1. io.lettuce.core.protocol.CommandHandler : null Unexpected exception during request: java.io.IOException: 远程主机强迫关闭了一个现有的连接。

报错信息

during request: java.io.IOException: 远程主机强迫关闭了一个现有的连接。
项目时基于若依框架开发，在生产环境报错：

io.lettuce.core.protocol.CommandHandler : null Unexpected exception
during request: java.io.IOException: 远程主机强迫关闭了一个现有的连接。

详细日志信息如下：

INFO 3352 --- [ioEventLoop-4-1] io.lettuce.core.protocol.CommandHandler  : null Unexpected exception during request: java.io.IOException: 远程主机强迫关闭了一个现有的连接。

java.io.IOException: 远程主机强迫关闭了一个现有的连接。
	at sun.nio.ch.SocketDispatcher.read0(Native Method) ~[na:1.8.0_221]
	at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:43) ~[na:1.8.0_221]
	at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223) ~[na:1.8.0_221]
	at sun.nio.ch.IOUtil.read(IOUtil.java:192) ~[na:1.8.0_221]
	at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:380) ~[na:1.8.0_221]
	at io.netty.buffer.PooledByteBuf.setBytes(PooledByteBuf.java:253) ~[netty-buffer-4.1.69.Final.jar!/:4.1.69.Final]
	at io.netty.buffer.AbstractByteBuf.writeBytes(AbstractByteBuf.java:1132) ~[netty-buffer-4.1.69.Final.jar!/:4.1.69.Final]
	at io.netty.channel.socket.nio.NioSocketChannel.doReadBytes(NioSocketChannel.java:350) ~[netty-transport-4.1.69.Final.jar!/:4.1.69.Final]
	at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:151) ~[netty-transport-4.1.69.Final.jar!/:4.1.69.Final]
	at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:719) [netty-transport-4.1.69.Final.jar!/:4.1.69.Final]
	at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:655) [netty-transport-4.1.69.Final.jar!/:4.1.69.Final]
	at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:581) [netty-transport-4.1.69.Final.jar!/:4.1.69.Final]
	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493) [netty-transport-4.1.69.Final.jar!/:4.1.69.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:986) [netty-common-4.1.69.Final.jar!/:4.1.69.Final]
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) [netty-common-4.1.69.Final.jar!/:4.1.69.Final]
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) [netty-common-4.1.69.Final.jar!/:4.1.69.Final]
	at java.lang.Thread.run(Thread.java:748) [na:1.8.0_221]
	2023-06-14 00:52:16.956  INFO 3352 --- [ionShutdownHook] org.quartz.core.QuartzScheduler          : Scheduler TaskScheduler_$_iZj575z0jja92rZ1686469913890 paused.
	2023-06-14 00:52:16.985  INFO 3352 --- [xecutorLoop-1-8] i.l.core.protocol.ConnectionWatchdog     : Reconnecting, last destination was /172.17.151.173:6379

---

原因分析

日志中容易看出报错信息与redis有关，并且springboot 使用 lettuce做redis 的连接池，lettuce 调用netty与redis服务器通讯

在gitee上找到了若依框架的相同问题，并且官方对于此问题给出了修改方案

解决方案

1. 修改配置文件redis.windows.conf的timeout参数
   

Close the connection after a client is idle for N seconds (0 to disable)
在客户端空闲N秒后关闭连接(0表示禁用)

2. 检查spring项目中redis的配置

redis:
   # 地址
   host: 192.168.0.1
   # 端口，默认为6379
   port: 6379
   # 数据库索引
   database: 10
   # 密码
   password: 147258
   # 连接超时时间 60s
   timeout: 60s
   lettuce:
     pool:
       # 连接池中的最小空闲连接 
       min-idle: 10
       # 连接池中的最大空闲连接 
       max-idle: 30
       # 连接池的最大数据库连接数
       max-active: 8
       # #连接池最大阻塞等待时间（使用负值表示没有限制）
       max-wait: -1ms

3.redis.windows.conf中设置tcp-keepalive时间为60s

# TCP keepalive.
#
# If non-zero, use SO_KEEPALIVE to send TCP ACKs to clients in absence
# of communication. This is useful for two reasons:
#
# 1) Detect dead peers.
# 2) Take the connection alive from the point of view of network
#    equipment in the middle.
#
# On Linux, the specified value (in seconds) is the period used to send ACKs.
# Note that to close the connection the double of the time is needed.
# On other kernels the period depends on the kernel configuration.
#
# A reasonable value for this option is 60 seconds.
tcp-keepalive 60

