Memory Leaks: HttpClients

Overview:
When running a check-in-check-out longevity (24hr) test with considerable load (20 virtual users) mod-pubsub shows clear signs of leaking HTTP Clients in which the client objects were not closed or reused. The CPU utilization also increased from 0 to 350%

Steps to Reproduce:
Run the attached check-in-check-out test for a long time at high load.

Expected Results:
Memory trend stabilizes after an hour max

Actual Results:
Memory trend rose for the first 12 hours, leveled out in the second half only because the database was overloaded with requests.

CPU usage showing the rising trend continues for at least 18 hours. Okapi's CPU usage went down over time, probably being dragged down by degrading performance of mod-pubsub.

Additional Information:
mod-pubsub's heap dump may be provided upon request. Because the compressed file is still big, over 100MB, it can't be attached here nor on Confluence.
Heap dump:
Interested parties:
OleksiiKuzminov Taras_Spashchenko