Distributed Tracing via OpenTelemetry

Trickster instruments Distributed Tracing with OpenTelemetry, which is a currently emergent, comprehensive observability stack that is in Public Beta. We import the OpenTelemetry golang packages to instrument support for tracing.

As OpenTelemetry evolves to support additional exporter formats, we will work to extend Trickster to support those as quickly as possible. We also make a best effort to update our otel package imports to the latest releases, whenever we publish a new Trickster release. You can check the go.mod file to see which release of opentelemetry-go we are is using. In this view, to see which version of otel a specific Trickster release imports, use the branch selector dropdown to switch to the tag corresponding to that version of Trickster.

Supported Tracing Backends

• Jaeger
• Jaeger Agent
• Zipkin
• Console/Stdout (printed locally by the Trickster process)

Configuration

Trickster allows the operator to configure multiple tracing configurations, which can be associated into each Backend configuration by name.

The example config has exhaustive examples of configuring Trickster for distributed tracing.

Span List

Trickster can insert several spans to the traces that it captures, depending upon the type and cacheability of the inbound client request, as described in the table below.

Tags / Attributes

Trickster supports adding custom tags to every span via the configuration. Depending upon your preferred tracing backend, these may be referred to as attributes. See the example config for examples of adding custom attributes.

Trickster also supports omitting any tags that Trickster inserts by default. The list of default tags are below. For example on the “request” span, an http.url tag is attached with the current full URL. In deployments where that tag may introduce too much cardinality in your backend trace storage system, you may wish to omit that tag and rely on the more concise path tag. Each tracer config can be provided a string list of tags to omit from traces.

Attributes added to top level (request) span

• http.url - the full HTTP request URL
• backend.name
• backend.provider
• cache.name
• cache.provider
• router.path - request path trimmed to the route match path for the request (e.g., /api/v1/query), good for aggregating when there are large variations in the full URL path

Attributes added to QueryCache span

• cache.status - the lookup status of cache query. See the cache status reference for a description of the attribute values.

Attributes added to the FetchRevalidation span

• isRange - is true if the client request includes an HTTP Range header

Attributes added to the FetchObject span

• isPCF - is true if the origin is configured for Progressive Collapsed Forwarding