Cranker-connector NPM

Cranker Connector for Javascript

Daniel Flower's crank4j is a reverse proxy which provides implicit discovery behaviour.

This is a cranker connector library for javascript so javascript clients can connect to crankers.

Install

Simply:

npm install cranker-connector

Example

You can embed and use this in your service like this:

let demoServer = http.createServer((request, response) => {
    console.log("demoserver request headers", request.headers);
    let toReturnStatus = request.headers["x-expected-return-status"];
    response.statusCode = toReturnStatus == undefined ? 200 : toReturnStatus;
    response.setHeader("server", "demoserver");
    response.setHeader("x-demo-response", "xxx");
    response.write("<html><head><title>this");
    response.write("is a server</title><link rel='shortcut icon' href='data:image/x-icon;,' type='image/x-icon'></head><body>");
    response.end("<h1>hello</h1></body></html>");
});

demoServer.listen(8300, function () {
  let routerCluster = await connectToRouters(["cranker.example.org:16489"], "demo", "http://localhost:8300");

  // ... and then later when you want to shutdown ...
  routerCluster.close();
  demoServer.close();
});

Using a randomly allocated local server port

Because cranker is providing your routing you do not need an addressable local server, instead make a server on port 0 and a port will be dynamically allocated by the operating system:

const listener = demoServer.listen(0, "localhost", function () {
  const port = listener.address().port;
  const routerCluster = await connectToRouters(
      ["cranker.example.org:16489"], 
      "demo", 
      "http://localhost:" + port
  );

  // ... and then later when you want to shutdown ...
  routerCluster.close();
  demoServer.close();
});

Doc

Here are docs for the functions and objects.

connectToRouters(cranker-router-authority-list, route-prefix, target-location, options)

A function to connect to the crankers specified in the cranker-router-authority-list with the specified route-prefix. Requests from the cranker routers will be proxied to the target-location which is an http or https base URI.

Parameter cranker-router-authority-list - an Array of authorities (host name + ":" + port) which specify cranker routers. The cranker routers are presumed to run version 1.0 of the cranker protocol and to be available on wss.

The function returns a Promise which resolves to a RouterCluster object.

*Security notice -- there is no facility for specifying certificate options for cranker right now. You can eiher turn off TLS certifcate validation (see Turning Off Node Certifcate Validation, below) or use only operating system trusted certifcates.*

Parameter route-prefix - a string which will be used by cranker router to send traffic to this connector.

It does not include the leading /.

For example, if you want a cranker router to send you traffic directed to the router's /demo such as /demo/new-car or just /demo, then you would use the route prefix: demo.

Parameter target-location - a string which specifies the base URI (scheme + "//" + authority and no path) for the target server. The target server you are proxying requests to from the cranker router.

Examples are: http://www.example.com:8100 or http://localhost:3100.

*Security notice -- npm-cranker-connector does not support proxying to https currently*

Parameter options - an associative object of optional features which may alter or further specify the behaviour of the connector.

Currently the following options only are supported:

limit - an integer expressing the limit of idle connections to the cranker router; the cranker connector will attempt to keep this number of idle connections open

Router Cluster Object

RouterCluster objects have 2 members:

close: a function which will shutdown all the idle cranker-router websocket connections
routers: an array of router objects, see Router Object, below

RouterClusters also emit events. These are the primary way of tracking what's going on inside the cranker connector.

Here's the list of events:

routerConnecting from a RouterObject
- the RouterObject is trying to connect it's connections to the cranker router
- this happens in a 5 second loop to ensure that we've always got the connections
crankerHeadersReceived from a RouterObject connection
- a connection has received a header from the cranker router so the connection is no longer idle and another connection to the router needs to be obtained
- quite low level debug
crankerFrameReceived from a RouterObject's connection
- cranker router has sent us a web socket frame
- very low level debug
crankerConnected from a RouterObject's connection
- a socket has connected to cranker router
- very low level debug
crankedTargetResponse from a RouterObject's connection
- we made a request to and received a response from a proxy target
- the event includes data on the request and the response as well as the associated cranker router websocket
- quite low level debug
crankedRouterConnecting from a RouterObject
- the router is trying to create the limit number of idle connections to the relevant cranker router
- includes data on:
  - the relevant cranker router authority
  - the current idle connection count
  - the idle connection limit
- very low level debug
crankedSocketClose from a RouterObject's connection
- a web socket to a cranker router is closing, because it has completed it's request or because there was an error
crankedSocketError from a RouterObject's connection
- a web socket to a cranker router has caused an error
- includes data on the relevant web socket and the error
- quite low level debug
crankedPing from a RouterObject
- response to a ping to a cranker router websocket
- includes data on the state of the socket which is a websocket readyState
- very low level debug

Router Object

An object which represents the connectivity to an individual cranker router.

There might be multiple idle connections to a cranker router.

A Router Object has 2 members:

connections: a map of connection objects, keyed by an Id
interval: the polling timer to check the router's idle connection limit is fully met

Turning Off Node Certificate Validation

Because you cannot specify certifcates for self signed certificate cranker routers, you may want to turn off Node's TLS libraries certificate validation.

This can be achieved like this:

process.env.NODE_TLS_REJECT_UNAUTHORIZED = "0";

*Security notice This is a blanket act. So please do not do this if you do not know what you are doing. It should NOT be included in production code.*