OpenTelemetry | Kong Docs

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

Propagate distributed tracing spans and report low-level spans to a OTLP-compatible server.

Queueing

The OpenTelemetry 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.

Trace IDs in serialized logs

When the OpenTelemetry plugin is configured along with a plugin that uses the Log Serializer, the trace ID of each request is added to the key trace_id in the serialized log output.

The value of this field is an object that can contain different formats of the current request’s trace ID. In case of multiple tracing headers in the same request, the trace_id field includes one trace ID format for each different header format, as in the following example:

"trace_id": {
  "w3c": "4bf92f3577b34da6a3ce929d0e0e4736",
  "datadog": "11803532876627986230"
},

Usage

Note: The OpenTelemetry plugin only works when Kong Gateway’s tracing_instrumentations configuration is enabled.

The OpenTelemetry plugin is fully compatible with the OpenTelemetry specification and can be used with any OpenTelemetry compatible backend.

There are two ways to set up an OpenTelemetry backend:

Using a OpenTelemetry compatible backend directly, like Jaeger (v1.35.0+) All the vendors supported by OpenTelemetry are listed in the OpenTelemetry’s Vendor support.
Using the OpenTelemetry Collector, which is middleware that can be used to proxy OpenTelemetry spans to a compatible backend. You can view all the available OpenTelemetry Collector exporters at open-telemetry/opentelemetry-collector-contrib.

Set up Kong Gateway

Enable the OpenTelemetry tracing capability in Kong Gateway’s configuration:

tracing_instrumentations = all, Valid values can be found in the Kong’s configuration.
tracing_sampling_rate = 1.0: Tracing instrumentation sampling rate. Tracer samples a fixed percentage of all spans following the sampling rate. Set the sampling rate to a lower value to reduce the impact of the instrumentation on Kong Gateway’s proxy performance in production.

Set up an OpenTelemetry compatible backend

This section is optional if you are using a OpenTelemetry compatible APM vendor. All the supported vendors are listed in the OpenTelemetry’s Vendor support.

Jaeger natively supports OpenTelemetry starting with v1.35 and can be used with the OpenTelemetry plugin.

Deploy a Jaeger instance with Docker:

docker run --name jaeger \
  -e COLLECTOR_OTLP_ENABLED=true \
  -p 16686:16686 \
  -p 4317:4317 \
  -p 4318:4318 \
  jaegertracing/all-in-one:1.36

The COLLECTOR_OTLP_ENABLED environment variable must be set to true to enable the OpenTelemetry Collector.
The 4318 port is the OTLP/HTTP port and the 4317 port is the OTLP/GRPC port that isn’t supported by the OpenTelemetry plugin yet.

Set up a OpenTelemetry Collector

This section is required if you are using an incompatible OpenTelemetry APM vendor.

Create a config file (otelcol.yaml) for the OpenTelemetry Collector:

receivers:
  otlp:
    protocols:
      grpc:
      http:

processors:
  batch:

exporters:
  logging:
    loglevel: debug
  zipkin:
    endpoint: "http://some.url:9411/api/v2/spans"
    tls:
      insecure: true

service:
  pipelines:
    traces:
      receivers: [otlp]
      processors: [batch]
      exporters: [logging, zipkin]

Run the OpenTelemetry Collector with Docker:

docker run --name opentelemetry-collector \
  -p 4317:4317 \
  -p 4318:4318 \
  -p 55679:55679 \
  -v $(pwd)/otelcol.yaml:/etc/otel-collector-config.yaml \
  otel/opentelemetry-collector-contrib:0.52.0 \
  --config=/etc/otel-collector-config.yaml

See the OpenTelemetry Collector documentation for more information.

Configure the OpenTelemetry plugin

Enable the plugin:

curl -X POST http://localhost:8001/plugins \
    -H 'Content-Type: application/json' \
    -d '{
      "name": "opentelemetry",
      "config": {
        "endpoint": "http://<opentelemetry-backend>:4318/v1/traces",
        "resource_attributes": {
          "service.name": "kong-dev"
        }
      }
    }'

How the OpenTelemetry plugin functions

This section describes how the OpenTelemetry plugin works.

Built-in tracing instrumentations

Kong Gateway has a series of built-in tracing instrumentations which are configured by the tracing_instrumentations configuration. Kong Gateway creates a top-level span for each request by default when tracing_instrumentations is enabled.

The top level span has the following attributes:

http.method: HTTP method
http.url: HTTP URL
http.host: HTTP host
http.scheme: HTTP scheme (http or https)
http.flavor: HTTP version
net.peer.ip: Client IP address

Propagation

The OpenTelemetry plugin propagates the following headers:

w3c: W3C trace context
b3 and b3-single: Zipkin headers
jaeger: Jaeger headers
ot: OpenTracing headers
datadog: Datadog headers (Enterprise only)
aws: AWS X-Ray header
gcp: GCP X-Cloud-Trace-Context header

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 w3c.

OTLP exporter

The OpenTelemetry plugin implements the OTLP/HTTP exporter, which uses Protobuf payloads encoded in binary format and is sent via HTTP/1.1.

connect_timeout, read_timeout, and write_timeout are used to set the timeouts for the HTTP request.

batch_span_count and batch_flush_delay are used to set the maximum number of spans and the delay between two consecutive batches.

Customize OpenTelemetry spans as a developer

The OpenTelemetry plugin is built on top of the Kong Gateway tracing PDK.

It’s possible to customize the spans and add your own spans through the universal tracing PDK.

The following is an example for adding a custom span using Kong Gateway’s serverless plugin:

Create a file named custom-span.lua with the following content:

   -- Modify the root span
   local root_span = kong.tracing.active_span()
   root_span:set_attribute("custom.attribute", "custom value")

   -- Create a custom span
   local span = kong.tracing.start_span("custom-span")

   -- Append attributes
   span:set_attribute("custom.attribute", "custom value")
      
   -- Close the span
   span:finish()

Apply the Lua code using the post-function plugin using a cURL file upload:

 curl -i -X POST http://localhost:8001/plugins \
   -F "name=post-function" \
   -F "config.access[1]=@custom-span.lua"

 HTTP/1.1 201 Created
 ...

Troubleshooting

The OpenTelemetry spans are printed to the console when the log level is set to debug in the Kong configuration file.

An example of debug logs output:

2022/06/02 15:28:42 [debug] 650#0: *111 [lua] instrumentation.lua:302: runloop_log_after(): [tracing] collected 6 spans:
Span #1 name=GET /wrk duration=1502.994944ms attributes={"http.url":"/wrk","http.method":"GET","http.flavor":1.1,"http.host":"127.0.0.1","http.scheme":"http","net.peer.ip":"172.18.0.1"}
Span #2 name=rewrite phase: opentelemetry duration=0.391936ms
Span #3 name=router duration=0.013824ms
Span #4 name=access phase: cors duration=1500.824576ms
Span #5 name=cors: heavy works duration=1500.709632ms attributes={"username":"kongers"}
Span #6 name=balancer try #1 duration=0.99328ms attributes={"net.peer.ip":"104.21.11.162","net.peer.port":80}

Known issues

Only supports the HTTP protocols (http/https) of Kong Gateway.
May impact the performance of Kong Gateway. It’s recommended to set the sampling rate (tracing_sampling_rate) via Kong configuration file when using the OpenTelemetry plugin.

Next OpenTelemetry Configuration