On teh way

Git Abstraction Git is widely used in current software development routine to do the version control of code. With the help of IDE like IntelliJ Idea , we can avoid manually inputing git command in command line, like git add , git commit , git push etc. But when some things goes wrong, it always need command line operations. Today, we are not going to introduce git command, but to understand how git works and what abstraction it have. As soon as we make it clear, we can understand many restrictions of git usage and many command in depth. So, when we met a new problem, we can infer a new solution from what we known, rather than just relying on Google. Abstraction As Torvalds explains, Git is first designed as a file system, so it has different concepts as old VCS system. In many ways you can just see git as a filesystem – it’s content-addressable , and it has a notion of versioning Git is a content-addressable filesystem, which means that we can retrieve th...

Iterator Design Pattern We have talked the usage of iterator when we need to interact with collections: Not expose internal state to outside world: Increasing cohesion of class and avoid mis-operation; A unified interface to operate on different kinds of operation; Enforce the order of method call; Iterator Pitfall public interface Iterator < E > { boolean hasNext ( ) ; E next ( ) ; default void remove ( ) { throw new UnsupportedOperationException ( "remove" ) ; } default void forEachRemaining ( Consumer < ? super E > action ) { Objects . requireNonNull ( action ) ; while ( hasNext ( ) ) action . accept ( next ( ) ) ; } } Checkout the interface of iterator (two more default method added in Java8), and we can see the common usage routine of Iterator . while ( hasNext ( ) ) T t = next ( ) ; // do with t But it is not so friendly for n...

SonarQube Gitlab Integration In order to improve the code quality, our team decided to install the SonarQube to do the static code analysis. Easy Install The installation can be done very easily using docker compose: version: "2" services: sonarqube: image: sonarqube ports: - "9002:9000" environment: - SONARQUBE_JDBC_URL = jdbc:postgresql://db:5432/sonar volumes: - ./sonarqube_conf:/opt/sonarqube/conf - ./sonarqube_data:/opt/sonarqube/data - ./sonarqube_extensions:/opt/sonarqube/extensions - ./sonarqube_bundled-plugins:/opt/sonarqube/lib/bundled-plugins db: image: postgres environment: - POSTGRES_USER = sonar - POSTGRES_PASSWORD = sonar volumes: - ./postgresql:/var/lib/postgresql # This needs explicit mapping due to https://github.com/docker-library/postgres/blob/4e48e3228a30763913ece952c611e5e9b95c8759/Dockerfile.template#L52 - ./postgresql...

Elasticsearch MySQL Sync Challenge (5): Redesign Multiple Syncer? “You may have already heard the new requirement: listening for the data change of main DB and send the data to auth system. What is your idea?” Leader said. "Em, the simple way is of course to write a similar config files as we did before like following: input : masters : - connection : address : 192.168.1.1 port : 3306 filter : ... output : mysql : - connection : address : auth - system --- - input : masters : - connection : address : 192.168.1.1 port : 3306 filter : ... output : elsticsearch : connection : search - system “Then we can start two separate syncer to finish the job of data synchronization for both search system and auth system.” Tony finished. “Yes, it works. But seems not so good.” “Em, yep. Two syncer connect to same data source in which they receive t...