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DittoCachingSignalEnrichmentFacade.java
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/
DittoCachingSignalEnrichmentFacade.java
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/*
* Copyright (c) 2021 Contributors to the Eclipse Foundation
*
* See the NOTICE file(s) distributed with this work for additional
* information regarding copyright ownership.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0
*
* SPDX-License-Identifier: EPL-2.0
*/
package org.eclipse.ditto.internal.models.signalenrichment;
import static org.eclipse.ditto.base.model.common.ConditionChecker.checkNotNull;
import java.util.Collection;
import java.util.List;
import java.util.Optional;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.Executor;
import java.util.stream.Collectors;
import javax.annotation.Nullable;
import org.eclipse.ditto.base.model.entity.id.EntityId;
import org.eclipse.ditto.base.model.headers.DittoHeaders;
import org.eclipse.ditto.base.model.signals.Signal;
import org.eclipse.ditto.base.model.signals.WithResource;
import org.eclipse.ditto.internal.utils.pekko.logging.DittoLoggerFactory;
import org.eclipse.ditto.internal.utils.pekko.logging.ThreadSafeDittoLogger;
import org.eclipse.ditto.internal.utils.cache.Cache;
import org.eclipse.ditto.internal.utils.cache.CacheFactory;
import org.eclipse.ditto.internal.utils.cache.config.CacheConfig;
import org.eclipse.ditto.json.JsonFactory;
import org.eclipse.ditto.json.JsonFieldSelector;
import org.eclipse.ditto.json.JsonObject;
import org.eclipse.ditto.json.JsonObjectBuilder;
import org.eclipse.ditto.json.JsonPointer;
import org.eclipse.ditto.json.JsonValue;
import org.eclipse.ditto.protocol.adapter.ProtocolAdapter;
import org.eclipse.ditto.things.model.Thing;
import org.eclipse.ditto.things.model.ThingId;
import org.eclipse.ditto.things.model.signals.events.ThingCreated;
import org.eclipse.ditto.things.model.signals.events.ThingDeleted;
import org.eclipse.ditto.things.model.signals.events.ThingEvent;
import org.eclipse.ditto.things.model.signals.events.ThingMerged;
/**
* Retrieve additional parts of things by asking an asynchronous cache.
* Instantiated once per cluster node so that it builds up a cache across all signal enrichments on a local cluster
* node.
*/
public class DittoCachingSignalEnrichmentFacade implements CachingSignalEnrichmentFacade {
private static final ThreadSafeDittoLogger LOGGER = DittoLoggerFactory.getThreadSafeLogger(DittoCachingSignalEnrichmentFacade.class);
private static final String CACHE_NAME_SUFFIX = "_signal_enrichment_cache";
protected final Cache<SignalEnrichmentCacheKey, JsonObject> extraFieldsCache;
protected DittoCachingSignalEnrichmentFacade(
final SignalEnrichmentFacade cacheLoaderFacade,
final CacheConfig cacheConfig,
final Executor cacheLoaderExecutor,
final String cacheNamePrefix) {
final var cacheLoader = SignalEnrichmentCacheLoader.of(cacheLoaderFacade);
final var cacheName = cacheNamePrefix + CACHE_NAME_SUFFIX;
extraFieldsCache = CacheFactory.createCache(cacheLoader, cacheConfig, cacheName, cacheLoaderExecutor);
}
/**
* Returns a new {@code DittoCachingSignalEnrichmentFacade} instance.
*
* @param cacheLoaderFacade the facade whose argument-result-pairs we are caching.
* @param cacheConfig the cache configuration to use for the cache.
* @param cacheLoaderExecutor the executor to use in order to asynchronously load cache entries.
* @param cacheNamePrefix the prefix to use as cacheName of the cache.
* @throws NullPointerException if any argument is null.
