Hystrix.reset for lifecycle management

I'm changing the design from the previous commits so it's more abstract and can handle any type of resources needing cleanup, not just threadpools.

ReactiveX/RxJava#45

hystrix-core/src/main/java/com/netflix/hystrix/Hystrix.java

@@ -0,0 +1,48 @@
+package com.netflix.hystrix;
+
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Lifecycle management of Hystrix.
+ */
+public class Hystrix {
+
+    /**
+     * Reset state and release resources in use (such as thread-pools).
+     * <p>
+     * NOTE: This can result in race conditions if HystrixCommands are concurrently being executed.
+     * </p>
+     */
+    public static void reset() {
+        // shutdown thread-pools
+        HystrixThreadPool.Factory.shutdown();
+        _reset();
+    }
+
+    /**
+     * Reset state and release resources in use (such as threadpools) and wait for completion.
+     * <p>
+     * NOTE: This can result in race conditions if HystrixCommands are concurrently being executed.
+     * </p>
+     *
+     * @param time time to wait for thread-pools to shutdown
+     * @param unit {@link TimeUnit} for <pre>time</pre> to wait for thread-pools to shutdown
+     */
+    public static void reset(long time, TimeUnit unit) {
+        // shutdown thread-pools
+        HystrixThreadPool.Factory.shutdown(time, unit);
+        _reset();
+    }
+
+    /**
+     * Reset logic that doesn't have time/TimeUnit arguments.
+     */
+    private static void _reset() {
+        // clear metrics
+        HystrixCommandMetrics.reset();
+        // clear collapsers
+        HystrixCollapser.reset();
+        // clear circuit breakers
+        HystrixCircuitBreaker.Factory.reset();
+    }
+}

hystrix-core/src/main/java/com/netflix/hystrix/HystrixCircuitBreaker.java

@@ -113,6 +113,13 @@ public static HystrixCircuitBreaker getInstance(HystrixCommandKey key, HystrixCo
         public static HystrixCircuitBreaker getInstance(HystrixCommandKey key) {
             return circuitBreakersByCommand.get(key.name());
         }
+
+        /**
+         * Clears all circuit breakers. If new requests come in instances will be recreated.
+         */
+        /* package */ static void reset() {
+            circuitBreakersByCommand.clear();
+        }
     }
 
     /**

hystrix-core/src/main/java/com/netflix/hystrix/HystrixCollapser.java

@@ -346,18 +346,6 @@ public Future<ResponseType> queue() {
         return response;
     }
 
-    /**
-     * Reset the global and request-scoped state for the given collapser key.
-     *
-     * This is intended to support uses of collapsers in an environment like a REPL
-     * where the definition of a collapser may change. It is not thread-safe and should
-     * not be used in a production environment.
-     */
-    public static void resetCollapser(HystrixCollapserKey key) {
-        globalScopedCollapsers.remove(key.name());
-        requestScopedCollapsers.remove(key.name());
-    }
-
     /**
      * Static global cache of RequestCollapsers for Scope.GLOBAL
      */
@@ -994,6 +982,16 @@ protected String getCacheKey() {
         return null;
     }
 
+    /**
+     * Clears all state. If new requests come in instances will be recreated and metrics started from scratch.
+     */
+    /* package */ static void reset() {
+        defaultNameCache.clear();
+        globalScopedCollapsers.clear();
+        requestScopedCollapsers.clear();
+        RealCollapserTimer.timer.reset();
+    }
+
     private static String getDefaultNameFromClass(@SuppressWarnings("rawtypes") Class<? extends HystrixCollapser> cls) {
         String fromCache = defaultNameCache.get(cls);
         if (fromCache != null) {

hystrix-core/src/main/java/com/netflix/hystrix/HystrixCommandMetrics.java

@@ -100,6 +100,13 @@ public static Collection<HystrixCommandMetrics> getInstances() {
         return Collections.unmodifiableCollection(metrics.values());
     }
 
+    /**
+     * Clears all state from metrics. If new requests come in instances will be recreated and metrics started from scratch.
+     */
+    /* package */ static void reset() {
+        metrics.clear();
+    }
+
     private final HystrixCommandProperties properties;
     private final HystrixRollingNumber counter;
     private final HystrixRollingPercentile percentileExecution;

hystrix-core/src/main/java/com/netflix/hystrix/util/HystrixTimer.java

@@ -66,6 +66,17 @@ public static HystrixTimer getInstance() {
         return INSTANCE;
     }
 
+    /**
+     * Clears all listeners.
+     * <p>
+     * NOTE: This will result in race conditions if {@link #addTimerListener(com.netflix.hystrix.util.HystrixTimer.TimerListener)} is being concurrently called.
+     * </p>
+     */
+    public static void reset() {
+        INSTANCE.listenersPerInterval.clear();
+        INSTANCE.intervals.clear();
+    }
+
     private TickThread tickThread = new TickThread();
     private ConcurrentHashMap<Integer, ConcurrentLinkedQueue<Reference<TimerListener>>> listenersPerInterval = new ConcurrentHashMap<Integer, ConcurrentLinkedQueue<Reference<TimerListener>>>();
     private ConcurrentLinkedQueue<TimerInterval> intervals = new ConcurrentLinkedQueue<TimerInterval>();