io.atomix.copycat.package-info Maven / Gradle / Ivy
/*
* Copyright 2015 the original author or authors.
*
* 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.
*/
/**
* Core interfaces for operating on replicated state machines in the Copycat cluster.
*
* The interfaces in this package are shared by both clients and servers. They are the interfaces through which clients and servers communicate
* state change and query information with one another.
*
* Clients operate on Copycat replicated state machines by submitting state change {@link io.atomix.copycat.Operation operations} to the cluster.
* Copycat supports separate operations - {@link io.atomix.copycat.Command} and {@link io.atomix.copycat.Query} - for submitting state change
* and read-only operations respectively. Each operation maps to a method of a replicated state machine. The handling of operations is dependent
* on a variety of factors, including the operation type and the operation's {@link io.atomix.copycat.Query.ConsistencyLevel consistency level}.
* When an operation is submitted to the cluster, the operation will eventually be translated into a method call on the replicated state machine
* and a response will be sent back to the client.
*
Commands
* {@link io.atomix.copycat.Command Commands} are operations that modify the state of the replicated state machine. A command is a serializable
* object that will be sent to the leader of the cluster and replicated to a persisted on a majority of the servers in the Copycat cluster before
* being applied to the state machine. Once a command is committed (stored on a majority of servers), it's translated into a method call on the
* state machine on each server. The return value of the state machine method on the leader is sent back to the client.
* Queries
* {@link io.atomix.copycat.Query Queries} are operations that read but do not modify the state of the replicated state machine. Because queries
* do not effect the state of the system, servers do not have to replicate them to a majority of the cluster, and no disk I/O is necessary to
* complete a query of the state machine's state. Like commands, queries translate to a method call on the replicated state machine, but only
* the server to which the query is submitted applies the query to its state machine. Once a query is completed, the return value of the state
* machine method called is sent back to the client.
*
* @author Jordan Halterman
*/
package io.atomix.copycat;