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/*
 * 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.flink.runtime.metrics;

import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.Kill;
import akka.pattern.Patterns;
import org.apache.flink.annotation.VisibleForTesting;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.configuration.ConfigConstants;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.metrics.Metric;
import org.apache.flink.metrics.MetricConfig;
import org.apache.flink.metrics.MetricGroup;
import org.apache.flink.metrics.View;
import org.apache.flink.metrics.reporter.MetricReporter;
import org.apache.flink.metrics.reporter.Scheduled;
import org.apache.flink.runtime.clusterframework.types.ResourceID;
import org.apache.flink.runtime.metrics.dump.MetricQueryService;
import org.apache.flink.runtime.metrics.groups.AbstractMetricGroup;
import org.apache.flink.runtime.metrics.groups.FrontMetricGroup;
import org.apache.flink.runtime.metrics.scope.ScopeFormats;
import org.apache.flink.util.Preconditions;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import scala.concurrent.Await;
import scala.concurrent.Future;
import scala.concurrent.duration.FiniteDuration;

import java.util.ArrayList;
import java.util.List;
import java.util.TimerTask;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * A MetricRegistry keeps track of all registered {@link Metric Metrics}. It serves as the
 * connection between {@link MetricGroup MetricGroups} and {@link MetricReporter MetricReporters}.
 */
public class MetricRegistry {
	static final Logger LOG = LoggerFactory.getLogger(MetricRegistry.class);

	private final Object lock = new Object();

	private List reporters;
	private ScheduledExecutorService executor;
	private ActorRef queryService;

	private ViewUpdater viewUpdater;

	private final ScopeFormats scopeFormats;
	private final char globalDelimiter;
	private final List delimiters = new ArrayList<>();

	/**
	 * Creates a new MetricRegistry and starts the configured reporter.
	 */
	public MetricRegistry(MetricRegistryConfiguration config) {
		this.scopeFormats = config.getScopeFormats();
		this.globalDelimiter = config.getDelimiter();

		// second, instantiate any custom configured reporters
		this.reporters = new ArrayList<>();

		List> reporterConfigurations = config.getReporterConfigurations();

		this.executor = Executors.newSingleThreadScheduledExecutor(new MetricRegistryThreadFactory());

		if (reporterConfigurations.isEmpty()) {
			// no reporters defined
			// by default, don't report anything
			LOG.info("No metrics reporter configured, no metrics will be exposed/reported.");
		} else {
			// we have some reporters so
			for (Tuple2 reporterConfiguration: reporterConfigurations) {
				String namedReporter = reporterConfiguration.f0;
				Configuration reporterConfig = reporterConfiguration.f1;

				final String className = reporterConfig.getString(ConfigConstants.METRICS_REPORTER_CLASS_SUFFIX, null);
				if (className == null) {
					LOG.error("No reporter class set for reporter " + namedReporter + ". Metrics might not be exposed/reported.");
					continue;
				}

				try {
					String configuredPeriod = reporterConfig.getString(ConfigConstants.METRICS_REPORTER_INTERVAL_SUFFIX, null);
					TimeUnit timeunit = TimeUnit.SECONDS;
					long period = 10;

					if (configuredPeriod != null) {
						try {
							String[] interval = configuredPeriod.split(" ");
							period = Long.parseLong(interval[0]);
							timeunit = TimeUnit.valueOf(interval[1]);
						}
						catch (Exception e) {
							LOG.error("Cannot parse report interval from config: " + configuredPeriod +
									" - please use values like '10 SECONDS' or '500 MILLISECONDS'. " +
									"Using default reporting interval.");
						}
					}

					Class reporterClass = Class.forName(className);
					MetricReporter reporterInstance = (MetricReporter) reporterClass.newInstance();

					MetricConfig metricConfig = new MetricConfig();
					reporterConfig.addAllToProperties(metricConfig);
					LOG.info("Configuring {} with {}.", reporterClass.getSimpleName(), metricConfig);
					reporterInstance.open(metricConfig);

					if (reporterInstance instanceof Scheduled) {
						LOG.info("Periodically reporting metrics in intervals of {} {} for reporter {} of type {}.", period, timeunit.name(), namedReporter, className);

						executor.scheduleWithFixedDelay(
								new MetricRegistry.ReporterTask((Scheduled) reporterInstance), period, period, timeunit);
					} else {
						LOG.info("Reporting metrics for reporter {} of type {}.", namedReporter, className);
					}
					reporters.add(reporterInstance);

