我的 MariaDB 服务器在 600 秒(10 分钟)不活动后使我的 C++ 客户端(使用 libmariadb)超时,我不确定为什么,因为我找不到任何指定该数字的已配置超时。
这是我的代码,我在其中执行一个简单的 SELECT 查询,等待 11 分钟,然后再次运行相同的查询并收到“服务器消失”错误:
#include <iostream>
#include <unistd.h>
#include <errmsg.h>
#include <mysql.h>
int main(int, char**)
{
// connect to the database
MYSQL* connection = mysql_init(NULL);
my_bool reconnect = 0;
mysql_options(connection, MYSQL_OPT_RECONNECT, &reconnect); // don't implicitly reconnect
mysql_real_connect(connection, "127.0.0.1", "testuser", "password",
"my_test_db", 3306, NULL, 0);
// run a simple query
mysql_query(connection, "select 5");
mysql_free_result(mysql_store_result(connection));
std::cout << "First query done...\n";
// sleep for 11 minutes
sleep(660);
// run the query again
if(! mysql_query(connection, "select 5"))
{
std::cout << "Second query succeeded after " << seconds << " seconds\n";
mysql_free_result(mysql_store_result(connection));
}
else
{
if(mysql_errno(connection) == CR_SERVER_GONE_ERROR)
{
// **** this happens every time ****
std::cout << "Server went away after " << seconds << " seconds\n";
}
}
// close the connection
mysql_close(connection);
connection = nullptr;
return 0;
}
服务器进程的标准输出报告我的连接超时:
$ sudo journalctl -u mariadb
...
Jul 24 17:58:31 myhost mysqld[407]: 2018-07-24 17:58:31 139667452651264 [Warning] Aborted connection 222 to db: 'my_test_db' user: 'testuser' host: 'localhost' (Got timeout reading communication packets)
...
查看 tcpdump 捕获,我还可以看到服务器向客户端发送 TCP FIN 数据包,从而关闭连接。
我感到困惑的原因是因为我没有更改任何默认超时值,none其中甚至有 600 秒:
MariaDB [(none)]> show variables like '%timeout%';
+-------------------------------------+----------+
| Variable_name | Value |
+-------------------------------------+----------+
| connect_timeout | 10 |
| deadlock_timeout_long | 50000000 |
| deadlock_timeout_short | 10000 |
| delayed_insert_timeout | 300 |
| innodb_flush_log_at_timeout | 1 |
| innodb_lock_wait_timeout | 50 |
| innodb_print_lock_wait_timeout_info | OFF |
| innodb_rollback_on_timeout | OFF |
| interactive_timeout | 28800 |
| lock_wait_timeout | 31536000 |
| net_read_timeout | 30 |
| net_write_timeout | 60 |
| slave_net_timeout | 3600 |
| thread_pool_idle_timeout | 60 |
| wait_timeout | 28800 |
+-------------------------------------+----------+
那么为什么服务器会导致我的连接超时呢?根据文档,我原以为这是因为wait_timeout
服务器变量,但默认为 8 小时...
顺便说一句,我正在使用 MariaDB 10.0 和 libmariadb 2.0(来自 Ubuntu Xenial Universe 存储库)
Edit: here's an image of a tcpdump capture catching the disconnect. My Wireshark filter is tcp.port == 55916
, so I'm looking at traffic to/from this one client connection. The FIN packet that the server sends is packet 1199, exactly 600 seconds after the previous packet (884).