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Zipkin

By Kong Inc.
You are browsing documentation for an outdated plugin version.

Looking for the plugin's configuration parameters? You can find them in the Zipkin configuration reference doc.

Propagate Zipkin distributed tracing spans and report spans to a Zipkin server.

Queueing

The zipkin plugin uses a queue to decouple the production and consumption of data. This reduces the number of concurrent requests made to the upstream server under high load situations and provides buffering during temporary network or upstream outages.

You can set several parameters to configure the behavior and capacity of the queues used by the plugin. For more information about how to use these parameters, see Plugin Queuing Reference in the Kong Gateway documentation.

The queue parameters all reside in a record under the key queue in the config parameter section of the plugin.

Queues are not shared between workers and queueing parameters are scoped to one worker. For whole-system capacity planning, the number of workers need to be considered when setting queue parameters.

How it Works

When enabled, this plugin traces requests in a way compatible with zipkin.

The code is structured around an OpenTracing core using the opentracing-lua library to collect timing data of a request in each of Kong’s phases. The plugin uses opentracing-lua compatible extractor, injector, and reporters to implement Zipkin’s protocols.

Reporter

An OpenTracing “reporter” is how tracing data is reported to another system. This plugin records tracing data for a given request, and sends it as a batch to a Zipkin server using the Zipkin v2 API. Note that zipkin version 1.31 or higher is required.

The http_endpoint configuration variable must contain the full uri including scheme, host, port and path sections (i.e. your uri likely ends in /api/v2/spans).

Spans

The plugin does request sampling. For each request which triggers the plugin, a random number between 0 and 1 is chosen.

If the number is smaller than the configured sample_ratio, then a trace with several spans will be generated. If sample_ratio is set to 1, then all requests will generate a trace (this might be very noisy).

For each request that gets traced, the following spans are produced:

  • Request span: 1 per request. Encompasses the whole request in kong (kind: SERVER). The Proxy and Balancer spans are children of this span. It contains the following logs/annotations for the rewrite phase:

    • krs - kong.rewrite.start
    • krf - kong.rewrite.finish

    The Request span has the following tags:

    • lc: Hardcoded to kong.
    • kong.service: The uuid of the service matched when processing the request, if any.
    • kong.service_name: The name of the service matched when processing the request, if service exists and has a name attribute.
    • kong.route: The uuid of the route matched when processing the request, if any (it can be nil on non-matched requests).
    • kong.route_name: The name of the route matched when processing the request, if route exists and has a name attribute.
    • http.method: The HTTP method used on the original request (only for HTTP requests).
    • http.path: The path of the request (only for HTTP requests).
    • If the plugin tags_header config option is set, and the request contains headers with the appropriate name and correct encoding tags, then the trace will include the tags.
    • If the plugin static_tags config option is set, then the tags in the config option will be included in the trace.
  • Proxy span: 1 per request, encompassing most of Kong’s internal processing of a request (kind: CLIENT). Contains the following logs/annotations for the start/finish of the of the Kong plugin phases:
    • kas - kong.access.start
    • kaf - kong.access.finish
    • kbs - kong.body_filter.start
    • kbf - kong.body_filter.finish
    • khs - kong.header_filter.start
    • khf - kong.header_filter.finish
    • kps - kong.preread.start (only for stream requests)
    • kpf - kong.preread.finish (only for stream requests)
  • Balancer span(s): 0 or more per request, each encompassing one balancer attempt (kind: CLIENT). Contains the following tags specific to load balancing:
    • kong.balancer.try: A number indicating the attempt (1 for the first load-balancing attempt, 2 for the second, and so on).
    • peer.ipv4 or peer.ipv6 for the balancer IP.
    • peer.port for the balanced port.
    • error: Set to true if the balancing attempt was unsuccessful, otherwise unset.
    • http.status_code: The HTTP status code received, in case of error.
    • kong.balancer.state: An NGINX-specific description of the error, next/failed for HTTP failures, or 0 for stream failures. Equivalent to state_name in OpenResty’s balancer’s get_last_failure function.

Propagation

The Zipkin plugin supports propagation of the following header formats:

The plugin detects the propagation format from the headers and will use the appropriate format to propagate the span context. If no appropriate format is found, the plugin will fallback to the default format, which is b3.

See also

For more information, read the Kong blog post.