global registry is now a composite

The static global registry returned by `Spectator.globalRegistry()`
is now a composite. During application initialization a user can
add another registry to the composite to subscribe to activity
hitting the global registry. If nothing is added the global will
behave similar to the NoopRegistry.

The primary benefit of this change is to make it easier to work
with DI systems. The DI library can be used to setup the main
registry and if there is interest in the global data add it to
the global registry.

If the legacy behavior is needed the user can call:

```java
Spectator.initializeUsingServiceLoader();
```

That method will add the registries found using the service loader
to the global composite.

The `Spectator.registry()` call is deprecated because it still
returns the `ExtendedRegistry` class that is already deprecated
and will go away in a later release.

spectator-api/src/main/java/com/netflix/spectator/api/CompositeRegistry.java

@@ -25,7 +25,7 @@
  * Maps calls to zero or more sub-registries. If zero then it will act similar to the noop
  * registry. Otherwise activity will be sent to all registries that are part of the composite.
  */
-final class CompositeRegistry implements Registry {
+public final class CompositeRegistry implements Registry {
 
   /**
    * Id used for a meter storing all gauges registered with the composite. Since there is no
@@ -71,6 +71,11 @@ public void remove(Registry registry) {
     registries.remove(registry);
   }
 
+  /** Remove all registries from the composite. */
+  public void removeAll() {
+    registries.clear();
+  }
+
   @Override public Clock clock() {
     return clock;
   }

spectator-api/src/main/java/com/netflix/spectator/api/Spectator.java

@@ -34,8 +34,8 @@ public final class Spectator {
 
   private static final ConfigMap CONFIG = newConfigMapUsingServiceLoader();
 
-  private static final ExtendedRegistry REGISTRY =
-    new ExtendedRegistry(newInstance(Config.registryClass()));
+  private static final CompositeRegistry COMPOSITE_REGISTRY = new CompositeRegistry(Clock.SYSTEM);
+  private static final ExtendedRegistry REGISTRY = new ExtendedRegistry(COMPOSITE_REGISTRY);
 
   /**
    * Create a new config map instance using {@link java.util.ServiceLoader}. If no implementations
@@ -58,7 +58,7 @@ static ConfigMap newConfigMapUsingServiceLoader() {
    * Create a new registry instance using {@link java.util.ServiceLoader}. If no implementations
    * are found the default will be used.
    */
-  static Registry newInstanceUsingServiceLoader() {
+  static void addRegistriesFromServiceLoader() {
     final ClassLoader cl = pickClassLoader();
     final ServiceLoader<Registry> loader = ServiceLoader.load(Registry.class, cl);
     final Iterator<Registry> registryIterator = loader.iterator();
@@ -75,18 +75,16 @@ static Registry newInstanceUsingServiceLoader() {
         }
       }
       if (rs.isEmpty()) {
-        return new DefaultRegistry();
+        COMPOSITE_REGISTRY.add(new DefaultRegistry());
       } else {
-        CompositeRegistry composite = new CompositeRegistry(Clock.SYSTEM);
         for (Registry r : rs) {
-          composite.add(r);
+          COMPOSITE_REGISTRY.add(r);
         }
         LOGGER.info("using registries found in classpath: {}", desc.toString());
-        return composite;
       }
     } else {
       LOGGER.warn("no registry impl found in classpath, using default");
-      return new DefaultRegistry();
+      COMPOSITE_REGISTRY.add(new DefaultRegistry());
     }
   }
 
@@ -106,23 +104,25 @@ private static ClassLoader pickClassLoader() {
    * Create a new registry instance using the class name specified by the system property
    * {@code spectator.api.registryClass}. If no implementations are found the default will be used.
    */
-  static Registry newInstanceUsingClassName(String name) {
+  static void addRegistryUsingClassName(String name) {
     try {
       final Class<?> c = Class.forName(name);
-      return (Registry) c.newInstance();
+      COMPOSITE_REGISTRY.add((Registry) c.newInstance());
     } catch (Exception e) {
       final String msg = "failed to instantiate registry class '" + name
         + "', falling back to default implementation";
       Throwables.propagate(new RuntimeException(msg, e));
-      return new DefaultRegistry();
+      COMPOSITE_REGISTRY.add(new DefaultRegistry());
     }
   }
 
