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Reduced chance of duplicate refresh processes

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- Access lock prevents duplicate processes being placed if two
  threads enter the same method in such a way that both get before
  the first one puts the update Future in the Map.
- Update threshold prevents all calls without timestamp causing a new
  refresh process from being created
- Bad request 400 prevents timestamp from being too far in the future
  to avoid bad actor increasing timestamp to create new refresh processes
This commit is contained in:
Risto Lahtela 2021-02-06 07:58:47 +02:00 committed by Risto Lahtela
parent 05a2c20fdd
commit 899d29f2d2
3 changed files with 115 additions and 22 deletions
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72
Plan/common/src/main/java/com/djrapitops/plan/delivery/webserver/resolver/json/AsyncJSONResolverService.java
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@ -18,7 +18,9 @@ package com.djrapitops.plan.delivery.webserver.resolver.json;
import com.djrapitops.plan.delivery.webserver.cache.DataID;
import com.djrapitops.plan.processing.Processing;
import com.djrapitops.plan.settings.config.PlanConfig;
import com.djrapitops.plan.storage.json.JSONStorage;
import com.djrapitops.plan.utilities.UnitSemaphoreAccessLock;
import javax.inject.Inject;
import javax.inject.Singleton;
@ -28,6 +30,7 @@ import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;
import java.util.function.Supplier;
@ -39,19 +42,26 @@ import java.util.function.Supplier;
@Singleton
public class AsyncJSONResolverService {
private final PlanConfig config;
private final Processing processing;
private final JSONStorage jsonStorage;
private final Map<String, Future<JSONStorage.StoredJSON>> currentlyProcessing;
private final Map<String, Long> previousUpdates;
private final UnitSemaphoreAccessLock accessLock; // Access lock prevents double processing same resource
@Inject
public AsyncJSONResolverService(
PlanConfig config,
Processing processing,
JSONStorage jsonStorage
) {
this.config = config;
this.processing = processing;
this.jsonStorage = jsonStorage;
currentlyProcessing = new ConcurrentHashMap<>();
previousUpdates = new ConcurrentHashMap<>();
accessLock = new UnitSemaphoreAccessLock();
}
public <T> JSONStorage.StoredJSON resolve(long newerThanTimestamp, DataID dataID, UUID serverUUID, Function<UUID, T> creator) {
@ -64,17 +74,26 @@ public class AsyncJSONResolverService {
}
// No new enough version, let's refresh and send old version of the file
long updateThreshold = TimeUnit.MINUTES.toMillis(1L); // TODO make configurable
// Check if the json is already being created
Future<JSONStorage.StoredJSON> updatedJSON = currentlyProcessing.get(identifier);
if (updatedJSON == null) {
// Submit a task to refresh the data if the json is old
updatedJSON = processing.submitNonCritical(() -> {
JSONStorage.StoredJSON created = jsonStorage.storeJson(identifier, creator.apply(serverUUID));
currentlyProcessing.remove(identifier);
jsonStorage.invalidateOlder(identifier, created.timestamp);
return created;
});
currentlyProcessing.put(identifier, updatedJSON);
Future<JSONStorage.StoredJSON> updatedJSON;
accessLock.enter();
try {
updatedJSON = currentlyProcessing.get(identifier);
if (updatedJSON == null && previousUpdates.getOrDefault(identifier, 0L) < newerThanTimestamp - updateThreshold) {
// Submit a task to refresh the data if the json is old
updatedJSON = processing.submitNonCritical(() -> {
JSONStorage.StoredJSON created = jsonStorage.storeJson(identifier, creator.apply(serverUUID));
currentlyProcessing.remove(identifier);
jsonStorage.invalidateOlder(identifier, created.timestamp);
previousUpdates.put(identifier, created.timestamp);
return created;
});
currentlyProcessing.put(identifier, updatedJSON);
}
} finally {
accessLock.exit();
}
// Get an old version from cache
@ -84,6 +103,8 @@ public class AsyncJSONResolverService {
} else {
// If there is no version available, block thread until the new finishes being generated.
try {
// updatedJSON is not null in this case ever because previousUpdates.getOrDefault(..., 0L) gets 0.
//noinspection ConstantConditions
return updatedJSON.get();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
@ -104,17 +125,26 @@ public class AsyncJSONResolverService {
}
// No new enough version, let's refresh and send old version of the file
long updateThreshold = TimeUnit.MINUTES.toMillis(1L); // TODO make configurable
// Check if the json is already being created
Future<JSONStorage.StoredJSON> updatedJSON = currentlyProcessing.get(identifier);
if (updatedJSON == null) {
// Submit a task to refresh the data if the json is old
updatedJSON = processing.submitNonCritical(() -> {
JSONStorage.StoredJSON created = jsonStorage.storeJson(identifier, creator.get());
currentlyProcessing.remove(identifier);
jsonStorage.invalidateOlder(identifier, created.timestamp);
return created;
});
currentlyProcessing.put(identifier, updatedJSON);
Future<JSONStorage.StoredJSON> updatedJSON;
accessLock.enter();
try {
updatedJSON = currentlyProcessing.get(identifier);
if (updatedJSON == null && previousUpdates.getOrDefault(identifier, 0L) < newerThanTimestamp - updateThreshold) {
// Submit a task to refresh the data if the json is old
updatedJSON = processing.submitNonCritical(() -> {
JSONStorage.StoredJSON created = jsonStorage.storeJson(identifier, creator.get());
currentlyProcessing.remove(identifier);
jsonStorage.invalidateOlder(identifier, created.timestamp);
previousUpdates.put(identifier, created.timestamp);
return created;
});
currentlyProcessing.put(identifier, updatedJSON);
}
} finally {
accessLock.exit();
}
// Get an old version from cache
@ -124,6 +154,8 @@ public class AsyncJSONResolverService {
} else {
// If there is no version available, block thread until the new finishes being generated.
try {
// updatedJSON is not null in this case ever because previousUpdates.getOrDefault(..., 0L) gets 0.
//noinspection ConstantConditions
return updatedJSON.get();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();