					String delimiterForReporter = reporterConfig.getString(ConfigConstants.METRICS_REPORTER_SCOPE_DELIMITER, String.valueOf(globalDelimiter));
					if (delimiterForReporter.length() != 1) {
						LOG.warn("Failed to parse delimiter '{}' for reporter '{}', using global delimiter '{}'.", delimiterForReporter, namedReporter, globalDelimiter);
						delimiterForReporter = String.valueOf(globalDelimiter);
					}
					this.delimiters.add(delimiterForReporter.charAt(0));
				}
				catch (Throwable t) {
					LOG.error("Could not instantiate metrics reporter {}. Metrics might not be exposed/reported.", namedReporter, t);
				}
			}
		}
	}

	/**
	 * Initializes the MetricQueryService.
	 * 
	 * @param actorSystem ActorSystem to create the MetricQueryService on
	 * @param resourceID resource ID used to disambiguate the actor name
     */
	public void startQueryService(ActorSystem actorSystem, ResourceID resourceID) {
		synchronized (lock) {
			Preconditions.checkState(!isShutdown(), "The metric registry has already been shut down.");

			try {
				queryService = MetricQueryService.startMetricQueryService(actorSystem, resourceID);
			} catch (Exception e) {
				LOG.warn("Could not start MetricDumpActor. No metrics will be submitted to the WebInterface.", e);
			}
		}
	}

	/**
	 * Returns the global delimiter.
	 *
	 * @return global delimiter
	 */
	public char getDelimiter() {
		return this.globalDelimiter;
	}

	/**
	 * Returns the configured delimiter for the reporter with the given index.
	 *
	 * @param reporterIndex index of the reporter whose delimiter should be used
	 * @return configured reporter delimiter, or global delimiter if index is invalid
	 */
	public char getDelimiter(int reporterIndex) {
		try {
			return delimiters.get(reporterIndex);
		} catch (IndexOutOfBoundsException e) {
			LOG.warn("Delimiter for reporter index {} not found, returning global delimiter.", reporterIndex);
			return this.globalDelimiter;
		}
	}

	public List getReporters() {
		return reporters;
	}

	/**
	 * Returns whether this registry has been shutdown.
	 *
	 * @return true, if this registry was shutdown, otherwise false
	 */
	public boolean isShutdown() {
		synchronized (lock) {
			return reporters == null && executor.isShutdown();
		}
	}

	/**
	 * Shuts down this registry and the associated {@link MetricReporter}.
	 */
	public void shutdown() {
		synchronized (lock) {
			Future stopFuture = null;
			FiniteDuration stopTimeout = null;

			if (queryService != null) {
				stopTimeout = new FiniteDuration(1L, TimeUnit.SECONDS);
				stopFuture = Patterns.gracefulStop(queryService, stopTimeout);
			}

			if (reporters != null) {
				for (MetricReporter reporter : reporters) {
					try {
						reporter.close();
					} catch (Throwable t) {
						LOG.warn("Metrics reporter did not shut down cleanly", t);
					}
				}
				reporters = null;
			}
			shutdownExecutor();

			if (stopFuture != null) {
				boolean stopped = false;

				try {
					stopped = Await.result(stopFuture, stopTimeout);
				} catch (Exception e) {
					LOG.warn("Query actor did not properly stop.", e);
				}

				if (!stopped) {
					// the query actor did not stop in time, let's kill him
					queryService.tell(Kill.getInstance(), ActorRef.noSender());
				}
			}
		}
	}
	
	private void shutdownExecutor() {
		if (executor != null) {
			executor.shutdown();

			try {
				if (!executor.awaitTermination(1L, TimeUnit.SECONDS)) {
					executor.shutdownNow();
				}
			} catch (InterruptedException e) {
				executor.shutdownNow();
			}
		}
	}

	public ScopeFormats getScopeFormats() {
		return scopeFormats;
	}

	// ------------------------------------------------------------------------
	//  Metrics (de)registration
	// ------------------------------------------------------------------------

