node-http-proxy plus a REST API
JavaScript HTML
Latest commit 7224fac Dec 9, 2016 @willingc willingc committed on GitHub Merge pull request #91 from minrk/handle_proxy_error-this
fix closure reference when serving custom error pages

Install | Using configurable-http-proxy | Using the REST API | Custom error pages | Host-based routing


Build Status

configurable-http-proxy, a simple wrapper around node-http-proxy, adds a REST API for updating the routing table.

The proxy is developed as a part of the JupyterHub multi-user server.

Note: node-http-proxy is an HTTP programmable proxying library that supports websockets. It is suitable for implementing components such as reverse proxies and load balancers. configurable-http-proxy wraps node-http-proxy to provide this functionality to JupyterHub.


Prerequisite: Node.js

To install globally from the configurable-http-proxy package release using the npm package manager:

npm install -g configurable-http-proxy

To install from the source code found in this GitHub repo:

git clone
cd configurable-http-proxy
# Use -g for global install
npm install [-g]

Using configurable-http-proxy

The configurable proxy runs two HTTP(S) servers:

  1. The public-facing interface to your application (controlled by --ip, --port, etc.). This listens on all interfaces by default.
  2. The inward-facing REST API (--api-ip, --api-port). This listens on localhost by default. The REST API uses token authorization, set by the CONFIGPROXY_AUTH_TOKEN environment variable.

Setting a default target

When you start the proxy from the command line, you can set a default target (--default-target option) to be used when no matching route is found in the proxy table:

configurable-http-proxy --default-target=http://localhost:8888

Command-line options

  Usage: configurable-http-proxy [options]


    -h, --help                       output usage information
    -V, --version                    output the version number
    --ip <ip-address>                Public-facing IP of the proxy
    --port <n> (defaults to 8000)    Public-facing port of the proxy

    --ssl-key <keyfile>              SSL key to use, if any
    --ssl-cert <certfile>            SSL certificate to use, if any
    --ssl-ca <ca-file>               SSL certificate authority, if any
    --ssl-request-cert               Request SSL certs to authenticate clients
    --ssl-reject-unauthorized        Reject unauthorized SSL connections (only meaningful if --ssl-request-cert is given)
    --ssl-protocol <ssl-protocol>    Set specific HTTPS protocol, e.g. TLSv1_2, TLSv1, etc.
    --ssl-ciphers <ciphers>          `:`-separated ssl cipher list. Default excludes RC4
    --ssl-allow-rc4                  Allow RC4 cipher for SSL (disabled by default)
    --ssl-dhparam <dhparam-file>     SSL Diffie-Helman Parameters pem file, if any

    --api-ip <ip>                    Inward-facing IP for API requests
    --api-port <n>                   Inward-facing port for API requests (defaults to --port=value+1)
    --api-ssl-key <keyfile>          SSL key to use, if any, for API requests
    --api-ssl-cert <certfile>        SSL certificate to use, if any, for API requests
    --api-ssl-ca <ca-file>           SSL certificate authority, if any, for API requests
    --api-ssl-request-cert           Request SSL certs to authenticate clients for API requests
    --api-ssl-reject-unauthorized    Reject unauthorized SSL connections (only meaningful if --api-ssl-request-cert is given)

    --default-target <host>          Default proxy target (proto://host[:port])
    --error-target <host>            Alternate server for handling proxy errors (proto://host[:port])
    --error-path <path>              Alternate server for handling proxy errors (proto://host[:port])
    --redirect-port <redirect-port>  Redirect HTTP requests on this port to the server on HTTPS
    --pid-file <pid-file>            Write our PID to a file
    --no-x-forward                   Don't add 'X-forward-' headers to proxied requests
    --no-prepend-path                Avoid prepending target paths to proxied requests
    --no-include-prefix              Don't include the routing prefix in proxied requests
    --insecure                       Disable SSL cert verification
    --host-routing                   Use host routing (host as first level of path)
    --statsd-host <host>             Host to send statsd statistics to
    --statsd-port <port>             Port to send statsd statistics to
    --statsd-prefix <prefix>         Prefix to use for statsd statistics
    --log-level <loglevel>           Log level (debug, info, warn, error)
    --proxy-timeout <n>              Timeout (in millis) when proxy receives no response from target

Using the REST API

The configurable-http-proxy API is documented and available at the interactive swagger site, petstore or as a swagger specification file in this repo.

Authenticating via passing a token

The REST API is authenticated via passing a token in the Authorization header. The API is served under the /api/routes base URL. For example, execute this curl command in the terminal to authenticate and retrieve the current routing table:

curl -H "Authorization: token $CONFIGPROXY_AUTH_TOKEN" http://localhost:8001/api/routes

Getting the current routing table


GET /api/routes[?inactive_since=ISO8601-timestamp]

The GET request returns a JSON dictionary of the current routing table.

This JSON dictionary excludes the default route. If the inactive_since URL parameter is given as an ISO8601 timestamp, only routes whose last_activity is earlier than the timestamp will be returned.


Status code:

status: 200 OK

Returned JSON dictionary of current routing table:

  "/user/foo": {
    "target": "http://localhost:8002",
    "last_activity": "2014-09-08T19:43:08.321Z"
  "/user/bar": {
    "target": "http://localhost:8003",
    "last_activity": "2014-09-08T19:40:17.819Z"

The last_activity timestamp is updated whenever the proxy passes data to or from the proxy target.

Adding new routes

POST requests create new routes. The body of the request should be a JSON dictionary with at least one key: target, the target host to be proxied.


POST /api/routes/[:path]

Input - request body

target: The host URL


status: 201 Created

After adding the new route, any request to /path/prefix on the proxy's public interface will be proxied to target.

Deleting routes


DELETE /api/routes/[:path]


status: 204 No Content

Removes a route from the proxy's routing table.

Custom error pages

With version 0.5, configurable-host-proxy (CHP) adds two ways to provide custom error pages when the proxy encounters an error, and has no proxy target to handle a request. There are two typical errors that CHP can hit, along with their status code:

  • 404: a client has requested a URL for which there is no routing target. This can be prevented if a default target is specified when starting the configurable-http-proxy.

  • 503: a route exists, but the upstream server isn't responding. This is more common, and can be due to any number of reasons, including the target service having died or not finished starting.


If you specify an error path --error-path /usr/share/chp-errors when starting the CHP:

configurable-http-proxy --error-path /usr/share/chp-errors

then when a proxy error occurs, CHP will look in /usr/share/chp-errors/<CODE>.html (where CODE is the status code number) for an html page to serve, e.g. 404.html or 503.html.

If no file exists for the error code, error.html file will be used. If you specify an error path, make sure you also create error.html.


When starting the CHP, you can pass a command line option for --error-target. If you specify --error-target http://localhost:1234, then when the proxy encounters an error, it will make a GET request to this server, with URL /CODE, and the URL of the failing request escaped in a URL parameter, e.g.:

GET /404?url=%2Fescaped%2Fpath

Host-based routing

If the CHP is started with the --host-routing option, the proxy will pick a target based on the host of the incoming request, instead of the URL prefix.

The API when using host-based routes is the same as if the hostname were the first part of the URL path, e.g.:

  "/": "https://localhost:1234",
  "/": "",