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Istio Canary Deployments
This guide shows you how to use Istio and Flagger to automate canary deployments.
Prerequisites
Flagger requires a Kubernetes cluster v1.16 or newer and Istio v1.5 or newer.
Install Istio with telemetry support and Prometheus:
istioctl manifest install --set profile=default
# Suggestion: Please change release-1.8 in below command, to your real istio version.
kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.8/samples/addons/prometheus.yaml
Install Flagger in the istio-system namespace:
kubectl apply -k github.com/fluxcd/flagger//kustomize/istio
Create an ingress gateway to expose the demo app outside of the mesh:
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
name: public-gateway
namespace: istio-system
spec:
selector:
istio: ingressgateway
servers:
- port:
number: 80
name: http
protocol: HTTP
hosts:
- "*"
Bootstrap
Flagger takes a Kubernetes deployment and optionally a horizontal pod autoscaler (HPA), then creates a series of objects (Kubernetes deployments, ClusterIP services, Istio destination rules and virtual services). These objects expose the application inside the mesh and drive the canary analysis and promotion.
Create a test namespace with Istio sidecar injection enabled:
kubectl create ns test
kubectl label namespace test istio-injection=enabled
Create a deployment and a horizontal pod autoscaler:
kubectl apply -k https://github.com/fluxcd/flagger//kustomize/podinfo?ref=main
Deploy the load testing service to generate traffic during the canary analysis:
kubectl apply -k https://github.com/fluxcd/flagger//kustomize/tester?ref=main
Create a canary custom resource (replace example.com with your own domain):
apiVersion: flagger.app/v1beta1
kind: Canary
metadata:
name: podinfo
namespace: test
spec:
# deployment reference
targetRef:
apiVersion: apps/v1
kind: Deployment
name: podinfo
# the maximum time in seconds for the canary deployment
# to make progress before it is rollback (default 600s)
progressDeadlineSeconds: 60
# HPA reference (optional)
autoscalerRef:
apiVersion: autoscaling/v2beta2
kind: HorizontalPodAutoscaler
name: podinfo
service:
# service port number
port: 9898
# container port number or name (optional)
targetPort: 9898
# Istio gateways (optional)
gateways:
- public-gateway.istio-system.svc.cluster.local
# Istio virtual service host names (optional)
hosts:
- app.example.com
# Istio traffic policy (optional)
trafficPolicy:
tls:
# use ISTIO_MUTUAL when mTLS is enabled
mode: DISABLE
# Istio retry policy (optional)
retries:
attempts: 3
perTryTimeout: 1s
retryOn: "gateway-error,connect-failure,refused-stream"
analysis:
# schedule interval (default 60s)
interval: 1m
# max number of failed metric checks before rollback
threshold: 5
# max traffic percentage routed to canary
# percentage (0-100)
maxWeight: 50
# canary increment step
# percentage (0-100)
stepWeight: 10
metrics:
- name: request-success-rate
# minimum req success rate (non 5xx responses)
# percentage (0-100)
thresholdRange:
min: 99
interval: 1m
- name: request-duration
# maximum req duration P99
# milliseconds
thresholdRange:
max: 500
interval: 30s
# testing (optional)
webhooks:
- name: acceptance-test
type: pre-rollout
url: http://flagger-loadtester.test/
timeout: 30s
metadata:
type: bash
cmd: "curl -sd 'test' http://podinfo-canary:9898/token | grep token"
- name: load-test
url: http://flagger-loadtester.test/
timeout: 5s
metadata:
cmd: "hey -z 1m -q 10 -c 2 http://podinfo-canary.test:9898/"
Note that when using Istio 1.4 you have to replace the request-duration with a
metric template.
Save the above resource as podinfo-canary.yaml and then apply it:
kubectl apply -f ./podinfo-canary.yaml
When the canary analysis starts, Flagger will call the pre-rollout webhooks before routing traffic to the canary. The canary analysis will run for five minutes while validating the HTTP metrics and rollout hooks every minute.