*/
public static DittoCachingSignalEnrichmentFacade newInstance(final SignalEnrichmentFacade cacheLoaderFacade,
final CacheConfig cacheConfig,
final Executor cacheLoaderExecutor,
final String cacheNamePrefix) {
return new DittoCachingSignalEnrichmentFacade(checkNotNull(cacheLoaderFacade, "cacheLoaderFacade"),
checkNotNull(cacheConfig, "cacheConfig"),
checkNotNull(cacheLoaderExecutor, "cacheLoaderExecutor"),
checkNotNull(cacheNamePrefix, "cacheNamePrefix"));
}
@Override
public CompletionStage<JsonObject> retrieveThing(final ThingId thingId, final List<ThingEvent<?>> events,
final long minAcceptableSeqNr) {
final DittoHeaders dittoHeaders = DittoHeaders.empty();
if (minAcceptableSeqNr < 0) {
final var cacheKey =
SignalEnrichmentCacheKey.of(thingId, SignalEnrichmentContext.of(dittoHeaders, null));
extraFieldsCache.invalidate(cacheKey);
return doCacheLookup(cacheKey, dittoHeaders);
} else {
final var cachingParameters =
new CachingParameters(null, events, false, minAcceptableSeqNr);
return doRetrievePartialThing(thingId, dittoHeaders, cachingParameters);
}
}
@Override
public CompletionStage<JsonObject> retrievePartialThing(final ThingId thingId,
@Nullable final JsonFieldSelector jsonFieldSelector, final DittoHeaders dittoHeaders,
@Nullable final Signal<?> concernedSignal) {
final List<ThingEvent<?>> thingEvents =
(concernedSignal instanceof ThingEvent) && !(ProtocolAdapter.isLiveSignal(concernedSignal)) ?
List.of((ThingEvent<?>) concernedSignal) : List.of();
// as second step only return what was originally requested as fields:
final var cachingParameters =
new CachingParameters(jsonFieldSelector, thingEvents, true, 0);
return doRetrievePartialThing(thingId, dittoHeaders, cachingParameters)
.thenApply(jsonObject -> applyJsonFieldSelector(jsonObject, jsonFieldSelector));
}
/**
* Retrieve parts of a thing.
*
* @param thingId ID of the thing.
* @param jsonFieldSelector the selected fields of the thing.
* @param dittoHeaders Ditto headers containing authorization information.
* @param concernedSignals the Signals which caused that this partial thing retrieval was triggered
* (e.g. a {@code ThingEvent})
* @param minAcceptableSeqNr minimum sequence number of the concerned signals to not invalidate the cache.
* @return future that completes with the parts of a thing or fails with an error.
*/
@SuppressWarnings("java:S1612")
public CompletionStage<JsonObject> retrievePartialThing(final EntityId thingId,
final JsonFieldSelector jsonFieldSelector,
final DittoHeaders dittoHeaders,
final Collection<? extends Signal<?>> concernedSignals,
final long minAcceptableSeqNr) {
final List<ThingEvent<?>> thingEvents = concernedSignals.stream()
.filter(signal -> signal instanceof ThingEvent && !Signal.isChannelLive(signal))
.map(signal -> (ThingEvent<?>) signal)
.collect(Collectors.toList());
// as second step only return what was originally requested as fields:
final var cachingParameters =
new CachingParameters(jsonFieldSelector, thingEvents, true, minAcceptableSeqNr);
return doRetrievePartialThing(thingId, dittoHeaders, cachingParameters)
.thenApply(jsonObject -> applyJsonFieldSelector(jsonObject, jsonFieldSelector));
}
protected CompletionStage<JsonObject> doRetrievePartialThing(final EntityId thingId,
final DittoHeaders dittoHeaders,
final CachingParameters cachingParameters) {
final var fieldSelector = cachingParameters.fieldSelector;
final JsonFieldSelector enhancedFieldSelector = enhanceFieldSelectorWithRevision(fieldSelector);
final var idWithResourceType =
SignalEnrichmentCacheKey.of(thingId, SignalEnrichmentContext.of(dittoHeaders, enhancedFieldSelector));
final var cachingParametersWithEnhancedFieldSelector = new CachingParameters(enhancedFieldSelector,
cachingParameters.concernedEvents,
cachingParameters.invalidateCacheOnPolicyChange,
cachingParameters.minAcceptableSeqNr);
return smartUpdateCachedObject(idWithResourceType, cachingParametersWithEnhancedFieldSelector);
}
@Nullable
private static JsonFieldSelector enhanceFieldSelectorWithRevision(
