Install | Usage | Using the REST API | Custom error pages | Host-based routing | Troubleshooting

configurable-http-proxy

configurable-http-proxy (CHP) provides you with a way to update and manage a proxy table using a command line interface or REST API. It is a simple wrapper around node-http-proxy. node-http-proxy is an HTTP programmable proxying library that supports websockets and is suitable for implementing components such as reverse proxies and load balancers. By wrapping node-http-proxy, configurable-http-proxy extends this functionality to JupyterHub deployments.

Install

Prerequisite:

Node.js ≥ 4

Note: Ubuntu < 16.04 and Debian Jessie ship with too-old versions of Node and must be upgraded. We recommend using the latest stable or LTS version of Node.

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

    npm install -g configurable-http-proxy

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

    git clone https://github.com/jupyterhub/configurable-http-proxy
    cd configurable-http-proxy 
    npm install # Use 'npm install -g' for global install

Usage

The configurable proxy runs two HTTP(S) servers:

1. The public-facing interface to your application (controlled by --ip, --port) listens on all interfaces by default.
2. The inward-facing REST API (--api-ip, --api-port) listens on localhost by default. The REST API uses token authorization, where the token is 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) which will 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]

  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 REST API is documented and available as:

• a nicely rendered, interactive version at the petstore swagger site
• a swagger specification file in this repo

Basics

API Root

HTTP method	Endpoint	Function
GET	/api/	API Root

Routes

HTTP method	Endpoint	Function
GET	/api/routes	Get all routes in routing table
POST	/api/routes/{route_spec}	Add a new route
DELETE	/api/routes/{route_spec}	Remove the given route

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, this curl command entered in the terminal passes this header "Authorization: token $CONFIGPROXY_AUTH_TOKEN" for authentication and this endpoint http://localhost:8001/api/routes to retrieve the current routing table:

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

Getting the routing table

Request:

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

Parameters:

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

Response:

Status code

status: 200 OK

Response body

A JSON dictionary of the current routing table. This JSON dictionary excludes the default route.

Behavior:

The current routing table is returned to the user if the request is successful.

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.

Request:

POST /api/routes/[:path]

Required input:

target: The host URL

Example request body:

{
  "/user/fred": {
    "target": "http://localhost:8002"
  },
  "/user/barbara": {
    "target": "http://localhost:8003"
  }
}

Response:

status: 201 Created

Behavior:

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

Deleting routes

Request:

DELETE /api/routes/[:path]

Response:

status: 204 No Content

Behavior:

Removes a route from the proxy's routing table.

Custom error pages

Beginning with version 0.5, custom error pages can be provided when the proxy encounters an error and has no proxy target to handle a request. There are two typical errors that CHP may hit, along with their status code:

• 404: a client has requested a URL for which there is no routing target. This can be prevented by setting a default target before 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.

Setting the path for custom error pages

Specify an error path --error-path /usr/share/chp-errors when starting the CHP:

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

When a proxy error occurs, CHP will look in the following location for a custom html error page to serve:

/usr/share/chp-errors/{CODE}.html

where {CODE} is a status code number for an html page to serve. If there is a 503 error, CHP will look for a custom error page in this location /usr/share/chp-errors/503.html.

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

Setting a target for custom error handling

You can specify a target to use when errors occur by using --error-target {URL} when starting the CHP. If, for example, CHP starts with --error-target http://localhost:1234, then when the proxy encounters an error, it will make a GET request to the error-target server, with URL http://localhost:1234 and status code /{CODE}, and failing request's URL 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 use the hostname of the incoming request to select a target.

When using host-based routes, the API uses the target in the same way as if the hostname were the first part of the URL path, e.g.:

{
  "/example.com": "https://localhost:1234",
  "/otherdomain.biz": "http://10.0.1.4:5555",
}

Troubleshooting

Q: My proxy is not starting. What could be happening?

• If this occurs on Ubuntu/Debian, check that the you are using a recent version of node. Some versions of Ubuntu/Debian come with a version of node that is very old, and it is necessary to update node.

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