/**
* 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.monitor;
import com.google.common.base.Function;
import com.google.common.collect.ImmutableList;
import com.netflix.servo.tag.TaggingContext;
import com.netflix.servo.tag.TagList;
import java.util.List;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ConcurrentHashMap;
/**
* Base class used to simplify creation of contextual monitors.
*/
public abstract class AbstractContextualMonitor<T, M extends Monitor<T>>
implements CompositeMonitor<T> {
/** Base configuration shared across all contexts. */
protected final MonitorConfig baseConfig;
/** Context to query when accessing a monitor. */
protected final TaggingContext context;
/** Factory funtion used to create a new instance of a monitor. */
protected final Function<MonitorConfig, M> newMonitor;
/** Thread-safe map keeping track of the distinct monitors that have been created so far. */
protected final ConcurrentMap<MonitorConfig, M> monitors;
/**
* Create a new instance of the monitor.
*
* @param baseConfig shared configuration
* @param context provider for context specific tags
* @param newMonitor function to create new monitors
*/
protected AbstractContextualMonitor(
MonitorConfig baseConfig,
TaggingContext context,
Function<MonitorConfig, M> newMonitor) {
this.baseConfig = baseConfig;
this.context = context;
this.newMonitor = newMonitor;
monitors = new ConcurrentHashMap<MonitorConfig, M>();
}
/** {@inheritDoc} */
@Override
public T getValue() {
return getValue(0);
}
/**
* Returns a monitor instance for the current context. If no monitor exists for the current
* context then a new one will be created.
*/
protected M getMonitorForCurrentContext() {
MonitorConfig contextConfig = getConfig();
M monitor = monitors.get(contextConfig);
if (monitor == null) {
M newMon = newMonitor.apply(contextConfig);
monitor = monitors.putIfAbsent(contextConfig, newMon);
if (monitor == null) {
monitor = newMon;
}
}
return monitor;
}
/** {@inheritDoc} */
@Override
public MonitorConfig getConfig() {
TagList contextTags = context.getTags();
return MonitorConfig.builder(baseConfig.getName())
.withTags(baseConfig.getTags())
.withTags(contextTags)
.build();
}
/** {@inheritDoc} */
@Override
public List<Monitor<?>> getMonitors() {
return ImmutableList.<Monitor<?>>copyOf(monitors.values());
}
}