   /** Create a new instance of the registry. */
-  static Registry newInstance(String name) {
-    return Config.SERVICE_LOADER.equals(name)
-      ? newInstanceUsingServiceLoader()
-      : newInstanceUsingClassName(name);
+  static void addRegistries(String name) {
+    if (Config.SERVICE_LOADER.equals(name)) {
+      addRegistriesFromServiceLoader();
+    } else {
+      addRegistryUsingClassName(name);
+    }
   }
 
   /**
@@ -133,19 +133,81 @@ public static ConfigMap config() {
   }
 
   /**
-   * Return the default global registry implementation. The implementation used will depend on the
+   * Setup the default global registry implementation. The implementation used will depend on the
    * system property {@code spectator.api.registryClass}. If not set or set to
    * {@code service-loader} the registry class will be determined by scanning the classpath using
    * {@link java.util.ServiceLoader}. Otherwise an instance of the classname specified will be
    * used. If a registry cannot be loaded the fallback is to use the {@link DefaultRegistry}.
    * When {@code spectator.api.propagateWarnings} is set to {@code true} and an explicit class name
    * is specified a {@link java.lang.RuntimeException} will be thrown if the specified class cannot
    * be used.
+   *
+   * @deprecated This provides the legacy behavior if needed. It is preferred to setup a registry
+   * and inject. If the static
+   */
+  @Deprecated
+  public static void initializeUsingServiceLoader() {
+    addRegistries(Config.registryClass());
+  }
+
+  /**
+   * Returns the global registry.
+   *
+   * @deprecated Use injection or {@link #globalRegistry()} instead.
    */
+  @Deprecated
   public static ExtendedRegistry registry() {
     return REGISTRY;
   }
 
+  /**
+   * Returns the global composite registry. This method can be used for use-cases where it is
+   * necessary to get a static reference to a registry. It will not do anything unless other
+   * registries are added. Example:
+   *
+   * <pre>
+   * class Main {
+   *   public static void main(String[] args) {
+   *     // This is the preferred usage and works well with DI libraries like guice. Setup a
+   *     // registry and pass it in as needed.
+   *     Registry registry = new DefaultRegistry();
+   *     (new Example1(registry)).start();
+   *
+   *     // If it is desirable to get data from things using the global registry, then the
+   *     // registry for the application can be added to the global context.
+   *     Spectator.globalRegistry().add(registry);
+   *     Example2 ex2 = new Example2();
+   *     ex2.start();
+   *
+   *     // If the lifecycle is not the same as the jvm, then the registry should be removed
+   *     // when shutting down.
+   *     ex2.onShutdown(() -> Spectator.globalRegistry().remove(registry));
+   *   }
+   * }
+   *
+   * class Example1 {
+   *   private final Counter c;
+   *
+   *   Example1(Registry registry) {
+   *     c = registry.counter("example1");
+   *   }
+   *   ...
+   * }
+   *
+   * class Example2 {
+   *   private final Counter c;
+   *
+   *   Example2() {
+   *     c = Spectator.globalRegistry().counter("example1");
+   *   }
+   *   ...
+   * }
+   * </pre>
+   */
+  public static CompositeRegistry globalRegistry() {
+    return COMPOSITE_REGISTRY;
+  }
+
   private Spectator() {
   }
 }

spectator-api/src/test/java/com/netflix/spectator/api/SpectatorTest.java

@@ -29,13 +29,14 @@ public void testRegistry() {
 
   @Test
   public void testNewInstanceBadClass() {
+    Spectator.globalRegistry().removeAll();
     System.setProperty("spectator.api.propagateWarnings", "false");
-    Assert.assertTrue(Spectator.newInstance("fubar") instanceof DefaultRegistry);
+    Spectator.addRegistries("fubar");
   }
 
   @Test(expected = RuntimeException.class)
   public void testNewInstanceBadClassPropagate() {
     System.setProperty("spectator.api.propagateWarnings", "true");
-    Spectator.newInstance("fubar");
+    Spectator.addRegistries("fubar");
   }
 }

spectator-ext-gc/src/main/java/com/netflix/spectator/gc/GcLogger.java

@@ -55,24 +55,24 @@ public final class GcLogger {
 
   // Max size of old generation memory pool
   private static final AtomicLong MAX_DATA_SIZE =
-    Spectator.registry().gauge("jvm.gc.maxDataSize", new AtomicLong(0L));
+    Spectator.globalRegistry().gauge("jvm.gc.maxDataSize", new AtomicLong(0L));
 
