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This blog is mainly about troubleshooting hadoop hdfs, including NameNode fault handling, cluster security mode and disk repair. If there is something bad, welcome everyone! thank! nn Fault Handling 1. Scene The NameNode process hangs and the stored data is lost. How to recover the NameNode 2. Fault simulation (1) kill -9 NameNode proce ...

01... Getting started with redis caching brief introduction background In our current project architecture, the Web server (Tomcat) and database are basically deployed independently and monopolize the server resources. With the growth of the number of users, concurrent reading and writing to the database will increase the pressure on dat ...

catalogue 1, Foreword 1. Introduction to moosefs 2. Characteristics of moosefs (1) Tomographic structure (directory tree) (2) Store file properties (permissions, access, and modification time) (3) Support special files (block device, character device, pipeline) (4) Symbolic link (5) Access to the file system can be restricted by IP addr ...

RabbitMQ practical tutorial In this paper, I personally experiment and modify some places for the notes in the video recorded when learning rabbitmq. The versions of centos and rabbitmq used are different from those in the video. You can give the video three links to support up master ha. The video address is: https://www.bilibili.com/video ...

Implementation of distributed lock There are three common implementations of distributed locks: Redis implementationZookeeper implementationDatabase implementation 1. Redis based implementation There are three important commands in Redis. Distributed locking can be realized through these three commands setnx key val: if and only if the key ...

1, Briefly talk about the redis sentinel sentinel mode 1. Make the redis cluster more robust and highly available. Compared with redis cluster, it can automatically failover and automatically transform the master 2. Its workflow is that Sentinel will constantly check whether your master server and slave server are operating normally. If there ...

problem When learning RocketMQ, I have several questions. If the subject does not exist, who will the client send the message to? When a message is sent to a topic that does not exist, when is the topic created? guess When I execute the following code, the topic does not exist, so when did I create the topic "TopicTest202112151152" ...

Distributed transaction overview In the microservice architecture, different services have their own independent databases. In the past, the transaction control of a single application is based on the connection, that is, all operations are one transaction after each connection to the database. This is obviously not applicable in distributed m ...

reference resources: Shiro Springboot cluster shared Session (Redis) + single user login https://zhuanlan.zhihu.com/p/54176956 Frame construction 1. Basic environment jdk8 maven lombok spring boot 2.5.7 2. Import shiro maven coordinates <dependency> <groupId>org.apache.shiro</groupId> <artifactId>shiro-sprin ...

When operating on the same resource, a single cache read is no problem, but what to do when concurrency exists. In order to avoid data inconsistency, we need to perform a "lock" operation before operating the shared resource. We are developing many business scenarios that use locks, such as inventory control, lucky draw, second kill, ...