Page 95-Redis Programming Tutorials: Learn Redis Online-php.cn

Article Tags

Redis

Home

Technical articles

Database

Redis

How to configure multiple databases in Redis

Preface Redis has databases 0-16 by default. Generally, when we operate redis, we use database 0. However, sometimes our projects want to operate multiple databases at the same time, and we do not want to choose to switch databases every time we access other database data. This is too Cumbersome. Therefore, we need to configure multiple JedisClients, but Jedis are prone to blocking and are not very efficient, so I use LettuceClient, which is a Reactive connection method and is relatively efficient. But how to use LettuceClient? In fact, generally we add spring-boot-starter-data-redis dependency through RedisTemp

May 28, 2023 pm 03:49 PM

数据库redis

How to get all keys in redis

Keys: Full traverse keys, used to list all keys that meet specific regular string rules. Assuming that redis is in a production environment at this time, using this command will cause hidden dangers. When the amount of redis data is relatively large: keys will be returned at once All keys that meet the conditions will cause redis to freeze. SCAN is a cursor-based iterator that needs to continue the previous iteration process based on the last cursor. SCAN starts a new iteration with 0 as the cursor until the command returns cursor 0 to complete a traversal. This command does not guarantee that each execution will return a given number of elements, or even 0 elements. However, as long as the cursor is not 0, the program will not consider the SCAN command to have ended, but the number of elements returned

May 28, 2023 pm 03:40 PM

rediskey

How to use Redis slow query log

Slow Query Log What is SLOWLOG? Slowlog is a logging system used by Redis to record command requests whose query execution time exceeds a given time. Query execution time refers to the time spent executing a query command, excluding IO operations such as client response (talking) and sending replies. In addition, slowlog is stored in memory, and the read and write speed is very fast, so you can use it with confidence and don't have to worry about damaging the speed of Redis by turning on slowlog. Setting up and viewing the SLOWLOG server configuration has two options related to slow query logs: slowlog-log-slower-than: The option specifies how many microseconds the execution time exceeds (1

May 28, 2023 pm 03:37 PM

redis

How to install redis in docker mode on centos

1.安装dockersudoyumremovedockerdocker-clientdocker-client-latestdocker-commondocker-latestdocker-latest-logrotatedocker-logrotatedocker-enginesudoyuminstall-yyum-utilssudoyuminstall-yyum-utilssudoyum-config-manager--add-repohttps://download.docker.com/

May 28, 2023 pm 03:34 PM

DockerredisCentOS

How to use python to crawl CSDN popular comment URLs and store them in redis

1. Configure webdriver to download the Google Chrome driver, and configure importtimeimportrandomfromPILimportImagefromseleniumimportwebdriverfromselenium.webdriver.common.byimportByfromselenium.webdriver.support.uiimportWebDriverWaitfromselenium.webdriver.supportimportexpected_conditio

May 28, 2023 pm 03:17 PM

PythonredisURL

What are the redis expiration strategies?

All data structures in Redis can set expiration time, and they will be automatically deleted when the time is up. You can imagine that there is a god of death inside Redis, always watching all the keys with expiration time set, and harvesting them as soon as their lifespan is reached. You can also think about it from the perspective of Death, whether too many keys expire at the same time, so that you are too busy. At the same time, because Redis is single-threaded, the harvesting time will also occupy the processing time of the thread. If the harvesting is too busy, it will cause lags in online read and write instructions. Expired key collection redis will put each key with an expiration time set into an independent dictionary. This dictionary will be traversed regularly to delete expired keys. In addition to scheduled traversal

May 28, 2023 pm 03:17 PM

redis

How to implement Redis connection and authentication in php

Redis connection and authentication //Connection parameters: ip, port, connection timeout, return true if the connection is successful, otherwise return false$ret=$redis->connect('127.0.0.1',6379,30);//Password authentication: Returns true successfully, otherwise returns false$ret=$redis->auth('123456');

May 28, 2023 pm 03:07 PM

PHPredis

How to implement code scanning login in redis

Requirements introduction First, let’s introduce what scanning QR code login is. Now, most students have QQ, Taobao, Tmall and other software installed on their mobile phones. The companies that develop these apps have their corresponding websites. In order to make login more convenient and secure for users when using their website. These companies provide services that allow you to log in using your mobile phone and scanning. The effect when logging in to the web page is as follows: Many friends may find it strange that only a QR code is displayed on the web page. How does it know which mobile phone scanned the QR code and logged in? Moreover, after the login is completed, the user information can be directly displayed to the user, which is really amazing. Principle explanation web page + server The next step is the detailed implementation of this service. head