   // Size of old generation memory pool after a full GC
   private static final AtomicLong LIVE_DATA_SIZE =
-    Spectator.registry().gauge("jvm.gc.liveDataSize", new AtomicLong(0L));
+    Spectator.globalRegistry().gauge("jvm.gc.liveDataSize", new AtomicLong(0L));
 
   // Incremented for any positive increases in the size of the old generation memory pool
   // before GC to after GC
   private static final Counter PROMOTION_RATE =
-    Spectator.registry().counter("jvm.gc.promotionRate");
+    Spectator.globalRegistry().counter("jvm.gc.promotionRate");
 
   // Incremented for the increase in the size of the young generation memory pool after one GC
   // to before the next
   private static final Counter ALLOCATION_RATE =
-    Spectator.registry().counter("jvm.gc.allocationRate");
+    Spectator.globalRegistry().counter("jvm.gc.allocationRate");
 
   // Pause time due to GC event
-  private static final Id PAUSE_TIME = Spectator.registry().createId("jvm.gc.pause");
+  private static final Id PAUSE_TIME = Spectator.globalRegistry().createId("jvm.gc.pause");
 
   private final long jvmStartTime;
 
@@ -200,7 +200,7 @@ private void processGcEvent(GarbageCollectionNotificationInfo info) {
     Id eventId = PAUSE_TIME
       .withTag("action", info.getGcAction())
       .withTag("cause", info.getGcCause());
-    Timer timer = Spectator.registry().timer(eventId);
+    Timer timer = Spectator.globalRegistry().timer(eventId);
     timer.record(info.getGcInfo().getDuration(), TimeUnit.MILLISECONDS);
 
     // Update promotion and allocation counters

spectator-ext-log4j2/src/main/java/com/netflix/spectator/log4j/SpectatorAppender.java

@@ -112,7 +112,7 @@ public static SpectatorAppender createAppender(
       return null;
     }
 
-    return new SpectatorAppender(Spectator.registry(), name, filter, layout, ignoreExceptions);
+    return new SpectatorAppender(Spectator.globalRegistry(), name, filter, layout, ignoreExceptions);
   }
 
   @Override public void start() {

spectator-ext-sandbox/src/main/java/com/netflix/spectator/sandbox/BucketCounter.java

@@ -39,7 +39,7 @@ public final class BucketCounter implements DistributionSummary {
    *     Distribution summary that manages sub-counters based on the bucket function.
    */
   public static BucketCounter get(Id id, BucketFunction f) {
-    return get(Spectator.registry(), id, f);
+    return get(Spectator.globalRegistry(), id, f);
   }
 
   /**

spectator-ext-sandbox/src/main/java/com/netflix/spectator/sandbox/BucketDistributionSummary.java

@@ -39,7 +39,7 @@ public final class BucketDistributionSummary implements DistributionSummary {
    *     Distribution summary that manages sub-counters based on the bucket function.
    */
   public static BucketDistributionSummary get(Id id, BucketFunction f) {
-    return get(Spectator.registry(), id, f);
+    return get(Spectator.globalRegistry(), id, f);
   }
 
   /**

spectator-ext-sandbox/src/main/java/com/netflix/spectator/sandbox/BucketTimer.java

@@ -41,7 +41,7 @@ public final class BucketTimer implements Timer {
    *     Timer that manages sub-timers based on the bucket function.
    */
   public static BucketTimer get(Id id, BucketFunction f) {
-    return get(Spectator.registry(), id, f);
+    return get(Spectator.globalRegistry(), id, f);
   }
 
   /**

spectator-ext-sandbox/src/main/java/com/netflix/spectator/sandbox/DoubleDistributionSummary.java

@@ -50,7 +50,7 @@ public class DoubleDistributionSummary implements Meter {
    *     Distribution summary corresponding to the id.
    */
   public static DoubleDistributionSummary get(Id id) {
-    return get(Spectator.registry(), id);
+    return get(Spectator.globalRegistry(), id);
   }
 