After a couple of seconds Flagger will create the canary objects:
# applied
deployment.apps/podinfo
horizontalpodautoscaler.autoscaling/podinfo
canary.flagger.app/podinfo
# generated
deployment.apps/podinfo-primary
horizontalpodautoscaler.autoscaling/podinfo-primary
service/podinfo
service/podinfo-canary
service/podinfo-primary
destinationrule.networking.istio.io/podinfo-canary
destinationrule.networking.istio.io/podinfo-primary
virtualservice.networking.istio.io/podinfo
Automated canary promotion
Trigger a canary deployment by updating the container image:
kubectl -n test set image deployment/podinfo \
podinfod=ghcr.io/stefanprodan/podinfo:6.0.1
Flagger detects that the deployment revision changed and starts a new rollout:
kubectl -n test describe canary/podinfo
Status:
Canary Weight: 0
Failed Checks: 0
Phase: Succeeded
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Synced 3m flagger New revision detected podinfo.test
Normal Synced 3m flagger Scaling up podinfo.test
Warning Synced 3m flagger Waiting for podinfo.test rollout to finish: 0 of 1 updated replicas are available
Normal Synced 3m flagger Advance podinfo.test canary weight 5
Normal Synced 3m flagger Advance podinfo.test canary weight 10
Normal Synced 3m flagger Advance podinfo.test canary weight 15
Normal Synced 2m flagger Advance podinfo.test canary weight 20
Normal Synced 2m flagger Advance podinfo.test canary weight 25
Normal Synced 1m flagger Advance podinfo.test canary weight 30
Normal Synced 1m flagger Advance podinfo.test canary weight 35
Normal Synced 55s flagger Advance podinfo.test canary weight 40
Normal Synced 45s flagger Advance podinfo.test canary weight 45
Normal Synced 35s flagger Advance podinfo.test canary weight 50
Normal Synced 25s flagger Copying podinfo.test template spec to podinfo-primary.test
Warning Synced 15s flagger Waiting for podinfo-primary.test rollout to finish: 1 of 2 updated replicas are available
Normal Synced 5s flagger Promotion completed! Scaling down podinfo.test
Note that if you apply new changes to the deployment during the canary analysis, Flagger will restart the analysis.
A canary deployment is triggered by changes in any of the following objects:
- Deployment PodSpec (container image, command, ports, env, resources, etc)
- ConfigMaps mounted as volumes or mapped to environment variables
- Secrets mounted as volumes or mapped to environment variables
You can monitor all canaries with:
watch kubectl get canaries --all-namespaces
NAMESPACE NAME STATUS WEIGHT LASTTRANSITIONTIME
test podinfo Progressing 15 2019-01-16T14:05:07Z
prod frontend Succeeded 0 2019-01-15T16:15:07Z
prod backend Failed 0 2019-01-14T17:05:07Z
Automated rollback
During the canary analysis you can generate HTTP 500 errors and high latency to test if Flagger pauses the rollout.
Trigger another canary deployment:
kubectl -n test set image deployment/podinfo \
podinfod=ghcr.io/stefanprodan/podinfo:6.0.2
Exec into the load tester pod with:
kubectl -n test exec -it flagger-loadtester-xx-xx sh
Generate HTTP 500 errors:
watch curl http://podinfo-canary:9898/status/500
Generate latency:
watch curl http://podinfo-canary:9898/delay/1
When the number of failed checks reaches the canary analysis threshold, the traffic is routed back to the primary, the canary is scaled to zero and the rollout is marked as failed.
kubectl -n test describe canary/podinfo
Status:
Canary Weight: 0
Failed Checks: 10
Phase: Failed
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Synced 3m flagger Starting canary deployment for podinfo.test
Normal Synced 3m flagger Advance podinfo.test canary weight 5
Normal Synced 3m flagger Advance podinfo.test canary weight 10
Normal Synced 3m flagger Advance podinfo.test canary weight 15
Normal Synced 3m flagger Halt podinfo.test advancement success rate 69.17% < 99%
Normal Synced 2m flagger Halt podinfo.test advancement success rate 61.39% < 99%
Normal Synced 2m flagger Halt podinfo.test advancement success rate 55.06% < 99%
Normal Synced 2m flagger Halt podinfo.test advancement success rate 47.00% < 99%
Normal Synced 2m flagger (combined from similar events): Halt podinfo.test advancement success rate 38.08% < 99%
Warning Synced 1m flagger Rolling back podinfo.test failed checks threshold reached 10
Warning Synced 1m flagger Canary failed! Scaling down podinfo.test
Session Affinity
While Flagger can perform weighted routing and A/B testing individually, with Istio it can combine the two leading to a Canary release with session affinity. For more information you can read the deployment strategies docs.
