limit the default max batch size

[fwbrasil]

@williamboxhall @stevenheidel

I spent many days trying to identify the cause for a production issue and in the end the main problem was the size of the batch requests to memcached. The system was making requests for batches with thousands of keys.

We need to avoid letting users run into similar problems. This pull request sets the default maxBatchSize to 100. Another alternative would be make the maxBatchSize required when creating a ClumpSource.

[stevenheidel]

I like this method, making the max batch size required would be too onerous on most use cases.

[williamboxhall]

can you think of a valid case where someone would want to use more than 100 / or use an unlimited batch size?

[fwbrasil]

I imagine that some cases would need bigger batches, but I think they would be the minority. IMHO having to define a custom batch size using source.maxBatchSize is reasonable for these cases.

[williamboxhall]

👍 it's a good default behaviour, one less thing for developers to need to think about out of the box

[williamboxhall]

merged