/**
* Copyright 2013 Netflix, Inc.
*
* 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.netflix.servo.publish;
import com.google.common.collect.Lists;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import com.google.common.util.concurrent.TimeLimiter;
import com.google.common.util.concurrent.SimpleTimeLimiter;
import com.google.common.util.concurrent.UncheckedTimeoutException;
import com.netflix.servo.DefaultMonitorRegistry;
import com.netflix.servo.Metric;
import com.netflix.servo.MonitorRegistry;
import com.netflix.servo.monitor.CompositeMonitor;
import com.netflix.servo.monitor.Monitor;
import com.netflix.servo.util.Clock;
import com.netflix.servo.util.ClockWithOffset;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
/**
* Poller for fetching {@link com.netflix.servo.annotations.Monitor} metrics
* from a monitor registry.
*/
public final class MonitorRegistryMetricPoller implements MetricPoller {
private static final Logger LOGGER = LoggerFactory.getLogger(MonitorRegistryMetricPoller.class);
private final MonitorRegistry registry;
private final long cacheTTL;
private final AtomicReference<List<Monitor<?>>> cachedMonitors =
new AtomicReference<List<Monitor<?>>>();
private final AtomicLong cacheLastUpdateTime = new AtomicLong(0L);
// Put limit on fetching the monitor value in-case someone does something silly like call a
// remote service inline
private final TimeLimiter limiter;
private final ExecutorService service;
private final Clock clock;
/**
* Creates a new instance using {@link com.netflix.servo.DefaultMonitorRegistry}.
*/
public MonitorRegistryMetricPoller() {
this(DefaultMonitorRegistry.getInstance(), 0L, TimeUnit.MILLISECONDS, true);
}
/**
* Creates a new instance using the specified registry.
*
* @param registry registry to query for annotated objects
*/
public MonitorRegistryMetricPoller(MonitorRegistry registry) {
this(registry, 0L, TimeUnit.MILLISECONDS, true, ClockWithOffset.INSTANCE);
}
/**
* Creates a new instance using the specified registry and a time limiter.
*
* @param registry registry to query for annotated objects
* @param cacheTTL how long to cache the filtered monitor list from the registry
* @param unit time unit for the cache ttl
*/
public MonitorRegistryMetricPoller(MonitorRegistry registry, long cacheTTL, TimeUnit unit) {
this(registry, cacheTTL, unit, true);
}
/**
* Creates a new instance using the specified registry.
*
* @param registry registry to query for annotated objects
* @param cacheTTL how long to cache the filtered monitor list from the registry
* @param unit time unit for the cache ttl
* @param useLimiter whether to use a time limiter for getting the values from the monitors
*/
public MonitorRegistryMetricPoller(MonitorRegistry registry, long cacheTTL, TimeUnit unit,
boolean useLimiter) {
this(registry, cacheTTL, unit, useLimiter, ClockWithOffset.INSTANCE);
}
/**
* Creates a new instance using the specified registry.
*
* @param registry registry to query for annotated objects
* @param cacheTTL how long to cache the filtered monitor list from the registry
* @param unit time unit for the cache ttl
* @param useLimiter whether to use a time limiter for getting the values from the monitors
* @param clock clock instance to use to get the time
*/
public MonitorRegistryMetricPoller(
MonitorRegistry registry, long cacheTTL, TimeUnit unit, boolean useLimiter,
Clock clock) {
this.registry = registry;
this.cacheTTL = TimeUnit.MILLISECONDS.convert(cacheTTL, unit);
this.clock = clock;
if (useLimiter) {
final ThreadFactory factory = new ThreadFactoryBuilder()
.setDaemon(true)
.setNameFormat("ServoMonitorGetValueLimiter-%d")
.build();
service = Executors.newSingleThreadExecutor(factory);
limiter = new SimpleTimeLimiter(service);
} else {
service = null;
limiter = null;
}
}
private Object getValue(Monitor<?> monitor, boolean reset) {
try {
if (limiter != null) {
final MonitorValueCallable c = new MonitorValueCallable(monitor);
return limiter.callWithTimeout(c, 1, TimeUnit.SECONDS, true);
} else {
return monitor.getValue();
}
} catch (UncheckedTimeoutException e) {
LOGGER.warn("timeout trying to get value for {}", monitor.getConfig());
} catch (Exception e) {
LOGGER.warn("failed to get value for " + monitor.getConfig(), e);
}
return null;
}
private void getMonitors(List<Monitor<?>> monitors, MetricFilter filter, Monitor<?> monitor) {
if (monitor instanceof CompositeMonitor<?>) {
for (Monitor<?> m : ((CompositeMonitor<?>) monitor).getMonitors()) {
getMonitors(monitors, filter, m);
}
} else if (filter.matches(monitor.getConfig())) {
monitors.add(monitor);
}
}
private void refreshMonitorCache(MetricFilter filter) {
final long age = System.currentTimeMillis() - cacheLastUpdateTime.get();
if (age > cacheTTL) {
List<Monitor<?>> monitors = Lists.newArrayList();
for (Monitor<?> monitor : registry.getRegisteredMonitors()) {
try {
getMonitors(monitors, filter, monitor);
} catch (Exception e) {
LOGGER.warn("failed to get monitors for composite " + monitor.getConfig(), e);
}
}
cacheLastUpdateTime.set(clock.now());
cachedMonitors.set(monitors);
LOGGER.debug("cache refreshed, {} monitors matched filter, previous age {} seconds",
monitors.size(), age / 1000);
} else {
LOGGER.debug("cache age of {} seconds is within ttl of {} seconds",
age / 1000, cacheTTL / 1000);
}
}
/**
* {@inheritDoc}
*/
public List<Metric> poll(MetricFilter filter) {
return poll(filter, false);
}
/**
* {@inheritDoc}
*/
public List<Metric> poll(MetricFilter filter, boolean reset) {
refreshMonitorCache(filter);
List<Monitor<?>> monitors = cachedMonitors.get();
List<Metric> metrics = Lists.newArrayListWithCapacity(monitors.size());
for (Monitor<?> monitor : monitors) {
Object v = getValue(monitor, reset);
if (v != null) {
metrics.add(new Metric(monitor.getConfig(), clock.now(), v));
}
}
return metrics;
}
/**
* Shutsdown the thread executor used for time limiting the get value calls. It is a good idea
* to call this and explicitly cleanup the thread. In most cases the threads will be cleaned
* up when the executor is garbage collected if shutdown is not called explicitly.
*/
public void shutdown() {
if (service != null) {
service.shutdownNow();
}
}
private static class MonitorValueCallable implements Callable<Object> {
private final Monitor<?> monitor;
public MonitorValueCallable(Monitor<?> monitor) {
this.monitor = monitor;
}
public Object call() throws Exception {
return monitor.getValue();
}
}
}