MultiCluster Ingress¶

A .NET application that provides multi-cluster Kubernetes DNS resolution and Global Server Load Balancing (GSLB).

Overview¶

Vecc.K8s.MultiCluster is a Kubernetes operator/orchestrator that watches Ingress, Service, and custom GSLB resources across multiple clusters and provides unified DNS resolution via a CoreDNS gRPC plugin.

Architecture¶

The application runs in four modes, each deployable independently:

Mode	Flag	Purpose	Leader Election
Operator	`--operator`	Watches K8s resources (Ingress, Service, EndpointSlice, GSLB)	Single leader
Orchestrator	`--orchestrator`	Watches V1ClusterCache, coordinates multi-cluster state	Single leader per namespace
DNS Server	`--dns-server`	gRPC DNS service on port 1153, watches V1HostnameCache	No (stateless)
Front End	`--front-end`	REST API with Swagger/OpenAPI docs	No

Data Flow¶

Cluster A (Operator) ──┐
                       ├── Orchestrator ── HostnameCache ── DNS Server ── CoreDNS
Cluster B (Operator) ──┘

Custom Resources¶

V1Gslb¶

Global Server Load Balancing resource (multicluster.veccsolutions.io/v1alpha):

Field	Required	Default	Description
`ObjectReference`	Yes	—	Reference to an Ingress or Service
`Hostnames`	Yes	—	DNS names to expose
`IPOverrides`	No	—	Alternate IP addresses
`Priority`	No	`0`	Higher value wins in failover
`Weight`	No	`50`	Round-robin weight (calculated as `weight / sum * 100`)

Other Resources¶

Resource	Purpose
`V1ClusterCache`	Cached cluster state for orchestration
`V1HostnameCache`	DNS hostname-to-IP mappings
`V1ResourceCache`	Cached K8s resource state
`V1ServiceCache`	Cached service endpoints

DNS Configuration¶

Setting	Default
DNS server name	`dns.vecck8smulticlusteringress.com`
Default TTL	5 seconds
Refresh interval	30 seconds
gRPC port	1153

Helm Chart¶

Chart: multicluster-ingress (v0.1.0)

Components¶

Component	Default Replicas	Port
API Server	1	8080
DNS Server	2	5000
Operator	2	8080
Orchestrator	2	8080

Installation¶

helm install multicluster-ingress charts/multicluster-ingress/ \
  --namespace multicluster \
  --create-namespace \
  --values my-values.yaml

Key Values¶

# API server configuration
api:
  replicas: 1
  resources:
    limits:
      cpu: 300m      # 100m after startup
      memory: 128Mi
    requests:
      cpu: 100m
      memory: 64Mi

# DNS server with CoreDNS
dns:
  replicas: 2
  coredns:
    image: coredns/coredns:1.12.0
  resources:
    limits:
      cpu: 500m
      memory: 256Mi
    requests:
      cpu: 100m
      memory: 128Mi

# Operator watches K8s resources
operator:
  replicas: 2

# Orchestrator coordinates clusters
orchestrator:
  replicas: 2

Generated Resources¶

Deployments (API, DNS, Operator, Orchestrator)
ServiceAccounts and RBAC (3 ClusterRoles + bindings)
Services (ClusterIP for API, LoadBalancer for DNS)
Optional Ingress for API with TLS
ConfigMaps (CoreDNS config, API settings)
Secrets (API keys, cluster authentication)
CRDs (optional, can be managed externally)

Authentication¶

Cluster-to-cluster authentication uses API keys:

Each cluster has a unique salt and API key
Remote peers are configured with their endpoint URL and API key
Heartbeat monitoring with configurable intervals (check: 1s, set: 10s, timeout: 90s)

Docker Image¶

Runtime: mcr.microsoft.com/dotnet/aspnet:10.0
SDK: mcr.microsoft.com/dotnet/sdk:10.0
Port: 80 (HTTP/1.1)
Debug mode: Set DEBUG=1 build arg to include diagnostic tools (procps, net-tools, dnsutils, curl)