Subversion is a version control system that is used to track all the changes made to files and folders. Using this, you can keep track of the applications being built. Features added months ago can also be tracked using the version code. It is all about tracking the code. Whenever any new features added or new code made, it is first tested and then committed by the developer. Then, the code is sent to the repository to track the changes, and a new version is given to it. A comment can also be made by the developer so that other developers can easily understand changes that were made. Other developers only have to update their checkout to see the changes made.

Differences between SVN and Git

SVN and Git are both very popular source code repositories; however, Git is getting more popular in recent times. Let's look at the major differences between them:

https://www.git-tower.com/learn/git/ebook/en/mac/appendix/from-subversion-to-git

Detailed description of Subversion and Git is illustrated in the following table:

Subversion	Git
Centralized version control system	Distributed version control system
Snapshot of a specific version of the project is available on the developer's machine	Complete clone of a full-fledged repository is available on the developer's machine
Perform operations such as commit, merge, blame, and revert and verifies branch and log from a central repository	Perform operations such as commit, merge, and blame and verifies branch and log from a local repository, along with pull and push operation to a remote repository if the developer needs to share work with others
URLs are used for trunks, branches, or tags: https://<URL/IP Address>/svn/trunk/AntExample1/	.git is the root of projects, and commands are used to address branches and not URLs: [email protected]:mitesh51/game-of-life.git
An SVN workflow:	A Git workflow:
File changes are included in the next commit	File changes have to be marked explicitly and only then are they included in the next commit
Committed work is directly transferred to the central repository, and hence, direct connection to the repository must be available	Committed work is not directly transferred to the remote repository and committed to local repository, and to share it with other developers, we need to push it to the remote repository, in which case we need a connection to the remote repository
Each commit gets ascending revision numbers	Each commit gets commit hashes rather than ascending revision numbers
Application directory:	Application directory:
.svn directory structure:	.git directory structure:
Short learning curve	Long learning curve

Apache Maven is a build tool with the Apache 2.0 license. It is used for Java projects and can be used in a cross-platform environment. It can be also be used for Ruby, Scala, C#, and other languages.

The following are the important features of Maven:

A Project Object Model (POM) XML file contains information about the name of the application, owner information, how the application distribution file can be created, and how dependencies can be managed.

Example pom.xml file

The pom.xml file has predefined targets, such as validate, generate-sources, process-sources, generate-resources, process-resources, compile, process-test-sources, process-test-resources, test-compile, test, package, install, and deploy.

The following is an example of a sample pom.xml file used in Maven:

Jenkins was originally an open source continuous integration software written in Java under the MIT License. However, Jenkins 2 an open source automation server that focuses on any automation, including continuous integration and continuous delivery.

Jenkins can be used across different platforms, such as Windows, Ubuntu/Debian, Red Hat/Fedora, Mac OS X, openSUSE, and FreeBSD. Jenkins enables users to utilize continuous integration services for software development in an agile environment. It can be used to build freestyle software projects based on Apache Ant and Maven 2/Maven 3. It can also execute Windows batch commands and shell scripts.

It can be easily customized with the use of plugins. There are different kinds of plugins available for customizing Jenkins based on specific needs for setting up continuous integration. Categories of plugins include source code management (the Git, CVS, and Bazaar plugins), build triggers (the Accelerated Build Now and Build Flow plugins), build reports (the Code Scanner and Disk Usage plugins), authentication and user management (the Active Directory and GitHub OAuth plugins), and cluster management and distributed build (Amazon EC2 and Azure Slave plugins).

Jenkins accelerates the software development process through automation:

Key features and benefits

Here are some striking benefits of Jenkins:

• Easy install, upgrade, and configuration.

• Supported platforms: Windows, Ubuntu/Debian, Red Hat/Fedora/CentOS, Mac OS X, openSUSE, FreeBSD, OpenBSD, Solaris, and Gentoo.

• Manages and controls development lifecycle processes.

• Non-Java projects supported by Jenkins: Such as .NET, Ruby, PHP, Drupal, Perl, C++, Node.js, Python, Android, and Scala.

• A development methodology of daily integrations verified by automated builds.

• Every commit can trigger a build.

• Jenkins is a fully featured technology platform that enables users to implement CI and CD.

• The use of Jenkins is not limited to CI and CD. It is possible to include a model and orchestrate the entire pipeline with the use of Jenkins as it supports shell and Windows batch command execution. Jenkins 2.0 supports a delivery pipeline that uses a Domain-Specific Language (DSL) for modeling entire deployments or delivery pipelines.

