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.

Table of Contents

• Install
• Usage
  • Starting the proxy
  • Setting a default target
  • Command-line options
• Using the REST API
  • REST API Basics
  • Authenticating via passing a token
  • Getting the routing table
  • Adding new routes
  • Deleting routes
• Custom error pages
  • Setting the path for custom error pages
  • Setting a target for custom error handling
• Host-based routing
• Troubleshooting

Install

Prerequisite: Node.js ≥ 10

If you're installing configurable-http-proxy in Linux, you can follow the instruction of nodesource to install arbitrary version of Node.js.

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

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Usage

The configurable proxy runs two HTTP(S) servers:

• The public-facing interface to your application (controlled by --ip, --port)
  • listens on all interfaces by default.
• 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 in the CONFIGPROXY_AUTH_TOKEN environment variable.

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Starting the proxy

configurable-http-proxy [options]

where [options] are the command-line options described below.

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Setting a default target

The default target is used when a client has requested a URL for which there is no routing target found in the proxy table. To set a default target, pass the command line option, --default-target, when starting the configurable proxy:

configurable-http-proxy --default-target=proto://host[:port]

For example:

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

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Command-line options

Usage: configurable-http-proxy [options]

Options:
  -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 SSL protocol, e.g. TLSv1_2, SSLv3
  --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 (default: "localhost")
  --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)
  --client-ssl-key <keyfile>         SSL key to use, if any, for proxy to client requests
  --client-ssl-cert <certfile>       SSL certificate to use, if any, for proxy to client requests
  --client-ssl-ca <ca-file>          SSL certificate authority, if any, for proxy to client requests
  --client-ssl-request-cert          Request SSL certs to authenticate clients for API requests
  --client-ssl-reject-unauthorized   Reject unauthorized SSL connections (only meaningful if --client-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
  --redirect-to <port>               Redirect HTTP requests from --redirect-port to this port
  --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
  --auto-rewrite                     Rewrite the Location header host/port in redirect responses
  --change-origin                    Changes the origin of the host header to the target URL
  --protocol-rewrite <proto>         Rewrite the Location header protocol in redirect responses to the specified protocol
  --custom-header <header>           Custom header to add to proxied requests. Use same option for multiple headers (--custom-header k1:v1 --custom-header k2:v2) (default: {})
  --insecure                         Disable SSL cert verification
  --host-routing                     Use host routing (host as first level of path)
  --metrics-ip <ip>                  IP for metrics server (default: "")
  --metrics-port <n>                 Port of metrics server. Defaults to no metrics server
  --log-level <loglevel>             Log level (debug, info, warn, error) (default: "info")
  --timeout <n>                      Timeout (in millis) when proxy drops connection for a request.
  --proxy-timeout <n>                Timeout (in millis) when proxy receives no response from target.
  --storage-backend <storage-class>  Define an external storage class. Defaults to in-MemoryStore.
  -h, --help                         display help for command

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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

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REST API 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

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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 retrieves the current routing table from this endpoint, http://localhost:8001/api/routes:

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

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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.

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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:

{
  "target": "http://localhost:8002"
}

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.

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Deleting routes

Request:

DELETE /api/routes/[:path]

Response:

status: 204 No Content

Behavior:

Removes a route from the proxy's routing table.

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Custom error pages

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 error: Returned when a client has requested a URL for which there is no routing target. This error can be prevented by setting a default target before starting the configurable-http-proxy.

• 503 error: Returned when 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, not finished starting, or network instability.

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Setting the path for custom error pages

When starting the CHP, specify an error path --error-path /usr/share/chp-errors to the location of the error page:

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 default error.html. If you specify an error path, make sure you also create a default error.html file.

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Setting a target for custom error handling

You can specify a target URL to use when errors occur by setting --error-target {URL} when starting the CHP.

If, for example, CHP starts with --error-target http://localhost:1234, and the proxy encounters an error, the proxy will make a GET request to the error-target server. The GET request will be sent to the error-target server URL, http://localhost:1234, appending the status code /{CODE}, and passing the failing request's URL escaped in a URL parameter:

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

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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",
}

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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 to a recent or LTS version.

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