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标题: 从Redis连接池获取连接失败的原因说起（4） [打印本页]

作者: look_w 时间: 2019-2-20 19:03 标题: 从Redis连接池获取连接失败的原因说起（4）

下图也进行了验证。第一次注释掉disconnect中关闭socket的代码，程序sleep10秒后退出，可以看到直到进程退出时，客户端的连接才被关闭。而第二次是恢复注释掉的代码，客户端在quit后马上就关闭了连接释放了资源。

redis连接开启和关闭时的系统调用

这个问题困扰了我一天，到底怎么产生的RST包？不管是客户端还是服务端，调用close后，都应该进行正常的四次握手吧？
我反复看了redis服务端关闭客户端连接的源码(redis 3.2.9 networking.c#unlinkClient)。也只是调用了系统调用close(fd)，甚至为了避免干扰还新建了一个redis实例，使用strace -f -p $pid -tt -T跟踪关闭附近的系统调用

[pid 25442] 10:29:42.299132 epoll_wait(3, {{EPOLLIN, {u32=4, u64=4}}}, 11024, 100) = 1 <0.004041>
[pid 25442] 10:29:42.303248 accept(4, {sa_family=AF_INET, sin_port=htons(52294), sin_addr=inet_addr("192.168.3.45")}, [16]) = 5 <0.000025>
[pid 25442] 10:29:42.303356 fcntl(5, F_GETFL) = 0x2 (flags O_RDWR) <0.000014>
[pid 25442] 10:29:42.303417 fcntl(5, F_SETFL, O_RDWR|O_NONBLOCK) = 0 <0.000010>
[pid 25442] 10:29:42.303456 setsockopt(5, SOL_TCP, TCP_NODELAY, [1], 4) = 0 <0.000012>
[pid 25442] 10:29:42.303499 epoll_ctl(3, EPOLL_CTL_ADD, 5, {EPOLLIN, {u32=5, u64=5}}) = 0 <0.000011>
[pid 25442] 10:29:42.303544 epoll_wait(3, {{EPOLLIN, {u32=5, u64=5}}}, 11024, 96) = 1 <0.073370>
[pid 25442] 10:29:42.376968 read(5, "*3\r\n$3\r\nSET\r\n$3\r\nfoo\r\n$3\r\nbar\r\n", 16384) = 31 <0.000014>
[pid 25442] 10:29:42.377071 epoll_ctl(3, EPOLL_CTL_MOD, 5, {EPOLLIN|EPOLLOUT, {u32=5, u64=5}}) = 0 <0.000013>
[pid 25442] 10:29:42.377144 epoll_wait(3, {{EPOLLOUT, {u32=5, u64=5}}}, 11024, 22) = 1 <0.000017>
[pid 25442] 10:29:42.377210 write(5, "+OK\r\n", 5) = 5 <0.000034>
[pid 25442] 10:29:42.377304 epoll_ctl(3, EPOLL_CTL_MOD, 5, {EPOLLIN, {u32=5, u64=5}}) = 0 <0.000025>
[pid 25442] 10:29:42.377377 epoll_wait(3, {{EPOLLIN, {u32=5, u64=5}}}, 11024, 22) = 1 <0.007943>
[pid 25442] 10:29:42.385376 read(5, "*2\r\n$3\r\nGET\r\n$3\r\nfoo\r\n", 16384) = 22 <0.000013>
[pid 25442] 10:29:42.385432 epoll_ctl(3, EPOLL_CTL_MOD, 5, {EPOLLIN|EPOLLOUT, {u32=5, u64=5}}) = 0 <0.000011>
[pid 25442] 10:29:42.385477 epoll_wait(3, {{EPOLLOUT, {u32=5, u64=5}}}, 11024, 14) = 1 <0.000010>
[pid 25442] 10:29:42.385518 write(5, "$3\r\nbar\r\n", 9) = 9 <0.000019>
[pid 25442] 10:29:42.385567 epoll_ctl(3, EPOLL_CTL_MOD, 5, {EPOLLIN, {u32=5, u64=5}}) = 0 <0.000011>
[pid 25442] 10:29:42.385617 epoll_wait(3, {}, 11024, 14) = 0 <0.014075>
[pid 25442] 10:29:42.399742 epoll_wait(3, {}, 11024, 100) = 0 <0.100126>
[pid 25442] 10:29:42.499930 epoll_wait(3, {}, 11024, 100) = 0 <0.100126>
[pid 25442] 10:29:42.600115 epoll_wait(3, {}, 11024, 100) = 0 <0.100071>
[pid 25442] 10:29:42.700276 epoll_wait(3, {}, 11024, 100) = 0 <0.100131>
