MemcachedHttpCacheStorage.java
/*
* ====================================================================
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF 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.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
*/
package org.apache.hc.client5.http.impl.cache.memcached;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CancellationException;
import org.apache.hc.client5.http.cache.HttpCacheEntrySerializer;
import org.apache.hc.client5.http.cache.ResourceIOException;
import org.apache.hc.client5.http.impl.cache.AbstractBinaryCacheStorage;
import org.apache.hc.client5.http.impl.cache.CacheConfig;
import org.apache.hc.client5.http.impl.cache.HttpByteArrayCacheEntrySerializer;
import org.apache.hc.core5.util.Args;
import net.spy.memcached.CASResponse;
import net.spy.memcached.CASValue;
import net.spy.memcached.MemcachedClient;
import net.spy.memcached.MemcachedClientIF;
import net.spy.memcached.OperationTimeoutException;
/**
* <p>
* This class is a storage backend that uses an external <i>memcached</i>
* for storing cached origin responses. This storage option provides a
* couple of interesting advantages over the default in-memory storage
* backend:
* </p>
* <ol>
* <li>in-memory cached objects can survive an application restart since
* they are held in a separate process</li>
* <li>it becomes possible for several cooperating applications to share
* a large <i>memcached</i> farm together</li>
* </ol>
* <p>
* Note that in a shared memcached pool setting you may wish to make use
* of the Ketama consistent hashing algorithm to reduce the number of
* cache misses that might result if one of the memcached cluster members
* fails (see the <a href="http://dustin.github.com/java-memcached-client/apidocs/net/spy/memcached/KetamaConnectionFactory.html">
* KetamaConnectionFactory</a>).
* </p>
* <p>
* Because memcached places limits on the size of its keys, we need to
* introduce a key hashing scheme to map the annotated URLs the higher-level
* caching HTTP client wants to use as keys onto ones that are suitable
* for use with memcached. Please see {@link KeyHashingScheme} if you would
* like to use something other than the provided {@link SHA256KeyHashingScheme}.
* </p>
*
* <p>
* Please refer to the <a href="http://code.google.com/p/memcached/wiki/NewStart">
* memcached documentation</a> and in particular to the documentation for
* the <a href="http://code.google.com/p/spymemcached/">spymemcached
* documentation</a> for details about how to set up and configure memcached
* and the Java client used here, respectively.
* </p>
*
* @since 4.1
*/
public class MemcachedHttpCacheStorage extends AbstractBinaryCacheStorage<CASValue<Object>> {
private final MemcachedClientIF client;
private final KeyHashingScheme keyHashingScheme;
/**
* Create a storage backend talking to a <i>memcached</i> instance
* listening on the specified host and port. This is useful if you
* just have a single local memcached instance running on the same
* machine as your application, for example.
* @param address where the <i>memcached</i> daemon is running
* @throws IOException in case of an error
*/
public MemcachedHttpCacheStorage(final InetSocketAddress address) throws IOException {
this(new MemcachedClient(address));
}
/**
* Create a storage backend using the pre-configured given
* <i>memcached</i> client.
* @param cache client to use for communicating with <i>memcached</i>
*/
public MemcachedHttpCacheStorage(final MemcachedClient cache) {
this(cache, CacheConfig.DEFAULT, HttpByteArrayCacheEntrySerializer.INSTANCE, SHA256KeyHashingScheme.INSTANCE);
}
/**
* Create a storage backend using the pre-configured given
* <i>memcached</i> client.
*
* @param cache client to use for communicating with <i>memcached</i>
*
* @since 5.2
*/
public MemcachedHttpCacheStorage(final MemcachedClientIF cache) {
this(cache, CacheConfig.DEFAULT, HttpByteArrayCacheEntrySerializer.INSTANCE, SHA256KeyHashingScheme.INSTANCE);
}
/**
* Create a storage backend using the given <i>memcached</i> client and
* applying the given cache configuration, serialization, and hashing
* mechanisms.
