Corrective saga

corrective-saga.js

// function that creates an async operation that can either fail or succeed based on the argument (bool)
const createAsyncOperation = (opName) => (succeeds) => !succeeds ? Promise.resolve(opName + ' success') : Promise.reject(new Error(opName + ' failure'));

// corrective operations are operations that
// sematically undo the original operation
//
// i.e - you cannot unsend an email or delete the booking at an hotel,
// but you can send an apology email and cancel a reservation
//
// to enable (unlimited) of both operations and corrective operations
// every operation and their counter should(must) be idempotent

const operation1 = createOperation('operation1');
const correctiveOperation1 = createOperation('corrective operation1');

const operation2 = createOperation('operation2');
const correctiveOperation2 = createOperation('corrective operation2');

const operation3 = createOperation('operation3');
const correctiveOperation3 = createOperation('corrective operation3');

const operation4 = createOperation('operation4');
const correctiveOperation4 = createOperation('corrective operation4');

const operation5 = createOperation('operation5');
const correctiveOperation5 = createOperation('corrective operation5');

// function that takes a promise creating function
// and wraps it so that it is retried until it succeeds
function retryUntilSuccess(promiseReturningFunction) {
  return promiseReturningFunction()
  .catch(error => {
    console.log('got error:', error);
    console.log('retrying..');
    // this should be tapered off to retry at
    // increasing intervals to avoid hammering
    return retryUntilSuccess(promiseReturningFunction);
  })
}

// a subSaga that corrects itself if it fails
function* subSaga(action) {
  const correctiveOperationsNeeded = [];
  
  try {
    yield operation1(true);
    correctiveOperationsNeeded.push(correctiveOperation1);
  
    yield operation2(true);
    correctiveOperationsNeeded.push(correctiveOperation2);
  
    yield operation3(true);
    correctiveOperationsNeeded.push(correctiveOperation3);
  
    yield operation4(true);
    correctiveOperationsNeeded.push(correctiveOperation4);
  
    yield operation5(true);
    correctiveOperationsNeeded.push(correctiveOperation5);
  } catch (error) {
    // run all corrective (counter)operations if something fails
    // NOTE: these are retried until every one of them succeeds
    yield Promise.all(correctiveOperationsNeeded.map(operation => retryUntilSuccess(operation.bind(null, true)));
  } finally {
    // retry the whole saga
    return yield* subSaga(action);
  }
}

// a main saga that delegates something to a sub-saga
function* mainSaga() {
  while (true) {
    const action = yield take(START_MULTIPART_TRANSACTION);
    yield* subSaga(action);
  }
}