org.apache.pulsar.common.topics.TopicCompactionStrategy Maven / Gradle / Ivy
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package org.apache.pulsar.common.topics;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.apache.pulsar.client.api.Schema;
import org.apache.pulsar.common.classification.InterfaceAudience;
import org.apache.pulsar.common.classification.InterfaceStability;
/**
* Defines a custom strategy to compact messages in a topic.
* This strategy can be passed to Topic Compactor and Table View to compact messages in a custom way.
*
* Examples:
*
* TopicCompactionStrategy strategy = new MyTopicCompactionStrategy();
*
* // Run topic compaction by the compaction strategy.
* // While compacting messages for each key,
* // it will choose messages only if TopicCompactionStrategy.shouldKeepLeft(prev, cur) returns false.
* StrategicTwoPhaseCompactor compactor = new StrategicTwoPhaseCompactor(...);
* compactor.compact(topic, strategy);
*
* // Run table view by the compaction strategy.
* // While updating messages in the table view map,
* // it will choose messages only if TopicCompactionStrategy.shouldKeepLeft(prev, cur) returns false.
* TableView tableView = pulsar.getClient().newTableViewBuilder(strategy.getSchema())
* .topic(topic)
* .loadConf(Map.of(
* "topicCompactionStrategyClassName", strategy.getClass().getCanonicalName()))
* .create();
*/
@InterfaceAudience.Private
@InterfaceStability.Unstable
public interface TopicCompactionStrategy {
String TABLE_VIEW_TAG = "table-view";
Map INSTANCES = new ConcurrentHashMap<>();
/**
* Returns the schema object for this strategy.
* @return
*/
Schema getSchema();
/**
* Tests if the compaction needs to keep the left(previous message)
* compared to the right(current message) for the same key.
*
* @param prev previous message value
* @param cur current message value
* @return True if it needs to keep the previous message and ignore the current message. Otherwise, False.
*/
boolean shouldKeepLeft(T prev, T cur);
default void handleSkippedMessage(String key, T cur) {
}
static TopicCompactionStrategy load(String tag, String topicCompactionStrategyClassName) {
if (topicCompactionStrategyClassName == null) {
return null;
}
try {
Class clazz = Class.forName(topicCompactionStrategyClassName);
TopicCompactionStrategy instance = (TopicCompactionStrategy) clazz.getDeclaredConstructor().newInstance();
INSTANCES.put(tag, instance);
return instance;
} catch (Exception e) {
throw new IllegalArgumentException(
"Error when loading topic compaction strategy: " + topicCompactionStrategyClassName, e);
}
}
static TopicCompactionStrategy getInstance(String tag) {
return INSTANCES.get(tag);
}
}