simply about difficult
If you need to set up a recursive watchers (watch on all nodes), the standard ZooKeeper’s Watcher class will not help much – it is installed on only 1 node (or one-level-forward when you calling getChildren()), and is also a one-time event. This means that after each watch trigger, you need to install a new […]
READ MOREIn this post I will describe the basic principles of how ACL works in ZooKeeper. ACL is not set recursively and is not inherited by the child nodes. If we have a read-only ACL for /path1/path2 or /path1/path2/path3, then deleting /path1 will fail, regardless of AСL of /path1. Several ACL records can be set on […]
READ MORELet’s imagine that we need to perform a certain sequence of actions when a spec fails. If you just need to close some resources when spec fails – don’t reinvent the wheel and use an easy and correct method – @AutoCleanup annotation. I wrote about it in detail earlier: https://mchesnavsky.tech/closing-resources-in-spock-framework. Keep in mind that in […]
READ MOREIf we have any resource and we need to close it when current spec fails or done (for example, ZooKeeper client), the easiest way is to use the @AutoCleanup annotation with the resource: By default, it calls the close() method, but you can put your own: And optionally use quiet mode, when Spock Framework are going […]
READ MORELet’s say we want to got working Apache Atlas instance with embedded Hbase & Solr on our machine. Notice, that you need to install JDK 8 before start. Go to the Apache Atlas GitHub page, and download the zip file with the source code of the latest stable release from here: https://github.com/apache/atlas/tags Important notice: DO […]
READ MORESuppose you need to add some_dir/your_file.txt to META-INF using Maven, so that the final path looks like this: To do this, you need to create a META-INF/some_dir folders in the src/main/resources directory, and put there your_file.txt file: Once compiled, Maven will move META-INF/some_dir/your_file.txt from resources to the right place without deleting the existing files in […]
READ MORELet’s imagine that we need to get the value of a certain Maven property in Java code. First, let’s create a text file with any name, for example version.txt in the src/main/resources folder: Now let’s add the following block to pom.xml: Now, when building, Maven will replace the construction ${project.version} in the file with the […]
READ MORESuppose that we were trying to call close() on an Apache Curator Framework object, and we encountered this exception: There will also be an answer to the question of how to know if a Curator Framework is running or started. This is happed because the Curator Framework has already been stopped or has not started […]
READ MOREImagine an error or exception occurs while running the Spring Boot Yarn container, and we need to kill container from itself and return an error code. You can use @OnContainerStart annotation as mentioned in this article: https://mchesnavsky.tech/how-to-set-up-exit-code-on-spring-boot-yarn-container. But if we need to stop the container immediately, we just need to call: – where parameter is […]
READ MORESuppose that you are faced with an exception like this: At first, you might think that java cannot find com.example.YourClass. But if you execute this line: Then it will work successfully and you will not see an exception. The point is that java sees the class, but a masked error occurred while initializing static fields […]
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