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为什么 MySQL 允许的连接数超过了 max_connections 的限制？

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为什么 MySQL 允许的连接数超过了 max_connections 的限制？

这是我的连接统计数据。

mysql> show status like 'Conn%';
+-----------------------------------+-------+
| Variable_name                     | Value |
+-----------------------------------+-------+
| Connection_errors_accept          | 0     |
| Connection_errors_internal        | 0     |
| Connection_errors_max_connections | 0     |
| Connection_errors_peer_address    | 0     |
| Connection_errors_select          | 0     |
| Connection_errors_tcpwrap         | 0     |
| Connections                       | 274   |
+-----------------------------------+-------+


mysql> SHOW VARIABLES LIKE 'max_%';
+----------------------------+----------------------+
| Variable_name              | Value                |
+----------------------------+----------------------+
| max_allowed_packet         | 16777216             |
| max_binlog_cache_size      | 18446744073709547520 |
| max_binlog_size            | 104857600            |
| max_binlog_stmt_cache_size | 18446744073709547520 |
| max_connect_errors         | 100                  |
| max_connections            | 151                  |
| max_delayed_threads        | 20                   |
| max_digest_length          | 1024                 |
| max_error_count            | 64                   |
| max_execution_time         | 0                    |
| max_heap_table_size        | 16777216             |
| max_insert_delayed_threads | 20                   |
| max_join_size              | 18446744073709551615 |
| max_length_for_sort_data   | 1024                 |
| max_points_in_geometry     | 65536                |
| max_prepared_stmt_count    | 16382                |
| max_relay_log_size         | 0                    |
| max_seeks_for_key          | 18446744073709551615 |
| max_sort_length            | 1024                 |
| max_sp_recursion_depth     | 0                    |
| max_tmp_tables             | 32                   |
| max_user_connections       | 0                    |
| max_write_lock_count       | 18446744073709551615 |
+----------------------------+----------------------+

我想知道为什么允许的连接数超出max_connections限制？mysql 不应该拒绝更多连接吗？还是它会慢慢删除旧连接？从日志来看，后者是正确的？

tail -f /var/log/mysql/error.log
2020-12-15T07:21:59.253969Z 60 [Note] Aborted connection 60 to db: 'my_db' user: 'my_user' host: 'my_ip' (Got an error reading communication packets)
2020-12-15T07:21:59.253979Z 57 [Note] Aborted connection 57 to db: 'my_db' user: 'my_user' host: 'my_ip' (Got an error reading communication packets)
2020-12-15T07:21:59.253994Z 56 [Note] Aborted connection 56 to db: 'my_db' user: 'my_user' host: 'my_ip' (Got an error reading communication packets)
2020-12-15T07:21:59.254119Z 58 [Note] Aborted connection 58 to db: 'my_db' user: 'my_user' host: 'my_ip' (Got an error reading communication packets)
2020-12-15T07:21:59.254136Z 54 [Note] Aborted connection 54 to db: 'my_db' user: 'my_user' host: 'my_ip' (Got an error reading communication packets)
2020-12-15T07:21:59.254143Z 59 [Note] Aborted connection 59 to db: 'my_db' user: 'my_user' host: 'my_ip' (Got an error reading communication packets)
2020-12-15T07:21:59.254154Z 61 [Note] Aborted connection 61 to db: 'my_db' user: 'my_user' host: 'my_ip' (Got an error reading communication packets)
2020-12-15T07:21:59.254565Z 55 [Note] Aborted connection 55 to db: 'my_db' user: 'my_user' host: 'my_ip' (Got an error reading communication packets)
2020-12-15T07:21:59.254581Z 53 [Note] Aborted connection 53 to db: 'my_db' user: 'my_user' host: 'my_ip' (Got an error reading communication packets)
2020-12-15T07:21:59.254593Z 62 [Note] Aborted connection 62 to db: 'my_db' user: 'my_user' host: 'my_ip' (Got an error reading communication packets)

这是否意味着如果不再需要数据，关闭旧连接并不重要，因为 mysql 无论如何都会慢慢修剪这些数据？

答案1

我认为您应该查看的参数是，以了解同时处理了多少个连接最大使用连接数。

连接字段应作为自上次重启以来的连接计数器。

連接

尝试连接 MySQL 服务器的次数（无论成功与否）。

最大使用连接数

自服务器启动以来同时使用的最大连接数。

您可以参考这个SE答案和文档进一步深入。

答案2

这不是活动连接数。Connections连接尝试次数是否成功。您需要查看Threads_connected数字。您还可以使用netstatmysql 端口进行检查和过滤。

这是来自 stackoverlow 的类似帖子。

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