Shulou(Shulou.com)05/31 Report--

Today, I will talk to you about the principle of database connection pooling technology, which may not be well understood by many people. in order to make you understand better, the editor has summarized the following contents for you. I hope you can gain something according to this article.

The disadvantage of the application getting the database connection directly

Users need to get a link from the database for each request, while the database usually consumes a relatively large amount of resources and takes a long time to create a connection. Assuming that the website has 100000 visits a day, the database server needs to create 100000 connections, which is a great waste of database resources, and can easily cause memory overflow and extension of the database server.

The basic concept of database connection pool

The so-called database connection pooling technology is used to allocate, manage and release database connections. You may ask, it seems that I can also implement these functions directly with JDBC.

Well, you're right, JDBC does work, but do you remember that when we use JDBC technology, do we close the connection every time we run out of it, and do we have to reopen the database connection when we use it next time?

In fact, database link resources are very valuable, we can not see it in small projects, in high concurrent projects, you will find that opening and closing database links so frequently is a kind of destruction to the server. very bad for efficiency.

So how does database connection pooling work?

The idea of implementation is as follows: every time there is access, the database connection pool will assign a database connection to the user. When the user runs out of the connection, the connection pool will reclaim the connection and put it back into a connection set.

That's how it works. Let's take a look at this picture to make an impression:

In this way, you may still not be clear, and the things to consider in database connection pooling are more complicated than above.

Action

Database connection pooling is responsible for allocating, managing, and releasing database connections, allowing applications to reuse an existing database connection rather than re-establish another one; release database connections that are idle for longer than the maximum idle time to avoid missing database connections because the database connection is not released. This technology can significantly improve the performance of database operations.

Influencing factors

The database connection pool will create a certain number of database connections into the connection pool during initialization, and the number of these database connections is set by the minimum number of database connections. Regardless of whether these database connections are used or not, connection pooling will always guarantee at least so many connections. The maximum number of database connections in the connection pool limits the maximum number of connections that can be occupied by the connection pool. when the number of connections requested by the application from the connection pool exceeds the maximum number of connections, these requests will be added to the waiting queue.

The setting of the minimum and maximum connections for the database connection pool should take into account the following factors:

Minimum number of connections: a database connection that is always maintained by the connection pool, so if the application does not use a lot of database connections, a lot of database connection resources will be wasted.

Maximum number of connections: the maximum number of connections that can be requested by the connection pool. if the number of database connection requests exceeds the number of times, the subsequent database connection requests will be added to the waiting queue, which will affect future database operations.

If there is a big difference between the minimum number of connections and the maximum number of connections: then the first connection request will benefit, and then a connection request exceeding the minimum number of connections is equivalent to establishing a new database connection. However, these database connections that are greater than the minimum number of connections will not be released immediately after use, but will be placed in the connection pool waiting for reuse or space timeout.

Principle

The basic idea of connection pool is to store the database connection as an object in memory when the system is initialized, and when the user needs to access the database, it is not to establish a new connection, but to extract an established idle connection object from the connection pool. After use, instead of closing the connection, the user puts the connection back into the connection pool for the next request for access. The establishment and disconnection of connections are managed by the connection pool itself. At the same time, you can also set the parameters of the connection pool to control the initial number of connections in the connection pool, the upper and lower limits of connections, the maximum number of times to use each connection, the maximum idle time, and so on. You can also monitor the number and usage of database connections through its own management mechanism.

After reading the above, do you have any further understanding of the principle of database connection pooling technology? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.