Add ability to inject extra dimensions for service emitter (#4982)

* Add ability to inject extra dimensions for service emitter

* Docs

server/src/main/java/io/druid/server/emitter/EmitterModule.java

@@ -31,6 +31,7 @@ import com.google.inject.Module;
 import com.google.inject.Provider;
 import com.google.inject.Provides;
 import com.google.inject.TypeLiteral;
+import com.google.inject.multibindings.MapBinder;
 import com.google.inject.name.Named;
 import com.google.inject.name.Names;
 import com.metamx.emitter.EmittingLogger;
@@ -45,6 +46,7 @@ import io.druid.server.DruidNode;
 
 import java.lang.annotation.Annotation;
 import java.util.List;
+import java.util.Map;
 import java.util.Properties;
 
 /**
@@ -76,24 +78,35 @@ public class EmitterModule implements Module
     binder.install(new ComposingEmitterModule());
 
     binder.bind(Emitter.class).toProvider(new EmitterProvider(emitterType)).in(LazySingleton.class);
+
+    MapBinder<String, String> extraServiceDimensions = MapBinder.newMapBinder(
+        binder,
+        String.class,
+        String.class,
+        ExtraServiceDimensions.class
+    );
+    String version = getClass().getPackage().getImplementationVersion();
+    extraServiceDimensions
+        .addBinding("version")
+        .toInstance(Strings.nullToEmpty(version)); // Version is null during `mvn test`.
   }
 
   @Provides
   @ManageLifecycle
-  public ServiceEmitter getServiceEmitter(@Self Supplier<DruidNode> configSupplier, Emitter emitter)
+  public ServiceEmitter getServiceEmitter(
+      @Self Supplier<DruidNode> configSupplier,
+      Emitter emitter,
+      @ExtraServiceDimensions Map<String, String> extraServiceDimensions
+  )
   {
     final DruidNode config = configSupplier.get();
-    String version = getClass().getPackage().getImplementationVersion();
-    final ImmutableMap<String, String> otherServiceDimensions = ImmutableMap.of(
-        "version",
-        Strings.nullToEmpty(version) // Version is null during `mvn test`.
-    );
     log.info("Underlying emitter for ServiceEmitter: %s", emitter);
+    log.info("Extra service dimensions: %s", extraServiceDimensions);
     final ServiceEmitter retVal = new ServiceEmitter(
         config.getServiceName(),
         config.getHostAndPortToUse(),
         emitter,
-        otherServiceDimensions
+        ImmutableMap.copyOf(extraServiceDimensions)
     );
     EmittingLogger.registerEmitter(retVal);
     return retVal;

server/src/main/java/io/druid/server/emitter/ExtraServiceDimensions.java

@@ -0,0 +1,45 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.server.emitter;
+
+import com.google.inject.BindingAnnotation;
+import io.druid.guice.annotations.PublicApi;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation to inject extra dimensions, added to all events, emitted via {@link EmitterModule#getServiceEmitter}.
+ *
+ * For example, write this in a body of {@link com.google.inject.Module#configure} of your extension module):
+ *
+ * MapBinder<String, String> extraDims =
+ *     MapBinder.newMapBinder(binder, String.class, String.class, ExtraServiceDimensions.class);
+ * extraDims.addBinding("foo").toInstance("bar");
+ */
+@Target(ElementType.PARAMETER)
+@Retention(RetentionPolicy.RUNTIME)
+@BindingAnnotation
+@PublicApi
+public @interface ExtraServiceDimensions
+{
+}