Implement a windowed batch shcheduler

[yornaath]

Fixes #6

Implement helper function

windowedFiniteBatchScheduler(config: {
  windowMs: number;
  maxBatchSize: number;
})

This example batcher will batch all fetch calls made within 10 ms OR if the number of fetch calls(batch size) exceeds 100 items.

const batcher = batshit.create({
  fetcher: async (ids: number[]) => {
    return fetchAllUsersByIds(ids);
  },
  scheduler: windowedFiniteBatchScheduler({
    windowMs: 10,
    maxBatchSize: 100,
  }),
  resolver: keyResolver("id"),
});

The behaviour of the scheduler could also be manually implemented since the BatcherScheduler function is now provided a third argument of batchSize: number.

const maxBatchSize = 100
const windowSize = 10

const batcher = batshit.create({
  fetcher: async (ids: number[]) => {
    return fetchAllUsersByIds(ids);
  },
  scheduler: (start, latest, batchSize) => {
    if (batchSize >= maxBatchSize) return "immediate";
    const spent = latest - start;
    return windowSize - spent;
  },
  resolver: keyResolver("id"),
});

Ref:

/**
 * A function to schedule batch execution timing
 */
export type BatcherScheduler = {
  /**
   * A scheduler function.
   *
   * @param start number - time stamp when the current batch started queuing fetches.
   * @param latest number - time stamp of the latest queued fetch.
   * @returns number - the number of ms to wait from latest queued fetch until executing batchh fetch call.
   */
  (start: number, latest: number, batchSize: number): Schedule;
};

/**
 * A schedule for when to execute a batched fetch call.
 */
export type Schedule = number | "immediate";

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Name	Status	Preview	Comments	Updated (UTC)
batshit-example	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 13, 2023 9:56am

[yornaath]

I have also added another helper maxBatchSizeScheduler that will not batch within a window of time but only wait for the batch size to be met:

const batcher = batshit.create({
  fetcher: async (ids: number[]) => {
    return fetchAllUsersByIds(ids);
  },
  scheduler: maxBatchSizeScheduler({
    maxBatchSize: 100,
  }),
  resolver: keyResolver("id"),
});

[tbowmo]

This one should probably be added to the .gitignore file?

[tbowmo]

Seems good from my point of view