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Simple Traffic Splitting Between Revisions
This samples builds off of the Creating a RESTful Service sample to illustrate updating a Service to create a new Revision as well as splitting traffic between the two created Revisions.
Prerequisites
- Complete the Service creation steps in Creating a RESTful Service.
- Move into the docs directory:
cd $GOPATH/src/github.com/knative/docs
Using the traffic:
block
The service was originally created without a traffic:
block, which means that
it will automatically deploy the latest updates as they become ready. To split
traffic between multiple Revisions, we will start to use a customized traffic:
block. The traffic:
block enables users to split traffic over any number of
fixed Revisions, or the floating “latest revision” for the Service. It also
enables users to name the specific sub-routes, so that they can be directly
addressed for qualification or debugging.
The first thing we will do is look at the traffic block that was defaulted for us in the previous sample:
- Fetch the state of the Service, and note the
traffic:
block that will run the latest ready revision, each time we update our template. Also note that understatus:
we see a specificrevisionName:
here, which is what it has resolved to (in this case the name we asked for).
$ kubectl get ksvc -oyaml stock-service-example
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
name: stock-service-example
...
spec:
template: ... # A defaulted version of what we provided.
traffic:
- latestRevision: true
percent: 100
status:
...
traffic:
- percent: 100
revisionName: stock-service-example-first
- The
release_sample.yaml
in this directory overwrites the defaulted traffic block with a block that fixes traffic to the revisionstock-service-example-first
, while keeping the latest ready revision available via the sub-route “latest”.
kubectl apply --filename docs/serving/samples/traffic-splitting/release_sample.yaml
- The
spec
of the Service should now show ourtraffic
block with the Revision name we specified above.
kubectl get ksvc stock-service-example --output yaml
Updating the Service
This section describes how to create a new Revision by updating your Service.
A new Revision is created every time a value in the template
section of the
Service spec
is updated. The updated_sample.yaml
in this folder changes the
environment variable RESOURCE
from stock
to share
. Applying this change
will result in a new Revision.
For comparison, you can diff the release_sample.yaml
with the
updated_sample.yaml
.
diff serving/samples/traffic-splitting/release_sample.yaml \
serving/samples/traffic-splitting/updated_sample.yaml
- Execute the command below to update Service, resulting in a new Revision.
kubectl apply --filename docs/serving/samples/traffic-splitting/updated_sample.yaml
- With our
traffic
block, traffic will not shift to the new Revision automatically. However, it will be available via the URL associated with ourlatest
sub-route. This can be verified through the Service status, by finding the entry ofstatus.traffic
forlatest
:
kubectl get ksvc stock-service-example --output yaml
- The readiness of the Service can be verified through the Service Conditions. When the Service conditions report it is ready again, you can access the new Revision using the same method as found in the previous sample using the Service hostname found above.
# Replace "latest" with whichever tag for which we want the hostname.
export LATEST_HOSTNAME=`kubectl get ksvc stock-service-example --output jsonpath="{.status.traffic[?(@.tag=='latest')].url}" | cut -d'/' -f 3`
curl --header "Host: ${LATEST_HOSTNAME}" http://${INGRESS_IP}
- Visiting the Service’s domain will still hit the original Revision, since we
configured it to receive 100% of our main traffic (you can also use the
current
sub-route).
curl --header "Host:${SERVICE_HOSTNAME}" http://${INGRESS_IP}
Traffic Splitting
Updating the service to split traffic between the two revisions is done by
extending our traffic
list, and splitting the percent
across them.
- Execute the command below to update Service, resulting in a 50/50 traffic split.
kubectl apply --filename docs/serving/samples/traffic-splitting/split_sample.yaml
- Verify the deployment by checking the service status:
kubectl get ksvc --output yaml
- Once updated,
curl
requests to the base domain should result in responses split evenly betweenWelcome to the share app!
andWelcome to the stock app!
.
curl --header "Host:${SERVICE_HOSTNAME}" http://${INGRESS_IP}
Clean Up
To clean up the sample service:
kubectl delete --filename docs/serving/samples/traffic-splitting/split_sample.yaml
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