/* =========================================================================================
* Copyright © 2013-2018 the kamon project
It is faster to use a mutable holder object and always perform ThreadLocal.get() and never use * ThreadLocal.set(), because the value is more likely to be found in the ThreadLocalMap direct hash * slot and avoid the slow path ThreadLocalMap.getEntryAfterMiss(). * *
Credit to @trask from the FastThreadLocal in glowroot. * *
One small change is that we don't use an kamon-defined holder object as that would prevent class unloading. * * */ object ThreadLocal { def apply(): Storage = { if(classOf[ContextHolder].getClassLoader == null) SuperFastThreadLocal() else FastThreadLocal() } } final class FastThreadLocal extends Storage { private val tls = new java.lang.ThreadLocal[Array[AnyRef]]() { override def initialValue(): Array[AnyRef] = Array(Context.Empty) } override def current(): Context = tls.get()(0).asInstanceOf[Context] override def store(newContext: Context): Scope = { val ref = tls.get() val previousContext = ref(0) ref(0) = newContext new Scope { override def context: Context = newContext override def close(): Unit = ref(0) = previousContext } } } object FastThreadLocal { def apply(): FastThreadLocal = new FastThreadLocal() } final class SuperFastThreadLocal extends Storage { private val tls = new java.lang.ThreadLocal[ContextHolder]() { override def initialValue(): ContextHolder = { new ContextHolder(Context.Empty) } } override def current(): Context = tls.get().value.asInstanceOf[Context] override def store(newContext: Context): Scope = { val ref = tls.get() val previousContext = ref.value ref.value = newContext new Scope { override def context: Context = newContext override def close(): Unit = ref.value = previousContext } } } object SuperFastThreadLocal { def apply(): SuperFastThreadLocal = new SuperFastThreadLocal() } }