   /**

spectator-ext-sandbox/src/main/java/com/netflix/spectator/sandbox/HttpLogEntry.java

@@ -42,7 +42,7 @@ public class HttpLogEntry {
   private static final Marker CLIENT = MarkerFactory.getMarker("http-client");
   private static final Marker SERVER = MarkerFactory.getMarker("http-server");
 
-  private static final Registry REGISTRY = Spectator.registry();
+  private static final Registry REGISTRY = Spectator.globalRegistry();
   private static final Id COMPLETE = REGISTRY.createId("http.req.complete");
   private static final Id ATTEMPT = REGISTRY.createId("http.req.attempt");
   private static final Id REQ_HEADER_SIZE = REGISTRY.createId("http.req.headerSize");

spectator-ext-spark/src/main/java/com/netflix/spectator/spark/SparkSink.java

@@ -16,7 +16,6 @@
 package com.netflix.spectator.spark;
 
 import com.codahale.metrics.MetricRegistry;
-import com.netflix.spectator.api.Spectator;
 import com.netflix.spectator.gc.GcLogger;
 import com.netflix.spectator.jvm.Jmx;
 import com.typesafe.config.Config;
@@ -62,7 +61,7 @@ public SparkSink(
       MetricRegistry registry,
       org.apache.spark.SecurityManager manager) throws MalformedURLException {
     final Config config = loadConfig();
-    sidecarRegistry = Spectator.registry().underlying(SidecarRegistry.class);
+    sidecarRegistry = new SidecarRegistry();
     reporter = SpectatorReporter.forRegistry(registry)
         .withNameFunction(SparkNameFunction.fromConfig(config, sidecarRegistry))
         .withValueFunction(SparkValueFunction.fromConfig(config))
@@ -89,7 +88,7 @@ private ClassLoader pickClassLoader() {
 
   private void startJvmCollection() {
     try {
-      Jmx.registerStandardMXBeans(Spectator.registry());
+      Jmx.registerStandardMXBeans(sidecarRegistry);
       gcLogger = new GcLogger();
       gcLogger.start(null);
     } catch (Exception e) {

spectator-ext-spark/src/main/java/com/netflix/spectator/spark/SpectatorReporter.java

@@ -107,7 +107,7 @@ public Builder withGaugeCounters(Pattern pattern) {
     /** Create a new instance of the reporter. */
     public SpectatorReporter build() {
       if (spectatorRegistry == null) {
-        spectatorRegistry = Spectator.registry();
+        spectatorRegistry = Spectator.globalRegistry();
       }
       return new SpectatorReporter(
           registry, spectatorRegistry, nameFunction, valueFunction, gaugeCounters);

spectator-nflx-plugin/src/main/java/com/netflix/spectator/nflx/ChronosGcEventListener.java

@@ -22,7 +22,6 @@
 import com.netflix.spectator.api.Registry;
 import iep.com.netflix.iep.http.RxHttp;
 import com.netflix.spectator.api.Id;
-import com.netflix.spectator.api.Spectator;
 import com.netflix.spectator.gc.GcEvent;
 import com.netflix.spectator.gc.GcEventListener;
 import com.sun.management.GcInfo;
@@ -33,6 +32,7 @@
 import rx.functions.Action0;
 import rx.functions.Action1;
 
+import javax.inject.Inject;
 import java.io.IOException;
 import java.net.URI;
 import java.util.HashMap;
@@ -55,8 +55,8 @@ class ChronosGcEventListener implements GcEventListener {
 
   private final Logger logger = LoggerFactory.getLogger(getClass());
 
-  private final Registry registry = Spectator.registry();
-  private final Id requestCount = registry.createId("spectator.gc.chronosPost");
+  private final Registry registry;
+  private final Id requestCount;
 
   private final ObjectMapper mapper = new ObjectMapper();
 
@@ -68,8 +68,11 @@ class ChronosGcEventListener implements GcEventListener {
   private final RxHttp rxHttp;
 
   /** Create a new instance. */
-  ChronosGcEventListener(RxHttp rxHttp) {
+  @Inject
+  ChronosGcEventListener(RxHttp rxHttp, Registry registry) {
     this.rxHttp = rxHttp;
+    this.registry = registry;
+    requestCount = registry.createId("spectator.gc.chronosPost");
   }
 
   private String getenv(String k) {