Tracing service

Applications that consist of multiple services can be difficult to debug, as a single request can span multiple services. Distributed tracing tells the story of your request as it is processed through your system. Distributed tracing is a powerful tool to debug and analyze your system in addition to request logging and metrics.

When enabled, the TracingService will instruct Emissary to initiate a trace on requests by generating and populating an x-request-id HTTP header. Services can make use of this x-request-id header in logging and forward it in downstream requests for tracing. Emissary also integrates with external trace visualization services, including LightStep and Zipkin-compatible APIs such as Zipkin and Jaeger to allow you to store and visualize traces. You can read further on Envoy’s Tracing capabilities.

A TracingService manifest configures Emissary to use an external trace visualization service:

---
apiVersion: getambassador.io/v2
kind:  TracingService
metadata:
  name:  tracing
spec:
  service: "example-zipkin:9411"
  driver: zipkin
  config: {}
  tag_headers:
  - ":authority"
  - ":path"
  sampling:
    overall: 100

• service gives the URL of the external HTTP trace service.
• driver provides the driver information that handles communicating with the service. Supported values are lightstep, zipkin, and datadog.
• config provides additional configuration options for the selected driver.
• tag_headers (optional) if present, specifies a list of other HTTP request headers which will be used as tags in the trace’s span.
• sampling (optional) if present, specifies some target percentages of requests that will be traced.
  • client: percentage of requests that will be force traced if the x-client-trace-id header is set. Defaults to 100.
  • random: percentage of requests that will be randomly traced. Defaults to 100.
  • overall: percentage of requests that will be traced after all other checks have been applied (force tracing, sampling, etc.). This field functions as an upper limit on the total configured sampling rate. For instance, setting client to 100% but overall to 1% will result in only 1% of client requests with the appropriate headers to be force traced. Defaults to 100.

Please note that you must use the HTTP/2 pseudo-header names. For example:

• the host header should be specified as the :authority header; and
• the method header should be specified as the :method header.

Lightstep driver configurations

• access_token_file provides the location of the file containing the access token to the LightStep API.

Zipkin driver configurations

• collector_endpoint gives the API endpoint of the Zipkin service where the spans will be sent. The default value is /api/v1/spans
• collector_endpoint_version gives the API version Envoy will use when sending data to your Zipkin collector. The default value is HTTP_JSON_V1
• collector_endpoint_hostname sets the hostname Envoy will use when sending data to your Zipkin collector. The default value is the name of the underlying Envoy cluster.
• trace_id_128bit whether a 128-bit trace id will be used when creating a new trace instance. Defaults to true. Setting to false will result in a 64-bit trace id being used.
• shared_span_context whether client and server spans will share the same span id. The default value is true.

Datadog Driver Configurations

• service_name the name of the service which is attached to the traces. The default value is ambassador.

You may only use a single TracingService manifest per Emissary deployment. Ensure ambassador_id is set correctly in the TracingService manifest.

Example

Check out the DataDog and Zipkin HOWTOs.