istio.io/content/docs/tasks/telemetry/distributed-tracing/index.md

title	description	weight	keywords	aliases
Distributed Tracing	How to configure the proxies to send tracing requests to Zipkin or Jaeger	10	telemetry tracing	/docs/tasks/zipkin-tracing.html

This task shows you how Istio-enabled applications can be configured to collect trace spans. After completing this task, you should understand all of the assumptions about your application and how to have it participate in tracing, regardless of what language/framework/platform you use to build your application.

The Bookinfo sample is used as the example application for this task.

Before you begin

• Setup Istio by following the instructions in the Installation guide.

  Either use the istio-demo.yaml or istio-demo-auth.yaml template, which includes tracing support, or use the Helm chart with tracing enabled by setting the --set tracing.enabled=true option.

• Deploy the Bookinfo sample application.

Accessing the dashboard

Setup access to the Jaeger dashboard by using port-forwarding:

{{< text bash >}} kubectl port-forward -n istio-system(kubectl get pod -n istio-system -l app=jaeger -o jsonpath='{.items[0].metadata.name}') 16686:16686 & {{< /text >}}

Access the Jaeger dashboard by opening your browser to http://localhost:16686.

Generating traces using the Bookinfo sample

With the Bookinfo application up and running, generate trace information by accessing http://$GATEWAY_URL/productpage one or more times.

From the left-hand pane of the Jaeger dashboard, select productpage from the Service drop-down list and click Find Traces. You should see something similar to the following:

{{< image width="100%" ratio="52.68%" link="./istio-tracing-list.png" caption="Tracing Dashboard" >}}

If you click on the top (most recent) trace, you should see the details corresponding to your latest refresh of the /productpage. The page should look something like this:

{{< image width="100%" ratio="36.32%" link="./istio-tracing-details.png" caption="Detailed Trace View" >}}

As you can see, the trace is comprised of spans, where each span corresponds to a Bookinfo service invoked during the execution of a /productpage request. Although every service has the same label, istio-proxy, because the tracing is being done by the Istio sidecar (Envoy proxy) which wraps the call to the actual service, the label of the destination (to the right) identifies the service for which the time is represented by each line.

The call from productpage to reviews is represented by two spans in the trace. The first of the two spans (labeled productpage reviews.default.svc.cluster.local:9080/) represents the client-side span for the call. It took 24.13ms . The second span (labeled reviews reviews.default.svc.cluster.local:9080/) is a child of the first span and represents the server-side span for the call. It took 22.99ms .

The trace for the call to the reviews services reveals two subsequent RPC's in the trace. The first is to the istio-policy service, reflecting the server-side Check call made for the service to authorize access. The second is the call out to the ratings service.

Understanding what happened

Although Istio proxies are able to automatically send spans, they need some hints to tie together the entire trace. Applications need to propagate the appropriate HTTP headers so that when the proxies send span information, the spans can be correlated correctly into a single trace.

To do this, an application needs to collect and propagate the following headers from the incoming request to any outgoing requests:

• x-request-id
• x-b3-traceid
• x-b3-spanid
• x-b3-parentspanid
• x-b3-sampled
• x-b3-flags
• x-ot-span-context

If you look in the sample services, you can see that the productpage service (Python) extracts the required headers from an HTTP request:

{{< text python >}} def getForwardHeaders(request): headers = {}

if 'user' in session:
    headers['end-user'] = session['user']

incoming_headers = [ 'x-request-id',
                     'x-b3-traceid',
                     'x-b3-spanid',
                     'x-b3-parentspanid',
                     'x-b3-sampled',
                     'x-b3-flags',
                     'x-ot-span-context'
]

for ihdr in incoming_headers:
    val = request.headers.get(ihdr)
    if val is not None:
        headers[ihdr] = val
        #print "incoming: "+ihdr+":"+val

return headers

{{< /text >}}

The reviews application (Java) does something similar:

{{< text jzvz >}} @GET @Path("/reviews/{productId}") public Response bookReviewsById(@PathParam("productId") int productId, @HeaderParam("end-user") String user, @HeaderParam("x-request-id") String xreq, @HeaderParam("x-b3-traceid") String xtraceid, @HeaderParam("x-b3-spanid") String xspanid, @HeaderParam("x-b3-parentspanid") String xparentspanid, @HeaderParam("x-b3-sampled") String xsampled, @HeaderParam("x-b3-flags") String xflags, @HeaderParam("x-ot-span-context") String xotspan) { int starsReviewer1 = -1; int starsReviewer2 = -1;

if (ratings_enabled) { JsonObject ratingsResponse = getRatings(Integer.toString(productId), user, xreq, xtraceid, xspanid, xparentspanid, xsampled, xflags, xotspan); {{< /text >}}

When you make downstream calls in your applications, make sure to include these headers.

Cleanup

• Remove any kubectl port-forward processes that may still be running:

  {{< text bash >}} $ killall kubectl {{< /text >}}

• If you are not planning to explore any follow-on tasks, refer to the Bookinfo cleanup instructions to shutdown the application.