Programmer Think

Server dynamic online and offline monitoring cases In a distributed system, there can be multiple master nodes, which can dynamically go online and offline. Any client can sense the online and offline of the master node server in real time. As shown in the figure above, we hope that the client can monitor the node changes of the server in rea ...

Redis is a high-performance key value in memory database. Redis is completely open source and free, and complies with the BSD protocol 1. Architecture KV database of single process and single thread modelIt is completely based on memory and provides data persistence functionThe data structure is simple and the operation is simpleUsing multipl ...

When it comes to RPC (Remote Procedure Call Protocol), the estimates in the minds of the partners are RESTful API, Dubbo, WebService, Java RMI, CORBA, etc.In fact, RabbitMQ also provides us with RPC function, which is very simple to use.Today, SongGe will share with you how spring boot + rabbit MQ implements a simple RPC call through a simple c ...

Spark DataFrame supports all basic SQL Join operations, such as inner, right outer, left anti, left semi, cross and self join. Spark SQL Join is a wide conversion operation, and the resulting data will be reorganized in the network. Therefore, there will be very big performance problems if it is not carefully designed On the other hand, Spark ...

In order to introduce these two mechanisms, here we write an operation to realize Pi. Here, we only need to calculate the probability ratio of the point falling in the circle to the point falling in the square Here we highlight slices indicates how many tasks are generated cnt indicates how many points are generated in each task For the nu ...

1. Core structure and conceptThe Validator process provided by calculate is extremely complex, but to sum up, it mainly does one thing: verify whether the semantics of each SqlNode is correct in combination with metadata. These semantics include:Verify whether the table name exists;Whether the selected column exists in the corresponding table a ...

1 ZooKeeper details ZooKeeper is an open source distributed Apache project that provides coordination services for distributed applications. 1-1 ZooKeeper working mechanism Zookeeper is understood from the perspective of design pattern: it is a distributed service management framework based on the observer design pattern. It is responsible ...

Jobs for the Baseball dataset 1. Topic 1 Note: I said at_before the title when I was doing my homework Bas>=100 of 209 data, I filtered, found that later topics began to use this subset, let's not change, they have spent so much time. (1) Experimental code baseball=read.csv("datasets/baseball.txt",stringsAsFactors=TRUE,sep='') base ...

Concept: ZooKeeper is a distributed, open-source distributed application coordination service. It is an open-source implementation of Chubby of Google and an important component of Hadoop and Hbase. It is a software that provides consistency services for distributed applications. Its functions include configuration maintenance, domain name ser ...

^_^ 1. Configure local hadoop Hadoop 2.7.5 link: https://pan.baidu.com/s/12ef3m0CV21NhjxO7lBH0Eg Extraction code: hhhh Unzip the downloaded hadoop package to disk D for easy search Then right-click the computer and click Properties → click Advanced system settings on the right → click environment variables → select the Path b ...