public int getCapacity() {
    // actual queue can hold more than the specified capacity because each writer and reader may have a batch they are
    // working on that is outside the queue
    return (pendingBatchesCapacity + writers.size() + readers.size()) * batchSize;
  }
Returns the total number of items that can be pending.
<p>
This will be larger than the initial capacity because each writer thread can buffer items into a batch and each
reader thread can read items from a batch.
planetiler-core/src/main/java/com/onthegomap/planetiler/worker/WorkQueue.java