Results and error handling in batcher

[tjhoo]

Hi,

I want to send requests to remote endpoints in batches because the remote server is not able to cope up the huge number of requests). So I want to send 3 requests, and then another 3 requests and then ...

So the following is how the batcher look like,

let all = []
const processBatch = batch<number[][]>(
  async (items) => {
      console.log("Send request in batch:", items);
      // should we wait for the promise to resolve here?
      const results = await Promise.all(items.map((item) => axios.get("https://...")));
      all = [...all, ...results];
  },
  {
    maxSize: 3,
    wait: 2000,
  },
);
...

// process 1000 data in batches
for (let i = 0; i < 1000 i++) {
  processBatch([[i]])
}

Questions

• Should we await the promise in batcher?
• What will happen to the rest of the batches if there is an error thrown from the batcher? I want it to stop process the next batches when error is thrown.

[KevinVandy]

If you use the asyncBatch or AsyncBatcher, there is an onError callback option.

const asyncBatcher = useAsyncBatcher(processBatch, {
    maxSize: 5, // Process in batches of 5 (if reached before wait time)
    wait: 4000, // Wait up to 4 seconds before processing a batch
    onError: (error: unknown, batcher) => {
      console.error('Batch failed:', error)
      batcher.stop() // stop auto-executing by wait time
      setErrorState() // set your custom error state to disable
    },
  })

But honestly, more around a disabled state could be done here. This batcher util is a little different from the others, as it can execute when batch size or wait time conditions are achieved. The current logic only disables the wait tiime portion.

[saurabhkumarsuman20]

Await the Promise: Yes, you should await the promise in the batcher to ensure each batch completes before the next starts.
Error Handling: Use a try-catch block in the batch function. If an error occurs, re-throw it to stop further processing of batches.

const processBatch = batch<number[][]>(
  async (items) => {
      try {
          const results = await Promise.all(items.map((item) => axios.get("https://...")));
          all = [...all, ...results];
      } catch (error) {
          throw error; // Stop further processing
      }
  },
  { maxSize: 3, wait: 2000 }
);

[KevinVandy]

Well, our goal in TanStack Pacer is to make it so that it handles the error handling for you