4.x Make RegistryFactory and its getInstance and getRegistry methods public

docs/src/main/asciidoc/includes/metrics/metrics-shared.adoc

@@ -153,24 +153,70 @@ In addition to your application {metrics}, the reports contain other
 To register or look up {metrics} programmatically, your service code uses the link:{microprofile-metrics-javadoc-url}/org/eclipse/microprofile/metrics/MetricRegistry.html[`MetricRegistry`] instance for the scope of interest: `base`, `vendor`, `application`, or a custom scope.
 
 ifdef::mp-flavor[]
-To get a `MetricRegistry` reference
+Either of the following techniques gets a `MetricRegistry` reference.
+Remember that injection works only if the class is a bean so CDI can inject into it.
 
-* `@Inject` the metric registry you want, perhaps also using the link:{microprofile-metrics-javadoc-annotation-url}/RegistryScope.html[`@RegistryScope`] annotation to select the registry type, or
-* Get a Helidon link:{metrics-mp-javadoc-base-url}/RegistryFactory.html[`RegistryFactory`]; either
+* `@Inject MetricRegistry`, optionally using link:{microprofile-metrics-javadoc-annotation-url}/RegistryScope.html[`@RegistryScope`] to indicate the registry scope.
 +
 --
-** `@Inject` `RegistryFactory` or
-** Invoke one of the static `getInstance` methods on `RegistryFactory`
+[source,java]
+.Injecting the default `MetricRegistry` (for the application scope)
+----
+class Example {
+
+    @Inject
+    private MetricRegistry applicationRegistry;
+}
+----
+
+[source,java]
+.Injecting a non-default `MetricRegistry`
+----
+class Example {
+
+    @RegistryScope("myCustomScope")
+    @Inject
+    private MetricRegistry myCustomRegistry;
+}
+----
 --
+* Get a Helidon link:{metrics-mp-javadoc-base-url}/RegistryFactory.html[`RegistryFactory`] instance and invoke its `getRegistry` method.
 +
-Then invoke `getRegistry` on the `RegistryFactory` instance.
-endif::[]
-ifdef::se-flavor[]
-To get a `MetricRegistry` reference, first get a Helidon link:{metrics-javadoc-base-url}/RegistryFactory.html[`RegistryFactory`].
-Then invoke `getRegistry` on the `RegistryFactory` instance.
+--
+Obtain the `RegistryFactory` using either of the following techniques:
+
+** `@Inject RegistryFactory`.
++
+[source,java]
+.Getting the `RegistryFactory` using injection
+----
+class InjectExample {
+
+    @Inject
+    private RegistryFactory registryFactory;
+
+    private MetricRegistry findRegistry(String scope) {
+        return registryFactory.getRegistry(scope);
+    }
+}
+----
++
+** Invoke the static `getInstance()` method on the `RegistryFactory` class.
++
+[source,java]
+.Getting the `RegistryFactory` programmatically
+----
+class Example {
+
+    private MetricRegistry findRegistry(String scope) {
+        return RegistryFactory.getInstance().getRegistry(scope);
+    }
+}
+----
+--
 endif::[]
 
-The `MetricRegistry` allows your code to register new metrics, look up previously-registered metrics, and remove metrics.
+Once it has a reference to a `MetricRegistry` your code can use the reference to register new metrics, look up previously-registered metrics, and remove metrics.
 // end::metric-registry-api[]
 
 // tag::example-apps[]

microprofile/metrics/src/main/java/io/helidon/microprofile/metrics/MetricProducer.java

@@ -206,7 +206,7 @@ static MetricLocator create(InjectionPoint ip) {
             final Metric metricAnno = ip.getAnnotated().getAnnotation(Metric.class);
             final Tag[] tags = tags(metricAnno);
             final String scope = metricAnno == null ? MetricRegistry.APPLICATION_SCOPE : metricAnno.scope();
-            Registry registry = RegistryFactory.getInstance().getRegistry(scope);
+            Registry registry = RegistryFactory.getInstance().registry(scope);
             final MetricID metricID = new MetricID(getName(metricAnno, ip), tags);
             return new MetricLocator(metricAnno, registry, metricID);
         }

microprofile/metrics/src/main/java/io/helidon/microprofile/metrics/RegistryFactory.java

