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This is a minimal and robust custom error backend for NGINX Ingress Controller based on the official example.


First, turn on custom-http-errors in your controller, e.g. custom-http-errors: 404,494,500,529.

FROM hexcles/nginx-errors:latest

# Map some non-standard status codes to their standard counterparts.
ENV STATUS_CODE_MAPPING="494:400,529:503"

# Customize HTML response for 404.
COPY 404.html /www/404.html

# Customize JSON response for 5xx.
COPY 5xx.json /www/5xx.json


The main design goal is minimalism, through which we also achieve robustness (the priority is in that order). It uses only Go standard libraries, effectively a bare http.ListenAndServe at its core.

The binary is statically built with CGO disabled. The Docker image is also minimal (built from scratch) without a shell or even the usual FHS.


Customization is done through building another Docker image on top of this one, where you can set environment variables to configure behaviours and/or overlay some files to customize the error responses.

Custom error responses

You can put [code].[ext] in /www of the container to customize the responses for certain status codes and Accepted MIME types as requested by the client.

  • The [code] portion of the file name can be either a specific status code (e.g. 404), or a range of codes in the form of e.g. 4xx.
  • The [ext] portion of the file name should correspond to the included /etc/mime.types (you can also overlay this file in your Docker image if you need a MIME type that is not included).

The image includes default error responses for 404, 4xx, 500 and 5xx in HTML and JSON respectively.

ENV Configurations

  • DEBUG: turn on debug logging and response headers. (Do NOT use in production.)
  • DEFAULT_RESPONSE_FORMAT: set the default response format when the there is no requested MIME type or it cannot be recognized. Default to text/html.
  • STATUS_CODE_MAPPING: in the format of SRC_A:DST_A,SRC_B:DST_B,... mapping source status codes (returned by your backend application) to destination status codes (seen by the client). Note that you should put the source status codes in custom-http-errors while the destination status codes will be used to look up error responses.


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