Earthquake API - Distributed tracing demo with Istio and ktor-header-forwarding

Demo application consisting of two Ktor microservices instrumented with ktor-header-forwarding, illustrating the use of distributed tracing features of Istio in a local Kubernetes cluster.

EarthquakeAdaptor retrieves data about earthquakes that happened today using an API from the U.S. Geological Survey.
EarthquakeStats calls EarthquakeStats and exposes statistics about today's earthquakes such as GET /earthquakes/latest or GET /earthquakes/biggest.

Requirements

This demo assumes that you have the following installed on your local machine.

Docker Desktop (or some other local Kubernetes installation)
Istioctl

Running

Build docker images for both services. This can take some time if you do not have the base images cached.

 docker build -f docker/Dockerfile.EarthquakeStats -t earthquake-stats .
 docker build -f docker/Dockerfile.EarthquakeAdaptor -t earthquake-adaptor .

Configure the default namespace to have istio sidecar proxy injection enabled.
```
 kubectl apply -f k8s/namespaces.yaml
```
Install Istio onto the cluter with the demo config (which includes a Jaeger instance).
```
 istioctl manifest apply --set profile=demo
```

Release the two docker containers to the cluster.

 kubectl apply -f k8s/earthquake-adaptor.yaml
 kubectl apply -f k8s/earthquake-stats.yaml

Check that both pods are running.

 kubectl get po
 NAME                                  READY   STATUS    RESTARTS   AGE
 earthquake-adaptor-7b69f76849-cxzpc   2/2     Running   0          25s
 earthquake-stats-8677997cf-jzwbk      2/2     Running   0          20s

Send some traffic to the earthquake-stats pod.

 curl localhost:30101/earthquake/latest
 {
 "location" : "80 km NNE of Hihifo, Tonga",
 "magnitude" : 5.9,
 "timeGMT" : "2020-11-07 09:27:04"
 }

Open the Jaeger UI to view traces.
```
 istioctl dashboard jaeger
```

Steps

Import ktor-header-forwarding in the build.gradle of the earthquake-stats application. Commit.
```
 implementation "com.github.fstien:ktor-header-forwarding:0.1.0"
```
Install the HeaderForwardingServer Ktor feature onto the application call pipeline, configured to forward requests as described in the Istio distributed tracing documentation. Commit.
```
 install(HeaderForwardingServer) {
    header("x-request-id")
    header("x-ot-span-context")
    filter { header -> header.startsWith("x-b3-") }
 }
```
Install the HeaderForwardingClient Ktor feature onto the http client. Commit.
```
 install(HeaderForwardingClient)
```
We do not need to instrument earthquake-adaptor as it does not make any requests within the cluster.

fstien/ktor-istio-distributed-tracing-demo

Earthquake API - Distributed tracing demo with Istio and ktor-header-forwarding

Requirements

Running

Steps