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How to set Trace Sampling rate for Jaeger in Istio?

The default trace sampling rate for Jaeger in Istio is 1%, meaning, to get a single trace in Jaeger you need to send at least 100 requests to your application. This is good for a production environment but in dev or QA you would want a better sampling rate.

Unfortunately, Istio doesn't give any UI or dashboard to view/edit lots of settings and options which it uses. The documentation related to this is also hard to find.

If you are installing using istioctl then keep an eye for 'values.pilot.traceSampling' option. See more details about this and other options here.

If istio is already installed and running, we need to edit the 'istio-pilot' deployment and change the PILOT_TRACE_SAMPLING environment variable by running below command:

$ kubectl -n istio-system edit deploy istio-pilot
  
This opens vim (or whatever your default text editor) window with the deployment config file and lets you edit the value (which ranges from 0.0 to 100.0)

Just make the change and save the file and the changes take effect almost immediately.

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