10
Plan/common/src/main/java/com/djrapitops/plan/delivery/webserver/resolver/json/ServerTabJSONResolver.java
View File

@ -28,6 +28,7 @@ import com.djrapitops.plan.identification.Identifiers;
import java.util.Optional;
import java.util.UUID;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;
/**
@ -72,9 +73,14 @@ public class ServerTabJSONResolver<T> implements Resolver {
private long getTimestamp(Request request) {
try {
return request.getQuery().get("timestamp")
long currentTime = System.currentTimeMillis();
long timestamp = request.getQuery().get("timestamp")
.map(Long::parseLong)
.orElseGet(System::currentTimeMillis);
.orElse(currentTime);
if (currentTime + TimeUnit.SECONDS.toMillis(10L) < timestamp) {
throw new BadRequestException("Attempt to get data from the future! " + timestamp + " > " + currentTime);
}
return timestamp;
} catch (NumberFormatException nonNumberTimestamp) {
throw new BadRequestException("'timestamp' was not a number: " + nonNumberTimestamp.getMessage());
}

55
Plan/common/src/main/java/com/djrapitops/plan/utilities/UnitSemaphoreAccessLock.java Normal file
View File

@ -0,0 +1,55 @@
/*
* This file is part of Player Analytics (Plan).
*
* Plan is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License v3 as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Plan is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with Plan. If not, see <https://www.gnu.org/licenses/>.
*/
package com.djrapitops.plan.utilities;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* Synchronizes a critical section of code so that only a single thread can access it at a time.
*
* @author Rsl1122
*/
public class UnitSemaphoreAccessLock {
private final AtomicBoolean accessing;
private final Object lockObject;
public UnitSemaphoreAccessLock() {
accessing = new AtomicBoolean(false);
lockObject = new Object();
}
public void enter() {
try {
if (accessing.get()) {
synchronized (lockObject) {
lockObject.wait();
}
}
accessing.set(true);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
public void exit() {
accessing.set(false);
synchronized (lockObject) {
lockObject.notify();
}
}
}