io.druid.server.lookup.cache.loading.LoadingCache Maven / Gradle / Ivy
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/*
* Licensed to Metamarkets Group Inc. (Metamarkets) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. Metamarkets licenses this file
* to you 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 io.druid.server.lookup.cache.loading;
import com.fasterxml.jackson.annotation.JsonSubTypes;
import com.fasterxml.jackson.annotation.JsonTypeInfo;
import com.google.common.cache.CacheLoader;
import com.google.common.util.concurrent.ExecutionError;
import com.google.common.util.concurrent.UncheckedExecutionException;
import javax.annotation.Nullable;
import java.io.Closeable;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
/**
* A semi-persistent mapping from keys to values. Cache entries are added using
* {@link #get(Object, Callable)} and stored in the cache until either evicted or manually invalidated.
*
*
Implementations of this interface are expected to be thread-safe, and can be safely accessed
* by multiple concurrent threads.
*
* This interface borrows ideas (and in some cases methods and javadoc) from Guava and JCache cache interface.
* Thanks Guava and JSR !
* We elected to make this as close as possible to JSR API like that users can build bridges between all the existing implementations of JSR.
*/
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type")
@JsonSubTypes(value = {
@JsonSubTypes.Type(name = "guava", value = OnHeapLoadingCache.class),
@JsonSubTypes.Type(name = "mapDb", value = OffHeapLoadingCache.class)
})
public interface LoadingCache extends Closeable
{
/**
* @param key must not be null
* Returns the value associated with {@code key} in this cache, or {@code null} if there is no
* cached value for {@code key}.
* a cache miss should be counted if the key is missing.
*/
@Nullable
V getIfPresent(K key);
/**
* Returns a map of the values associated with {@code keys} in this cache. The returned map will
* only contain entries which are already present in the cache.
*/
Map getAllPresent(Iterable keys);
/**
* Returns the value associated with {@code key} in this cache, obtaining that value from
* {@code valueLoader} if necessary. No observable state associated with this cache is modified
* until loading completes.
*
* Warning: as with {@link CacheLoader#load}, {@code valueLoader} must not return
* {@code null}; it may either return a non-null value or throw an exception.
*
* @throws ExecutionException if a checked exception was thrown while loading the value
* @throws UncheckedExecutionException if an unchecked exception was thrown while loading the
* value
* @throws ExecutionError if an error was thrown while loading the value
*
*/
V get(K key, Callable valueLoader) throws ExecutionException;
/**
* Copies all of the mappings from the specified map to the cache. This method is used for bulk put.
*
* @throws IllegalStateException if the cache is {@link #isClosed()}
*/
void putAll(Map m);
/**
* Discards any cached value for key {@code key}. Eviction can be lazy or eager.
*
* @throws IllegalStateException if the cache is {@link #isClosed()}
*/
void invalidate(K key);
/**
* Discards any cached values for keys {@code keys}. Eviction can be lazy or eager.
*
* @throws IllegalStateException if the cache is {@link #isClosed()}
*/
void invalidateAll(Iterable keys);
/**
* Clears the contents of the cache.
*
* @throws IllegalStateException if the cache is {@link #isClosed()}
*/
void invalidateAll();
/**
* @return Stats of the cache.
*
* @throws IllegalStateException if the cache is {@link #isClosed()}
*/
LookupCacheStats getStats();
/**
* @return true if the Cache is closed
*/
boolean isClosed();
/**
* Clean the used resources of the cache. Still not sure about cache lifecycle but as an initial design
* the namespace deletion event should call this method to clean up resources.
*/
void close();
}