@Nullable final Iterable<JsonPointer> fieldSelector) {
final JsonFieldSelector result;
if (fieldSelector == null) {
result = null;
} else {
result = JsonFactory.newFieldSelectorBuilder()
.addPointers(fieldSelector)
.addFieldDefinition(Thing.JsonFields.REVISION) // additionally always select the revision
.build();
}
return result;
}
private CompletableFuture<JsonObject> smartUpdateCachedObject(final SignalEnrichmentCacheKey cacheKey,
final CachingParameters cachingParameters) {
final CompletableFuture<JsonObject> result;
final var invalidateCacheOnPolicyChange = cachingParameters.invalidateCacheOnPolicyChange;
final var concernedSignals = cachingParameters.concernedEvents;
final var fieldSelector = cachingParameters.fieldSelector;
final Optional<List<ThingEvent<?>>> thingEventsOptional =
extractConsecutiveTwinEvents(concernedSignals, cachingParameters.minAcceptableSeqNr);
final var dittoHeaders = getLastDittoHeaders(concernedSignals);
// there are twin events, but their sequence numbers have gaps or do not reach the min acceptable seq nr
if (thingEventsOptional.isEmpty()) {
extraFieldsCache.invalidate(cacheKey);
result = doCacheLookup(cacheKey, dittoHeaders);
} else {
final var thingEvents = thingEventsOptional.orElseThrow();
// there are no twin events; return the cached thing
if (thingEvents.isEmpty()) {
result = doCacheLookup(cacheKey, dittoHeaders);
} else if (thingEventsStartWithCreated(thingEvents)) {
// the twin was created; continue without revision checks.
final var nextExpectedThingEventsParameters =
new CachingParameters(fieldSelector, thingEvents, invalidateCacheOnPolicyChange,
cachingParameters.minAcceptableSeqNr);
result = doCacheLookup(cacheKey, dittoHeaders).thenCompose(
cachedJsonObject -> handleNextExpectedThingEvents(cacheKey, cachedJsonObject,
nextExpectedThingEventsParameters));
} else {
// there are twin events; perform smart update
result = doCacheLookup(cacheKey, dittoHeaders).thenCompose(
cachedJsonObject -> doSmartUpdateCachedObject(cacheKey, cachedJsonObject,
cachingParameters, dittoHeaders));
}
}
return result;
}
private static Optional<List<ThingEvent<?>>> extractConsecutiveTwinEvents(
final List<ThingEvent<?>> thingEvents, final long minAcceptableSeqNr) {
// ignore events before ThingDeleted or ThingCreated
// not safe to ignore events before ThingModified because ThingModified has merge semantics at the top level
final var events = findLastThingDeletedOrCreated(thingEvents)
.map(i -> thingEvents.subList(i, thingEvents.size()))
.orElse(thingEvents);
// Check if minimum acceptable sequence number is met
if (minAcceptableSeqNr < 0 || events.isEmpty() || getLast(events).getRevision() < minAcceptableSeqNr) {
return Optional.empty();
}
// Validate sequence numbers. Discard if events have gaps
long lastSeq = -1;
for (final ThingEvent<?> event : events) {
if (lastSeq >= 0 && event.getRevision() != lastSeq + 1) {
return Optional.empty();
} else {
lastSeq = event.getRevision();
}
}
return Optional.of(events);
}
private static Optional<Integer> findLastThingDeletedOrCreated(final List<ThingEvent<?>> thingEvents) {
for (int i = thingEvents.size() - 1; i >= 0; --i) {
final var event = thingEvents.get(i);
if (event instanceof ThingDeleted || event instanceof ThingCreated) {
return Optional.of(i);
}
}
return Optional.empty();
}
private static DittoHeaders getLastDittoHeaders(final List<? extends Signal<?>> concernedSignals) {
if (concernedSignals.isEmpty()) {
return DittoHeaders.empty();
} else {
return getLast(concernedSignals).getDittoHeaders();
}
}
protected CompletableFuture<JsonObject> doCacheLookup(final SignalEnrichmentCacheKey cacheKey,
final DittoHeaders dittoHeaders) {
LOGGER.withCorrelationId(dittoHeaders).debug("Looking up cache entry for <{}>", cacheKey);
return extraFieldsCache.get(cacheKey)
.thenApply(optionalJsonObject -> optionalJsonObject.orElseGet(JsonObject::empty));
}
private static boolean thingEventsStartWithCreated(final List<ThingEvent<?>> thingEvents) {
