DestinationRule

Supported Version: Istio 1.28+ API Version: networking.istio.io/v1Last Updated: February 19, 2026

DestinationRule is a core Istio resource that defines how to handle traffic after VirtualService routes it to the destination.

Table of Contents

1. What is DestinationRule?
2. VirtualService vs DestinationRule
3. Subset Concept
4. Basic Structure
5. Defining Subsets
6. Traffic Policy Overview
7. Using with VirtualService
8. Practical Examples
9. Best Practices
10. Troubleshooting

What is DestinationRule?

DestinationRule defines traffic policies after routing. If VirtualService determines "where" to send traffic, DestinationRule determines "how" to handle it.

Key Roles of DestinationRule

Role	Description	Example
Subset Definition	Group service versions	v1, v2, canary, stable
Load Balancing	Load distribution algorithm	ROUND_ROBIN, LEAST_REQUEST
Connection Pool	Connection pool settings	Max connections, Timeout
Circuit Breaker	Failure isolation	Outlier Detection
TLS Settings	Encryption policy	mTLS, SIMPLE TLS

VirtualService vs DestinationRule

These two resources work together to provide complete traffic management.

Role Comparison

Separation of Responsibilities

VirtualService (Where?):

apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: reviews
spec:
  hosts:
  - reviews
  http:
  - match:
    - headers:
        end-user:
          exact: jason
    route:
    - destination:
        host: reviews
        subset: v2  # ← References subset from DestinationRule
  - route:
    - destination:
        host: reviews
        subset: v1  # ← References subset from DestinationRule

DestinationRule (How?):

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: reviews
spec:
  host: reviews
  trafficPolicy:  # ← Default policy applied to all subsets
    loadBalancer:
      simple: LEAST_REQUEST
  subsets:  # ← Subset definitions referenced by VirtualService
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2
    trafficPolicy:  # ← Policy applied only to v2
      loadBalancer:
        simple: ROUND_ROBIN

Subset Concept

A Subset defines a logical group of a service. It's typically distinguished by version, deployment stage, region, etc.

The Essence of Subsets

Subset Use Cases

1. Version-based Routing

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: reviews-versions
spec:
  host: reviews
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2
  - name: v3
    labels:
      version: v3

# Pod labels
apiVersion: v1
kind: Pod
metadata:
  labels:
    app: reviews
    version: v1  # ← Matches Subset

2. Deployment Stage Separation

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: reviews-deployment-stages
spec:
  host: reviews
  subsets:
  - name: stable
    labels:
      stage: stable
  - name: canary
    labels:
      stage: canary
  - name: test
    labels:
      stage: test

3. Regional Separation

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: api-regions
spec:
  host: api-service
  subsets:
  - name: us-west
    labels:
      region: us-west
  - name: us-east
    labels:
      region: us-east
  - name: eu-central
    labels:
      region: eu-central

4. Environment Separation

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: payment-environments
spec:
  host: payment-service
  subsets:
  - name: production
    labels:
      env: production
  - name: staging
    labels:
      env: staging

Basic Structure

Required Fields

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: my-destination-rule
  namespace: default
spec:
  host: my-service  # Required: Target service
  subsets:          # Optional: Subset definitions
  - name: v1
    labels:
      version: v1
  trafficPolicy:    # Optional: Traffic policy
    loadBalancer:
      simple: ROUND_ROBIN

Host Specification Methods

1. Service Name (Same Namespace)

spec:
  host: reviews

2. FQDN (Different Namespace)

spec:
  host: reviews.production.svc.cluster.local

3. Wildcard

spec:
  host: "*.example.com"

4. External Service (with ServiceEntry)

spec:
  host: api.external.com

Defining Subsets

Simple Subset

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: reviews-simple
spec:
  host: reviews
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2

Subset-specific Policies

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: reviews-subset-policies
spec:
  host: reviews
  trafficPolicy:  # Default policy (all subsets)
    loadBalancer:
      simple: LEAST_REQUEST
  subsets:
  - name: v1
    labels:
      version: v1
    # v1 uses default policy

  - name: v2
    labels:
      version: v2
    trafficPolicy:  # v2-only policy (overrides default)
      loadBalancer:
        simple: ROUND_ROBIN
      connectionPool:
        http:
          http1MaxPendingRequests: 10

Complex Label Matching

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: api-complex
spec:
  host: api-service
  subsets:
  - name: us-west-v2
    labels:
      version: v2
      region: us-west
      tier: premium
  - name: us-east-v1
    labels:
      version: v1
      region: us-east
      tier: standard

Traffic Policy Overview

The trafficPolicy in DestinationRule provides various traffic control features.

