View Source Plug.RequestId (Plug v1.16.0)

A plug for generating a unique request ID for each request.

The generated request ID will be in the format:


If a request ID already exists in a configured HTTP request header (see options below), then this plug will use that value, assuming it is between 20 and 200 characters. If such header is not present, this plug will generate a new request ID.

The request ID is added to the Logger metadata as :request_id, and to the response as the configured HTTP response header (see options below). To see the request ID in your log output, configure your logger backends to include the :request_id metadata. For example:

config :logger, :console, metadata: [:request_id]

We recommend to include this metadata configuration in your production configuration file.

Programmatic access to the request ID

To access the request ID programmatically, use the :assign_as option (see below) to assign the request ID to a key in conn.assigns, and then fetch it from there.


To use this plug, just plug it into the desired module:

plug Plug.RequestId


  • :http_header - The name of the HTTP request header to check for existing request IDs. This is also the HTTP response header that will be set with the request id. Default value is "x-request-id".

    plug Plug.RequestId, http_header: "custom-request-id"
  • :assign_as - The name of the key that will be used to store the discovered or generated request id in conn.assigns. If not provided, the request id will not be stored. Available since v1.16.0.

    plug Plug.RequestId, assign_as: :plug_request_id