May 28, 2023 pm 02:58 PM

redis

How to solve the Redis coupon flash sale problem

1 When placing an order to implement the coupon flash sale function, two points need to be judged: 1. Whether the flash sale has started or ended 2. Whether the inventory is sufficient. Therefore, our business logic is as follows 1. Obtain coupon information through the coupon ID 2. Determine whether the flash sale has started. If no error message is returned 3. Determine whether the flash sale is over. If it has ended, return an error message 4. If it is within the flash sale time, determine whether the inventory is sufficient 5. If sufficient, deduct the inventory 6. Create order information and save it to the coupon order In the table 6.1 Save the order id 6.2 Save the user id 6.3 Save the coupon id 7. Return the order id code implementation: (Service layer implementation class) packagecom.hmdp.service.impl;import

May 28, 2023 pm 02:52 PM

redis

How to implement Redis Set operation in php

Set operation //Add an element to the set, and ignore elements that already exist in the set. If the collection does not exist, it will be created first. If the key is not a collection type, it will return false. If the element already exists, it will return 0. If the insertion is successful, it will return 1. $ret=$redis->sAdd('myset','hello');//Return all members in the set. $ret=$redis->sMembers('myset');//Judge whether the specified element is a member of the specified set, return true, otherwise return false. $r

May 28, 2023 pm 02:04 PM

PHPredisset

How to implement task scheduling based on Redis distributed lock

In the process of distributed large-scale data collection, the management of information sources is particularly important. In order to ensure that the same task can only be processed by one collector at the same time, the uniqueness of task scheduling must be ensured. Usually when we carry out distributed data collection, there will usually be a scheduling module, whose main responsibility is to distribute the collection tasks and ensure the uniqueness of the tasks. Because it is distributed, it involves multiple servers (multiple machines), each server involves multiple collectors (multiple processes), and each collector may involve multiple threads. Therefore, the lock in the task scheduling module Mechanism is particularly important. Generally speaking, the lock implementation method may have the following types according to the application implementation architecture: If the handler is single-process and multi-threaded, in p

May 28, 2023 pm 01:37 PM

redis

What is the difference between redis and memcached in PHP

1. Supported data types: memcached only supports key-value types, redis also supports list, set, hash, that is, redis supports more abundant data types 2. Storage data security: after memcached hangs up, the data cannot be recovered, redis supports data For persistence, the data in the memory can be saved to the disk, and can be loaded again for use when restarting. The main difference: redis supports persistence. What are the PHP frameworks: 1. Laravel, Laravel is a free and open source PHP application framework. 2. Phalcon, Phalcon is the fastest PHP framework. 3.Sym

May 28, 2023 pm 01:22 PM

PHPredismemcached

How to solve the problem that Redis bigkeys command will block

1. A senior development engineer of SF Express executed a dangerous Redis command online, causing a company to lose 4 million and millions for one command. Does this require compensation? The code is not standardized and my colleagues burst into tears. Please be careful when coding! Out of curiosity, let me test it out. What is the problem? 2. Test the performance of 10 million data 1. Write a script file to write 10 million data. for((i=1;i>/tmp/test1.txt;done; Check whether the writing is successful through /tmp/test1.txt. 2. Write 10 million data to Redis cat/tmp/test1.txt|redis-cli -a111111--pipe3, pass

May 28, 2023 pm 01:22 PM

redis

What is the source code related to Redis SDS?

The source code related to sds in Redis is in src/sds.c and src/sds.h. sds.h defines all SDS APIs. Of course, it also implements some APIs, such as sds length and sds remaining available space. ..., don’t rush to read the code, let’s take a look at the data structure of sds first. After reading it, you will understand at a glance why the code is written like that. The sdshdr data structure redis provides the implementation of several sds such as sdshdr5sdshdr8sdshdr16sdshdr32sdshdr64. Except for sdshdr5, which is special, the difference between the other sdshdr is not only the type difference between the two fields. I'll take sdshdr8 and

May 28, 2023 pm 01:10 PM

redissds