task-runner

Task runner framework

Defining a task

A task is a single isolated module that exports an object with the following api:

// this is the "mytask" module
function myTask(options, callback) {
  // in the case of a non-deterministic error you simply
  // invoke the callback with one like in all node operations
  callback(new Error('....'));

  // and in the success case
  callback(null, outcome, { someData: true });
}

module.exports = myTask;

Invoking a task

var runner = require('isolated-task-runner');

runner.perform(
  require.resolve('myask'), /* module to run: use require.resolve to use npm packages */
  1000, /* timeout in ms */
  { somedata: true }, /* options to pass to task */
  function(err, outcome, result) {
    /* result of task */
  }
);

The callback takes a standard node-style error object, a boolean and an Object. The error object is a standard node error callback object. The boolean contains the outcome of the task. A true value means that the operation completely succeeded. A false value means that the operation failed and should be retried. The Object contains information relevant to status and reporting. The task running system will not make any choices based on the contents of this Object.

Isolation and error handling

• Your task is run in a totally separate process and has no direct access the memory in the process where it was started.

• Each task may fail (process dies, on the sync exception, off the async exception) and it will be handled gracefully and passed to the task runner.

• Tasks should only generate errors when they fail non-deterministically. Deterministic failures should be noted by having an outcome of false. An api call that fails because the connection died should generate an error, where trying to comment on a bug that doesn't exist should have a false outcome