@@ -35,6 +35,7 @@
 import org.eclipse.microprofile.metrics.Gauge;
 import org.eclipse.microprofile.metrics.Histogram;
 import org.eclipse.microprofile.metrics.Metric;
+import org.eclipse.microprofile.metrics.MetricRegistry;
 import org.eclipse.microprofile.metrics.Timer;
 
 /**
@@ -52,7 +53,7 @@
  * method creates a new instance but does not record it internally.
  * </p>
  */
-class RegistryFactory {
+public class RegistryFactory {
 
     static final Collection<Class<? extends Metric>> METRIC_TYPES = Set.of(Counter.class,
                                                                            Gauge.class,
@@ -86,7 +87,7 @@ static RegistryFactory getInstance(MeterRegistry meterRegistry) {
      *
      * @return registry factory singleton
      */
-    static RegistryFactory getInstance() {
+    public static RegistryFactory getInstance() {
         RegistryFactory result = REGISTRY_FACTORY.get();
         if (result == null) {
             LOGGER.log(Level.WARNING, "Attempt to retrieve current " + RegistryFactory.class.getName()
@@ -115,7 +116,11 @@ static void closeAll() {
      * @param scope scope of registry
      * @return Registry for the scope requested
      */
-    Registry getRegistry(String scope) {
+    public MetricRegistry getRegistry(String scope) {
+        return registry(scope);
+    }
+
+    Registry registry(String scope) {
         return accessMetricsSettings(() -> registries.computeIfAbsent(scope, s ->
                 Registry.create(s, meterRegistry)));
     }
@@ -150,15 +155,15 @@ private void registerMetricForExistingMeter(Meter delegate) {
         if (scope == null) {
             LOGGER.log(Level.WARNING, "Attempt to register an existing meter with no scope: " + delegate);
         }
-        getRegistry(scope).onMeterAdded(delegate);
+        registry(scope).onMeterAdded(delegate);
     }
 
     private void removeMetricForMeter(Meter meter) {
         String scope = meter.scope().orElse(null);
         if (scope == null) {
             LOGGER.log(Level.WARNING, "Attempt to register an existing meter with no scope: " + meter);
         }
-        getRegistry(scope).onMeterRemoved(meter);
+        registry(scope).onMeterRemoved(meter);
     }
 
 }

microprofile/metrics/src/main/java/io/helidon/microprofile/metrics/RegistryProducer.java

@@ -71,6 +71,11 @@ public static org.eclipse.microprofile.metrics.MetricRegistry getVendorRegistry(
         return RegistryFactory.getInstance().getRegistry(MetricRegistry.VENDOR_SCOPE);
     }
 
+    @Produces
+    public static RegistryFactory getRegistryFactory() {
+        return RegistryFactory.getInstance();
+    }
+
     /**
      * Clears Application registry. This is required for the Metric TCKs as they
      * all run on the same VM and must not interfere with each other.

microprofile/metrics/src/test/java/io/helidon/microprofile/metrics/ProducerTest.java

@@ -25,6 +25,7 @@
 
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.not;
+import static org.hamcrest.Matchers.notNullValue;
 import static org.hamcrest.Matchers.sameInstance;
 import static org.hamcrest.MatcherAssert.assertThat;
 
@@ -46,6 +47,9 @@ public class ProducerTest extends MetricsBaseTest {
     @Inject
     private MetricRegistry appRegistry;
 
+    @Inject
+    private RegistryFactory registryFactory;
+
     private final MetricID counter1 = new MetricID("counter1");
     private final MetricID counter2 = new MetricID("counter2");
 
@@ -79,4 +83,10 @@ void testRegistryProducer() {
         assertThat("App registry counter", appCounter.getCount(), is(appCounterIncr));
         assertThat("Special registry counter", specialCounter.getCount(), is(specialCounterIncr));
     }
+
+    @Test
+    void testRegistryFactoryProducer() {
+        MetricRegistry customRegistry = registryFactory.getRegistry("myCustomScope");
+        assertThat("Custom scoped MetricRegistry", customRegistry, notNullValue());
+    }
 }