K8s based service discovery

[kaustubhbabar5]

Kubernetes Discovery PR Summary (#316)

Summary

Adds Kubernetes-native cluster discovery for Tinode. Users can now run Tinode as
a StatefulSet and let pods discover peers automatically from the headless
Service EndpointSlice, instead of maintaining a static
cluster_config.nodes list.

How To Use

Apply the provided manifests:

kubectl apply -f docker/k8s/
kubectl rollout status statefulset/tinode

Enable Kubernetes discovery in tinode.conf:

"cluster_config": {
  "self": "",
  "discovery": {
    "mode": "kubernetes",
    "kubernetes": {
      "namespace": "",
      "service": "tinode-headless",
      "port_name": "cluster"
    }
  }
}

Scale the cluster with Kubernetes:

kubectl scale statefulset/tinode --replicas=5

Notes

• Requires a StatefulSet; Deployment is not supported because Tinode derives
  stable worker IDs from pod ordinals.
• Requires the POD_NAME downward API environment variable.
• The headless Service must expose the cluster RPC port with the name cluster.
• Static nodes and failover config are ignored in Kubernetes discovery mode.
• Cluster size can be checked through TotalClusterNodes in stats.

[kaustubhbabar5]

@or-else requesting your review for this

[or-else]

I'll try to review this weekend.

[Copilot]

Pull request overview

Adds Kubernetes-native cluster membership discovery (EndpointSlice watch) and readiness/liveness health endpoints so Tinode can run as a StatefulSet and automatically reconcile cluster peers without a static cluster_config.nodes list.

Changes:

• Add Kubernetes discovery backend + reconciler to dynamically add/remove peers and rebuild the ring from EndpointSlices.
• Add /livez and /readyz endpoints backed by new store/DB CheckHealth() plumbing across adapters.
• Add K8s/Minikube deployment manifests/docs and update Go module dependencies for client-go.

Reviewed changes

Copilot reviewed 38 out of 40 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
server/tinode.conf	Documents new cluster_config.discovery configuration.
server/store/store_health_test.go	Unit tests for Store.CheckHealth() behavior.
server/store/store.go	Adds CheckHealth() to store interface/implementation.
server/store/mock_store/mock_store.go	Updates gomock store interface to include CheckHealth().
server/main.go	Registers health handlers and minor comment fix.
server/hub.go	Avoids nil deref by using a single owner/proxy snapshot from cluster.
server/http_health_test.go	Tests /livez and /readyz handlers and HEAD behavior.
server/http.go	Adds health endpoints + readiness check against persistent store.
server/db/rethinkdb/tests/rethink_test.go	Adds build tags for rethinkdb tests.
server/db/rethinkdb/adapter.go	Implements RethinkDB CheckHealth().
server/db/postgres/tests/postgres_test.go	Adds build tags for postgres tests.
server/db/postgres/adapter.go	Implements Postgres CheckHealth() via Ping.
server/db/mysql/tests/mysql_test.go	Adds build tags for mysql tests.
server/db/mysql/adapter.go	Implements MySQL CheckHealth() via PingContext.
server/db/mongodb/tests/mongo_test.go	Adds build tags for mongodb tests.
server/db/mongodb/adapter.go	Implements MongoDB CheckHealth() via Ping.
server/db/common/common.go	Adds shared HealthCheckTimeout constant.
server/db/adapter.go	Extends DB adapter interface with CheckHealth().
server/cluster_test.go	Adds tests for peer add/remove, snapshot apply, worker ID parsing, concurrency.
server/cluster_leader.go	Uses ring signature accessor compatible with locked ring updates.
server/cluster_discovery_test.go	Unit tests for EndpointSlice-based discovery using fake clientset.
server/cluster_discovery.go	Implements discovery abstraction (static + Kubernetes informer backend).
server/cluster.go	Adds discovery mode, reconciler, runtime peer retirement, ring locking helpers, k8s worker ID derivation.
go.sum	Updates dependency checksums (adds k8s + related transitive deps).
go.mod	Adds k8s.io/* dependencies and updates several module versions / Go version directive.
docs/cluster-peer-retirement-options.md	Design notes for safe peer retirement under churn.
docker/tinode/entrypoint-k8s.sh	K8s-specific entrypoint wrapper (POD_NAME validation, stdout/stderr behavior).
docker/tinode/Dockerfile.k8s	Adds a workspace-built Tinode image for Minikube/local K8s testing.
docker/tinode/Dockerfile	Copies in entrypoint-k8s.sh for use as a command override.
docker/local-k8s/README.postgres-minikube.md	Local Minikube validation guide for k8s discovery.
docker/local-k8s/15-postgres.yaml	Local Postgres deployment/service manifest for Minikube testing.
docker/k8s/README.md	Reference docs for StatefulSet + EndpointSlice discovery deployment.
docker/k8s/30-statefulset.yaml	StatefulSet manifest with probes, POD_NAME env, and preStop delay.
docker/k8s/20-configmap.yaml	ConfigMap enabling cluster_config.discovery.mode = kubernetes.
docker/k8s/10-service.yaml	Headless Service exposing ws/grpc/cluster ports for EndpointSlices.
docker/k8s/00-rbac.yaml	Namespace-scoped RBAC for watching EndpointSlices.
docker-compose.dev.yml	Adds a dev postgres compose file.
README.md	Links to Kubernetes manifests and Minikube guide.
INSTALL.md	Adds Kubernetes deployment instructions and constraints.
.gitignore	Ignores local editor/tooling directories.

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[or-else]

@kaustubhbabar5 while waiting for my review, please address copilot comments.
Did you sign the CLA?
https://github.com/tinode/chat/blob/master/docs/CLA.md

Thanks!

[Abeabenut]

kaustubhbabar5:k8s_based_service_discovery