* @param client how to talk to <i>memcached</i>
* @param config apply HTTP cache-related options
* @param serializer alternative serialization mechanism
* @param keyHashingScheme how to map higher-level logical "storage keys"
* onto "cache keys" suitable for use with memcached
*/
public MemcachedHttpCacheStorage(
final MemcachedClient client,
final CacheConfig config,
final HttpCacheEntrySerializer<byte[]> serializer,
final KeyHashingScheme keyHashingScheme) {
this((MemcachedClientIF) client, config, serializer, keyHashingScheme);
}
/**
* Create a storage backend using the given <i>memcached</i> client and
* applying the given cache configuration, serialization, and hashing
* mechanisms.
*
* @param client how to talk to <i>memcached</i>
* @param config apply HTTP cache-related options
* @param serializer alternative serialization mechanism
* @param keyHashingScheme how to map higher-level logical "storage keys"
* onto "cache keys" suitable for use with memcached
* @since 5.2
*/
public MemcachedHttpCacheStorage(
final MemcachedClientIF client,
final CacheConfig config,
final HttpCacheEntrySerializer<byte[]> serializer,
final KeyHashingScheme keyHashingScheme) {
super((config != null ? config : CacheConfig.DEFAULT).getMaxUpdateRetries(),
serializer != null ? serializer : HttpByteArrayCacheEntrySerializer.INSTANCE);
this.client = Args.notNull(client, "Memcached client");
this.keyHashingScheme = keyHashingScheme;
}
@Override
protected String digestToStorageKey(final String key) {
return keyHashingScheme.hash(key);
}
@Override
protected void store(final String storageKey, final byte[] storageObject) throws ResourceIOException {
try {
client.set(storageKey, 0, storageObject);
} catch (final CancellationException ex) {
throw new MemcachedOperationCancellationException(ex);
}
}
private byte[] castAsByteArray(final Object storageObject) throws ResourceIOException {
if (storageObject == null) {
return null;
}
if (storageObject instanceof byte[]) {
return (byte[]) storageObject;
}
throw new ResourceIOException("Unexpected cache content: " + storageObject.getClass());
}
@Override
protected byte[] restore(final String storageKey) throws ResourceIOException {
try {
return castAsByteArray(client.get(storageKey));
} catch (final CancellationException ex) {
throw new MemcachedOperationCancellationException(ex);
} catch (final OperationTimeoutException ex) {
throw new MemcachedOperationTimeoutException(ex);
}
}
@Override
protected CASValue<Object> getForUpdateCAS(final String storageKey) throws ResourceIOException {
try {
return client.gets(storageKey);
} catch (final CancellationException ex) {
throw new MemcachedOperationCancellationException(ex);
} catch (final OperationTimeoutException ex) {
throw new MemcachedOperationTimeoutException(ex);
}
}
@Override
protected byte[] getStorageObject(final CASValue<Object> casValue) throws ResourceIOException {
return castAsByteArray(casValue.getValue());
}
@Override
protected boolean updateCAS(
final String storageKey, final CASValue<Object> casValue, final byte[] storageObject) throws ResourceIOException {
try {
final CASResponse casResult = client.cas(storageKey, casValue.getCas(), storageObject);
return casResult == CASResponse.OK;
} catch (final CancellationException ex) {
throw new MemcachedOperationCancellationException(ex);
} catch (final OperationTimeoutException ex) {
throw new MemcachedOperationTimeoutException(ex);
}
}
@Override
protected void delete(final String storageKey) throws ResourceIOException {
try {
client.delete(storageKey);
} catch (final CancellationException ex) {
throw new MemcachedOperationCancellationException(ex);
}
}
@Override
protected Map<String, byte[]> bulkRestore(final Collection<String> storageKeys) throws ResourceIOException {
try {
final Map<String, ?> storageObjectMap = client.getBulk(storageKeys);
final Map<String, byte[]> resultMap = new HashMap<>(storageObjectMap.size());
for (final Map.Entry<String, ?> resultEntry: storageObjectMap.entrySet()) {
resultMap.put(resultEntry.getKey(), castAsByteArray(resultEntry.getValue()));
}
return resultMap;
} catch (final CancellationException ex) {
throw new MemcachedOperationCancellationException(ex);
} catch (final OperationTimeoutException ex) {
throw new MemcachedOperationTimeoutException(ex);
}
}
}