Interview questions 30-day check-in-day08

1. How do you backup MySQL data? For example, how to restore the data half a month ago?

Physical backup: back up data files and save the physical files of the database to a directory. MySQL can use the xtrabackup tool for physical backups. takes up a lot of space

Logical backup: MySQL can use mysqlddump for logical backup, mainly to back up a SQL statement, and execute this SQL statement when it needs to be restored. Logical backups can be restored quickly, occupy less space, and are more flexible.

MySQL data backup is a very important job to ensure data security and reliability. There are many ways to back up data, the following is one of the basic backup and restore methods:

1. Back up the MySQL database

We can use the mysqldump tool to back up the MySQL database, which can generate SQL script files that contain statements of all tables and data in the database. Run the following command in a terminal:

mysqldump -u [username] -p [database_name] > [backup_file].sql

Among them, [username] is the MySQL user name, [database_name] is the name of the database to be backed up, and [backup_file].sql is the name of the backup file.

This command will export the SQL script file to the current directory.

Second, restore the MySQL database

If you need to restore the previously backed up data, you can run the following command:

mysql -u [username] -p [database_name] < [backup_file].sql

Among them, [username] is the MySQL user name, [database_name] is the name of the database to be restored, and [backup_file].sql is the name of the backup file.

This command will execute the SQL statements in the backup file to restore the data to the specified database.

If you need to restore the data half a month ago, you can choose the data in the backup file before a certain point in time, and use the above method to restore.

In addition, there are other backup methods, such as using the mysqlbinlog tool that comes with MySQL for incremental backup, or using third-party backup software for backup. Choose an appropriate backup method according to actual needs, and store the backup files in a reliable location.

2. What is a message queue? What are the application scenarios for message queues?

Message Queue (MQ for short) is a communication method between applications, mainly used for asynchronous processing and decoupling. It is a middleware that provides an asynchronous messaging service for passing messages between different applications or different systems.
Common components of message queues:

1. Producer: The producer of the message, which sends the message to the queue.
2. Consumer: The consumer of the message, receives and processes the message from the queue.
3. Message: The entity of the message, including the data and metadata to be delivered.
4. Queue: Message queue for storing messages.
5. Broker: The middleware of the message queue, which is used to manage the delivery of queues and messages.

Message queue application scenarios:

1. Asynchronous processing: Time-consuming operations are processed asynchronously to improve system throughput and response speed.
2. Decoupling: Decoupling the dependencies between applications to improve system maintainability and scalability.
3. Shaving peaks and filling valleys: Buffer requests through message queues to prevent the system from being overwhelmed by a large number of requests in an instant.
4. Flow control: Control the number of concurrent requests through message queues to prevent excessive consumption of system resources.
5. Log collection: Collect distributed system logs into a centralized message queue for centralized management and analysis.
6. Off-site disaster recovery: Deploy message queues in different geographical locations to achieve off-site disaster recovery and disaster recovery.

Message queue is an important middleware technology, which can realize asynchronous communication and decoupling in distributed systems, and improve the reliability and scalability of the system.

3. What is a design pattern? Why learn and use design patterns?

Design pattern: It refers to a code design experience that is used repeatedly in software design, and some of the best experiences obtained through practice and summary. The purpose of using design patterns is to reusable code, improve code scalability and maintainability ; the benefits of learning and using design patterns:

1. Improve code quality: Design patterns are best practices that have been proven through a lot of practice. Using them can avoid some common mistakes and pitfalls, thereby improving the quality of the code.
2. Improves code maintainability: Design patterns provide a structured way to organize code, making it easier to understand and maintain. At the same time, using design patterns can make the code more flexible and extensible.
3. Promote teamwork: Design patterns provide a common language and way of thinking, which can promote teamwork and communication, and improve team collaboration efficiency.
4. Improve programming ability: Learning and using design patterns can enable developers to master more programming skills and experience, and improve programming ability and level.

Design patterns are tools that help improve code quality and development productivity.