Hi everyone, I just deployed Istio demo application and kiali dashboard as well. Everything works good so far. There is one thing I couldn’t understand. Do I still have to install Jaeger client libraries into my code? Or am I good to go now?
I believe you have to if you want to tracing those applications or measure their performance or else how will the application send out the telemetry data!
I thought Istio automatically does that.
No, the book application must have that configuration. An application by itself cannot do unless you write the code to do it.
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Oh I see. 
I do not believe this is correct.
While it is true you CAN include and use the client libraries to get more customized tracing, Istio/Jaeger in combination will trace your apps without you doing anything. It’s magic 
If Jaeger is installed, and Kiali integration is configured for it, you can see the traces.
@Gary_Brown can provide more details and correct me if I’m wrong.
@jmazzitelli is correct. You don’t need to use the Jaeger client lib in your application - the Istio/Envoy sidecar proxies generate the tracing data for you.
Your application does have one responsibility (so its not completely magic ) , which is to propagate the trace context (i.e. headers) from any inbound requests to outbound requests, otherwise your traces will appear fragmented.
Take a very simple example. If you write a Hello World application and want to measure how much time it is up or down or how long it takes your users to get a response from your application then you need to tell your application to send some data, any monitoring tool will grab and then you can measure.
Thank you, experts! Good that corrected and shed some light.