• The pipeline as code provides a common language-DSL-to help the development and operations teams to collaborate in an effective manner.

• Jenkins 2 brings a new GUI with stage view to observe the progress across the delivery pipeline.

• Jenkins 2.0 is fully backward compatible with the Jenkins 1.x series.

• Jenkins 2 now requires Servlet 3.1 to run.

• You can use embedded Winstone-Jetty or a container that supports Servlet 3.1 (such as Tomcat 8).

• GitHub, Collabnet, SVN, TFS code repositories, and so on are supported by Jenkins for collaborative development.

• Continuous integration: Automate build and the test automated testing (continuous testing), package, and static code analysis.

• Supports common test frameworks such as HP ALM Tools, JUnit, Selenium, and MSTest.

• For continuous testing, Jenkins has plugins for both; Jenkins slaves can execute test suites on different platforms.

• Jenkins supports static code analysis tools such as code verification by CheckStyle and FindBug. It also integrates with Sonar.

• Continuous delivery and continuous deployment: It automates the application deployment pipeline, integrates with popular configuration management tools, and automates environment provisioning.

• To achieve continuous delivery and deployment, Jenkins supports automatic deployment; it provides a plugin for direct integration with IBM uDeploy.

• Highly configurable: Plugins-based architecture that provides support to many technologies, repositories, build tools and test tools; it has an open source CI server and provides over 400 plugins to achieve extensibility.

• Supports distributed builds: Jenkins supports "master/slave" mode, where the workload of building projects is delegated to multiple slave nodes.

• It has a machine-consumable remote access API to retrieve information from Jenkins for programmatic consumption, to trigger a new build, and so on.

• It delivers a better application faster by automating the application development lifecycle, allowing faster delivery.

The Jenkins build pipeline (quality gate system) provides a build pipeline view of upstream and downstream connected jobs, as a chain of jobs, each one subjecting the build to quality-assurance steps. It has the ability to define manual triggers for jobs that require intervention prior to execution, such as an approval process outside of Jenkins. In the following diagram Quality Gates and Orchestration of Build Pipeline are illustrated:

Jenkins can be used with the following tools in different categories as shown here:

Language	Java	.Net
Code repositories	Subversion, Git, CVS, StarTeam	Subversion, Git, CVS, StarTeam
Build tools	Ant, Maven	NAnt, MS Build
Code analysis tools	Sonar, CheckStyle, FindBugs, NCover, Visual Studio Code Metrics, PowerTool	Sonar, CheckStyle, FindBugs, NCover, Visual Studio Code Metrics, PowerTool
Continuous integration	Jenkins	Jenkins
Continuous testing	Jenkins plugins (HP Quality Center 10.00 with the QuickTest Professional add-in, HP Unified Functional Testing 11.5x and 12.0x, HP Service Test 11.20 and 11.50, HP LoadRunner 11.52 and 12.0x, HP Performance Center 12.xx, HP QuickTest Professional 11.00, HP Application Lifecycle Management 11.00, 11.52, and 12.xx, HP ALM Lab Management 11.50, 11.52, and 12.xx, JUnit, MSTest, and VsTest)	Jenkins plugins (HP Quality Center 10.00 with the QuickTest Professional add-in, HP Unified Functional Testing 11.5x and 12.0x, HP Service Test 11.20 and 11.50, HP LoadRunner 11.52 and 12.0x, HP Performance Center 12.xx, HP QuickTest Professional 11.00, HP Application Lifecycle Management 11.00, 11.52, and 12.xx, HP ALM Lab Management 11.50, 11.52, and 12.xx, JUnit, MSTest, and VsTest)
Infrastructure provisioning	Configuration management tool-Chef	Configuration management tool-Chef
Virtualization/cloud service provider	VMware, AWS, Microsoft Azure (IaaS), traditional environment	VMware, AWS, Microsoft Azure (IaaS), traditional environment
Continuous delivery/deployment	Chef/deployment plugin/shell scripting/Powershell scripts/Windows batch commands	Chef/deployment plugin/shell scripting/Powershell scripts/Windows batch commands

Software Configuration Management (SCM) is a software engineering discipline comprising tools and techniques that an organization uses to manage changes in software components. It includes technical aspects of the project, communication, and control of modifications to the projects during development. It also called software control management. It consists of practices for all software projects ranging from development to rapid prototyping and ongoing maintenance. It enriches the reliability and quality of software.

