Generally when building servers on top of a jvm, it's a good idea to be able to capture eg 1m requests, replay them, and monitor your memory allocation / gc as

Generally when building servers on top of a jvm, it's a good idea to be able to capture eg 1m requests, replay them, and monitor your memory allocation / gc as part of quality tests. If you create nests of objects in java, it quickly gets expensive, both in terms of net memory and gc costs. One common place this happens is parsing json/xml; use thrift or protobufs instead. If you are eg building an ad server that is supposed to sustain some XX thousand requests per second, you want to also monitor eg eden, survivor, tenured, and promotions. Bump pointer allocation and gc is very fast -- normally faster even than manual memory management -- as long as almost nothing survives. The problem is if some objects start accidentally living past requests, stuff goes boom fast.