return thingEvents.get(0) instanceof ThingCreated;
}
private CompletionStage<JsonObject> doSmartUpdateCachedObject(final SignalEnrichmentCacheKey cacheKey,
final JsonObject cachedJsonObject, final CachingParameters cachingParameters,
final DittoHeaders dittoHeaders) {
final CompletionStage<JsonObject> result;
final long cachedRevision = cachedJsonObject.getValue(Thing.JsonFields.REVISION).orElse(0L);
final List<ThingEvent<?>> relevantEvents = cachingParameters.concernedEvents.stream()
.filter(e -> e.getRevision() > cachedRevision)
.toList();
if (relevantEvents.isEmpty()) {
// the cache entry was more up-to-date
result = CompletableFuture.completedFuture(cachedJsonObject);
} else if (cachedRevision + 1 == getFirst(relevantEvents).getRevision()) {
// the cache entry was already present and the first thingEvent was the next expected revision no
// -> we have all information necessary to calculate it without making another roundtrip
final var nextExpectedThingEventsParameters =
new CachingParameters(cachingParameters.fieldSelector, relevantEvents,
cachingParameters.invalidateCacheOnPolicyChange,
cachingParameters.minAcceptableSeqNr);
result = handleNextExpectedThingEvents(cacheKey, cachedJsonObject,
nextExpectedThingEventsParameters);
} else {
// the cache entry was already present, but we missed sth and need to invalidate the cache
// and to another cache lookup (via roundtrip)
extraFieldsCache.invalidate(cacheKey);
result = doCacheLookup(cacheKey, dittoHeaders);
}
return result;
}
private static <T> T getLast(final List<T> list) {
return list.get(list.size() - 1);
}
private static <T> T getFirst(final List<T> list) {
return list.get(0);
}
private CompletionStage<JsonObject> handleNextExpectedThingEvents(final SignalEnrichmentCacheKey cacheKey,
final JsonObject cachedJsonObject, final CachingParameters cachingParameters) {
final var concernedSignals = cachingParameters.concernedEvents;
final var enhancedFieldSelector = cachingParameters.fieldSelector;
final Optional<String> cachedPolicyIdOpt = cachedJsonObject.getValue(Thing.JsonFields.POLICY_ID);
JsonObject jsonObject = cachedJsonObject;
for (final ThingEvent<?> thingEvent : concernedSignals) {
switch (thingEvent.getCommandCategory()) {
case MERGE:
jsonObject = getMergeJsonObject(jsonObject, thingEvent);
break;
case DELETE:
jsonObject = getDeleteJsonObject(jsonObject, thingEvent);
break;
default:
jsonObject = getDefaultJsonObject(jsonObject, thingEvent);
}
// invalidate cache on policy change if the flag is set
if (cachingParameters.invalidateCacheOnPolicyChange) {
final var optionalCompletionStage =
invalidateCacheOnPolicyChange(cacheKey, jsonObject, cachedPolicyIdOpt.orElse(null),
thingEvent.getDittoHeaders());
if (optionalCompletionStage.isPresent()) {
return optionalCompletionStage.get();
}
}
}
final var enhancedJsonObject = enhanceJsonObject(jsonObject, concernedSignals, enhancedFieldSelector);
// update local cache with enhanced object:
extraFieldsCache.put(cacheKey, enhancedJsonObject);
return CompletableFuture.completedFuture(enhancedJsonObject);
}
private static JsonObject getMergeJsonObject(final JsonValue jsonObject, final ThingEvent<?> thingEvent) {
final var thingMerged = (ThingMerged) thingEvent;
final JsonValue mergedValue = thingMerged.getValue();
final JsonObjectBuilder mergePatchBuilder = JsonFactory.newObject(thingMerged.getResourcePath(), mergedValue)
.toBuilder();
thingMerged.getMetadata()
.ifPresent(metadata -> mergePatchBuilder.set(
Thing.JsonFields.METADATA.getPointer().append(thingMerged.getResourcePath()), metadata)
.build());
return JsonFactory.mergeJsonValues(mergePatchBuilder.build(), jsonObject).asObject();
}
private static JsonObject getDeleteJsonObject(final JsonObject jsonObject, final WithResource thingEvent) {
final JsonObject result;
final var resourcePath = thingEvent.getResourcePath();
if (thingEvent instanceof ThingDeleted) {
// NoOp because we just want to keep the original known thing.
