Motivation: When Netty runs in a managed environment such as web application server, Netty needs to provide an explicit way to remove the thread-local variables it created to prevent class loader leaks. FastThreadLocal uses different execution paths for storing a thread-local variable depending on the type of the current thread. It increases the complexity of thread-local removal. Modifications: - Moved FastThreadLocal and FastThreadLocalThread out of the internal package so that a user can use it. - FastThreadLocal now keeps track of all thread local variables it has initialized, and calling FastThreadLocal.removeAll() will remove all thread-local variables of the caller thread. - Added FastThreadLocal.size() for diagnostics and tests - Introduce InternalThreadLocalMap which is a mixture of hard-wired thread local variable fields and extensible indexed variables - FastThreadLocal now uses InternalThreadLocalMap to implement a thread-local variable. - Added ThreadDeathWatcher.unwatch() so that PooledByteBufAllocator tells it to stop watching when its thread-local cache has been freed by FastThreadLocal.removeAll(). - Added FastThreadLocalTest to ensure that removeAll() works - Added microbenchmark for FastThreadLocal and JDK ThreadLocal - Upgraded to JMH 0.9 Result: - A user can remove all thread-local variables Netty created, as long as he or she did not exit from the current thread. (Note that there's no way to remove a thread-local variable from outside of the thread.) - FastThreadLocal exposes more useful operations such as isSet() because we always implement a thread local variable via InternalThreadLocalMap instead of falling back to JDK ThreadLocal. - FastThreadLocalBenchmark shows that this change improves the performance of FastThreadLocal even more. |
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