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/*
* Copyright 2016 Markus Ellinger
*
* Licensed 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 de.javakaffee.web.msm.storage;
import java.util.concurrent.Future;
/**
* Abstracts access to a memcached service, or another service, which provides a protocol similar to memcached.
*
* @author Markus Ellinger
*/
public interface StorageClient {
/**
*
* Adds an object to the cache iff it does not exist already.
* The operation is performed asynchronously if the underlying implementation supports it.
*
*
* The expiration is defined according to the memcached protocol as follows: The actual value sent may either be
* Unix time (number of seconds since January 1, 1970, as a 32-bit value), or a number of seconds starting from
* current time. In the latter case, this number of seconds may not exceed 60*60*24*30
* (number of seconds in 30 days); if the number sent by a client is larger than that, the server will consider it
* to be real Unix time value rather than an offset from current time.
*
*
* @param key object key
* @param exp object expiration
* @param o object bytes to store
*
* @return a future representing the processing of this operation.
* If the boolean value returned by the future is true, the key was added successfully.
* If the boolean value returned by the future is false, the key was already there.
*/
Future add(String key, int exp, byte[] o);
/**
*
* Sets an object in the cache regardless of any existing value.
* The operation is performed asynchronously if the underlying implementation supports it.
*
*
* The expiration is defined according to the memcached protocol as follows: The actual value sent may either be
* Unix time (number of seconds since January 1, 1970, as a 32-bit value), or a number of seconds starting from
* current time. In the latter case, this number of seconds may not exceed 60*60*24*30
* (number of seconds in 30 days); if the number sent by a client is larger than that, the server will consider it
* to be real Unix time value rather than an offset from current time.
*
*
* @param key object key
* @param exp object expiration
* @param o object bytes to store
*
* @return a future representing the processing of this operation. The boolean value indicates whether the value
* was set successfully. Setting a value can fail e.g. if the memory limit of the storage was reached.
*/
Future set(String key, int exp, byte[] o);
/**
* Gets an object by key.
*
* @param key object key
*
* @return object bytes or null if an object with the given key does not exist
*/
byte[] get(String key);
/**
* Deletes the given key from the cache.
* The operation is performed asynchronously if the underlying implementation supports it.
*
* @param key object key
*
* @return a future representing the processing of this operation. The boolean value indicates whether the value
* was deleted successfully. The main reason why false would be returned is if the value to
* delete does not exist.
*/
Future delete(String key);
/**
* Shuts this client down immediately.
*/
void shutdown();
}