Distributed Tracing FAQ

Istio integrates with distributed tracing systems using Envoy-based tracing. With Envoy-based tracing integration, applications are responsible for forwarding tracing headers for subsequent outgoing requests.

You can find additional information in the Istio Distributed Tracing (Jaeger, Lightstep, Zipkin) Tasks and in the Envoy tracing docs.

Istio enables reporting of trace spans for workload-to-workload communications within a mesh. However, in order for various trace spans to be stitched together for a complete view of the traffic flow, applications must propagate the trace context between incoming and outgoing requests.

In particular, Istio relies on applications to propagate the B3 trace headers, as well as the Envoy-generated request ID. These headers include:

• x-request-id
• x-b3-traceid
• x-b3-spanid
• x-b3-parentspanid
• x-b3-sampled
• x-b3-flags
• b3

If you are using Lightstep, you will also need to forward the following headers:

• x-ot-span-context

Header propagation may be accomplished through client libraries, such as Zipkin or Jaeger. It may also be accomplished manually, as documented in the Distributed Tracing Task.

For Envoy-based tracing integrations, Envoy (the sidecar proxy) sends tracing information directly to tracing backends on behalf of the applications being proxied.

Envoy:

• generates request IDs and trace headers (i.e., X-B3-TraceId) for requests as they flow through the proxy
• generates trace spans for each request based on request and response metadata (i.e., response time)
• sends the generated trace spans to the tracing backends
• forwards the trace headers to the proxied application

Istio supports the Envoy-based integrations of Lightstep and Zipkin, as well as all Zipkin API-compatible backends, including Jaeger.

The Istio minimal profile with tracing enabled is all that is required for Istio to integrate with Zipkin-compatible backends.

The Istio sidecar proxy (Envoy) generates the initial headers, if they are not provided by the request.

Although an Istio sidecar will process both inbound and outbound requests for an associated application instance, it has no implicit way of correlating the outbound requests to the inbound request that caused them. The only way this correlation can be achieved is if the application propagates relevant information (i.e. headers) from the inbound request to the outbound requests. Header propagation may be accomplished through client libraries or manually. Further discussion is provided in What is required for distributed tracing with Istio?.

Since Istio 1.0.3, the sampling rate for tracing has been reduced to 1% in the default configuration profile. This means that only 1 out of 100 trace instances captured by Istio will be reported to the tracing backend. The sampling rate in the demo profile is still set to 100%. See this section for more information on how to set the sampling rate.

If you still do not see any trace data, please confirm that your ports conform to the Istio port naming conventions and that the appropriate container port is exposed (via pod spec, for example) to enable traffic capture by the sidecar proxy (Envoy).

If you only see trace data associated with the egress proxy, but not the ingress proxy, it may still be related to the Istio port naming conventions. Starting with Istio 1.3 the protocol for outbound traffic is automatically detected.

Istio, via Envoy, currently supports a percentage-based sampling strategy for trace generation. Please see this section for more information on how to set this sampling rate.

If you already have installed Istio with tracing enabled, you can disable it as follows:

# Fill <istio namespace> with the namespace of your istio mesh.Ex: istio-system
TRACING_POD=`kubectl get po -n <istio namespace> | grep istio-tracing | awk '{print $1}'`
$ kubectl delete pod $TRACING_POD -n <istio namespace>
$ kubectl delete services tracing zipkin   -n <istio namespace>
# Now, manually remove instances of trace_zipkin_url from the file and save it.

Then follow the steps of the cleanup section of the Distributed Tracing task.

If you don’t want tracing functionality at all, then disable tracing when installing Istio.

To do so, you must you use the fully qualified domain name of the Zipkin-compatible instance. For example: zipkin.mynamespace.svc.cluster.local.

Istio does not currently provide support for pub/sub and event bus protocols. Any use of those technologies is best-effort and subject to breakage.