Sagas: Global Error Handling

SagasGlobalErrorHandling.js

// I usually use the request-sequence pattern
// (https://gist.github.com/josepot/cf63578fa81c7dba89ba156e71274537)
// And since 99% of the times that a saga errors it's because something
// went wrong with a request. That's not the only case when a saga can crash.
// The problem is that if there is an unhandled exception is a saga, that
// exception gets propagated all the way up to the rootSaga and the root
// saga will cancell all watchers... Which can be pretty annoying.
// This is one way to avoid such thing from happening:

// This is just a silly example on how to deal with a general exception.
// I'm sure that in your project you will have a better way to deal
// with it.
function errorHandler(error, watcher) {
  console.log('The following unexpected exeption happened.');
  console.log(error.message);
  console.log(error.stack);
  console.log('Which made the following watcher crash:');
  console.log(watcher.toString());
  console.log('The watcher has been restarted');
}

function* startFaultTolerantWatcher(watcher) {
  try {
    yield call(watcher);
  } catch(e) {
    errorHandler(e, watcher);
    yield call(startFaultTolerantWatcher, watcher);
  }
}

function* startMainWatchers(...watchers) {
  yield watchers.map(watcher => call(startFaultTolerantWatcher, watcher));
  // This will run the watchers in parallel like `fork` does, but without
  // forking them.
}

export default function* rootSaga() {
  // Whatever non permanent watchers that we need to run on init:
  // These ones should be able to handle their own exceptions.
  yield call(initilizeStuff);
  yield call(getConfigInfo);
  // ...Whatever
  
  // These are the "eternal" watchers.
  yield call(startMainWatchers, watcher1, watcher2, watcher3);
}