Return x-b3-trace id in response

[bluetechy]

Description:

Since Zipkin's Lens UI allows one to search on the trace id, it would be helpful if there was a flag in envoy's typed_config to include in the response header the x-b3-traceid, such as return_trace_id: true (similar to the generate_request_id: true flag).

For example:

tracing:
    http:
        name: envoy.zipkin
        typed_config:
            "@type": type.googleapis.com/envoy.config.trace.v2.ZipkinConfig
            return_trace_id: true
            collector_cluster: zipkin-svc
            collector_endpoint: "/api/v1/spans"

Or alternatively in the tracing object:

                    - name: envoy.http_connection_manager
                      typed_config:
                          "@type": type.googleapis.com/envoy.config.filter.network.http_connection_manager.v2.HttpConnectionManager
                          generate_request_id: true
                          tracing:
                              operation_name: egress
                              return_trace_id: true

so that it could be used to search here:

Relevant Links:

• How does a caller figure out the trace id of a request? openzipkin/b3-propagation#4

[dio]

@bluetechy I'm wondering if response_headers_to_add is sufficient for this case:

e.g.

Tried adding it in: examples/zipkin-tracing/front-envoy-zipkin.yaml.

             name: local_route
             virtual_hosts:
             - name: backend
+              response_headers_to_add:
+                - header:
+                    key: x-b3-traceid
+                    value: "%REQ(x-b3-traceid)%"
               domains:
               - "*"
               routes:

$ # in examples/zipkin-tracing
$ docker-compose up -d
$ curl -I localhost:8000/trace/2
HTTP/1.1 200 OK
content-type: text/html; charset=utf-8
content-length: 89
server: envoy
date: Thu, 05 Dec 2019 21:35:54 GMT
x-envoy-upstream-service-time: 14
x-b3-traceid: a1f1fc48e8599203

[bluetechy]

@dio Yes, I would think that would work nicely. Is value: "%REQ(x-b3-traceid)%" currently supported as I just tried it locally and my pod crashed? If it is, I will double-check my yaml then to figure out if I got a yaml error or not.

[dio]

@bluetechy mind to share your envoy version?

[bluetechy]

@dio Yes, sorry....I should have included my version in my last question to you. Here you go:

[bluetechy]

@dio Just came across this issue (#8683) which looks to discuss this same syntax.

[dio]

Yeap. You can use envoyproxy/envoy-dev:latest if you are OK with that. 😉

[dio]

Since it seems it is answered, I'm closing this.

[bluetechy]

@dio I can confirm it does work using envoyproxy/envoy-dev:latest so thank you for the excellent help. It would be nice that once this is released that the example above that you provided is added to examples/zipkin-tracing/front-envoy-zipkin.yaml. These would be the headers I think are most important:

                                    response_headers_to_add:
                                        - header:
                                              key: "x-b3-traceid"
                                              value: "%REQ(x-b3-traceid)%"
                                        - header:
                                              key: "x-request-id"
                                              value: "%REQ(x-request-id)%"

[dio]

@bluetechy, sure! Thanks for confirming. To make it available in the example, I think you can send out a PR?