What does the number of mysql connections mean?

The number of mysql connections refers to the maximum number of customer connections that the database can accept at the same time. The number of MySQL connections is a component that must be considered. It can help the database run safely while maximizing the current performance of the database. The number of MySQL connections is an important configuration that can affect the client transmission and processing in the database. The amount of data. If the number of connections is too small, the connection request may be blocked and timeout may occur; if the number of connections is too large, a large amount of memory will be occupied, resulting in low performance.

The operating environment of this tutorial: windows7 system, mysql8 version, Dell G3 computer.

MySQL connection number introduction

The number of database connections is the maximum number of customer connections that the database can accept at the same time.

The number of MySQL connections is a component that must be considered. It can help the database run safely while maximizing the current performance of the database. It is used to control which clients can connect to the database, also known as "Maximum Connection".

The number of MySQL connections is an important configuration that can affect the amount of data transferred and processed by the client in the database. If the number of MySQL connections is too small, the connection request may be blocked and timeout may occur; if the number of MySQL connections is too large, a large amount of memory will be occupied, resulting in low performance. Therefore, the number of MySQL connections must be set reasonably.

The number of MySQL connections can be adjusted through the MySQL configuration file my.cnf, or dynamically adjusted using the following MySQL commands:

SET GLOBAL max_connections=300;

The above command can set the maximum number of MySQL connections to 300. You can also set this parameter in the corresponding my.cnf file:

max_connections=300

The number of MySQL connections can be checked with the following MySQL command:

SHOW STATUS LIKE 'Max_used_connections';
+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Max_used_connections    | 123   |
+-------------------------+-------+

The above value 123 indicates the maximum number of simultaneous connections on the VW system There are 123 connections to MySQL. It also helps to evaluate whether the current maximum number of connections in the system is reasonable:

• If the value is high, it indicates that the system may have a large number of clients accessing MySQL at the same time. At this time, it is best to consider adjusting MySQL The maximum number of connections;

• If the value is small, it indicates that the available resources of the system cannot be fully utilized. At this time, you can consider increasing the maximum number of MySQL connections.

In general, the number of MySQL connections is a component that must be considered, and it has an important impact on system security and performance. Therefore, it needs to be adjusted appropriately to maximize MySQL performance.

How to check the number of connections in Mysql (total number of connections, active number, maximum number of concurrent connections)

show variables like '%max_connection%'; 查看最大连接数
set global max_connections=1000;        重新设置最大连接数

mysql> show status like  'Threads%';
+-------------------+-------+
| Variable_name     | Value |
+-------------------+-------+
| Threads_cached    | 32    |
| Threads_connected | 10    |
| Threads_created   | 50    |
| Threads_rejected  | 0     |
| Threads_running   | 1     |
+-------------------+-------+
5 rows in set (0.00 sec)

• Threads_connected: This The value refers to the number of open connections.

• Threads_running: This value refers to the number of activated connections. This value is generally much lower than the connected value.

• Threads_connected has the same result as show processlist, indicating the current number of connections. To be precise, Threads_running represents the current number of concurrency

query the maximum number of connections currently set in the database

mysql> show variables like '%max_connection%';
+-----------------------+-------+
| Variable_name         | Value |
+-----------------------+-------+
| extra_max_connections |       |
| max_connections       | 2512  |
+-----------------------+-------+
2 rows in set (0.00 sec)

in/etc/my. Set the maximum number of database connections in cnf

[mysqld]
max_connections = 100

mysql> show global status like 'Thread%';
+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Threadpool_idle_threads | 0     |
| Threadpool_threads      | 0     |
| Threads_cached          | 29    |
| Threads_connected       | 13    |
| Threads_created         | 50    |
| Threads_rejected        | 0     |
| Threads_running         | 1     |
+-------------------------+-------+
7 rows in set (0.00 sec)

mysql> show variables like 'thread_cache_size';
+-------------------+-------+
| Variable_name     | Value |
+-------------------+-------+
| thread_cache_size | 100   |
+-------------------+-------+
1 row in set (0.00 sec)

mysql> show processlist;

mysql>show status like '%变量名%';