com.hazelcast.cp.session.CPSession Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2024, Hazelcast, Inc. All Rights Reserved.
*
* 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 com.hazelcast.cp.session;
import com.hazelcast.config.cp.CPSubsystemConfig;
import com.hazelcast.cluster.Address;
/**
* Represents a CP session.
*
* For CP data structures that involve resource ownership management, such as
* locks or semaphores, sessions are required to keep track of liveliness of
* callers. In this context, "caller" means an entity that uses CP Subsystem
* APIs. It can be either a Hazelcast server or client. A caller initially
* creates a session before sending its very first session-based request to a
* CP group, such as a lock / semaphore acquire. After creating a session on
* the CP group, the caller stores its session id locally and sends it
* alongside its session-based operations. A single session is used for all
* lock and semaphore proxies of the caller. When a CP group receives
* a session-based operation, it checks the validity of the session using
* the session id information available in the operation. A session is valid if
* it is still open in the CP group. An operation with a valid session id is
* accepted as a new session heartbeat. While a caller is idle, in other words,
* it does not send any session-based operation to the CP group for a while, it
* commits periodic heartbeats to the CP group in the background in order to
* keep its session alive. This interval is specified in
* {@link CPSubsystemConfig#getSessionHeartbeatIntervalSeconds()}.
*
* A session is closed when the caller does not touch the session during
* a predefined duration. In this case, the caller is assumed to be crashed and
* all its resources are released automatically. This duration is specified in
* {@link CPSubsystemConfig#getSessionTimeToLiveSeconds()}. Please check
* {@link CPSubsystemConfig} for recommendations to choose a reasonable session
* time-to-live duration.
*
* Sessions offer a trade-off between liveliness and safety. If a very small
* value is set to {@link CPSubsystemConfig#setSessionTimeToLiveSeconds(int)},
* then a session owner could be considered crashed very quickly and its
* resources can be released prematurely. On the other hand, if a large value
* is set, a session could be kept alive for an unnecessarily long duration
* even if its owner actually crashes. However, it is a safer approach
* not to use a small session time to live duration. If a session owner is
* known to be crashed, its session could be closed manually via
* {@link CPSessionManagementService#forceCloseSession(String, long)}.
*
* @see CPSubsystemConfig
*/
public interface CPSession {
/**
* Represents type of endpoints that create CP sessions
*/
enum CPSessionOwnerType {
/**
* Represents a Hazelcast server
*/
SERVER,
/**
* Represents a Hazelcast client
*/
CLIENT
}
/**
* Returns id of the session
*/
long id();
/**
* Returns the timestamp of when the session was created
*/
long creationTime();
/**
* Returns the timestamp of when the session will expire
*/
long expirationTime();
/**
* Returns version of the session.
* A session's version is incremented on each heartbeat.
*/
long version();
/**
* Returns true if the session expires before the given timestamp.
*/
boolean isExpired(long timestamp);
/**
* Returns the endpoint that has created this session
*/
Address endpoint();
/**
* Returns type of the endpoint that has created this session
*/
CPSessionOwnerType endpointType();
/**
* Returns name of the endpoint that has created this session
*/
String endpointName();
}