com.opentable.metrics.ready.ReadyCheckRegistry Maven / Gradle / Ivy

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Manages metrics and healthchecks and sends them to Graphite and exposes them via endpoints
There is a newer version: 6.0.1
/*
 * Licensed 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 com.opentable.metrics.ready;

import java.time.Duration;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledThreadPoolExecutor;

import javax.annotation.PreDestroy;

import com.google.common.util.concurrent.ThreadFactoryBuilder;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.opentable.concurrent.OTExecutors;

/**
 * A registry for ready checks.
 */
public class ReadyCheckRegistry {
    private static final Logger LOGGER = LoggerFactory.getLogger(ReadyCheckRegistry.class);
    private static final int ASYNC_EXECUTOR_POOL_SIZE = 2;

    private final ConcurrentMap readyChecks;
    private final List listeners;
    private final ScheduledExecutorService asyncExecutorService;
    private final Object lock = new Object();

    /**
     * Creates a new {@link ReadyCheckRegistry}.
     */
    public ReadyCheckRegistry() {
        this(ASYNC_EXECUTOR_POOL_SIZE);
    }

    /**
     * Creates a new {@link ReadyCheckRegistry}.
     *
     * @param asyncExecutorPoolSize core pool size for async ready check executions
     */
    public ReadyCheckRegistry(int asyncExecutorPoolSize) {
        this(createExecutorService(asyncExecutorPoolSize));
    }

    /**
     * Creates a new {@link ReadyCheckRegistry}.
     *
     * @param asyncExecutorService executor service for async ready check executions
     */
    public ReadyCheckRegistry(ScheduledExecutorService asyncExecutorService) {
        this.readyChecks = new ConcurrentHashMap<>();
        this.listeners = new CopyOnWriteArrayList<>();
        this.asyncExecutorService = asyncExecutorService;
    }

    /**
     * Adds a {@link ReadyCheckRegistryListener} to a collection of listeners that will be notified on ready check
     * registration. Listeners will be notified in the order in which they are added. The listener will be notified of all
     * existing ready checks when it first registers.
     *
     * @param listener listener to add
     */
    public void addListener(ReadyCheckRegistryListener listener) {
        listeners.add(listener);
        for (Map.Entry entry : readyChecks.entrySet()) {
            listener.onReadyCheckAdded(entry.getKey(), entry.getValue());
        }
    }

    /**
     * Removes a {@link ReadyCheckRegistryListener} from this registry's collection of listeners.
     *
     * @param listener listener to remove
     */
    public void removeListener(ReadyCheckRegistryListener listener) {
        listeners.remove(listener);
    }

    /**
     * Registers an application {@link ReadyCheck}.
     *
     * @param name       the name of the ready check
     * @param readyCheck the {@link ReadyCheck} instance
     */
    public void register(String name, ReadyCheck readyCheck) {
        ReadyCheck registered = null;
        synchronized (lock) {
            if (!readyChecks.containsKey(name)) {
                registered = readyCheck;
                readyChecks.put(name, registered);
            }
        }
        if (registered != null) {
            onReadyCheckAdded(name, registered);
        }
    }

    /**
     * Unregisters the application {@link ReadyCheck} with the given name.
     *
     * @param name the name of the {@link ReadyCheck} instance
     */
    public void unregister(String name) {
        ReadyCheck readyCheck;
        synchronized (lock) {
            readyCheck = readyChecks.remove(name);
        }
        if (readyCheck != null) {
            onReadyCheckRemoved(name, readyCheck);
        }
    }

    /**
     * Returns a set of the names of all registered ready checks.
     *
     * @return the names of all registered ready checks
     */
    public SortedSet getNames() {
        return Collections.unmodifiableSortedSet(new TreeSet<>(readyChecks.keySet()));
    }

    /**
     * Returns the {@link ReadyCheck} instance with a given name
     *
     * @param name the name of the {@link ReadyCheck} instance
     */
    public ReadyCheck getReadyCheck(String name) {
        return readyChecks.get(name);
    }

    /**
     * Runs the ready check with the given name.
     *
     * @param name the ready check's name
     * @return the result of the ready check
     * @throws NoSuchElementException if there is no ready check with the given name
     */
    public Result runReadyCheck(String name) throws NoSuchElementException {
        final ReadyCheck readyCheck = readyChecks.get(name);
        if (readyCheck == null) {
            throw new NoSuchElementException("No ready check named " + name + " exists");
        }
        return readyCheck.execute();
    }

    /**
     * Runs the registered ready checks matching the filter and returns a map of the results.
     *
     * @return a map of the ready check results
     */
    public SortedMap runReadyChecks() {
        final SortedMap results = new TreeMap<>();
        for (Map.Entry entry : readyChecks.entrySet()) {
            final Result result = entry.getValue().execute();
            results.put(entry.getKey(), result);
        }
        return Collections.unmodifiableSortedMap(results);
    }


    /**
     * Runs the registered ready checks matching the filter in parallel and returns a map of the results.
     *
     * @param executor object to launch and track ready checks progress
     * @return a map of the ready check results
     */
    public SortedMap runReadyChecks(ExecutorService executor) {
        final Map> futures = new HashMap<>();
        for (final Map.Entry entry : readyChecks.entrySet()) {
            final String name = entry.getKey();
            final ReadyCheck readyCheck = entry.getValue();
            futures.put(name, executor.submit(readyCheck::execute));
        }

        final SortedMap results = new TreeMap<>();
        for (Map.Entry> entry : futures.entrySet()) {
            try {
                results.put(entry.getKey(), entry.getValue().get());
            } catch (Exception e) {
                LOGGER.warn("Error executing ready check {}", entry.getKey(), e);
                results.put(entry.getKey(), Result.unready(e));
            }
        }

        return Collections.unmodifiableSortedMap(results);
    }

    private void onReadyCheckAdded(String name, ReadyCheck readyCheck) {
        for (ReadyCheckRegistryListener listener : listeners) {
            listener.onReadyCheckAdded(name, readyCheck);
        }
    }

    private void onReadyCheckRemoved(String name, ReadyCheck readyCheck) {
        for (ReadyCheckRegistryListener listener : listeners) {
            listener.onReadyCheckRemoved(name, readyCheck);
        }
    }

    /**
     * Shuts down the scheduled executor for async ready checks
     */
    @PreDestroy
    public void shutdown() {
        try {
            OTExecutors.shutdownAndAwaitTermination(asyncExecutorService, Duration.ofSeconds(1));
        } catch (InterruptedException ie) {
            Thread.currentThread().interrupt();
        }
    }

    private static ScheduledExecutorService createExecutorService(int corePoolSize) {
        final ScheduledThreadPoolExecutor asyncExecutorService = new ScheduledThreadPoolExecutor(corePoolSize,
                new ThreadFactoryBuilder().setDaemon(true).setNameFormat("readycheck-async-executor-%d").build());
        asyncExecutorService.setRemoveOnCancelPolicy(true);
        return asyncExecutorService;
    }
}