return Err(err);
          }

          thread::sleep(Duration::from_secs(seconds));
        }
        Ok(result) => return Ok(result),
      }
    }
  }

  fn spawn_fetcher(index: &Index) -> Result<(Sender<OutPoint>, Receiver<u64>)> {
    let fetcher = Fetcher::new(&index.options)?;

    // Not sure if any block has more than 20k inputs, but none so far after first inscription block
    const CHANNEL_BUFFER_SIZE: usize = 20_000;
    let (outpoint_sender, mut outpoint_receiver) =
      tokio::sync::mpsc::channel::<OutPoint>(CHANNEL_BUFFER_SIZE);
    let (value_sender, value_receiver) = tokio::sync::mpsc::channel::<u64>(CHANNEL_BUFFER_SIZE);

    // Batch 2048 missing inputs at a time. Arbitrarily chosen for now, maybe higher or lower can be faster?
    // Did rudimentary benchmarks with 1024 and 4096 and time was roughly the same.
    const BATCH_SIZE: usize = 2048;
    // Default rpcworkqueue in bitcoind is 16, meaning more than 16 concurrent requests will be rejected.
    // Since we are already requesting blocks on a separate thread, and we don't want to break if anything