使用Dexie.js处理请求队列异步

Question

I'm currently working on processing "cached" requests out of an IndexedDB using Dexie.js. At first I save my requests into an IndexedDB queue for than to be flushed all at once. Unfortunately it seems that I can't delete my entries after they got sent out.

I followed the guides/samples from the official docs but I just can't get it to work. I even tried to campsulate it into a db.transaction with 'rw'

function flushQueue(){
  queueRunning = true; // used to mimic singleton pattern

  return db.queue.orderBy(':id').modify(async function(value){
    var _this = this;
    return deserializeRequest(value.serializedReq).then(async function(request){
      return fetch(request).then(function(){
        notifyClients("Request has been sent: ", request);
        // deleting request from queue
        delete _this.value;
      });
    });
  });
}

Any ideas what could have gone wrong?

Kind regards, Felix

Answer 1

The callback to modify must be synchronous and cannot be async. If you need to do async work, you have to pull the existing entries first using toArray(), then modify them in memory, and when done, use bulkPut() to update them.

In your case, you are processing a queue. Seems to involve other async operations per queue item.

I'd suggest you to instead, have a separate function that only processes the first item in queue, when process succeeds, remove the item. Then call that function asynchronicallt until the queue is empty.