content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.metrics.sink;
  
  import com.codahale.metrics.MetricFilter;
  import com.codahale.metrics.MetricRegistry;
  import com.codahale.metrics.Slf4jReporter;
  
  import java.util.Properties;
  import java.util.concurrent.TimeUnit;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * A sink which outputs metric values to the metrics logger.
   */
  @ThreadSafe
  public class Slf4jSink implements Sink {
    private static final int SLF4J_DEFAULT_PERIOD = 10;
    private static final String SLF4J_DEFAULT_UNIT = "SECONDS";
    private static final String SLF4J_KEY_PERIOD = "period";
    private static final String SLF4J_KEY_UNIT = "unit";
    private static final String SLF4J_KEY_FILTER_CLASS = "filter-class";
  
    private final Slf4jReporter mReporter;
    private final Properties mProperties;
  
    /**
     * Creates a new {@link Slf4jSink} with a {@link Properties} and {@link MetricRegistry}.
     *
     * @param properties the properties
     * @param registry   the metric registry to register
     */
    public Slf4jSink(Properties properties, MetricRegistry registry) throws Exception {
      mProperties = properties;
      MetricFilter filter = getMetricFilter();
      mReporter = Slf4jReporter.forRegistry(registry).filter(filter).build();
    }
  
    @Override
    public void start() {
      mReporter.start(getPollPeriod(), getPollUnit());
    }
  
    @Override
    public void stop() {
      mReporter.stop();
    }
  
    @Override
    public void report() {
      mReporter.report();
    }
  
    /**
     * Gets the polling period.
     *
     * @return the polling period set by properties. If it is not set, a default value 10 is
     * returned.
     */
    private int getPollPeriod() {
      String period = mProperties.getProperty(SLF4J_KEY_PERIOD);
      return period != null ? Integer.parseInt(period) : SLF4J_DEFAULT_PERIOD;
    }
  
    /**
     * Gets the polling time unit.
     *
     * @return the polling time unit set by properties, If it is not set, a default value SECONDS is
     * returned.
     */
    private TimeUnit getPollUnit() {
      String unit = mProperties.getProperty(SLF4J_KEY_UNIT);
      if (unit == null) {
        unit = SLF4J_DEFAULT_UNIT;
      }
      return TimeUnit.valueOf(unit.toUpperCase());
    }
  
    /**
     * Gets the metrics filter.
     *
     * @return the metrics filter set by properties, If it is not set, it will return null
     * @throws Exception if any error happens
     */
    private MetricFilter getMetricFilter() throws Exception {
      String filterClass = mProperties.getProperty(SLF4J_KEY_FILTER_CLASS);
      if (filterClass == null) {
        return MetricFilter.ALL;
      }
  
      return (MetricFilter) Class.forName(filterClass)
          .getConstructor(Properties.class).newInstance(mProperties);
    }
  }
  