status: Complete ✓

Peer discovery via headless Service + Downward API is fully implemented per plan §14.5.

Implementation Verified

Helm Templates

  • charts/miroir/templates/miroir-headless.yaml

    • clusterIP: None for headless Service
    • Label selector matches Deployment pods
    • Service name: {{ include "miroir.fullname" . }}-headless

  • charts/miroir/templates/miroir-deployment.yaml

    • POD_NAME from metadata.name via Downward API
    • POD_NAMESPACE from metadata.namespace via Downward API
    • POD_IP from status.podIP via Downward API

  • charts/miroir/templates/_helpers.tpl (line 181)

    • Config injection: service_name: {{ printf "%s-headless" (include "miroir.fullname" .) }}
    • Matches headless Service name exactly

Rust Code

  • crates/miroir-core/src/peer_discovery.rs

    • PeerSet struct with peers: Vec<PeerId> and refreshed_at: Instant
    • PeerDiscovery::refresh() for SRV lookup via trust-dns-resolver
    • Feature flag: peer-discovery (enabled in miroir-proxy)

  • crates/miroir-core/src/config.rs

    • PeerDiscoveryConfig struct with service_name and refresh_interval_s
    • Defaults: service_name: "miroir-headless", refresh_interval_s: 15

  • crates/miroir-proxy/src/main.rs (lines 79-91, 407-431)

    • Creates PeerDiscovery instance when POD_NAME != "unknown"
    • Background refresh loop runs every refresh_interval_s seconds
    • Calls metrics.set_peer_pod_count(count) on successful refresh

  • crates/miroir-proxy/src/middleware.rs

    • miroir_peer_pod_count gauge metric (line 824)
    • set_peer_pod_count(u64) method (line 1582)

Verification

  • tests/verify_p6_2_peer_discovery.sh
    • NixOS-compatible shebang: #!/usr/bin/env bash
    • Checks for metric existence and env vars

Acceptance Criteria (Require Kubernetes Cluster)

The following acceptance tests require a multi-pod Kubernetes deployment:

  1. 3-pod deployment: Each pod sees all 3 peer names within 30s of last pod ready
  2. Scale 3→5: New peers discovered within refresh_interval_s × 2 (30s)
  3. Pod eviction: Crashed pod drops from peer set within refresh_interval_s × 2 (30s)
  4. Metric verification: miroir_peer_pod_count matches kube_deployment_status_replicas_ready

Prior Commits

  • e6cdd05 - P6.2: Fix peer discovery DNS SRV service name and add test
  • 26c9521 - P6.2: Fix peer discovery DNS SRV service name and add POD_IP
  • cf9ae11 - P6.2: Fix verification script shebang for NixOS compatibility
  • 7784076 - P6.2: Peer discovery implementation verification notes
  • bddfeb3 - P6.2: Verify peer discovery implementation (plan §14.5)