Add support for asynchronous cacheMap about dataloader HOT 4 CLOSED

Hey Lee, @leebyron

Do you think this concept could be used on the level of the internal Cache Storage?

Thanks.

from dataloader.

@vieks is correct here. DataLoader's cache is purely a local (in memory per instance) cache. It is not a distributed cache like memcached.

Here is a rough example of how you might implement a "read through" distributed cache with DataLoader:

function loadValue(id) {
  return fastLoader.load(id).catch(err => slowLoader.load(id));
}

let fastLoader = new DataLoader(ids => batchLoadFromMemcache(ids));

let slowLoader = new DataLoader(ids => batchLoadFromSQL(ids).then(values => {
  writeToMemcache(ids, values); // fire and forget
  return values;
}));

from dataloader.

This is exactly the issue I have created #23 but I auto-closed it because it's silly.

The purpose of Dataloader is to prevent at most round trips generated by a data source (Redis, PostgreSQL, whatever...) induced by their network nature. So permitting to create a async remote cache goes against the benefit of using Dataloader hence becoming useless.

Strictly speaking Dataloader doesn't realy implement a cache but a memoize mechanism.

Furthermore, if you look at the source: _promiseCache: CacheMap<K, Promise<V>>;
Dataloader memoize/cache Promise objects, no pure raw data types, so you can't serialize them into a remote cache.

If you want a real cache in front of a slow data source/store/base, make it in an upstream batch function.

as it could be too much for just memory storage

Or at least use the custom cache api with an in-memory LRU local cache:

LRU node
LRU memoize

from dataloader.

@vieks it makes sense in how you put it, thank you for explanation & closing issue.

from dataloader.