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Dynatrace OpenKit - Java Reference Implementation
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/**
* Copyright 2018-2021 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 java.util.Collections;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* Represents an entry in the {@link BeaconCacheImpl}.
*
*
* The caller is responsible to lock this element, before the first method is invoked using
* {@link #lock()} and after the last operation is invoked {@link #unlock()} must be called.
*
*/
class BeaconCacheEntry {
/**
* List storing all active event data.
*/
private LinkedList eventData = new LinkedList<>();
/**
* List storing all active session data.
*/
private LinkedList actionData = new LinkedList<>();
/**
* Lock object for locking access to session & event data.
*/
private final Lock lock = new ReentrantLock();
/**
* List storing all event data being sent.
*/
private LinkedList eventDataBeingSent;
/**
* List storing all action data being sent.
*/
private LinkedList actionDataBeingSent;
/**
* Total number of bytes consumed by this entry.
*/
private long totalNumBytes = 0;
/**
* Lock this {@link BeaconCacheEntry} for reading & writing.
*
*
* When locking is no longer required, {@link #unlock()} must be called.
*
*/
void lock() {
lock.lock();
}
/**
* Release this {@link BeaconCacheEntry} lock, so that other threads can access this object.
*
*
* When calling this method ensure {@link #lock()} was called before.
*
*/
void unlock() {
lock.unlock();
}
/**
* Add new event data record to cache.
*
* @param record The new record to add.
*/
void addEventData(BeaconCacheRecord record) {
eventData.add(record);
totalNumBytes += record.getDataSizeInBytes();
}
/**
* Add new action data record to the cache.
*
* @param record The new record to add.
*/
void addActionData(BeaconCacheRecord record) {
actionData.add(record);
totalNumBytes += record.getDataSizeInBytes();
}
/**
* Test if data shall be copied, before creating chunks for sending.
*
* @return {@code true} if data must be copied, {@code false} otherwise.
*/
boolean needsDataCopyBeforeSending() {
return !hasDataToSend();
}
/**
* Copy data for sending.
*/
void copyDataForSending() {
actionDataBeingSent = actionData;
eventDataBeingSent = eventData;
actionData = new LinkedList<>();
eventData = new LinkedList<>();
totalNumBytes = 0; // data which is being sent is not counted
}
/**
* Get next data chunk to send to the Dynatrace backend system.
*
*
* This method is called from beacon sending thread.
*
*
* @param chunkPrefix The prefix to add to each chunk.
* @param maxSize The maximum size in characters for one chunk.
* @param delimiter The delimiter between data chunks.
*
* @return The string to send or an empty string if there is no more data to send.
*/
String getChunk(String chunkPrefix, int maxSize, char delimiter) {
if (!hasDataToSend()) {
return "";
}
return getNextChunk(chunkPrefix, maxSize, delimiter);
}
/**
* Test if there is more data to send (to chunk).
*
* @return {@code true} if there is more data, {@code false} otherwise.
*/
boolean hasDataToSend() {
return (eventDataBeingSent != null && !eventDataBeingSent.isEmpty())
|| (actionDataBeingSent != null && !actionDataBeingSent.isEmpty());
}
/**
* Get the next chunk.
*
* @param chunkPrefix The prefix to add to each chunk.
* @param maxSize The maximum size in characters for one chunk.
* @param delimiter The delimiter between data chunks.
*
* @return The string to send or an empty string if there is no more data to send.
*/
private String getNextChunk(String chunkPrefix, int maxSize, char delimiter) {
// create the string builder
StringBuilder beaconBuilder = new StringBuilder(maxSize);
// append the chunk prefix
beaconBuilder.append(chunkPrefix);
// append data from both lists
// note the order is currently important -> event data goes first, then action data
chunkifyDataList(beaconBuilder, eventDataBeingSent, maxSize, delimiter);
chunkifyDataList(beaconBuilder, actionDataBeingSent, maxSize, delimiter);
return beaconBuilder.toString();
}
private static void chunkifyDataList(StringBuilder chunkBuilder, LinkedList dataBeingSent, int maxSize, char delimiter) {
Iterator iterator = dataBeingSent.iterator();
while (iterator.hasNext() && chunkBuilder.length() <= maxSize) {
// mark the record for sending
BeaconCacheRecord record = iterator.next();
record.markForSending();
// append delimiter & data
chunkBuilder.append(delimiter).append(record.getData());
}
}
/**
* Remove data that was previously marked for sending when {@link #getNextChunk(String, int, char)} was called.
*/
void removeDataMarkedForSending() {
if (!hasDataToSend()) {
// data has not been copied yet - avoid NPE
return;
}
Iterator iterator = eventDataBeingSent.iterator();
while (iterator.hasNext() && iterator.next().isMarkedForSending()) {
iterator.remove();
}
if (!iterator.hasNext()) {
// only check action data, if all event data has been traversed, otherwise it's just waste of cpu time
iterator = actionDataBeingSent.iterator();
while (iterator.hasNext() && iterator.next().isMarkedForSending()) {
iterator.remove();
}
}
}
/**
* This method removes the marked for sending and prepends the copied data back to the data.
