docs/serving/samples/telemetry-go/README.md

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# Telemetry Sample
This sample runs a simple web server that makes calls to other in-cluster services
and responds to requests with "Hello World!".
The purpose of this sample is to show generating [metrics](../../accessing-metrics.md),
[logs](../../accessing-logs.md) and distributed [traces](../../accessing-traces.md).
This sample also shows how to create a dedicated Prometheus instance rather than
using the default installation.
## Prerequisites
1. A Kubernetes cluster with [Knative Serving](https://github.com/knative/docs/blob/master/install/README.md)
installed.
2. Check if Knative monitoring components are installed:
```
kubectl get pods --namespace knative-monitoring
```
* If pods aren't found, install [Knative monitoring component](../../installing-logging-metrics-traces.md).
3. Install [Docker](https://docs.docker.com/get-started/#prepare-your-docker-environment).
4. Check out the code:
```
go get -d github.com/knative/docs/serving/samples/telemetry-go
```
## Setup
Build the application container and publish it to a container registry:
1. Move into the sample directory:
```
cd $GOPATH/src/github.com/knative/docs
```
2. Set your preferred container registry:
```
export REPO="gcr.io/<YOUR_PROJECT_ID>"
```
This example shows how to use Google Container Registry (GCR). You will need
a Google Cloud Project and to enable the [Google Container Registry
API](https://console.cloud.google.com/apis/library/containerregistry.googleapis.com).
3. Use Docker to build your application container:
```
docker build \
--tag "${REPO}/serving/samples/telemetry-go" \
--file=serving/samples/telemetry-go/Dockerfile .
```
4. Push your container to a container registry:
```
docker push "${REPO}/serving/samples/telemetry-go"
```
5. Replace the image reference path with our published image path in the
configuration file (`serving/samples/telemetry-go/sample.yaml`):
* Manually replace:
`image: github.com/knative/docs/serving/samples/telemetry-go` with
`image: <YOUR_CONTAINER_REGISTRY>/serving/samples/telemetry-go`
Or
* Use run this command:
```
perl -pi -e "s@github.com/knative/docs@${REPO}@g" serving/samples/telemetry-go/sample.yaml
```
## Deploy the Service
Deploy this application to Knative Serving:
```
kubectl apply --filename serving/samples/telemetry-go/
```
## Explore the Service
Inspect the created resources with the `kubectl` commands:
* View the created Route resource:
```
kubectl get route --output yaml
```
* View the created Configuration resource:
```
kubectl get configurations --output yaml
```
* View the Revision that was created by the Configuration:
```
kubectl get revisions --output yaml
```
## Access the Service
To access this service via `curl`, you need to determine its ingress address.
1. To determine if your service is ready:
Check the status of your Knative gateway:
```
kubectl get svc knative-ingressgateway --namespace istio-system --watch
```
When the service is ready, you'll see an IP address in the `EXTERNAL-IP` field:
```
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
knative-ingressgateway LoadBalancer 10.23.247.74 35.203.155.229 80:32380/TCP,443:32390/TCP,32400:32400/TCP 2d
```
CTRL+C to end watch.
Check the status of your route:
```
kubectl get route --output yaml
```
When the route is ready, you'll see the following fields reported as:
```YAML
status:
conditions:
...
status: "True"
type: Ready
domain: telemetrysample-route.default.example.com
```
2. Export the ingress hostname and IP as environment
variables:
```
export SERVICE_HOST=`kubectl get route telemetrysample-route --output jsonpath="{.status.domain}"`
export SERVICE_IP=`kubectl get svc knative-ingressgateway --namespace istio-system --output jsonpath="{.status.loadBalancer.ingress[*].ip}"`
```
3. Make a request to the service to see the `Hello World!` message:
```
curl --header "Host:$SERVICE_HOST" http://${SERVICE_IP}
```
4. Make a request to the `/log` endpoint to generate logs to the `stdout` file
and generate files under `/var/log` in both `JSON` and plain text formats:
```
curl --header "Host:$SERVICE_HOST" http://${SERVICE_IP}/log
```
## Access Logs
You can access to the logs from Kibana UI - see [Logs](../../accessing-logs.md)
for more information.
## Access per Request Traces
You can access to per request traces from Zipkin UI - see [Traces](../../accessing-traces.md)
for more information.
## Accessing Custom Metrics
You can see published metrics using Prometheus UI. To access to the UI, forward
the Prometheus server to your machine:
```
kubectl port-forward $(kubectl get pods --selector=app=prometheus,prometheus=test --output=jsonpath="{.items[0].metadata.name}") 9090
```
Then browse to http://localhost:9090.
## Clean up
To clean up the sample service:
```
kubectl delete --filename serving/samples/telemetry-go/
```