webhdfs-proxy

webhdfs-proxy is a naive proxy layer for Hadoop WebHDFS REST API, which can be used to mock WebHDFS API requests in the tests or help to replace/migrate existing HDFS data storage (migration to S3, GridFS or custom storage etc.).

Usage

Storage specific logic is implemented in storage middleware. webhdfs-proxy itself implements basic requests validation, parsing and redirects simulation, and utilities for handling WehbHDFS API requests and responses.

Supported WebHDFS REST API operations (Hadoop 2.4.x compatible) at the moment are:

• APPEND
• CREATE
• CREATESYMLINK
• DELETE
• GETFILESTATUS
• LISTSTATUS
• MKDIRS
• OPEN
• RENAME
• SETOWNER
• SETPERMISSIONS

Install module:

npm install webhdfs-proxy --save

Basic middleware skeleton:

var WebHDFSProxy = require('webhdfs-proxy');

WebHDFSProxy.createServer({
  path: '/webhdfs/v1',
  validate: true,

  http: {
    port: 80
  },

  https: {
    port: 443,
    key: '/path/to/key',
    cert: '/path/to/cert'
  }
}, function storageHandler (err, path, operation, params, req, res, next) {
  // Pass error to WebHDFS REST API user
  if (err) {
    return next(err);
  }

  switch (operation) {
    case 'open':
      // Implement operation logic here
      return next();
      break;

    case 'create':
      // Implement operation logic here
      return next();
      break;
      
    case 'mkdirs':
      // Implement operation logic here
      return next(new Error('Internal error'));
      break;
  }
}, function onServerCreate (err, servers) {
  if (err) {
    console.log('WebHDFS proxy server was not created: ' + err.message);
    return;
  }

  // Proxy server was successfully created
});

For extended usage and implementing your own storage middleware, please see example middlewares.

Server options

• path (optional, string, '/webhdfs/v1') - API endpoint path
• validate (optional, boolean, 'true') - Enables requests validation. Supported schemas are loacated in schemas/ directory.
• http (optional, object) - HTTP options. HTTP server is created always.
• http.port (optional, number, 80) - HTTP listening port.
• https (optional, object) - HTTPS options.
• https.port (optional, number, 443) - HTTPS listening port. If set then it enables HTTPS server automatically.
• https.key (optional, string) - User defined path to key file. If not set then key will be generated on runtime.
• https.cert (optional, string) - User defined path to cert file. If not set then certificate will be generated on runtime.

Middleware parameters

• err - It can be ignored or passed to the client. Is set if request validation failed or unexpected runtime error occurred.
• path - WebHDFS resource path
• operation - WebHDFS API operation name
• params - Map of parsed query parameters
• req - Internal request object
• res - Internal response object
• next - Function which should be called when the request is fulfilled. Returns an error response if first argument is a valid error object.

Tests

Running tests:

npm test

Middlewares

Licence

MIT