[foobarian]

In the entire time I worked at a web shop with a large Java backend I never found the parallelization to be necessary, and in many cases was outright dangerous. We just had it disabled on high-traffic services (thread limit set at 1) to prevent foot injuries.

Don't mean to detract from the point :-). I love how neat and elegant the feature is.

[victor106]

> We just had it disabled on high-traffic services (thread limit set at 1) to prevent foot injuries.

Can you please elaborate?

[foobarian]

The default thread pool will use all available cores on the machine. With multiple developers arbitrarily using parallel streams in business logic because it "sounds faster" there is more risk of disrupting concurrent requests.

[marginalia_nu]

> The default thread pool will use all available cores on the machine

This is actually a bit of a headache on many-core machines for another reason.

e.g. my production machine has 128 cores, and carelessly parallelizing a memory hungry task (not realizing it will run across 128 threads), risks allocating sevral hundred gigabytes of RAM, and may not even be faster given all the NUMA overhead when thrashing on all cores.

Have to be careful to always down-tune the common pool size to 32 or something.