result = jsonObject;
} else if (resourcePath.isEmpty()) {
result = JsonObject.empty();
} else {
result = jsonObject.remove(resourcePath).remove(Thing.JsonFields.METADATA.getPointer().append(resourcePath));
}
return result;
}
private static JsonObject getDefaultJsonObject(final JsonObject jsonObject, final ThingEvent<?> thingEvent) {
final var resourcePath = thingEvent.getResourcePath();
final var jsonObjectBuilder = jsonObject.toBuilder();
final Optional<JsonValue> optEntity = thingEvent.getEntity();
if (resourcePath.isEmpty() && optEntity.filter(JsonValue::isObject).isPresent()) {
optEntity.map(JsonValue::asObject).ifPresent(jsonObjectBuilder::setAll);
} else {
optEntity.ifPresent(entity -> jsonObjectBuilder.set(resourcePath.toString(), entity)
);
}
thingEvent.getMetadata().ifPresent(
metadata -> jsonObjectBuilder.set(Thing.JsonFields.METADATA.getPointer().append(resourcePath),
metadata));
return jsonObjectBuilder.build();
}
private Optional<CompletionStage<JsonObject>> invalidateCacheOnPolicyChange(final SignalEnrichmentCacheKey cacheKey,
final JsonObject jsonObject, @Nullable final String cachedPolicyIdOpt, final DittoHeaders dittoHeaders) {
final boolean shouldInvalidate = Optional.ofNullable(cachedPolicyIdOpt).flatMap(cachedPolicyId ->
jsonObject.getValue(Thing.JsonFields.POLICY_ID)
.filter(currentPolicyId -> !cachedPolicyId.equals(currentPolicyId)))
.isPresent();
if (shouldInvalidate) {
// invalidate the cache
extraFieldsCache.invalidate(cacheKey);
// and to another cache lookup (via roundtrip):
return Optional.of(doCacheLookup(cacheKey, dittoHeaders));
} else {
return Optional.empty();
}
}
private JsonObject enhanceJsonObject(final JsonObject jsonObject, final List<ThingEvent<?>> concernedSignals,
@Nullable final JsonFieldSelector enhancedFieldSelector) {
final ThingEvent<?> last = getLast(concernedSignals);
final var jsonObjectBuilder = jsonObject.toBuilder()
.set(Thing.JsonFields.REVISION, last.getRevision());
concernedSignals.stream()
.filter(ThingCreated.class::isInstance)
.map(ThingCreated.class::cast)
.forEach(thingCreated -> thingCreated.getTimestamp().ifPresent(timestamp ->
jsonObjectBuilder.set(Thing.JsonFields.CREATED, timestamp.toString())));
last.getTimestamp().ifPresent(timestamp ->
jsonObjectBuilder.set(Thing.JsonFields.MODIFIED, timestamp.toString()));
return applyJsonFieldSelector(jsonObjectBuilder.build(), enhancedFieldSelector);
}
protected static final class CachingParameters {
@Nullable private final JsonFieldSelector fieldSelector;
private final List<ThingEvent<?>> concernedEvents;
private final boolean invalidateCacheOnPolicyChange;
private final long minAcceptableSeqNr;
public CachingParameters(@Nullable final JsonFieldSelector fieldSelector,
final List<ThingEvent<?>> concernedEvents,
final boolean invalidateCacheOnPolicyChange,
final long minAcceptableSeqNr) {
this.fieldSelector = fieldSelector;
this.concernedEvents = concernedEvents;
this.invalidateCacheOnPolicyChange = invalidateCacheOnPolicyChange;
this.minAcceptableSeqNr = minAcceptableSeqNr;
}
@Override
public String toString() {
return getClass().getSimpleName() + " [" +
"fieldSelector=" + fieldSelector +
", concernedEvents=" + concernedEvents +
", invalidateCacheOnPolicyChange=" + invalidateCacheOnPolicyChange +
", minAcceptableSeqNr=" + minAcceptableSeqNr +
"]";
}
}
}