Redis连接超时异常的处理方法
0、问题描述
使用Jedis连接redis进行数据查询操作,正常的代码运行没有问题,但是时不时会报出如下错误:
Exception in thread "main" 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.read(RedisInputStream.java:181)
at redis.clients.jedis.Protocol.processBulkReply(Protocol.java:181)
at redis.clients.jedis.Protocol.process(Protocol.java:155)
at redis.clients.jedis.Protocol.processMultiBulkReply(Protocol.java:206)
at redis.clients.jedis.Protocol.process(Protocol.java:157)
at redis.clients.jedis.Protocol.processMultiBulkReply(Protocol.java:206)
at redis.clients.jedis.Protocol.process(Protocol.java:157)
at redis.clients.jedis.Protocol.read(Protocol.java:215)
at redis.clients.jedis.Connection.readProtocolWithCheckingBroken(Connection.java:340)
at redis.clients.jedis.Connection.getRawObjectMultiBulkReply(Connection.java:285)
at redis.clients.jedis.Connection.getObjectMultiBulkReply(Connection.java:291)
at redis.clients.jedis.BinaryJedis.hscan(BinaryJedis.java:3390)
at com.ict.mcg.filter.DuplicateClueFilterV2.hscan(DuplicateClueFilterV2.java:867)
at com.ict.mcg.filter.DuplicateClueFilterV2.collectRecentCluekeywords(DuplicateClueFilterV2.java:487)
at com.ict.mcg.main.GetCluesMain.run_online(GetCluesMain.java:208)
at com.ict.mcg.main.GetCluesMain.main(GetCluesMain.java:1685)
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:171)
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)
... 16 more
究其原因,可以定位为java.net.SocketTimeoutException: Read timed out,即网络连接异常;
1、 可能的原因
1.1 服务器资源包括内存、磁盘、cpu等利用率高
经过查看redis部署机器的状态信息,发现整体机器运行状态良好
1.2 服务器设置防火墙,导致连接失败
因为正常的代码流程都可以跑通,所以防火墙设置没有问题;
1.3 redis配置文件bind监听host配置不当
redis的配置文件中bind对应host的配置如下:
# By default Redis listens for connections from all the network interfaces # available on the server. It is possible to listen to just one or multiple # interfaces using the "bind" configuration directive, followed by one or # more IP addresses. # # Examples: # # bind 192.168.1.100 10.0.0.1 # bind 127.0.0.1
默认的bind绑定的host为0.0.0.0,即可以监听每一个可用的网络接口;相当于配置为:
bind 0.0.0.0
我们的配置文件也配置正常,而且正常的代码流程运行正常,也可以佐证这一点;
1.4 Jedis使用配置问题
目前Jedis的连接池配置如下:
private static JedisPool getPool() { if (pool == null) { JedisPoolConfig config = new JedisPoolConfig(); //控制一个pool可分配多少个jedis实例,通过pool.getResource()来获取; //如果赋值为-1,则表示不限制;如果pool已经分配了maxActive个jedis实例,则此时pool的状态为exhausted(耗尽)。 config.setMaxActive(10); //控制一个pool最多有多少个状态为idle(空闲的)的jedis实例。 config.setMaxIdle(2); //表示当borrow(引入)一个jedis实例时,最大的等待时间,如果超过等待时间,则直接抛出JedisConnectionException; config.setMaxWait(1000 * 200000); //在borrow一个jedis实例时,是否提前进行validate操作;如果为true,则得到的jedis实例均是可用的; config.setTestOnBorrow(true); config.setTestOnReturn(true); //目前redis只有一个服务器 pool = new JedisPool(config, "localhost", 6379); } return pool; } private static Jedis getJedis() { Jedis jedis = null; int count = 0; do { try { pool = getPool(); jedis = pool.getResource(); } catch(Exception e) { // System.out.println(e.getMessage()); e.printStackTrace(); pool.returnBrokenResource(jedis); } count++; } while (jedis==null && count < 3); return jedis; }
构建JedisPool的逻辑中,只是设置了config.setMaxWait(1000 * 200000);,这个是引入新的jedis实例的最大等待时间,并没有进行其他相关的连接超时的配置;于是查看JedisPool的源代码,发现如下:
public JedisPool(final Config poolConfig, final String host) { this(poolConfig, host, Protocol.DEFAULT_PORT, Protocol.DEFAULT_TIMEOUT, null, Protocol.DEFAULT_DATABASE); } public JedisPool(String host, int port) { this(new Config(), host, port, Protocol.DEFAULT_TIMEOUT, null, Protocol.DEFAULT_DATABASE); } public JedisPool(final String host) { this(host, Protocol.DEFAULT_PORT); } public JedisPool(final Config poolConfig, final String host, int port, int timeout, final String password) { this(poolConfig, host, port, timeout, password, Protocol.DEFAULT_DATABASE); } public JedisPool(final Config poolConfig, final String host, final int port) { this(poolConfig, host, port, Protocol.DEFAULT_TIMEOUT, null, Protocol.DEFAULT_DATABASE); } public JedisPool(final Config poolConfig, final String host, final int port, final int timeout) { this(poolConfig, host, port, timeout, null, Protocol.DEFAULT_DATABASE); } public JedisPool(final Config poolConfig, final String host, int port, int timeout, final String password, final int database) { super(poolConfig, new JedisFactory(host, port, timeout, password, database)); }
由上述代码可以看到,JedisPool有多个重载的构造函数,并且构造函数中需要传入一个timeout参数作为连接的超时时间,如果没有传,则采用Protocol.DEFAULT_TIMEOUT作为默认的超时时间,继续跟踪源码:
public final class Protocol { public static final int DEFAULT_PORT = 6379; public static final int DEFAULT_TIMEOUT = 2000; public static final int DEFAULT_DATABASE = 0; public static final String CHARSET = "UTF-8"; public static final byte DOLLAR_BYTE = '$'; public static final byte ASTERISK_BYTE = '*'; public static final byte PLUS_BYTE = '+'; public static final byte MINUS_BYTE = '-'; public static final byte COLON_BYTE = ':'; private Protocol() { // this prevent the class from instantiation }
可以得出结论,默认JedisPool中连接的默认超时时间为2秒,而我们调用的JedisPool构造函数,恰恰采用的是这个配置,只要两秒钟没有连接成功,redis的连接就断开,从而报错,这在数据库请求并发量比较大的时候是有可能发生的,遂做如下更改,在创建JedisPool的时候,传入一个较大的超时时间:
pool = new JedisPool(config, ParamUtil.REDIS_ADDRESS[0], ParamUtil.REDIS_PORT, 1000 * 10);
2、总结
遇到问题还是多查,多看源码,多看源码中的配置,仔细一项一项地排查问题!
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