For the latest stable version, please use Korvet 0.19!

Deployment

This guide covers deploying Korvet in production environments.

Deployment shapes

A Korvet JVM runs the broker (Kafka listener and group coordinator) and the leader-locked storage worker by default. The storage worker rolls eligible segments, offloads sealed segments, and enforces local and remote retention.

Disable a component explicitly only when a deployment needs a single-role JVM.

Shape Configuration Components started

All-in-one (default)

no component flags required

broker + storage worker

Broker-only pod

KORVET_STORAGE_WORKER_ENABLED=false

broker

Storage-worker pod

KORVET_BROKER_ENABLED=false

storage worker

Single-role pod

set one of KORVET_BROKER_ENABLED / KORVET_STORAGE_WORKER_ENABLED to false

the selected role

Custom

set KORVET_BROKER_ENABLED and/or KORVET_STORAGE_WORKER_ENABLED

the components whose flag is true

korvet.storage.remote.path makes the cold tier available. Without it, Korvet runs local-only on Redis Streams.

Docker Deployment

Single Instance

docker run -d \
  --name korvet \
  -p 9092:9092 \
  -e JAVA_OPTS="-Xms2g -Xmx2g -XX:MaxDirectMemorySize=256m" \
  -e KORVET_REDIS_URI=redis://redis.example.com:6379 \
  -e KORVET_REDIS_USERNAME=default \
  -e KORVET_REDIS_PASSWORD=${REDIS_PASSWORD} \
  redisfield/korvet:latest server

Use JAVA_OPTS to pass heap settings and additional JVM flags to the container at startup.

Docker Compose

services:
  redis:
    image: redis:8.6
    command: redis-server --requirepass ${REDIS_PASSWORD}
    ports:
      - "6379:6379"

  korvet:
    image: redisfield/korvet:latest
    command: server
    ports:
      - "9092:9092"
    environment:
      JAVA_OPTS: "-Xms2g -Xmx2g -XX:MaxDirectMemorySize=256m"
      KORVET_REDIS_URI: redis://redis:6379
      KORVET_REDIS_PASSWORD: ${REDIS_PASSWORD}
    depends_on:
      - redis

Kubernetes Deployment

For single-broker or simple deployments, use a standard Deployment. For multi-broker clusters with proper broker discovery, see Multi-Broker Deployment.

Simple Deployment (Single Broker)

apiVersion: apps/v1
kind: Deployment
metadata:
  name: korvet
spec:
  replicas: 1  # Single broker
  selector:
    matchLabels:
      app: korvet
  template:
    metadata:
      labels:
        app: korvet
    spec:
      containers:
      - name: korvet
        image: redisfield/korvet:latest
        args: ["server"]
        ports:
        - containerPort: 9092
        env:
        - name: KORVET_REDIS_URI
          value: redis://redis-service:6379
        - name: KORVET_BROKER_HOST
          value: 0.0.0.0
        - name: KORVET_BROKER_PORT
          value: "9092"
        resources:
          requests:
            memory: "512Mi"
            cpu: "500m"
          limits:
            memory: "2Gi"
            cpu: "2000m"
        livenessProbe:
          httpGet:
            path: /actuator/health/liveness
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /actuator/health/readiness
            port: 8080
          initialDelaySeconds: 10
          periodSeconds: 5

Service Manifest

apiVersion: v1
kind: Service
metadata:
  name: korvet-service
spec:
  selector:
    app: korvet
  ports:
  - protocol: TCP
    port: 9092
    targetPort: 9092
  type: LoadBalancer
For multi-broker deployments with high availability, use a StatefulSet instead. See Kubernetes StatefulSet.

Multi-Broker Deployment

Korvet supports multi-broker deployments where multiple Korvet instances share the same Redis backend. This provides high availability and load distribution while maintaining full data consistency.

