JIRA Rest Java API: sessions don't close immediately after calling restClient.close();

Dear Sir/Madam,

I’m using Jira Rest API version 2.0.0-m31, also tried 3.0.0. I always call restClient.close() after every request, but most of the time the session doesn’t close immediately and remains open for some time (30 mins in my case), which resulting a lot open sessions in JIRA server.

More specifically, we use
AsynchronousJiraRestClientFactory.createWithBasicHttpAuthentication() to get an instance of JiraRestClient (restClient),
then in the try … finally block we call restClient.close(); to close the session.

Would you please help? I really need to close sessions immediately after request is finished. We have too many JIRA session opened so it may used up connections anytime.

Thanks a lot in advanced!