Kiali is a service mesh observability utility that was originally developed at Red Hat and now is an open- source project. Kiali provides a visual network flow/dependency diagram between different microservices behind the Ingress gateway. Let's take a look:

1. Open http://kiali.istio.io/kiali/console and use admin/admin as the user ID and password. 
2. If the previous curl command to drive the traffic has stopped in the command-line window, start it again to keep sending the traffic to the productpage.
3. Navigate to the menu icon from the top left of the page and click on Graph. Select the istio-lab namespace: 

• • Toggle the Display drop-down and check Node Names, Service Nodes, Traffic animation, Virtual Services, and Security. 
  • Select Requests per second from Edge Labels.
  • Select App from Graph Type, as follows:

The animation shows how traffic flows from service to service. The lock icon shows the mTLS-enabled services. The traffic rate/seconds is also between services. The blue line between ratings and mongodb shows the TCP connection. The right-hand sidebar shows HTTP requests/second and TCP traffic bytes sent and received per second. These are useful metrics to gain insight into the application and, more importantly, to see if services are throwing 5XX or 4XX errors.

Next, we'll explore the real-time animation of the network flow between services:

1. Select the istio-system namespace, inclusive of istio-lab, and notice the animation and flow of metrics from the different services to the Istio components:

The live animation shows how each service is sending metrics to Istio Mixer.

2. Select istio-lab from the namespace drop-down and click Applications. The health of the applications will appear:

3. Click Service details and click Destination Rules (notice the red cross sign, indicating that we have an issue):

4. Click View YAML:

5. Notice that subset v2 is shown in red. This is happening because there is no details service that has a label of v2. 
6. Navigate to Services (left navigation bar) and click productpage. Click Inbound Metrics, which can be found in the middle of the tab:

The 50, 95, and 99 percentiles for the request and response sizes show the network traffic that was generated by a particular service.

Istio Config open (left nav bar) shows the configuration for the destination rules, virtual services, and service entries. These can be modified using the web UI.

Kiali is one of the most useful tools in Istio for gaining immediate insight into a service's dependencies. Kiali shows real-time animated traffic of the application. This tool helps Service Reliability Engineering (SRE) or application infrastructure teams to provide immediate feedback to the application owners about potential performance issues. 

Next, we will explore the Jaeger web UI regarding distributed tracing details, service mesh dependencies, and so on.