Architecture Overview

In a multi-broker deployment:

  • All brokers connect to the same Redis instance or cluster

  • Brokers automatically discover each other via the Broker Registry stored in Redis

  • Kafka clients can connect to any broker and receive metadata about all brokers in the cluster

  • Messages produced to one broker are immediately available from any other broker

                    ┌─────────────────┐
                    │  Load Balancer  │
                    │   (TCP/9092)    │
                    └────────┬────────┘
                             │
        ┌────────────────────┼────────────────────┐
        │                    │                    │
        ▼                    ▼                    ▼
┌───────────────┐   ┌───────────────┐   ┌───────────────┐
│   Korvet 0    │   │   Korvet 1    │   │   Korvet 2    │
│  id=0         │   │  id=1         │   │  id=2         │
│  port=9092    │   │  port=9092    │   │  port=9092    │
└───────┬───────┘   └───────┬───────┘   └───────┬───────┘
        │                   │                   │
        └───────────────────┼───────────────────┘
                            │
                            ▼
                ┌───────────────────────┐
                │        Redis          │
                │  (Streams + Registry) │
                └───────────────────────┘

Broker Configuration

Each broker requires a unique id and proper network configuration:

korvet:
  namespace: korvet         # Must be the same across all brokers

  broker:
    id: 0                  # Unique ID for this broker (0, 1, 2, etc.)
    host: 0.0.0.0          # Listen on all interfaces
    port: 9092             # Kafka protocol port
    advertised-host: korvet-0.korvet.default.svc.cluster.local  # Hostname clients use
    advertised-port: 9092  # Port clients use

  redis:
    uri: redis://redis:6379  # Same Redis for all brokers
All brokers in a cluster must use the same korvet.namespace and connect to the same Redis instance.

Broker Discovery

Korvet uses a Broker Registry stored in Redis for automatic broker discovery:

  • Each broker registers itself on startup with its ID, host, and port

  • Brokers send periodic heartbeats (every 10 seconds by default)

  • Entries are considered stale 30 seconds after their last heartbeat and are then ignored

  • Kafka clients receive all live registered brokers in metadata responses

Redis keys used by the registry:

korvet:broker:nodes   # Single hash: field = broker id, value = host/port/rack + heartbeat timestamp
There is no Redis TTL on the key. Staleness is determined client-side by comparing each entry’s heartbeat timestamp against the 30-second threshold.

Docker Compose Example

services:
  redis:
    image: redis:8.6
    ports:
      - "6379:6379"

  korvet-0:
    image: redisfield/korvet:latest
    command: server
    ports:
      - "9092:9092"
    environment:
      KORVET_BROKER_ID: 0
      KORVET_BROKER_HOST: 0.0.0.0
      KORVET_BROKER_ADVERTISED_HOST: localhost
      KORVET_BROKER_ADVERTISED_PORT: 9092
      KORVET_REDIS_URI: redis://redis:6379

  korvet-1:
    image: redisfield/korvet:latest
    command: server
    ports:
      - "9093:9092"
    environment:
      KORVET_BROKER_ID: 1
      KORVET_BROKER_HOST: 0.0.0.0
      KORVET_BROKER_ADVERTISED_HOST: localhost
      KORVET_BROKER_ADVERTISED_PORT: 9093
      KORVET_REDIS_URI: redis://redis:6379

  korvet-2:
    image: redisfield/korvet:latest
    command: server
    ports:
      - "9094:9092"
    environment:
      KORVET_BROKER_ID: 2
      KORVET_BROKER_HOST: 0.0.0.0
      KORVET_BROKER_ADVERTISED_HOST: localhost
      KORVET_BROKER_ADVERTISED_PORT: 9094
      KORVET_REDIS_URI: redis://redis:6379

Clients can connect using multiple bootstrap servers:

kafka-console-producer --bootstrap-server localhost:9092,localhost:9093,localhost:9094 --topic test

Kubernetes StatefulSet

For Kubernetes, use a StatefulSet to ensure each broker gets a unique, stable identity. The StatefulSet provides:

  • Stable network identity: Each pod gets a predictable DNS name (korvet-0, korvet-1, etc.)

