Viadutoo

About

Viadutoo (From the Portuguese word for viaduct, "viaduto". Pronounced as "vee-uh-DOO-too" or in IPA: [vi.a.dˈu.tʊ].) is a kind of caching proxy endpoint for Caliper event data. As a proxy, its purpose is to accept Caliper event payloads from sensors as quickly as possible, then resend them to a preconfigured upstream endpoint. If the upstream endpoint is unable to accept the event payload for some reason, the caching feature will store the event data in a database for future processing.

Requirements

• PHP 5.4 or greater
• One of the following PHP HTTP client extensions:
  • curl (usually this is already included with PHP interpreter)
  • pecl_http
• Composer (not strictly required, but highly recommended)
  • For installation details, see: https://getcomposer.org/download/

Usage

• Update the composer.json file in the root directory of your project as follows:

  • The require section should include the following:

    {
        "require": {
            "php": ">=5.4",
            "umich-its-tl/viadutoo": "1.1.0"
        }
    }

  • If a repository is not specified, Composer will install Viadutoo from Packagist (https://packagist.org/packages/umich-its-tl/viadutoo). However, to specify a GitHub repository as the source instead, include the following in the repositories section:

    {
        "repositories": [
            {
                "type": "vcs",
                "url": "https://github.com/tl-its-umich-edu/viadutoo"
            }
        ]
    }

    This is one way to specify your own repository, for example, if you want to modify your own fork of Viadutoo. You would specify the URL of your own repository.

• Use Composer to install the package with the command:

  composer install

  Composer will create the vendor directory to hold the package and other related information.

• Composer will create PHP classes to help you load Viadutoo (and any other packages it has loaded) into your application. In your PHP code, use it like:

  /*
   * If necessary, use set_include_path() to ensure the directory
   * containing the "vendor" directory is in the PHP include path.
   */
  require_once 'vendor/autoload.php';  // Composer loader for Viadutoo, etc.

• Initialize and use Viadutoo in your PHP code like this:

  $proxy = (new MessageProxy())
      ->setTransportInterface(
          (new CurlTransport()) // Recommended transport with cURL, supports Basic Auth and OAuth 1.0
              ->setAuthZType(CurlTransport::AUTHZ_TYPE_OAUTH1, 'OAuth 1.0 key', 'OAuth 1.0 secret') // Optional authZ
      )
      ->setEndpointUrl('http://example.com/endpoint')
      ->setTimeoutSeconds(10)
      ->setAutostoreOnSendFailure(true)
      ->setStorageInterface(
          new MysqlStorage(
              'mysql.example.org', 'dbUser', 'dbPassword',
              'dbName', 'viadutoo_events'
          )
      );
  // ...
  try {
      $proxy
          ->setHeaders($headers)
          ->setBody($jsonBody)
          ->send();
  } catch (Exception $exception) {
      error_log($exception->getMessage());
  }

  For a more detailed example of using Viadutoo in an application, see public/index.php.

Example

An example application is included in the public directory. Execute it as:

cd public
php -S 127.0.0.1:8989

The application is written to send all data to http://lti.tools/caliper/event?key=viadutoo. Simply configure a Caliper sensor to send events to http://127.0.0.1:8989/ and they will be sent on to the lti.tools endpoint.