配置完成后重启redis服务

2. io.netty.util.internal.OutOfDirectMemoryError: failed to allocate 16777216 byte(s) of direct memory (used: 1073741824, max: 1073741824)

报错信息

io.netty.util.internal.OutOfDirectMemoryError: failed to allocate 16777216 byte(s) of direct memory (used: 1073741824, max: 1073741824)
    at io.netty.util.internal.PlatformDependent.incrementMemoryCounter(PlatformDependent.java:802) ~[netty-common-4.1.72.Final.jar:4.1.72.Final]
    at io.netty.util.internal.PlatformDependent.allocateDirectNoCleaner(PlatformDependent.java:731) ~[netty-common-4.1.72.Final.jar:4.1.72.Final]
    at io.netty.buffer.PoolArena$DirectArena.allocateDirect(PoolArena.java:648) ~[netty-buffer-4.1.72.Final.jar:4.1.72.Final]
    at io.netty.buffer.PoolArena$DirectArena.newChunk(PoolArena.java:623) ~[netty-buffer-4.1.72.Final.jar:4.1.72.Final]
    at io.netty.buffer.PoolArena.allocateNormal(PoolArena.java:202) ~[netty-buffer-4.1.72.Final.jar:4.1.72.Final]
    at io.netty.buffer.PoolArena.tcacheAllocateSmall(PoolArena.java:172) ~[netty-buffer-4.1.72.Final.jar:4.1.72.Final]
    at io.netty.buffer.PoolArena.allocate(PoolArena.java:134) ~[netty-buffer-4.1.72.Final.jar:4.1.72.Final]
    at io.netty.buffer.PoolArena.allocate(PoolArena.java:126) ~[netty-buffer-4.1.72.Final.jar:4.1.72.Final]
    at io.netty.buffer.PooledByteBufAllocator.newDirectBuffer(PooledByteBufAllocator.java:395) ~[netty-buffer-4.1.72.Final.jar:4.1.72.Final]
    at io.netty.buffer.AbstractByteBufAllocator.directBuffer(AbstractByteBufAllocator.java:188) ~[netty-buffer-4.1.72.Final.jar:4.1.72.Final]
    at io.netty.buffer.AbstractByteBufAllocator.directBuffer(AbstractByteBufAllocator.java:179) ~[netty-buffer-4.1.72.Final.jar:4.1.72.Final]
    at io.netty.buffer.AbstractByteBufAllocator.buffer(AbstractByteBufAllocator.java:116) ~[netty-buffer-4.1.72.Final.jar:4.1.72.Final]
    ...

原因分析

当前引入的依赖pom.xml

<!-- redis 缓存操作 -->
 <dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-data-redis</artifactId>
 </dependency>

Springboot2.x以后弃用jedis改为使用lettuce作为操作redis数据库的客户端，而Lettuce使用的 netty 框架，引用的netty包netty-common-4.1.49.Final.jar里PlatformDependent.java类 中的incrementMemoryCounter方法。该方法判断堆外内存是否大于当前服务可使用的内存，是则抛出throw new OutOfDirectMemoryError。因此该问题的发生是Spring对Lettuce的支持不够好，还存在问题。

 private static void incrementMemoryCounter(int capacity) {
        if (DIRECT_MEMORY_COUNTER != null) {
            long newUsedMemory = DIRECT_MEMORY_COUNTER.addAndGet(capacity);
            //校验堆外内存是否大于当前服务可使用的内存，如果大于则抛出 OutOfDirectMemoryError（堆外内存溢出）
            if (newUsedMemory > DIRECT_MEMORY_LIMIT) {
                DIRECT_MEMORY_COUNTER.addAndGet(-capacity);
                throw new OutOfDirectMemoryError("failed to allocate " + capacity
                        + " byte(s) of direct memory (used: " + (newUsedMemory - capacity)
                        + ", max: " + DIRECT_MEMORY_LIMIT + ')');
            }
        }
    }

解决方案

1. 调大堆外内存 -Dio.netty.maxDirectMemory，但是治标不治本
2. 放弃Lettuce客户端，改回Jedis客户客户端

<!--引入redis,排除lettuce的引用-->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
    <exclusions> 
        <exclusion>
            <groupId>io.lettuce</groupId>
            <artifactId>lettuce-core</artifactId>
        </exclusion>
    </exclusions>
</dependency>

<!-- 引入Jedis客戶端-->
<dependency>
    <groupId>redis.clients</groupId>
    <artifactId>jedis</artifactId>
</dependency>