  • Ordered deployment: Pods are created sequentially, ensuring broker registration order

  • Stable storage: PersistentVolumeClaims are retained across pod restarts (if needed)

Complete Kubernetes Manifests

# ConfigMap for shared configuration
apiVersion: v1
kind: ConfigMap
metadata:
  name: korvet-common
data:
  KORVET_BROKER_HOST: "0.0.0.0"
  KORVET_BROKER_PORT: "9092"
  KORVET_NAMESPACE: "korvet"
  KORVET_BROKER_REBALANCE_DELAY: "5s"  # Allow time for consumers to join in K8s
---
# Headless service for StatefulSet DNS
apiVersion: v1
kind: Service
metadata:
  name: korvet
  labels:
    app: korvet
spec:
  clusterIP: None
  selector:
    app: korvet
  ports:
  - port: 9092
    name: kafka
  - port: 8080
    name: actuator
---
# LoadBalancer service for external access
apiVersion: v1
kind: Service
metadata:
  name: korvet-lb
spec:
  type: LoadBalancer
  selector:
    app: korvet
  ports:
  - port: 9092
    targetPort: 9092
    name: kafka
---
# StatefulSet
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: korvet
spec:
  serviceName: korvet
  replicas: 3
  podManagementPolicy: Parallel  # Start all pods simultaneously
  selector:
    matchLabels:
      app: korvet
  template:
    metadata:
      labels:
        app: korvet
      annotations:
        prometheus.io/scrape: "true"
        prometheus.io/port: "8080"
        prometheus.io/path: "/actuator/prometheus"
    spec:
      terminationGracePeriodSeconds: 30
      initContainers:
      # Extract broker ID from pod name (korvet-0 -> 0, korvet-1 -> 1, etc.)
      - name: init-broker-id
        image: busybox:1.36
        command:
        - sh
        - -c
        - |
          ORDINAL=${HOSTNAME##*-}
          echo "KORVET_BROKER_ID=${ORDINAL}" > /config/broker.env
          echo "KORVET_BROKER_ADVERTISED_HOST=${HOSTNAME}.korvet.${NAMESPACE}.svc.cluster.local" >> /config/broker.env
          echo "Broker ID: ${ORDINAL}, Advertised Host: ${HOSTNAME}.korvet.${NAMESPACE}.svc.cluster.local"
        env:
        - name: NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
        volumeMounts:
        - name: config-volume
          mountPath: /config
      containers:
      - name: korvet
        image: redisfield/korvet:latest
        command:
        - sh
        - -c
        - |
          # Source the broker-specific config
          export $(cat /config/broker.env | xargs)
          # Start the application
          exec java --sun-misc-unsafe-memory-access=allow -jar /app/korvet.jar
        ports:
        - containerPort: 9092
          name: kafka
        - containerPort: 8080
          name: actuator
        envFrom:
        - configMapRef:
            name: korvet-common
        - secretRef:
            name: korvet-redis-credentials
            optional: true
        env:
        - name: KORVET_REDIS_URI
          value: redis://redis:6379
        - name: KORVET_BROKER_ADVERTISED_PORT
          value: "9092"
        # JVM tuning for containers
        - name: JAVA_TOOL_OPTIONS
          value: "-XX:MaxRAMPercentage=75.0 -XX:+UseG1GC -XX:MaxDirectMemorySize=256m --sun-misc-unsafe-memory-access=allow"
        resources:
          requests:
            memory: "512Mi"
            cpu: "500m"
          limits:
            memory: "2Gi"
            cpu: "2000m"
        volumeMounts:
        - name: config-volume
          mountPath: /config
        livenessProbe:
          httpGet:
            path: /actuator/health/liveness
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 10
          failureThreshold: 3
        readinessProbe:
          httpGet:
            path: /actuator/health/readiness
            port: 8080
          initialDelaySeconds: 10
          periodSeconds: 5
          failureThreshold: 3
        startupProbe:
          httpGet:
            path: /actuator/health/liveness
            port: 8080
          initialDelaySeconds: 10
          periodSeconds: 5
          failureThreshold: 30
      volumes:
      - name: config-volume
        emptyDir: {}

