Incrementing id recipe - takeEvery, but queue worker till worker ahead of has taken id

Question

Is there a best practice way for incrementing id's in redux-saga?

This is how I am doing it, but if multiple requests dispatched at same time, multiple things are getting the same id:

My data shape of the reducer is this:

const INITIAL = {
    lastId: -1,
    entries: []
}

And here is my saga:

function* requestDownloadWorker(action: RequestAction) {

    // other workers should wait

    const id = (yield select()).downloads.lastId;
    yield put(increment());
    console.log('incremented the lastId incremented, for whoever needs it next');
    // other workers can now continue

    // below logic - should happen in parallel with other workers
}
function* requestDownloadWatcher() {
    yield takeEvery(REQUEST, requestDownloadWorker);
}
sagas.push(requestDownloadWatcher);

I think I need to takeEvery but queue worker until the previous worker has declared it has finished taking an id, is this possible?

Answer 1

You could create an actionChannel that buffers all REQUEST actions until you "take" them.

import { actionChannel, select, take } from 'redux-saga/effects'
...

function* requestDownloadWorker() {
  const channel = yield actionChannel(REQUEST)
  while (true) {
    const action = yield take(channel)
    const id = (yield select()).downloads.lastId
    yield put(increment())

    yield fork(doOtherParallelStuff)
  }
}

It should work.