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Fix concurrency bug in CachedDataManager MRU cache

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This resolves a longstanding issue with TownyPerms (#1330)
This commit is contained in:
Luck 2019-11-25 20:31:14 +00:00
parent 787f691f44
commit 4d3c692402
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2 changed files with 52 additions and 19 deletions
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66
common/src/main/java/me/lucko/luckperms/common/cacheddata/AbstractCachedDataManager.java
View File

@ -52,6 +52,7 @@ import java.util.Objects;
import java.util.Set;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
/**
* Abstract implementation of {@link CachedDataManager}.
@ -178,25 +179,53 @@ public abstract class AbstractCachedDataManager implements CachedDataManager {
this.metaDataManager.cache.synchronous().cleanUp();
}
private final class Permission implements Container<CachedPermissionData> {
/**
* Implementation of a most-recently-used cache with a mod counter, to prevent race conditions
* occurring when the cache is cleared whilst a calculation is taking place.
*
* @param <T> the cached type
*/
private abstract static class MRUCache<T> {
private volatile T recent;
private final AtomicInteger modCount = new AtomicInteger();
protected int modCount() {
return this.modCount.get();
}
protected T getRecent() {
return this.recent;
}
protected void offerRecent(int validAt, T offer) {
if (validAt == this.modCount.get()) {
this.recent = offer;
}
}
protected void clearRecent() {
this.recent = null;
this.modCount.incrementAndGet();
}
}
private final class Permission extends MRUCache<RecentPermissionData> implements Container<CachedPermissionData> {
private final AsyncLoadingCache<QueryOptions, PermissionCache> cache = CaffeineFactory.newBuilder()
.expireAfterAccess(2, TimeUnit.MINUTES)
.buildAsync(new PermissionCacheLoader());
// cache the most recent lookup.
private RecentPermissionData recentPermissionData = null;
@Override
public @NonNull PermissionCache get(@NonNull QueryOptions queryOptions) {
Objects.requireNonNull(queryOptions, "queryOptions");
RecentPermissionData recent = this.recentPermissionData;
RecentPermissionData recent = getRecent();
if (recent != null && queryOptions.equals(recent.queryOptions)) {
return recent.permissionData;
}
int modCount = modCount();
PermissionCache data = this.cache.synchronous().get(queryOptions);
this.recentPermissionData = new RecentPermissionData(queryOptions, data);
offerRecent(modCount, new RecentPermissionData(queryOptions, data));
//noinspection ConstantConditions
return data;
@ -212,7 +241,7 @@ public abstract class AbstractCachedDataManager implements CachedDataManager {
public void recalculate(@NonNull QueryOptions queryOptions) {
Objects.requireNonNull(queryOptions, "queryOptions");
this.cache.synchronous().refresh(queryOptions);
this.recentPermissionData = null;
clearRecent();
}
@Override
@ -224,7 +253,7 @@ public abstract class AbstractCachedDataManager implements CachedDataManager {
// invalidate any previous setting
this.cache.synchronous().invalidate(queryOptions);
this.recentPermissionData = null;
clearRecent();
// if the previous value is already calculated, use it when recalculating.
PermissionCache value = getIfReady(previous);
@ -252,35 +281,34 @@ public abstract class AbstractCachedDataManager implements CachedDataManager {
public void invalidate(@NonNull QueryOptions queryOptions) {
Objects.requireNonNull(queryOptions, "queryOptions");
this.cache.synchronous().invalidate(queryOptions);
this.recentPermissionData = null;
clearRecent();
}
@Override
public void invalidate() {
this.cache.synchronous().invalidateAll();
this.recentPermissionData = null;
clearRecent();
}
}
private final class Meta implements Container<CachedMetaData> {
private final class Meta extends MRUCache<RecentMetaData> implements Container<CachedMetaData> {
private final AsyncLoadingCache<QueryOptions, MetaCache> cache = CaffeineFactory.newBuilder()
.expireAfterAccess(2, TimeUnit.MINUTES)
.buildAsync(new MetaCacheLoader());
// cache the most recent lookup.
private RecentMetaData recentMetaData = null;
@Override
public @NonNull MetaCache get(@NonNull QueryOptions queryOptions) {
Objects.requireNonNull(queryOptions, "queryOptions");
RecentMetaData recent = this.recentMetaData;
RecentMetaData recent = getRecent();
if (recent != null && queryOptions.equals(recent.queryOptions)) {
return recent.metaData;
}
int modCount = modCount();
MetaCache data = this.cache.synchronous().get(queryOptions);
this.recentMetaData = new RecentMetaData(queryOptions, data);
offerRecent(modCount, new RecentMetaData(queryOptions, data));
//noinspection ConstantConditions
return data;
@ -296,7 +324,7 @@ public abstract class AbstractCachedDataManager implements CachedDataManager {
public void recalculate(@NonNull QueryOptions queryOptions) {
Objects.requireNonNull(queryOptions, "queryOptions");
this.cache.synchronous().refresh(queryOptions);
this.recentMetaData = null;
clearRecent();
}
@Override
@ -308,7 +336,7 @@ public abstract class AbstractCachedDataManager implements CachedDataManager {
// invalidate any previous setting
this.cache.synchronous().invalidate(queryOptions);
this.recentMetaData = null;
clearRecent();
// if the previous value is already calculated, use it when recalculating.
MetaCache value = getIfReady(previous);
@ -336,13 +364,13 @@ public abstract class AbstractCachedDataManager implements CachedDataManager {
public void invalidate(@NonNull QueryOptions queryOptions) {
Objects.requireNonNull(queryOptions, "queryOptions");
this.cache.synchronous().invalidate(queryOptions);
this.recentMetaData = null;
clearRecent();
}
@Override
public void invalidate() {
this.cache.synchronous().invalidateAll();
this.recentMetaData = null;
clearRecent();
}
}

5
common/src/main/java/me/lucko/luckperms/common/query/QueryOptionsImpl.java
View File

@ -123,6 +123,11 @@ public class QueryOptionsImpl implements QueryOptions {
return new QueryOptionsBuilderImpl(this.mode, this.context, this.flags, this.options);
}
@Override
public String toString() {
return "QueryOptions(mode=" + this.mode + ", context=" + this.context + ", flags=" + flags() + ", options=" + this.options + ')';
}
@Override
public boolean equals(Object o) {
if (this == o) return true;