【Azure Redis 缓存 Azure Cache For Redis】Redis出现 java.net.SocketTimeoutException: Read timed out 异常

问题描述

在使用Azure Redis时，遇见Read Timed out异常， Redis的客户端使用的时jedis。问题发生时，执行redis部分指令出错，大部分get指令，set指令能正常执行。 但程序间段性还是出现Read Timed out错误。

Caused by: redis.clients.jedis.exceptions.JedisConnectionException: Could not get a resource from the pool
    at redis.clients.util.Pool.getResource(Pool.java:53)
    at redis.clients.jedis.JedisPool.getResource(JedisPool.java:226)
    at redis.clients.jedis.JedisPool.getResource(JedisPool.java:16)
    at io.terminus.session.redis.JedisPoolExecutor.execute(JedisPoolExecutor.java:56)
    at io.terminus.session.redis.SessionRedisSource.findSessionById(SessionRedisSource.java:61)
    ... 58 common frames omitted
Caused by: redis.clients.jedis.exceptions.JedisConnectionException: java.net.SocketTimeoutException: Read timed out
    at redis.clients.util.RedisInputStream.ensureFill(RedisInputStream.java:202)
    at redis.clients.util.RedisInputStream.readByte(RedisInputStream.java:40)
    at redis.clients.jedis.Protocol.process(Protocol.java:151)
    at redis.clients.jedis.Protocol.read(Protocol.java:215)
    at redis.clients.jedis.Connection.readProtocolWithCheckingBroken(Connection.java:340)
    at redis.clients.jedis.Connection.getStatusCodeReply(Connection.java:239)
    at redis.clients.jedis.BinaryJedis.auth(BinaryJedis.java:2139)
    at redis.clients.jedis.JedisFactory.makeObject(JedisFactory.java:108)
    at org.apache.commons.pool2.impl.GenericObjectPool.create(GenericObjectPool.java:868)
    at org.apache.commons.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:435)
    at org.apache.commons.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:363)
    at redis.clients.util.Pool.getResource(Pool.java:49)
    ... 62 common frames omitted
Caused by: java.net.SocketTimeoutException: Read timed out
    at java.net.SocketInputStream.socketRead0(Native Method)
    at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
    at java.net.SocketInputStream.read(SocketInputStream.java:170)
    at java.net.SocketInputStream.read(SocketInputStream.java:141)
    at java.net.SocketInputStream.read(SocketInputStream.java:127)
    at redis.clients.util.RedisInputStream.ensureFill(RedisInputStream.java:196)
    ... 73 common frames omitted

异常分析

从异常分析，当前客户端与Redis服务器的连接已经建立成功，但是在执行某些指令时，出现超时情况，而根据Jedis默认对JedisPool中设置的超时时间2秒作为判断标准，需要在Redis服务器中查看是否时执行某些命令时间超过了2秒。可以通过showlog指令显示出日志记录。

If you get java.net.SocketTimeoutException: Read timed out exception

Try setting own timeout value when constructing JedisPool using the following constructor:

JedisPool(GenericObjectPoolConfig poolConfig, String host, int port, int timeout)

where timeout is given as milliseconds.

Default timeout value is 2 seconds.

在Redis的日志中，查看到执行KEYS命令时，超过了2秒

解决办法

在知道异常的根源是由于执行KEYS，超过了2秒的超时时间。解决办法有两点，

• 替换KEYS命令，因为KEYS命令回全Redis键值扫描，非常消耗资源。而在Redis的官方推荐中也建议使用SCAN来替代它。

• 增加timeout时间，把默认的超时时间2秒，增加到5秒

参考文档

If you get java.net.SocketTimeoutException: Read timed out exception：https://github.com/xetorthio/jedis/wiki/FAQ#if-you-get-javanetsockettimeoutexception-read-timed-out-exception

KEYS: https://redis.io/commands/keys

SCAN: https://redis.io/commands/scan