# Istio Traffic Shifting Patterns
Advanced traffic management with VirtualServices.
## Weight-Based Routing (Canary)
### Gradual Rollout
```yaml
apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
name: reviews
spec:
hosts:
- reviews
http:
- route:
- destination:
host: reviews
subset: v1
weight: 90
- destination:
host: reviews
subset: v2
weight: 10
```
### Progressive Weights
| Phase | v1 Weight | v2 Weight | Duration |
|-------|-----------|-----------|----------|
| Start | 100% | 0% | - |
| Canary | 90% | 10% | 1 hour |
| Expand | 75% | 25% | 2 hours |
| Half | 50% | 50% | 4 hours |
| Promote | 0% | 100% | - |
### MCP Commands
```python
# Apply weight change
apply_manifest(virtualservice_yaml, namespace)
# Verify
istio_virtualservice_get_tool(name, namespace)
```
## Header-Based Routing
### Beta Users
```yaml
http:
- match:
- headers:
x-user-type:
exact: beta
route:
- destination:
host: reviews
subset: v2
- route:
- destination:
host: reviews
subset: v1
```
### Internal Testing
```yaml
http:
- match:
- headers:
x-internal:
exact: "true"
route:
- destination:
host: reviews
subset: canary
```
## Cookie-Based Routing
```yaml
http:
- match:
- headers:
cookie:
regex: "^(.*?;)?(user=beta)(;.*)?$"
route:
- destination:
host: reviews
subset: v2
```
## Source-Based Routing
### By Service Identity
```yaml
http:
- match:
- sourceLabels:
app: productpage
version: v2
route:
- destination:
host: reviews
subset: v2
```
## Mirroring (Shadow Traffic)
Test new version with production traffic:
```yaml
http:
- route:
- destination:
host: reviews
subset: v1
mirror:
host: reviews
subset: v2
mirrorPercentage:
value: 100.0
```
## Fault Injection
### Delay
```yaml
http:
- fault:
delay:
percentage:
value: 10
fixedDelay: 5s
route:
- destination:
host: reviews
```
### Abort
```yaml
http:
- fault:
abort:
percentage:
value: 10
httpStatus: 500
route:
- destination:
host: reviews
```
## Timeout and Retry
```yaml
http:
- timeout: 10s
retries:
attempts: 3
perTryTimeout: 3s
retryOn: 5xx,reset
route:
- destination:
host: reviews
```
## DestinationRule for Subsets
Required companion to VirtualService:
```yaml
apiVersion: networking.istio.io/v1beta1
kind: DestinationRule
metadata:
name: reviews
spec:
host: reviews
subsets:
- name: v1
labels:
version: v1
- name: v2
labels:
version: v2
- name: canary
labels:
version: canary
```
## Traffic Shifting Workflow
```python
# 1. Ensure DestinationRule exists
istio_destinationrules_list_tool(namespace)
# 2. Check current VirtualService
istio_virtualservice_get_tool(name, namespace)
# 3. Apply new weights
apply_manifest(updated_vs, namespace)
# 4. Verify change
istio_virtualservice_get_tool(name, namespace)
# 5. Monitor (with Kiali or Prometheus)
istio_analyze_tool(namespace)
```
## Rollback
Quick rollback to stable version:
```yaml
http:
- route:
- destination:
host: reviews
subset: v1
weight: 100
```
Apply immediately:
```python
apply_manifest(rollback_vs, namespace)
```
