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This feature is supported in Ambassador Pro. Ambassador Pro helps developers and operators accelerate their adoption of Kubernetes.
Register here to get started with a free trial of Ambassador Pro.
How do you verify that the code you've written actually works? Ambassador Pro's Service Preview lets developers see exactly how their service works in a realistic enviroment -- without impacting other developers or end users. Service Preview integrates Telepresence, the popular CNCF project for local development and debugging on Kubernetes.
apictl is the command client for Ambassador Pro.
Download the latest version of the client:
Make sure the client is somewhere on your PATH. In addition, place your license key in
Information about open source code used in
apictl can be found by running
In this quick start, we're going to preview a change we make to the backend service of the tour application, without impacting normal users of the application. Before getting started, make sure the tour application is installed on your cluster and you've installed the
apictl command line tool, as explained above.
We're first going to get the tour backend service running locally. Clone the tour repository and build a local image.
git clone https://github.com/datawire/tour cd tour make docker.run
Note that Preview doesn't depend on a locally running container; you can just run a service locally on your laptop. We're using a container in this tutorial to minimize environmental issues with different golang environments.
makecommand above, we build the backend application in a docker container named
localhost:31000/tour:backend-latestand run it on port 8080.
Now, in another terminal window, redeploy the tour application with the Preview sidecar. The sidecar is special process which will route requests to your local machine or to the production cluster. The
apictl traffic injectcommand will automatically create the appropriate YAML to inject the sidecar. In the
tourdirectory, pass the file name of the QOTM deployment:
apictl traffic inject k8s/tour.yaml -d tour -s tour -p 8080 > k8s/tour-traffic-sidecar.yaml
This will create a YAML file called
qotm-sidecar.yaml. The file will look like the following:
apiVersion: v1 kind: Service metadata: annotations: getambassador.io/config: | --- apiVersion: ambassador/v1 kind: Mapping name: tour-ui_mapping prefix: / service: tour:5000 --- apiVersion: ambassador/v1 kind: Mapping name: tour-backend_mapping prefix: /backend/ service: tour:8080 labels: ambassador: - request_label: - backend name: tour spec: ports: - name: ui port: 5000 targetPort: 5000 - name: backend port: 8080 targetPort: 9900 selector: app: tour --- apiVersion: apps/v1 kind: Deployment metadata: name: tour spec: replicas: 1 selector: matchLabels: app: tour strategy: type: RollingUpdate template: metadata: labels: app: tour spec: containers: - image: quay.io/datawire/tour:ui-0.2.6 name: tour-ui ports: - containerPort: 5000 name: http - image: quay.io/datawire/tour:backend-0.2.6 name: quote ports: - containerPort: 8080 name: http resources: limits: cpu: "0.1" memory: 100Mi - env: - name: APPNAME value: tour - name: APPPORT value: "8080" - name: AMBASSADOR_LICENSE_KEY value: eJcbGciOiaIUzI1NiIsInR5cCkpXVCJ9.eCI6Im5rcmF1c2UiLCJleHAiOjE1Nzg0MTg4ODZ9.S_6-zdPyy4z1N4Jmo5e4A7fME4CbQVL_13ikw image: quay.io/datawire/ambassador_pro:app-sidecar-0.6.0 name: traffic-sidecar ports: - containerPort: 9900
If you examine this file, you will notice a couple of important difference:
traffic-sidecarcontainer has been added to the deployment
- In the service,
backendport mapping has been changed to point to port 9900 which is the port the
traffic-sidecarcontainer is listening on
Redeploy tour with the sidecar:
kubectl apply -f k8s/tour-traffic-sidecar.yaml
Test to make sure that both your production and development instances of QOTM work:
curl $AMBASSADOR_IP/backend/ # test production curl localhost:8080/ # test development
Initialize the traffic manager for the cluster.
apictl traffic initialize
We need to create an
interceptrule that tells Ambassador where to route specific requests. The following command will tell Ambassador to route any traffic for the
tourdeployment where the header
devto go to port 8080 on localhost:
apictl traffic intercept tour -n x-service-preview -m dev -t 8080
Requests with the header
x-service-preview: devwill now get routed locally:
curl -H "x-service-preview: dev" $AMBASSADOR_IP/backend/` # will go to local Docker instance curl $AMBASSADOR_IP/backend/ # will go to production instance
Make a change to the backend source code. In
backend/main.go, uncomment out line 85, and comment out line 84, so it reads like so:
... //quote := s.random.RandomSelectionFromStringSlice(s.quotes) quote := "Service Preview Rocks!" ...
This will insure that the backend service will return a quote of "Service Preview rocks" every time.
Rebuild the docker container and rerun the
curlabove, which will now route to your (modified) local copy of the QOTM service:
make docker.run -C backend/ curl -H "x-service-preview: dev" $AMBASSADOR_IP/qotm/` # will go to local Docker instance
To recap: With Preview, we can now see test and visualize changes to our service that we've mode locally, without impacting other users of the stable version of that service.
Service Preview will match HTTP headers based on the headers that are seen by the sidecar, and not the edge gateway. Matches are made on the whole header, e.g., a match rule of
dev will not match in the example above, while
/backend/dev will match.
While any HTTP header will match, in practice, using host-based routing (i.e., the
:authority header), a custom HTTP header (e.g., the
x-service-preview header used above), or an authentication header is recommended.