Chef is a configuration management tool used to transform infrastructure into code. It automates the building, deploying, and managing of the infrastructure. By using Chef, infrastructure can be considered as code. The concept behind Chef is that of reusability. It uses recipes to automate the infrastructure. Recipes are instructions required for configuring databases, web servers, and load balances. It describes every part of the infrastructure and how it should be configured, deployed, and managed. It uses building blocks known as resources. A resource describes parts of the infrastructure, such as the template, package, and files to be installed.

These recipes and configuration data are stored on Chef servers. The Chef client is installed on each node of the network. A node can be a physical or virtual server.

As shown in the following diagram, the Chef client periodically checks the Chef server for the latest recipes and to see whether the node is in compliance with the policy defined by the recipes. If it is out of date, the Chef client runs them on the node to bring it up to date:

AWS and Microsoft Azure are popular public cloud providers right now. They provide cloud services in different areas, and both have their strong areas. Based on the organization's culture and past partnerships, either can be considered after a detailed assessment based on requirements.

The following is a side-by-side comparison:

Containers use OS-level virtualization, where the kernel is shared between isolated user-spaces. Docker and OpenVZ are popular open source example of OS—level virtualization technologies.

Docker

Docker is an open source initiative to wrap code, the runtime environment, system tools, and libraries. Docker containers share the kernel they are running on and hence start instantly and in a lightweight manner. Docker containers run on Windows as well as Linux distributions. It is important to understand how containers and virtual machines are different. Here is a comparison table of virtual machines and containers:

Note

You can download Docker by visiting https://github.com/docker/docker .

There are many open source tools available for monitoring resources. Zenoss and Nagios are two of the most popular open source tools and have been adopted by many organizations.

Zenoss

Zenoss is an agentless and open source management platform for applications, servers, and networks released under the GNU General Public License (GPL) version 2 and is based on the Zope application server. Zenoss Core consists of the extensible programming language Python, object-oriented web server Zope, monitoring protocol network, graph and log time series data by RRD tool, MySQL, and event-driven networking engine Twisted. It provides an easy-to-use web portal to monitor alerts, performance, configuration, and inventory. In the following diagram, Zenoss features are illustrated:

Note

You can visit Zenoss Core 5 website at http://www.zenoss.org/ .

The build pipeline, also called the deployment or application delivery pipeline, can be used to achieve end-to-end automation for all operations, including continuous integration, cloud provisioning, configuration management, continuous delivery, continuous deployment, and notifications. The following Jenkins plugins can be used for overall orchestration of all the activities involved in end-to-end automation:

End-to-end orchestration: Jenkins plugins

Here is a sample representation of end-to-end automation using different tools:

Jenkins can be used to manage unit testing and code verification; Chef can be used for setting up a runtime environment; Knife plugins can be used for creating a virtual machine in AWS or Microsoft Azure; the build pipeline or deployment pipeline plugins in Jenkins can be used for managing deployment orchestration.

From a single pipeline dashboard, we can view the status of all the builds that are configured in the pipeline. Each build in the pipeline is a kind of quality gate. If one build fails, then the execution won't go further. Additional dimensions can be added, such as notification based on compilation failures, unit test failures, or for unsuccessful deployment. The final deployment can be based on some sort of permission from a specific stakeholder. Consider a scenario for a parameterized build or promoted build concept-what should we do? All will be revealed in the chapters to follow!

One of the most liked components of DevOps culture is the dashboard or GUI that provides a combined status of all end-to-end activities. For automation tools, an easy-to-use web GUI is handy for managing resources. For end-to-end automation in application deployment activities, multiple open source or commercial tools are used. There is a high possibility that a single product may not be used for all activities, for example, Git or SVN as the repository, Jenkins as the CI server, and IBM UrbanCode Deploy as the deployment orchestration tool. In such a scenario, it is easier if there is a single-pane-of-glass view where we can track multiple tools for a specific application.

Hygieia is an open source DevOps dashboard that provides a way to track the status of a deployment pipeline. It basically tracks six different areas as of now, including features (Jira, VersionOne), code repository (GitHub, Subversion), builds (Jenkins, Hudson), quality (Sonar, Cucumber/Selenium), monitoring, and deployment (IBM UrbanCode Deploy). Following is a sample image of configured DevOps dashboard: