org.projectnessie.events.service.EventSubscribers Maven / Gradle / Ivy
/*
* Copyright (C) 2023 Dremio
*
* 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 org.projectnessie.events.service;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.ServiceLoader;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
import org.projectnessie.events.api.EventType;
import org.projectnessie.events.spi.EventSubscriber;
import org.projectnessie.events.spi.EventSubscription;
import org.projectnessie.versioned.ResultType;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Loads and holds all {@link EventSubscriber}s.
*
* The main purpose of this class is to provide a single point of access to all subscribers, and
* also to provide a bit-mask of all event types that subscribers are subscribed to, for a fast and
* efficient type-based event filtering.
*
*
This class is meant to be used as a singleton, or in CDI Dependent pseudo-scope.
*/
public class EventSubscribers implements AutoCloseable {
private static final Logger LOGGER = LoggerFactory.getLogger(EventSubscribers.class);
/** Load all {@link EventSubscriber}s via {@link ServiceLoader}. */
public static List loadSubscribers() {
List subscribers = new ArrayList<>();
for (EventSubscriber subscriber : ServiceLoader.load(EventSubscriber.class)) {
subscribers.add(subscriber);
}
return subscribers;
}
// Visible for testing
final List subscribers;
private final EnumSet acceptedEventTypes;
private final EnumSet acceptedResultTypes;
// guarded by this
private boolean started;
// guarded by this
private boolean closed;
private Map subscriptions;
public EventSubscribers(EventSubscriber... subscribers) {
this(Arrays.asList(subscribers));
}
public EventSubscribers(Iterable subscribers) {
this.subscribers =
Collections.unmodifiableList(
StreamSupport.stream(subscribers.spliterator(), false).collect(Collectors.toList()));
acceptedEventTypes =
Arrays.stream(EventType.values())
.filter(t -> this.subscribers.stream().anyMatch(s -> s.accepts(t)))
.collect(Collectors.toCollection(() -> EnumSet.noneOf(EventType.class)));
acceptedResultTypes =
acceptedEventTypes.stream()
.flatMap(EventSubscribers::map)
.collect(Collectors.toCollection(() -> EnumSet.noneOf(ResultType.class)));
}
/**
* Starts all subscribers.
*
* @param subscriptionFactory a function that creates a subscription for a subscriber
*/
public synchronized void start(Function subscriptionFactory) {
if (!started) {
LOGGER.info("Starting subscribers...");
Map subscriptions = new HashMap<>();
for (EventSubscriber subscriber : subscribers) {
try {
EventSubscription subscription = subscriptionFactory.apply(subscriber);
subscriber.onSubscribe(subscription);
subscriptions.put(subscription, subscriber);
} catch (Exception e) {
throw new RuntimeException("Error starting subscriber", e);
}
}
this.subscriptions = Collections.unmodifiableMap(subscriptions);
LOGGER.info("Done starting subscribers.");
started = true;
}
}
@Override
public synchronized void close() {
if (!closed) {
LOGGER.info("Closing subscribers...");
List errors = new ArrayList<>();
for (EventSubscriber subscriber : subscribers) {
try {
subscriber.close();
} catch (Exception e) {
errors.add(e);
}
}
if (!errors.isEmpty()) {
RuntimeException e = new RuntimeException("Error closing at least one subscriber");
errors.forEach(e::addSuppressed);
throw e;
}
LOGGER.info("Done closing subscribers.");
closed = true;
}
}
/** Returns an unmodifiable list of all subscribers. */
public List getSubscribers() {
return subscribers;
}
/**
* Returns an unmodifiable map of all active subscriptions with their subscribers. Returns null if
* {@link #start(Function)} has not been called yet.
*/
public Map getSubscriptions() {
return subscriptions;
}
/** Returns {@code true} if there are any subscribers for the given {@link EventType}. */
public boolean hasSubscribersFor(EventType type) {
return acceptedEventTypes.contains(type);
}
/** Returns {@code true} if there are any subscribers for the given {@link ResultType}. */
public boolean hasSubscribersFor(ResultType resultType) {
return acceptedResultTypes.contains(resultType);
}
/**
* Maps a {@link ResultType} to all {@link EventType}s that could be emitted for a result of that
* type.
*/
private static Stream map(EventType resultType) {
switch (resultType) {
case COMMIT:
case CONTENT_STORED:
case CONTENT_REMOVED:
return Stream.of(ResultType.COMMIT, ResultType.MERGE, ResultType.TRANSPLANT);
case MERGE:
return Stream.of(ResultType.MERGE);
case TRANSPLANT:
return Stream.of(ResultType.TRANSPLANT);
case REFERENCE_CREATED:
return Stream.of(ResultType.REFERENCE_CREATED);
case REFERENCE_UPDATED:
return Stream.of(ResultType.REFERENCE_ASSIGNED);
case REFERENCE_DELETED:
return Stream.of(ResultType.REFERENCE_DELETED);
default:
throw new IllegalArgumentException("Unknown result type: " + resultType);
}
}
}