Correlate requests and responses using a unique ID transmitted over an HTTP header.


Terminology

  • plugin: a plugin executing actions inside Kong before or after a request has been proxied to the upstream API.
  • Service: the Kong entity representing an external upstream API or microservice.
  • Route: the Kong entity representing a way to map downstream requests to upstream services.
  • Consumer: the Kong entity representing a developer or machine using the API. When using Kong, a Consumer only communicates with Kong which proxies every call to the said upstream API.
  • Credential: a unique string associated with a Consumer, also referred to as an API key.
  • upstream service: this refers to your own API/service sitting behind Kong, to which client requests are forwarded.
  • API: a legacy entity used to represent your upstream services. Deprecated in favor of Services since CE 0.13.0 and EE 0.32.

Configuration

Enabling the plugin on a Service

Configure this plugin on a Service by making the following request:

$ curl -X POST http://kong:8001/services/{service}/plugins \
    --data "name=correlation-id"  \
    --data "config.header_name=Kong-Request-ID" \
    --data "config.generator=uuid#counter" \
    --data "config.echo_downstream=false"

  • service: the id or name of the Service that this plugin configuration will target.

Enabling the plugin on a Route

Configure this plugin on a Route with:

$ curl -X POST http://kong:8001/routes/{route_id}/plugins \
    --data "name=correlation-id"  \
    --data "config.header_name=Kong-Request-ID" \
    --data "config.generator=uuid#counter" \
    --data "config.echo_downstream=false"

  • route_id: the id of the Route that this plugin configuration will target.

Enabling the plugin on a Consumer

You can use the http://localhost:8001/plugins endpoint to enable this plugin on specific Consumers:

$ curl -X POST http://kong:8001/plugins \
    --data "name=correlation-id" \
    --data "consumer_id={consumer_id}"  \
    --data "config.header_name=Kong-Request-ID" \
    --data "config.generator=uuid#counter" \
    --data "config.echo_downstream=false"

Where consumer_id is the id of the Consumer we want to associate with this plugin.

You can combine consumer_id and service_id

in the same request, to furthermore narrow the scope of the plugin.

Enabling the plugin on an API

If you are using an older version of Kong with the legacy API entity (deprecated in favor of Services since CE 0.13.0 and EE 0.32.), you can configure this plugin on top of such an API by making the following request:

$ curl -X POST http://kong:8001/apis/{api}/plugins \
    --data "name=correlation-id"  \
    --data "config.header_name=Kong-Request-ID" \
    --data "config.generator=uuid#counter" \
    --data "config.echo_downstream=false"

  • api: either id or name of the API that this plugin configuration will target.

Global plugins

All plugins can be configured using the http://kong:8001/plugins/ endpoint. A plugin which is not associated to any Service, Route or Consumer (or API, if you are using an older version of Kong) is considered "global", and will be run on every request. Read the Plugin Reference and the Plugin Precedence sections for more information.

Parameters

Here's a list of all the parameters which can be used in this plugin's configuration:

form parameterdefaultdescription
nameThe name of the plugin to use, in this case correlation-id
service_idThe id of the Service which this plugin will target.
route_idThe id of the Route which this plugin will target.
enabledtrueWhether this plugin will be applied.
consumer_idThe id of the Consumer which this plugin will target.
api_idThe id of the API which this plugin will target. Note: The API Entity is deprecated in favor of Services since CE 0.13.0 and EE 0.32.
config.header_name
optional

Kong-Request-ID

The HTTP header name to use for the correlation ID.

config.generator
optional

uuid#counter

The generator to use for the correlation ID. Accepted values are uuid, uuid#counter and tracker See Generators.

config.echo_downstream
optional

false

Whether to echo the header back to downstream (the client).

How it works

When enabled, this plugin will add a new header to all of the requests processed by Kong. This header bears the name configured in config.header_name, and a unique value generated according to config.generator.

This header is always added to calls to your upstream services, and optionally echoed back to your clients according to the config.echo_downstream setting.

If a header bearing the same name is already present in the client request, it is honored and this plugin will not temper with it.

Generators

uuid

Format:

xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

Using this format, a UUID is generated in its hexadecimal form for each request.

uuid#counter

Format:

xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx#counter

In this format, a single UUID is generated on a per-worker basis, and further requests simply append a counter to the UUID after a # character. The counter value starts at 0 for each worker, and gets incremented independently of the others.

This format provides a better performance, but might be harder to store or process for analyzing (due to its format and low cardinality).

tracker

Format:

ip-port-pid-connection-connection_requests-timestamp

In this format, the correlation id contains more practical implications for each request.

The following is a detailed description of the field

form parameter description
ip an address of the server which accepted a request
port port of the server which accepted a request
pid pid of the nginx worker process
connection connection serial number
connection_requests current number of requests made through a connection
timestamp a floating-point number for the elapsed time in seconds (including milliseconds as the decimal part) from the epoch for the current time stamp from the nginx cached time

FAQ

Can I see my correlation ids in my Kong logs?

The correlation id will not show up in the Nginx access or error logs. As such, we suggest you use this plugin alongside one of the Logging plugins, or store this id on your backend-side.