Lettuce是基于netty来实现的，Netty支持通过设置ChannelOption.SO_KEEPALIVE属性来控制保活机制，底层实现是基于操作系统，操作系统的保活机制一般要等待7200秒，如centos的net.ipv4.tcp_keepalive_time设置；lettuce客户端另外提供了扩展保活机制，方便客户端灵活的控制保活机制的空闲时间、次数、间隔。
一个对springboot redis框架进行重写，支持lettuce、jedis、连接池、同时连接多个集群、多个redis数据库、开发自定义属性配置的开源SDK
<dependency><groupId>io.github.mingyang66</groupId><artifactId>emily-spring-boot-redis</artifactId><version>4.3.9</version>
</dependency>
GitHub地址：https://github.com/mingyang66/spring-parent
一、Lettuce提供基于操作系统的保活机制
- 通过SocketOptions属性设置keepAlive，默认：false
ClientOptions.Builder builder = this.initializeClientOptionsBuilder(properties);Duration connectTimeout = properties.getConnectTimeout();if (connectTimeout != null) {builder.socketOptions(SocketOptions.builder().keepAlive(true).build());}
- io.lettuce.core.ConnectionBuilder#configureBootstrap设置保活参数
bootstrap.option(ChannelOption.SO_KEEPALIVE, options.isKeepAlive());
二、Lettuce提供扩展keepAlive保活机制
- 通过SocketOptions属性设置扩展保活机制参数
ClientOptions.Builder builder = this.initializeClientOptionsBuilder(properties);Duration connectTimeout = properties.getConnectTimeout();if (connectTimeout != null) {builder.socketOptions(SocketOptions.builder().connectTimeout(connectTimeout).keepAlive(SocketOptions.KeepAliveOptions.builder()//两次keep-alive之间的间隔.interval(Duration.ofSeconds(5))//连接空闲多久开始keep-alive.idle(Duration.ofSeconds(5))//keep-alive多少次之后断开连接.count(3)//是否开启保活连接.enable().build()).build());}
- io.lettuce.core.ConnectionBuilder#configureBootstrap保活连接配置
public void configureBootstrap(boolean domainSocket,Function<Class<? extends EventLoopGroup>, EventLoopGroup> eventLoopGroupProvider) {...SocketOptions options = clientOptions.getSocketOptions();EventLoopGroup eventLoopGroup = eventLoopGroupProvider.apply(eventLoopGroupClass);bootstrap.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, Math.toIntExact(options.getConnectTimeout().toMillis()));if (!domainSocket) {//基于操作系统的keepAlive机制bootstrap.option(ChannelOption.SO_KEEPALIVE, options.isKeepAlive());bootstrap.option(ChannelOption.TCP_NODELAY, options.isTcpNoDelay());}bootstrap.channel(channelClass).group(eventLoopGroup);//开启扩展保活机制的前提是必须开启基于操作系统的保活机制if (options.isKeepAlive() && options.isExtendedKeepAlive()) {SocketOptions.KeepAliveOptions keepAlive = options.getKeepAlive();//判断是否可以使用IOUringProvider，即是否可用IO uring库。如果可用，调用IOUringProvider提供的applyKeepAlive方法，传入bootstrap（Netty的引导类）和keepAlive的参数（count、idle、interval），应用IOUringProvider提供的keepalive参数配置if (IOUringProvider.isAvailable()) {IOUringProvider.applyKeepAlive(bootstrap, keepAlive.getCount(), keepAlive.getIdle(), keepAlive.getInterval());} else if (EpollProvider.isAvailable()) {//判断是否可以使用EpollProvider，即是否可用Epoll网络库。如果可用，调用EpollProvider提供的applyKeepAlive方法，传入bootstrap和keepAlive的参数，应用EpollProvider提供的keepalive参数配置。EpollProvider.applyKeepAlive(bootstrap, keepAlive.getCount(), keepAlive.getIdle(), keepAlive.getInterval());} else if (ExtendedNioSocketOptions.isAvailable() && !KqueueProvider.isAvailable()) {//判断是否可以使用ExtendedNioSocketOptions，并且不可使用KqueueProvider。如果可用，调用ExtendedNioSocketOptions提供的applyKeepAlive方法，传入bootstrap和keepAlive的参数，应用ExtendedNioSocketOptions提供的keepalive参数配置ExtendedNioSocketOptions.applyKeepAlive(bootstrap, keepAlive.getCount(), keepAlive.getIdle(),keepAlive.getInterval());} else {logger.warn("Cannot apply extended TCP keepalive options to channel type " + channelClass.getName());}}}
- IOUring是Netty中的一个实验性模块，用于支持Linux上的IO uring库。IOUring是Netty中的一个实验性模块，用于支持Linux上的IO uring库
- EpollProvider是Netty中的一个类，用于在Linux上提供基于Epoll的网络通信支持。Epoll是Linux内核提供的一种事件通知机制，用于处理大量并发连接的高性能I/O操作。它通过将文件描述符（包括套接字）注册到一个事件集合中，并且可以监听多个事件类型（如可读、可写、错误等），从而实现了高效的事件驱动模型。
三、SocketOptions.KeepAliveOptions保活机制参数配置类
public static class KeepAliveOptions {//默认保活机制检查次数上限public static final int DEFAULT_COUNT = 9;//默认信道空闲2小时开始进行keep-alivepublic static final Duration DEFAULT_IDLE = Duration.ofHours(2);//每次keep-alive的时间间隔，默认：75秒public static final Duration DEFAULT_INTERVAL = Duration.ofSeconds(75);private final int count;private final boolean enabled;private final Duration idle;private final Duration interval;private KeepAliveOptions(KeepAliveOptions.Builder builder) {this.count = builder.count;this.enabled = builder.enabled;this.idle = builder.idle;this.interval = builder.interval;}
}