*/
void resetDataMarkedForSending() {
if (!hasDataToSend()) {
// data has not been copied yet - avoid NPE
return;
}
// reset the "sending marks" and in the same traversal count the bytes which are added back
long numBytes = 0;
for (BeaconCacheRecord record : eventDataBeingSent) {
record.unsetSending();
numBytes += record.getDataSizeInBytes();
}
for (BeaconCacheRecord record : actionDataBeingSent) {
record.unsetSending();
numBytes += record.getDataSizeInBytes();
}
// merge data
eventDataBeingSent.addAll(eventData);
actionDataBeingSent.addAll(actionData);
eventData = eventDataBeingSent;
actionData = actionDataBeingSent;
eventDataBeingSent = null;
actionDataBeingSent = null;
totalNumBytes += numBytes;
}
/**
* Get total number of bytes used.
*
*
* Note: The number of bytes is calculated from the lists where active records are added.
* Data that is currently being sent is not taken into account, since we assume sending is
* successful and therefore this data is just temporarily stored.
*
*
* @return Sum of data size in bytes for each {@link BeaconCacheRecord}.
*/
long getTotalNumberOfBytes() {
return totalNumBytes;
}
/**
* Remove all {@link BeaconCacheRecord beacon cache records} from event and action data
* which are older than given minTimestamp
*
*
* Records which are currently being sent are not evicted.
*
*
* @param minTimestamp The minimum timestamp allowed.
*
* @return The total number of removed records.
*/
int removeRecordsOlderThan(long minTimestamp) {
int numRecordsRemoved = removeRecordsOlderThan(eventData, minTimestamp);
numRecordsRemoved += removeRecordsOlderThan(actionData, minTimestamp);
return numRecordsRemoved;
}
/**
* Remove all {@link BeaconCacheRecord beacon cache records} from {@code records}.
*
* @param minTimestamp The minimum timestamp allowed.
*
* @return The number of records removed from {@code records}.
*/
private static int removeRecordsOlderThan(List records, long minTimestamp) {
int numRecordsRemoved = 0;
Iterator iterator = records.iterator();
while (iterator.hasNext()) {
BeaconCacheRecord record = iterator.next();
if (record.getTimestamp() < minTimestamp) {
iterator.remove();
numRecordsRemoved++;
}
}
return numRecordsRemoved;
}
/**
* Remove up to {@code numRecords} records from event & action data, compared by their age.
*
*
* Note not all event/action data entries are traversed, only the first action data & first event
* data is removed and compared against each other, which one to remove first. If the first action's timestamp and
* first event's timestamp are equal, the first event is removed.
*
*
* @param numRecords The number of records.
*
* @return Number of actually removed records.
*/
int removeOldestRecords(int numRecords) {
int numRecordsRemoved = 0;
Iterator eventsIterator = eventData.iterator();
Iterator actionsIterator = actionData.iterator();
BeaconCacheRecord currentEvent = eventsIterator.hasNext() ? eventsIterator.next() : null;
BeaconCacheRecord currentAction = actionsIterator.hasNext() ? actionsIterator.next() : null;
while (numRecordsRemoved < numRecords && (currentEvent != null || currentAction != null)) {
if (currentEvent == null) {
// actions is not null -> remove action
currentAction = removeAndAdvanceIterator(actionsIterator);
} else if (currentAction == null) {
// events is not null -> remove event
currentEvent = removeAndAdvanceIterator(eventsIterator);
} else {
// both are not null -> compare by timestamp and take the older one
if (currentAction.getTimestamp() < currentEvent.getTimestamp()) {
// first action is older than first event
currentAction = removeAndAdvanceIterator(actionsIterator);
} else {
// first event is older than first action
currentEvent = removeAndAdvanceIterator(eventsIterator);
}
}
numRecordsRemoved++;
}
return numRecordsRemoved;
}
private static E removeAndAdvanceIterator(Iterator iterator) {
iterator.remove();
return iterator.hasNext() ? iterator.next() : null;
}
/**
* Get a shallow copy of event data.
*
*
* This method shall only be used for testing purposes.
*
*/
List getEventData() {
return new LinkedList<>(eventData);
}
/**
* Get a snapshot of action data.
*
*
* This method shall only be used for testing purposes.
*
*/
List getActionData() {
return new LinkedList<>(actionData);
}
/**
* Get a readonly list of event data being sent.
*
*
* This method shall only be used for testing purposes.
*
*/
List getEventDataBeingSent() {
return eventDataBeingSent == null ? null : Collections.unmodifiableList(eventDataBeingSent);
}
/**
* Get a readonly list of action data being sent.
*
*
* This method shall only be used for testing purposes.
*
*/
List getActionDataBeingSent() {
return actionDataBeingSent == null ? null : Collections.unmodifiableList(actionDataBeingSent);
}
}
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