Redis Credentials Secret

If Redis requires authentication, create a secret:

kubectl create secret generic korvet-redis-credentials \
  --from-literal=KORVET_REDIS_PASSWORD=your-password

Scaling the Cluster

Scale up or down with:

# Scale to 5 brokers
kubectl scale statefulset korvet --replicas=5

# Scale down to 3 brokers
kubectl scale statefulset korvet --replicas=3

When scaling down, brokers are removed in reverse order (highest ID first). The broker registry stops advertising an entry once its last heartbeat is older than 30 seconds.

Pod Disruption Budget

For high availability, configure a PodDisruptionBudget:

apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: korvet-pdb
spec:
  minAvailable: 2
  selector:
    matchLabels:
      app: korvet

External Access

For clients outside the Kubernetes cluster, you have several options:

Option 1: LoadBalancer Service (shown above)

Clients connect to the LoadBalancer IP. All traffic is distributed across brokers.

Option 2: NodePort Service

apiVersion: v1
kind: Service
metadata:
  name: korvet-nodeport
spec:
  type: NodePort
  selector:
    app: korvet
  ports:
  - port: 9092
    targetPort: 9092
    nodePort: 30092

Option 3: Ingress with TCP support (e.g., NGINX Ingress Controller)

Configure TCP services in the ingress controller’s ConfigMap.

Monitoring in Kubernetes

Korvet exposes Prometheus metrics at /actuator/prometheus. With the annotations in the StatefulSet, Prometheus will automatically scrape metrics.

For Grafana dashboards, query metrics like:

  • korvet_broker_produce_seconds_count - Total produce requests

  • korvet_broker_fetch_seconds_count - Total fetch requests

  • korvet_broker_request_seconds_count - Kafka API request rate, by api_key and result

  • korvet_broker_backpressure_connections - Connections currently under backpressure

Consumer Group Coordination

In multi-broker deployments, consumer group coordination is handled specially:

  • The group coordinator is selected using consistent hashing based on the group ID

  • Clients are directed to the correct coordinator via the FindCoordinator response

  • All consumer group state is stored in Redis, so any broker can serve offset commits/fetches

Best Practices

Broker IDs

Use sequential IDs starting from 0 (0, 1, 2, …​). Each broker must have a unique ID.

Advertised Listeners

Always configure advertised-host and advertised-port to the address clients should use to connect. This is especially important in Docker/Kubernetes where internal and external addresses differ.

Load Balancing

Use a TCP load balancer (not HTTP) in front of your brokers. Any load balancing strategy works since all brokers serve the same data.

Bootstrap Servers

Configure Kafka clients with multiple bootstrap servers for fault tolerance:

bootstrap.servers=korvet-0:9092,korvet-1:9092,korvet-2:9092
Redis High Availability

For production, use a highly available Redis deployment, such as Redis Enterprise, to ensure the storage layer is also highly available.

High Availability

For production deployments:

  • Multiple instances: Run 3+ Korvet instances for redundancy

  • Redis HA: Use a highly available Redis deployment, such as Redis Enterprise, for HA

  • Health checks: Configure liveness and readiness probes

  • Graceful shutdown: Allow time for in-flight requests to complete

Scaling

Korvet can be scaled horizontally:

  • Stateless: Each instance shares state via Redis

  • Load balancing: Use any TCP load balancer

  • Add brokers: Simply start new instances with unique broker IDs

Next Steps