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Ansible provides features that make it relatively easy to write automation for large-scale server installation, application deployment, and service operations. It’s one of the methods enabling DevOps, Ansible runs over SSH and requires SSH access to remote machines. No separate daemons or agents are needed. Remote machines (for default Ansible Modules) only need Python 2.6 or higher installed. (Some modules may require additional Python modules.) Ansible Modules are recommended to guarantee idempotency. For modules that exceptionally don’t guarantee idempotency, be sure to document warnings. Introduction An Ansible Module can be thought of as a set of functions with a specific purpose in one Task of an Ansible Playbook. For example, if you need to “move a file from path A to path B”, you can use the “file” module provided by default in Ansible. ...

This article focuses only on Callback Plugin among Ansible Plugins. Callback Plugin is a module used for various purposes such as logging data when specific events occur in Ansible, or writing to external channels like Slack, Mail, etc. This content is based on Ansible 2.2.1.0. What is Callback Plugin? Introduction Ansible Callback Plugin refers to plugins that can hook into various Ansible events and execute desired logic at those points. These callback plugins support defining callback functions for events like “before execution” and “after execution” for Ansible Tasks, Playbooks, etc. ...

Introduction String searching is a common problem in software development. Finding a single keyword is straightforward, but what if you need to search for hundreds of keywords simultaneously? Iterating through the text for each keyword would be inefficient. The Aho-Corasick algorithm elegantly solves this problem. Developed by Alfred V. Aho and Margaret J. Corasick in 1975, this algorithm can efficiently search for multiple patterns at once. ACOR is a Go library that implements Aho-Corasick with Redis as the backend storage. In this post, we’ll introduce ACOR, cover the basics of the Aho-Corasick algorithm, and walk through its usage. ...

When using Python, you’ll encounter various version environments. First, distributions like RedHat and Debian have their own system Python installed, and you can also use Python built from source on a per-account basis as needed. Python has major syntax and built-in library differences between 2.x and 3.x versions, and minor versions can have different behaviors or implementations in some features - a free but sometimes risky situation. Of course, if you only operate one project on a single system and the version will never change, you may not need to worry about this. However, generally, a single system can have various Python projects, and these may often be implemented based on different Python versions. If you reduce cohesion between projects through dependency isolation, individual projects don’t need to worry about other environments. ...

alternatives (or update-alternatives) is a GNU-licensed command-line tool that provides functionality to create, remove, manage, and query symbolic links. In other words, it allows defining default versions or paths for specific commands through symbolic links. Note that Debian-based Linux distributions only provide the update-alternatives command (the original alternatives script was reimplemented to remove perl language dependency), and there are some differences in functionality compared to RedHat-based Linux commands, but this article covers only common functionality and options. Examples are based on RedHat. ...

Uploading Ansible Role to Git Repository First, create a Git repository for developing an Ansible Role. Then, generate the initial Ansible Role project structure using Ansible Galaxy. Clone the Git repository to your local machine. 1 $ git clone "https://github.com/xxxxx/sample-role.git" Generate Ansible Role initial directory and files. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 $ ansible-galaxy init --force sample-role - sample-role was created successfully $ tree sample-role/ sample-role/ ├── README.md ├── defaults │ └── main.yml ├── files ├── handlers │ └── main.yml ├── meta │ └── main.yml ├── tasks │ └── main.yml ├── templates ├── tests │ ├── inventory │ └── test.yml └── vars └── main.yml After developing the Ansible Role, push to Git repository. 1 $ git commit * -m "Add ansible role" && git push Downloading Ansible Role from Git Repository Method 1) Download via Ansible Galaxy CLI 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 $ ansible-galaxy install git+https://github.com/xxxx/sample-role.git,master -p roles/ $ tree roles/ roles/ └── sample-role ├── README.md ├── defaults │ └── main.yml ├── handlers │ └── main.yml ├── meta │ └── main.yml ├── tasks │ └── main.yml ├── tests │ ├── inventory │ └── test.yml └── vars └── main.yml Method 2) Specify in dependency file and download via CLI 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 $ vi requirements.yml - src: git+https://github.com/xxxx/sample-role.git version: master $ ansible-galaxy install -r requirements.yml -p roles/ - extracting sample-role to roles/sample-role - sample-role was installed successfully $ tree roles/ roles/ └── sample-role ├── README.md ├── defaults │ └── main.yml ├── handlers │ └── main.yml ├── meta │ └── main.yml ├── tasks │ └── main.yml ├── tests │ ├── inventory │ └── test.yml └── vars └── main.yml Writing ‘requirements.yml’ src username.role_name: Used to download Ansible Roles registered in the official Ansible Galaxy repository. url: Used to download from SCMs supported by Ansible Galaxy. scm Specify the SCM name to integrate. Default is ‘git’ (as of ansible-galaxy 2.2.1.0, only git and hg are supported) version Specify tag name / commit hash / branch name. Default is ‘master’ Only used when downloading from SCM. name Specify the name of the downloaded Ansible Role. By default, uses the name registered in Ansible Galaxy or the Git repository name. See the examples below: ...

Started as ‘Project Lambda’ in 2010, it was officially released in Java 8. This article details how functional programming was incorporated into the existing Java language. Brief Overview of Functional Programming Before introducing Java’s lambda expressions, we need to briefly understand functional programming. (Functional programming based on lambda calculus is a paradigm, and lambda expressions represent it!) Functional programming is a paradigm that creates output relying only on function input, avoiding changing external state, minimizing side-effects. Functional programming must satisfy the following conditions: ...

This article summarizes the features added in Java 8. It covers the overall content, and more detailed information can be found in the attached related links. Summary of New Features Lambda Expression (a.k.a Anonymous Method) The foundation of Java’s lambda expressions is based on ’lambda calculus’ proposed by Alonzo Church in the 1930s. It’s a formal system that abstracts function definition, function application, and recursive functions! For more details, refer to Lambda Calculus Wiki. ...