Github user aledsage commented on a diff in the pull request:
https://github.com/apache/incubator-brooklyn/pull/919#discussion_r41167202
--- Diff:
core/src/main/java/org/apache/brooklyn/enricher/stock/reducer/Reducer.java ---
@@ -0,0 +1,187 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF 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 org.apache.brooklyn.enricher.stock.reducer;
+
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.brooklyn.api.entity.Entity;
+import org.apache.brooklyn.api.entity.EntityLocal;
+import org.apache.brooklyn.api.sensor.AttributeSensor;
+import org.apache.brooklyn.api.sensor.Sensor;
+import org.apache.brooklyn.api.sensor.SensorEvent;
+import org.apache.brooklyn.api.sensor.SensorEventListener;
+import org.apache.brooklyn.config.ConfigKey;
+import org.apache.brooklyn.core.config.ConfigKeys;
+import org.apache.brooklyn.core.enricher.AbstractEnricher;
+import org.apache.brooklyn.util.core.flags.SetFromFlag;
+import org.apache.brooklyn.util.core.sensor.SensorPredicates;
+import org.apache.brooklyn.util.core.task.Tasks;
+import org.apache.brooklyn.util.core.task.ValueResolver;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.api.client.util.Lists;
+import com.google.common.base.Function;
+import com.google.common.base.Optional;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
+import com.google.common.reflect.TypeToken;
+
+@SuppressWarnings("serial")
+public abstract class Reducer<S, T> extends AbstractEnricher implements
SensorEventListener<Object> {
+
+ private static final Logger LOG =
LoggerFactory.getLogger(Reducer.class);
+
+ @SetFromFlag("producer")
+ public static ConfigKey<Entity> PRODUCER =
ConfigKeys.newConfigKey(Entity.class, "enricher.producer");
+ public static ConfigKey<Sensor<?>> TARGET_SENSOR =
ConfigKeys.newConfigKey(new TypeToken<Sensor<?>>() {}, "enricher.targetSensor");
+ public static ConfigKey<List<? extends AttributeSensor<?>>>
SOURCE_SENSORS = ConfigKeys.newConfigKey(new TypeToken<List<? extends
AttributeSensor<?>>>() {}, "enricher.sourceSensors");
+ public static ConfigKey<Function<List<?>,?>> REDUCER_FUNCTION =
ConfigKeys.newConfigKey(new TypeToken<Function<List<?>, ?>>() {},
"enricher.reducerFunction");
+ @SetFromFlag("transformation")
+ public static final ConfigKey<String> REDUCER_FUNCTION_TRANSFORMATION
= ConfigKeys.newStringConfigKey("enricher.reducerFunction.transformation",
+ "A string matching a pre-defined named reducer function, such as
joiner");
+ public static final ConfigKey<Map<String, Object>> PARAMETERS =
ConfigKeys.newConfigKey(new TypeToken<Map<String, Object>>() {},
"enricher.reducerFunction.parameters",
+ "A map of parameters to pass into the reducer function");
+
+ protected Entity producer;
+ protected List<AttributeSensor<S>> subscribedSensors;
+ protected Sensor<T> targetSensor;
+ protected Function<List<S>, T> reducerFunction;
+
+ @SuppressWarnings({ "unchecked", "rawtypes" })
+ @Override
+ public void setEntity(EntityLocal entity) {
+ super.setEntity(entity);
+ Preconditions.checkNotNull(getConfig(SOURCE_SENSORS), "source
sensors");
+
+ this.producer = getConfig(PRODUCER) == null ? entity :
getConfig(PRODUCER);
+ List<AttributeSensor<S>> sensorListTemp = Lists.newArrayList();
+
+ for (Object sensorO : getConfig(SOURCE_SENSORS)) {
+ AttributeSensor<S> sensor =
Tasks.resolving(sensorO).as(AttributeSensor.class).timeout(ValueResolver.REAL_QUICK_WAIT).context(producer).get();
+ Optional<? extends Sensor<?>> foundSensor =
Iterables.tryFind(sensorListTemp,
+ SensorPredicates.sensorNameEqualTo(sensor.getName()));
+
+ if(!foundSensor.isPresent()) {
+ sensorListTemp.add(sensor);
+ }
+ }
+
+ String reducerName = config().get(REDUCER_FUNCTION_TRANSFORMATION);
+ Function<List<S>, T> reducerFunction = (Function)
config().get(REDUCER_FUNCTION);
+ if(reducerFunction == null){
+ Map<String, ?> parameters = config().get(PARAMETERS);
+ reducerFunction = createReducerFunction(reducerName,
parameters);
+ }
+
+ this.reducerFunction = reducerFunction;
+ Preconditions.checkState(sensorListTemp.size() > 0, "Nothing to
reduce");
+
+ for (Sensor<S> sensor : sensorListTemp) {
+ subscribe(producer, sensor, this);
+ }
+
+ subscribedSensors = ImmutableList.copyOf(sensorListTemp);
+ }
+
+ protected abstract Function<List<S>, T> createReducerFunction(String
reducerName, Map<String, ?> parameters);
+
+ @SuppressWarnings("unchecked")
+ @Override
+ public void onEvent(SensorEvent<Object> event) {
+ Sensor<T> destinationSensor = (Sensor<T>) getConfig(TARGET_SENSOR);
+
+ List<S> values = Lists.newArrayList();
+
+ for (AttributeSensor<S> sourceSensor : subscribedSensors) {
+ S resolvedSensorValue = entity.sensors().get(sourceSensor);
+ if (resolvedSensorValue == null) {
+ // only apply function if all values are resolved
+ return;
+ }
+
+ values.add(resolvedSensorValue);
+ }
+
+ Object result = reducerFunction.apply(values);
+
+ if (LOG.isTraceEnabled()) LOG.trace("enricher {} got {},
propagating via {} as {}",
+ new Object[] {this, event, entity, reducerFunction,
destinationSensor});
+
+ emit((Sensor<T>)destinationSensor, result);
+ }
+
+ public static class JoinerReducerFunction<A> implements
Function<List<A>, String> {
+
+ private Object separator;
+
+ public JoinerReducerFunction(Object separator) {
+ this.separator = (separator == null) ? ", " : separator;
+ }
+
+ @Override
+ public String apply(List<A> input) {
+
+ StringBuilder sb = new StringBuilder();
+ Iterator<A> it = input.iterator();
+ while(it.hasNext()) {
+ sb.append(it.next().toString());
+ if(it.hasNext()){
+ sb.append(separator);
+ }
+ }
+ return sb.toString();
+ }
+
+ }
+
+ public static class JoinerFunction extends
JoinerReducerFunction<String>{
+
+ public JoinerFunction(Object separator) {
+ super(separator);
+ }
+ }
+
+ public static class ToStringReducerFunction<A> implements
Function<List<A>, String> {
--- End diff --
See guava's `Functions#toStringFunction()` (which we delegate to in
Brooklyn's `StringFunctions.toStringFunction`).
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