[pid 25442] 10:29:42.800482 epoll_wait(3, {}, 11024, 100) = 0 <0.100129>
[pid 25442] 10:29:42.900687 epoll_wait(3, {}, 11024, 100) = 0 <0.100141>
[pid 25442] 10:29:43.000895 epoll_wait(3, {}, 11024, 100) = 0 <0.100132>
[pid 25442] 10:29:43.101095 epoll_wait(3, {}, 11024, 100) = 0 <0.100131>
[pid 25442] 10:29:43.201305 epoll_wait(3, {}, 11024, 100) = 0 <0.100134>
[pid 25442] 10:29:43.301521 epoll_wait(3, {}, 11024, 100) = 0 <0.100136>
[pid 25442] 10:29:43.401725 epoll_wait(3, {{EPOLLIN, {u32=5, u64=5}}}, 11024, 100) = 1 <0.003552>
[pid 25442] 10:29:43.405350 read(5, "*2\r\n$3\r\nGET\r\n$3\r\nfoo\r\n", 16384) = 22 <0.000016>
[pid 25442] 10:29:43.405425 epoll_ctl(3, EPOLL_CTL_MOD, 5, {EPOLLIN|EPOLLOUT, {u32=5, u64=5}}) = 0 <0.000011>
[pid 25442] 10:29:43.405477 epoll_wait(3, {{EPOLLOUT, {u32=5, u64=5}}}, 11024, 96) = 1 <0.000014>
[pid 25442] 10:29:43.405531 write(5, "$3\r\nbar\r\n", 9) = 9 <0.000022>
[pid 25442] 10:29:43.405601 epoll_ctl(3, EPOLL_CTL_MOD, 5, {EPOLLIN, {u32=5, u64=5}}) = 0 <0.000011>
[pid 25442] 10:29:43.405660 epoll_wait(3, {}, 11024, 96) = 0 <0.096129>
[pid 25442] 10:29:43.501877 epoll_wait(3, {{EPOLLIN, {u32=5, u64=5}}}, 11024, 100) = 1 <0.003474>
[pid 25442] 10:29:43.505429 read(5, "*1\r\n$4\r\nQUIT\r\n", 16384) = 14 <0.000018>
[pid 25442] 10:29:43.505514 epoll_ctl(3, EPOLL_CTL_MOD, 5, {EPOLLIN|EPOLLOUT, {u32=5, u64=5}}) = 0 <0.000015>
[pid 25442] 10:29:43.505578 epoll_wait(3, {{EPOLLOUT, {u32=5, u64=5}}}, 11024, 96) = 1 <0.000012>
[pid 25442] 10:29:43.505623 write(5, "+OK\r\n", 5) = 5 <0.000028>
[pid 25442] 10:29:43.505693 epoll_ctl(3, EPOLL_CTL_MOD, 5, {EPOLLIN, {u32=5, u64=5}}) = 0 <0.000016>
[pid 25442] 10:29:43.505764 epoll_ctl(3, EPOLL_CTL_DEL, 5, {0, {u32=5, u64=5}}) = 0 <0.000016>
[pid 25442] 10:29:43.505830 close(5) = 0 <0.000111>
[pid 25442] 10:29:43.505992 epoll_wait(3, {}, 11024, 96) = 0 <0.096134>

java客户端junit测试代码(根据jedis测试用例JedisPoolTest#checkConnections修改)：

      JedisPool pool = new JedisPool(new JedisPoolConfig(), hnp.getHost(), hnp.getPort(), 2000);
      Jedis jedis = pool.getResource();
      jedis.set("foo", "bar");
      assertEquals("bar", jedis.get("foo"));
      pool.returnResource(jedis);

      try {
      Thread.sleep(1*1000);
      } catch (InterruptedException e) {
      e.printStackTrace();
      }
      System.out.println("hello");
      jedis.get("foo");
      pool.destroy();
      assertTrue(pool.isClosed());

观察服务端系统调用，

setsockopt(5, SOL_TCP, TCP_NODELAY, [1], 4) = 0
...
close(5) = 0

在socket连接时只设置了TCP_NODELAY，禁用了Nagle算法。

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