	/**
	 * Registers a new {@link Metric} with this registry.
	 *
	 * @param metric      the metric that was added
	 * @param metricName  the name of the metric
	 * @param group       the group that contains the metric
	 */
	public void register(Metric metric, String metricName, AbstractMetricGroup group) {
		synchronized (lock) {
			if (isShutdown()) {
				LOG.warn("Cannot register metric, because the MetricRegistry has already been shut down.");
			} else {
				try {
					if (reporters != null) {
						for (int i = 0; i < reporters.size(); i++) {
							MetricReporter reporter = reporters.get(i);
							if (reporter != null) {
								FrontMetricGroup front = new FrontMetricGroup>(i, group);
								reporter.notifyOfAddedMetric(metric, metricName, front);
							}
						}
					}
					if (queryService != null) {
						MetricQueryService.notifyOfAddedMetric(queryService, metric, metricName, group);
					}
					if (metric instanceof View) {
						if (viewUpdater == null) {
							viewUpdater = new ViewUpdater(executor);
						}
						viewUpdater.notifyOfAddedView((View) metric);
					}
				} catch (Exception e) {
					LOG.error("Error while registering metric.", e);
				}
			}
		}
	}

	/**
	 * Un-registers the given {@link Metric} with this registry.
	 *
	 * @param metric      the metric that should be removed
	 * @param metricName  the name of the metric
	 * @param group       the group that contains the metric
	 */
	public void unregister(Metric metric, String metricName, AbstractMetricGroup group) {
		synchronized (lock) {
			if (isShutdown()) {
				LOG.warn("Cannot unregister metric, because the MetricRegistry has already been shut down.");
			} else {
				try {
					if (reporters != null) {
						for (int i = 0; i < reporters.size(); i++) {
							MetricReporter reporter = reporters.get(i);
							if (reporter != null) {
								FrontMetricGroup front = new FrontMetricGroup>(i, group);
								reporter.notifyOfRemovedMetric(metric, metricName, front);
							}
						}
					}
					if (queryService != null) {
						MetricQueryService.notifyOfRemovedMetric(queryService, metric);
					}
					if (metric instanceof View) {
						if (viewUpdater != null) {
							viewUpdater.notifyOfRemovedView((View) metric);
						}
					}
				} catch (Exception e) {
					LOG.error("Error while registering metric.", e);
				}
			}
		}
	}

	// ------------------------------------------------------------------------

	@VisibleForTesting
	public ActorRef getQueryService() {
		return queryService;
	}

	// ------------------------------------------------------------------------

	/**
	 * This task is explicitly a static class, so that it does not hold any references to the enclosing
	 * MetricsRegistry instance.
	 *
	 * This is a subtle difference, but very important: With this static class, the enclosing class instance
	 * may become garbage-collectible, whereas with an anonymous inner class, the timer thread
	 * (which is a GC root) will hold a reference via the timer task and its enclosing instance pointer.
	 * Making the MetricsRegistry garbage collectible makes the java.util.Timer garbage collectible,
	 * which acts as a fail-safe to stop the timer thread and prevents resource leaks.
	 */
	private static final class ReporterTask extends TimerTask {

		private final Scheduled reporter;

		private ReporterTask(Scheduled reporter) {
			this.reporter = reporter;
		}

		@Override
		public void run() {
			try {
				reporter.report();
			} catch (Throwable t) {
				LOG.warn("Error while reporting metrics", t);
			}
		}
	}

	private static final class MetricRegistryThreadFactory implements ThreadFactory {
		private final ThreadGroup group;
		private final AtomicInteger threadNumber = new AtomicInteger(1);

		MetricRegistryThreadFactory() {
			SecurityManager s = System.getSecurityManager();
			group = (s != null) ? s.getThreadGroup() : Thread.currentThread().getThreadGroup();
		}

		public Thread newThread(Runnable r) {
			Thread t = new Thread(group, r, "Flink-MetricRegistry-" + threadNumber.getAndIncrement(), 0);
			if (t.isDaemon()) {
				t.setDaemon(false);
			}
			if (t.getPriority() != Thread.NORM_PRIORITY) {
				t.setPriority(Thread.NORM_PRIORITY);
			}
			return t;
		}
	}
}




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