Traffic Policy Hierarchy

Traffic Policy Components

1. Load Balancer

trafficPolicy:
  loadBalancer:
    simple: ROUND_ROBIN  # LEAST_REQUEST, RANDOM, PASSTHROUGH

See Load Balancing for details

2. Connection Pool

trafficPolicy:
  connectionPool:
    tcp:
      maxConnections: 100
    http:
      http1MaxPendingRequests: 50
      http2MaxRequests: 100
      maxRequestsPerConnection: 2

See Circuit Breaker for details

3. Outlier Detection

trafficPolicy:
  outlierDetection:
    consecutiveErrors: 5
    interval: 30s
    baseEjectionTime: 30s
    maxEjectionPercent: 50

See Circuit Breaker for details

4. TLS Settings

trafficPolicy:
  tls:
    mode: ISTIO_MUTUAL  # DISABLE, SIMPLE, MUTUAL

See Security for details

5. Port Level Settings

trafficPolicy:
  portLevelSettings:
  - port:
      number: 80
    loadBalancer:
      simple: ROUND_ROBIN
  - port:
      number: 443
    tls:
      mode: SIMPLE

Using with VirtualService

VirtualService and DestinationRule work together to provide complete traffic control.

Basic Pattern: Canary Deployment

# DestinationRule: Subset definition
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: reviews
spec:
  host: reviews
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2
---
# VirtualService: Traffic distribution
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: reviews
spec:
  hosts:
  - reviews
  http:
  - route:
    - destination:
        host: reviews
        subset: v1  # ← References DestinationRule subset
      weight: 90
    - destination:
        host: reviews
        subset: v2  # ← References DestinationRule subset
      weight: 10

Header-based Routing

# DestinationRule
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: reviews
spec:
  host: reviews
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2
---
# VirtualService
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: reviews
spec:
  hosts:
  - reviews
  http:
  # Developers use v2
  - match:
    - headers:
        x-dev-user:
          exact: "true"
    route:
    - destination:
        host: reviews
        subset: v2
  # Regular users use v1
  - route:
    - destination:
        host: reviews
        subset: v1

URI-based Routing + Subset-specific Policies

# DestinationRule: Different policies per subset
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: api-service
spec:
  host: api-service
  subsets:
  - name: v1
    labels:
      version: v1
    trafficPolicy:
      loadBalancer:
        simple: ROUND_ROBIN
  - name: v2
    labels:
      version: v2
    trafficPolicy:
      loadBalancer:
        simple: LEAST_REQUEST
      connectionPool:
        http:
          http1MaxPendingRequests: 10
---
# VirtualService: URI-based routing
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: api-service
spec:
  hosts:
  - api-service
  http:
  - match:
    - uri:
        prefix: "/api/v2"
    route:
    - destination:
        host: api-service
        subset: v2
  - route:
    - destination:
        host: api-service
        subset: v1

Practical Examples

Example 1: Microservice Version Management

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: reviews-versions
  namespace: production
spec:
  host: reviews
  trafficPolicy:
    loadBalancer:
      simple: LEAST_REQUEST
    connectionPool:
      tcp:
        maxConnections: 100
      http:
        http1MaxPendingRequests: 50
        maxRequestsPerConnection: 2
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2
  - name: v3
    labels:
      version: v3

Use Cases:

• v1: Stable version (most traffic)
• v2: Canary version (10% traffic)
• v3: Test version (developers only)

Example 2: Multi-Region Deployment

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: api-multi-region
spec:
  host: api-service
  trafficPolicy:
    loadBalancer:
      simple: LEAST_REQUEST
      localityLbSetting:
        enabled: true
  subsets:
  - name: us-west
    labels:
      region: us-west
    trafficPolicy:
      connectionPool:
        tcp:
          maxConnections: 1000
  - name: us-east
    labels:
      region: us-east
    trafficPolicy:
      connectionPool:
        tcp:
          maxConnections: 1000
  - name: eu-central
    labels:
      region: eu-central
    trafficPolicy:
      connectionPool:
        tcp:
          maxConnections: 500

Example 3: Deployment Stage Policies

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: payment-service-stages
spec:
  host: payment-service
  subsets:
  # Production: Strict policy
  - name: production
    labels:
      stage: production
    trafficPolicy:
      connectionPool:
        tcp:
          maxConnections: 100
        http:
          http1MaxPendingRequests: 10
          maxRequestsPerConnection: 1
      outlierDetection:
        consecutiveErrors: 3
        interval: 10s
        baseEjectionTime: 60s

  # Canary: Moderate policy
  - name: canary
    labels:
      stage: canary
    trafficPolicy:
      connectionPool:
        tcp:
          maxConnections: 50
        http:
          http1MaxPendingRequests: 20
      outlierDetection:
        consecutiveErrors: 5
        interval: 30s
        baseEjectionTime: 30s

  # Staging: Lenient policy
  - name: staging
    labels:
      stage: staging
    trafficPolicy:
      connectionPool:
        tcp:
          maxConnections: 200
        http:
          http1MaxPendingRequests: 100
      outlierDetection:
        consecutiveErrors: 10
        interval: 60s
        baseEjectionTime: 30s

Example 4: External Service Integration

# ServiceEntry: Register external API
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: external-payment-api
spec:
  hosts:
  - api.payment-gateway.com
  ports:
  - number: 443
    name: https
    protocol: HTTPS
  location: MESH_EXTERNAL
  resolution: DNS
---
# DestinationRule: External API policy
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: external-payment-api
spec:
  host: api.payment-gateway.com
  trafficPolicy:
    connectionPool:
      tcp:
        maxConnections: 10
      http:
        http1MaxPendingRequests: 5
        maxRequestsPerConnection: 1
    outlierDetection:
      consecutiveErrors: 3
      interval: 30s
      baseEjectionTime: 120s
    tls:
      mode: SIMPLE

