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Dynatrace OpenKit - Java Reference Implementation
/**
* Copyright 2018-2019 Dynatrace LLC
*
* 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.dynatrace.openkit.core.caching;
import com.dynatrace.openkit.api.Logger;
import com.dynatrace.openkit.core.configuration.BeaconCacheConfiguration;
import java.util.*;
/**
* Space based eviction strategy for the beacon cache.
*
*
* This strategy checks if the number of cached bytes is greater than {@link BeaconCacheConfiguration#getCacheSizeLowerBound()}
* and in this case runs the strategy.
*
*/
class SpaceEvictionStrategy implements BeaconCacheEvictionStrategy {
private final Logger logger;
private final BeaconCache beaconCache;
private final BeaconCacheConfiguration configuration;
private boolean infoShown = false;
/**
* Constructor.
*
* @param logger Instance implementing the {@link Logger} interface for writing some useful debug messages.
* @param beaconCache The beacon cache to evict if necessary.
* @param configuration The configuration providing the boundary settings for this strategy.
*/
SpaceEvictionStrategy(Logger logger, BeaconCache beaconCache, BeaconCacheConfiguration configuration) {
this.logger = logger;
this.beaconCache = beaconCache;
this.configuration = configuration;
}
@Override
public void execute() {
if (isStrategyDisabled()) {
// immediately return if this strategy is disabled
if (!infoShown && logger.isInfoEnabled()) {
logger.info(getClass().getSimpleName() + " execute() - strategy is disabled");
// suppress any further log output
infoShown = true;
}
return;
}
if (shouldRun()) {
doExecute();
}
}
/**
* Checks if the strategy is disabled.
*
*
* The strategy might be disabled on purpose, if upper and lower boundary are less than or equal to 0
* or accidentally, when either lower or upper boundary is less than or equal to zero or upper boundary is less
* than lower boundary.
*
*
* @return {@code true} if strategy is disabled, {@code false} otherwise.
*/
boolean isStrategyDisabled() {
return configuration.getCacheSizeLowerBound() <= 0
|| configuration.getCacheSizeUpperBound() <= 0
|| configuration.getCacheSizeUpperBound() < configuration.getCacheSizeLowerBound();
}
/**
* Checks if the strategy should run.
*
*
* The strategy should run, if the currently stored number of bytes in the Beacon cache exceeds the configured
* upper limit.
*
*
* @return {@code true} if the strategy should run, {@code false} otherwise.
*/
boolean shouldRun() {
return beaconCache.getNumBytesInCache() > configuration.getCacheSizeUpperBound();
}
/**
* Performs execution of strategy.
*/
private void doExecute() {
Map removedRecordsPerBeacon = new HashMap();
while (!Thread.currentThread().isInterrupted()
&& beaconCache.getNumBytesInCache() > configuration.getCacheSizeLowerBound()) {
Set beaconIDs = beaconCache.getBeaconIDs();
Iterator iterator = beaconIDs.iterator();
while (!Thread.currentThread().isInterrupted()
&& iterator.hasNext()
&& beaconCache.getNumBytesInCache() > configuration.getCacheSizeLowerBound()) {
Integer beaconID = iterator.next();
// remove 1 record from Beacon cache for given beaconID
// the result is the number of records removed, which might be in range [0, numRecords=1]
int numRecordsRemoved = beaconCache.evictRecordsByNumber(beaconID, 1);
if (logger.isDebugEnabled()) {
if (!removedRecordsPerBeacon.containsKey(beaconID)) {
removedRecordsPerBeacon.put(beaconID, numRecordsRemoved);
} else {
removedRecordsPerBeacon.put(beaconID, removedRecordsPerBeacon.get(beaconID) + numRecordsRemoved);
}
}
}
}
if (logger.isDebugEnabled()) {
for (Map.Entry entries : removedRecordsPerBeacon.entrySet()) {
logger.debug(getClass().getSimpleName() + " doExecute() - Removed " + entries.getValue() + " records from Beacon with ID " + entries.getKey());
}
}
}
}
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