AnyFetch file hydrater

Base library for file hydration on http://anyfetch.com.

This library allows you to create a hydrater server from a single function. Taking a file path and initial data, it should return improved or augmented data.

Read first

To better understand the role of "hydraters", read the dedicated documentation page.

Usage

'use strict';
 
var anyfetchFileHydrater = require('anyfetch-file-hydrater');
 
/**
 * Hydration function, to add metadata to the document
 *
 * @param {String} filePath Path to the file from which hydrate, downloaded for you on the filesystem
 * @param {Object} document Data currently known (from previous hydraters, or from providers). Always includes `document_type`, `metadata`, `data` and `actions` keys.
 * @param {Object} changes Convenience object provided with empty keys `document_type`, `metadata`, `data` and `actions`. Add your changes in there.
 * @param {Function} cb(err, changes) Call this with an error if any, or pass your changes as second parameter.
 */
var myHydrationFunction = function(path, document, changes, cb)
  // Extract interesting stuff from the file...
  // Improve the document...
 
  cb(err, changes);
};
 
var config = {
  'hydrater_function': myHydrationFunction
};
 
var hydrationServer = anyfetchFileHydrater.createServer(config);
hydrationServer.listen(8000);

You're all set! Your server is running on port 8000. Access /hydrate with a standard AnyFetch POST request to start hydrating your file.

POST <your_hydrater_server_url>/hydrate
  {
    file_path: <url-file-to-hydrate>
    callback: <url-to-ping>
    document: {base document}
  }

In some cases, you may want to bypass the lib and send the result yourself. The property cb.callbackUrl tells you where to send the data back to the client. After having sent the data, call cb() without any error or document. This will finalize hydration, clean the file and start the next task.

Optional parameters

createServer() takes an object hash for argument. hydrater_function is mandatory, optional values includes:

• concurrency: max number of simultaneous calls to your hydrater function (default: 1)
• logger: function to use for logging error and success. It will get called with strings when a task is started or ended. When an error occured, you'll get the path of the file, and the err as second argument).

Errors

You may use require('anyfetch-file-hydrater').hydrationError as a special error to inform the hydration was unable to complete, and should not be tried again:

var myHydrationFunction = function(filePath, document, cb) {
  // Do stuff with the file...
  cb(new anyfetchFileHydrater.hydrationError("Corrupted file"));
};

For other (transient) errors, use standard Error objects.