Create a canary custom resource (replace app.example.com with your own domain):
apiVersion: flagger.app/v1beta1
kind: Canary
metadata:
name: podinfo
namespace: test
spec:
# deployment reference
targetRef:
apiVersion: apps/v1
kind: Deployment
name: podinfo
# the maximum time in seconds for the canary deployment
# to make progress before it is rollback (default 600s)
progressDeadlineSeconds: 60
# HPA reference (optional)
autoscalerRef:
apiVersion: autoscaling/v2beta2
kind: HorizontalPodAutoscaler
name: podinfo
service:
# service port number
port: 9898
# container port number or name (optional)
targetPort: 9898
# Istio gateways (optional)
gateways:
- public-gateway.istio-system.svc.cluster.local
# Istio virtual service host names (optional)
hosts:
- app.example.com
# Istio traffic policy (optional)
trafficPolicy:
tls:
# use ISTIO_MUTUAL when mTLS is enabled
mode: DISABLE
# Istio retry policy (optional)
retries:
attempts: 3
perTryTimeout: 1s
retryOn: "gateway-error,connect-failure,refused-stream"
analysis:
# schedule interval (default 60s)
interval: 1m
# max number of failed metric checks before rollback
threshold: 5
# max traffic percentage routed to canary
# percentage (0-100)
maxWeight: 50
# canary increment step
# percentage (0-100)
stepWeight: 10
# session affinity config
sessionAffinity:
# name of the cookie used
cookieName: flagger-cookie
# max age of the cookie (in seconds)
# optional; defaults to 86400
maxAge: 21600
metrics:
- name: request-success-rate
# minimum req success rate (non 5xx responses)
# percentage (0-100)
thresholdRange:
min: 99
interval: 1m
- name: request-duration
# maximum req duration P99
# milliseconds
thresholdRange:
max: 500
interval: 30s
# testing (optional)
webhooks:
- name: acceptance-test
type: pre-rollout
url: http://flagger-loadtester.test/
timeout: 30s
metadata:
type: bash
cmd: "curl -sd 'test' http://podinfo-canary:9898/token | grep token"
- name: load-test
url: http://flagger-loadtester.test/
timeout: 5s
metadata:
cmd: "hey -z 1m -q 10 -c 2 http://podinfo-canary.test:9898/"
Save the above resource as podinfo-canary-session-affinity.yaml and then apply it:
kubectl apply -f ./podinfo-canary-session-affinity.yaml
Trigger a canary deployment by updating the container image:
kubectl -n test set image deployment/podinfo \
podinfod=ghcr.io/stefanprodan/podinfo:6.0.1
You can load app.example.com in your browser and refresh it until you see the requests being served by podinfo:6.0.1.
All subsequent requests after that will be served by podinfo:6.0.1 and not podinfo:6.0.0 because of the session affinity
configured by Flagger with Istio.
Traffic mirroring
For applications that perform read operations, Flagger can be configured to drive canary releases with traffic mirroring. Istio traffic mirroring will copy each incoming request, sending one request to the primary and one to the canary service. The response from the primary is sent back to the user and the response from the canary is discarded. Metrics are collected on both requests so that the deployment will only proceed if the canary metrics are within the threshold values.
Note that mirroring should be used for requests that are idempotent or capable of being processed twice (once by the primary and once by the canary).
You can enable mirroring by replacing stepWeight/maxWeight with iterations and by setting analysis.mirror to true:
apiVersion: flagger.app/v1beta1
kind: Canary
metadata:
name: podinfo
namespace: test
spec:
analysis:
# schedule interval
interval: 1m
# max number of failed metric checks before rollback
threshold: 5
# total number of iterations
iterations: 10
# enable traffic shadowing
mirror: true
# weight of the traffic mirrored to your canary (defaults to 100%)
mirrorWeight: 100
metrics:
- name: request-success-rate
thresholdRange:
min: 99
interval: 1m
- name: request-duration
thresholdRange:
max: 500
interval: 1m
webhooks:
- name: acceptance-test
type: pre-rollout
url: http://flagger-loadtester.test/
timeout: 30s
metadata:
type: bash
cmd: "curl -sd 'test' http://podinfo-canary:9898/token | grep token"
- name: load-test
url: http://flagger-loadtester.test/
timeout: 5s
metadata:
cmd: "hey -z 1m -q 10 -c 2 http://podinfo.test:9898/"
With the above configuration, Flagger will run a canary release with the following steps:
- detect new revision (deployment spec, secrets or configmaps changes)
- scale from zero the canary deployment
- wait for the HPA to set the canary minimum replicas
- check canary pods health
- run the acceptance tests
- abort the canary release if tests fail
- start the load tests
- mirror 100% of the traffic from primary to canary
- check request success rate and request duration every minute
- abort the canary release if the metrics check failure threshold is reached
- stop traffic mirroring after the number of iterations is reached
- route live traffic to the canary pods
- promote the canary (update the primary secrets, configmaps and deployment spec)
- wait for the primary deployment rollout to finish
- wait for the HPA to set the primary minimum replicas
- check primary pods health
- switch live traffic back to primary
- scale to zero the canary
- send notification with the canary analysis result
The above procedure can be extended with custom metrics checks, webhooks, manual promotion approval and Slack or MS Teams notifications.