Kong OpenAPI 3.0 prometheus exporter

This exporter takes an OpenAPI 3.0 specification and a kong http request log to generate prometheus metrics, grouping metrics by specific path, method, status code, duration and optionally operation ID and selected headers.

Setup guide

1. Deploy the exporter

• Download the kubernetes manifest from deployment/exporter.yaml.
• Change the openapi.url and other configuration values as needed in the ConfigMap.
• Deploy the exporter to your kubernetes cluster.

2. Add global kong HTTP log plugin

Next you need to add a global kong HTTP log plugin to the kong gateway. This plugin will log all requests to the exporter.

apiVersion: configuration.konghq.com/v1
kind: KongClusterPlugin
metadata:
    name: kong-openapi-prometheus-exporter-http-log
    annotations:
        kubernetes.io/ingress.class: kong
    labels:
        global: "true"
config:
    http_endpoint: http://logs.kong-openapi-prometheus-exporter.svc.cluster.local:8080
    method: POST
    timeout: 1000
    keepalive: 1000
    retry_count: 1
plugin: http-log

Also found in deployment/kong-plugin.yaml

Configuration

Variable	Default Value	Description
log.level	info	The level of logging detail. Common values are debug, info, warn, error.
log.format	json	The format of the log output. Common formats are text and json.
prometheus.path	/metrics	The URL path where metrics are exposed.
prometheus.port	9090	The port on which the Prometheus metrics endpoint listens.
openapi.url		The URL of the OpenAPI 3.0 specification.
openapi.file		The path to the OpenAPI 3.0 specification file.
openapi.reload	6h	The interval at which the OpenAPI 3.0 documentation is reloaded.
metrics.headers	[]	List of HTTP headers to be included in the metrics.

Warning:

Including headers in the metrics can lead to a high cardinality of metrics, which can lead to performance issues in Prometheus. Use this feature with caution. The cardinality of the metrics can be calculated by:

cardinality = (unique values of custom header) * (hosts) * (status_codes) * (methods) * (paths)

Example: One host with 1 custom header which can have 200 unique values, 5 status codes, 5 methods, and 10 paths will have a cardinality of:

cardinality = 200 * 1 * 5 * 5 * 10 = 50000

Don't include sensitive information in the headers, as they will be exposed in the metrics.