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


Configuration

Configuring the plugin is straightforward. You can associate it with an API by executing the following request to your Kong server:

$ 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: The id or name of the API that this plugin configuration will target

You can also apply it for every API using the http://kong:8001/plugins/ endpoint. Read the Plugin Reference for more information.

form parameter default description
name The name of the plugin to use, in this case: correlation-id
header_name
optional
Kong-Request-ID The HTTP header name to use for the correlation ID.
generator
optional
uuid#counter The generator to use for the correlation ID. Accepted values are uuid, uuid#counter and tracker See Generators.
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 independantly of the others.

This format provides a better performance, but might be harder to store or process for analizing (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.