Example 5: Database Connection Pool

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: postgres-connection-pool
spec:
  host: postgres-primary
  trafficPolicy:
    connectionPool:
      tcp:
        maxConnections: 50  # DB connection limit
        connectTimeout: 5s
        tcpKeepalive:
          time: 7200s
          interval: 75s
      http:
        http1MaxPendingRequests: 10
        maxRequestsPerConnection: 100
    outlierDetection:
      consecutiveErrors: 3
      interval: 60s
      baseEjectionTime: 120s
  subsets:
  - name: primary
    labels:
      role: primary
  - name: replica
    labels:
      role: replica
    trafficPolicy:
      connectionPool:
        tcp:
          maxConnections: 100  # More for replicas

Best Practices

1. Subset Naming Conventions

# ✅ Good example: Meaningful names
subsets:
- name: v1
- name: v2
- name: stable
- name: canary
- name: us-west
- name: production

# ❌ Bad example: Vague names
subsets:
- name: subset1
- name: test
- name: new

2. Default Policy + Override Pattern

# ✅ Good example: Define default policy and override when needed
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: reviews
spec:
  host: reviews
  trafficPolicy:  # Default policy
    loadBalancer:
      simple: LEAST_REQUEST
  subsets:
  - name: v1
    labels:
      version: v1
    # v1 uses default policy
  - name: v2
    labels:
      version: v2
    trafficPolicy:  # Override only for v2
      loadBalancer:
        simple: ROUND_ROBIN

3. Circuit Breaker is Essential

# ✅ Always set outlierDetection
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: api-service
spec:
  host: api-service
  trafficPolicy:
    loadBalancer:
      simple: LEAST_REQUEST
    outlierDetection:  # Required
      consecutiveErrors: 5
      interval: 30s
      baseEjectionTime: 30s

4. Connection Pool Settings

# ✅ Connection Pool appropriate for service characteristics
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: high-traffic-service
spec:
  host: api-gateway
  trafficPolicy:
    connectionPool:
      tcp:
        maxConnections: 1000
      http:
        http2MaxRequests: 1000
        maxRequestsPerConnection: 100

5. Gradual Rollout

# ✅ Gradually increase canary ratio
# Step 1: 5%
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: reviews-canary-step1
spec:
  hosts:
  - reviews
  http:
  - route:
    - destination:
        host: reviews
        subset: v1
      weight: 95
    - destination:
        host: reviews
        subset: v2
      weight: 5

# Step 2: After monitoring, increase to 10%
# Step 3: 25% → 50% → 100%

6. Documentation

apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: payment-service
  annotations:
    description: "Payment service traffic management"
    owner: "payments-team"
    subset-purpose: |
      - production: Main production traffic
      - canary: New version testing (10%)
      - staging: Pre-production testing
spec:
  host: payment-service
  # ...

Troubleshooting

Subset Not Working

Symptom:

# VirtualService exists but traffic isn't routed
kubectl get virtualservice reviews -o yaml

Cause and Solution:

# 1. Check DestinationRule
kubectl get destinationrule reviews -o yaml

# 2. Verify subset names match
# VirtualService: subset: v2
# DestinationRule: name: v2

# 3. Check pod labels
kubectl get pods --show-labels | grep reviews

# 4. Verify pods have version=v2 label
kubectl label pod reviews-v2-xxx version=v2

Traffic Policy Not Applied

# Check Envoy configuration
istioctl proxy-config cluster <pod-name> --fqdn reviews.default.svc.cluster.local -o json

# Check Circuit Breaker settings
istioctl proxy-config cluster <pod-name> -o json | jq '.[] | select(.name=="outbound|9080||reviews.default.svc.cluster.local") | .circuitBreakers'

Subset Conflicts

Problem:

# Multiple DestinationRules for the same host cause conflicts
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: reviews-1
spec:
  host: reviews
  subsets:
  - name: v1
    labels:
      version: v1
---
# ❌ Conflict occurs
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: reviews-2
spec:
  host: reviews
  subsets:
  - name: v2
    labels:
      version: v2

Solution:

# ✅ Define all subsets in one DestinationRule
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: reviews
spec:
  host: reviews
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2

istioctl Analysis

# Validate DestinationRule
istioctl analyze

# Specific namespace
istioctl analyze -n production

# Example output
# Error [IST0101] (DestinationRule reviews.default) Referenced host not found: "reviews"

Next Steps

After understanding DestinationRule, move on to these topics:

1. Traffic Splitting: Canary, Blue/Green deployments
2. Load Balancing: Various algorithms and policies
3. Circuit Breaker: Failure isolation and resilience
4. Retry and Timeout: Retry and timeout settings

References

• Istio DestinationRule Reference
• Istio Traffic Management
• Envoy Cluster Configuration