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// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.metrics.simple;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
/**
* The persistence layer for metrics. Both CPU and memory hungry, but
* it runs in its own little world.
*
* @author <a href="mailto:steinar@yahoo-inc.com">Steinar Knutsen</a>
*/
class DimensionCache {
private final Map<String, LinkedHashMap<Point, UntypedMetric>> persistentData = new HashMap<>();
private final int pointsToKeep;
public DimensionCache(int pointsToKeep) {
this.pointsToKeep = pointsToKeep;
}
void updateDimensionPersistence(Bucket toDelete, Bucket toPresent) {
updatePersistentData(toDelete);
padPresentation(toPresent);
}
private void padPresentation(Bucket toPresent) {
Map<String, List<Entry<Point, UntypedMetric>>> currentMetricNames = toPresent.getValuesByMetricName();
for (Map.Entry<String, List<Entry<Point, UntypedMetric>>> metric : currentMetricNames.entrySet()) {
final int currentDataPoints = metric.getValue().size();
if (currentDataPoints < pointsToKeep) {
padMetric(metric.getKey(), toPresent, currentDataPoints);
}
}
Set<String> keysMissingFromPresentation = new HashSet<>(persistentData.keySet());
keysMissingFromPresentation.removeAll(currentMetricNames.keySet());
for (String cachedMetric : keysMissingFromPresentation) {
padMetric(cachedMetric, toPresent, 0);
}
}
private void updatePersistentData(Bucket toDelete) {
if (toDelete == null) {
return;
}
for (Map.Entry<String, List<Entry<Point, UntypedMetric>>> metric : toDelete.getValuesByMetricName().entrySet()) {
LinkedHashMap<Point, UntypedMetric> cachedPoints = getCachedMetric(metric.getKey());
for (Entry<Point, UntypedMetric> newestInterval : metric.getValue()) {
// overwriting an existing entry does not update the order
// in the map
cachedPoints.remove(newestInterval.getKey());
cachedPoints.put(newestInterval.getKey(), newestInterval.getValue());
}
}
}
private void padMetric(String metric,
Bucket toPresent,
int currentDataPoints) {
final LinkedHashMap<Point, UntypedMetric> cachedPoints = getCachedMetric(metric);
int toAdd = pointsToKeep - currentDataPoints;
@SuppressWarnings({"unchecked","rawtypes"})
Entry<Point, UntypedMetric>[] cachedEntries = cachedPoints.entrySet().toArray(new Entry[0]);
for (int i = cachedEntries.length - 1; i >= 0 && toAdd > 0; --i) {
Entry<Point, UntypedMetric> leastOld = cachedEntries[i];
final Identifier id = new Identifier(metric, leastOld.getKey());
if (!toPresent.hasIdentifier(id)) {
toPresent.put(id, leastOld.getValue().pruneData());
--toAdd;
}
}
}
@SuppressWarnings("serial")
private LinkedHashMap<Point, UntypedMetric> getCachedMetric(String metricName) {
LinkedHashMap<Point, UntypedMetric> points = persistentData.get(metricName);
if (points == null) {
points = new LinkedHashMap<Point, UntypedMetric>(16, 0.75f, false) {
protected boolean removeEldestEntry(Map.Entry<Point, UntypedMetric> eldest) {
return size() > pointsToKeep;
}
};
persistentData.put(metricName, points);
}
return points;
}
}
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