openhim-mediator-file-queue

File queue

To install, execute npm install -g openhim-mediator-file-queue

Once installed you will have to manually edit the config files in the location where global npm modules are installed.

• With NVM this is usually: ~/.nvm/versions/node/v4.1.0/lib/node_modules/openhim-mediator-file-queue/config
• With a standard node install this is usually: /usr/local/lib/node_modules/openhim-mediator-file-queue/config

You may add a production.json file to the config folder to override or add any config values.

See this visual example of how this work as an OpenHIM mediator. Note the curl commands return instantly but the mediator knows to tell the OpenHIM that these are still processing and updates them after they complete asynchronously.

How it works

The file queue simply handles incoming requests, writing the files to a directory on the filesystem, and then processes the queue, sending the files to a configured endpoint. If the file is successfully sent then the queued file is deleted from the filesystem, otherwise it is moved to an error directory.

Multiple "endpoints" can be configured. Each endpoint handles incoming requests for a specific URL, queues them, and then sends them to another configured URL. An endpoint has a "worker" which is responsible for reading the files from the queue and processing them. Workers can process multiple files in parallel as configured (by default 2 at a time). Workers can be paused/unpaused or repopulated via a RESTlike endpoint. Pausing a worker will stop it from processing files from the queue, but the endpoint will continue accepting requests and writing the files to the queue. Repopulating a worker will cause it to refresh its queue from the files on the filesystem. This is useful when manually adding files to or removing files from the queue.

Endpoint config

An array of endpoints should be configured in the config file. An endpoint can have the following properties:

• name (required) - The name of the endpoint which is used for setting up the RESTlike routes for the worker.
• path (required) - The path to use for handling incoming requests. A '*' may be used to match any number of characters in a path. E.g. 'this/is/a/test/*'.
• url (required) - The URL to send the files to when processing them from the queue.
• paused - Whether or not the endpoint's worker should be paused by default. This must be a boolean value. Defaults to false.
• parallel - The number of files that the worker should process in parallel. Defaults to 2.
• updateTx - Whether or not to attempt to update the OpenHIM transaction once the message has been processed. Defaults to false.
• forwardMetadata - Whether or not to use the url, headers and HTTP method of the original request when it is forwarded. The path of the original request will be appended to the url property. Defaults to false.

Here is an example config file:

{
  "port": 4002,
  "log_level": "info",
  "endpoints": [
    {
      "name": "test",
      "path": "/test",
      "url": "http://localhost:9999",
      "updateTx": true,
      "forwardMetadata": true
    }
  ]
}