Continuous Delivery versus Continuous Deployment – Comparing the CDs

Let’s take a look here at Continuous Delivery versus Deployment, which are both two key DevOps processes.

Big Picture

Continuous Delivery is a software engineering approach wherein code changes are automatically built, tested, and prepared for a potential release to production. It focuses on ensuring the software can be reliably released at any time. The main objective is to make the release process predictable, routine, and safe.  

Continuous Deployment goes a step further than Continuous Delivery. It automates the deployment process so that every change that passes all stages of the production pipeline is released to users automatically, without manual intervention.  

It may be confusing that “delivery” is not the final step in getting the software to the users; that is the “deployment” part for rollout to users and their devices.

Key Details of Continuous Delivery versus Deployment

Continuous Delivery and Continuous Deployment are methodologies that have reshaped how software is developed and released. Organizations can ensure faster, safer, and more frequent releases by automating most of the delivery and deployment processes.

Here are several key technical details that play a key role:  

• Infrastructure as Code (IaC): Both CD methodologies rely on IaC, which means infrastructure (servers, networks, databases, etc.) is provisioned and managed using code and software development techniques. This ensures that the environment remains consistent across different stages.
• Feature Toggles: To release unfinished features without affecting users, feature toggles (or feature flags) are used. They allow teams to turn on or off particular functionalities in production.
• Monitoring and Alerts: Given the automated nature of continuous deployment, robust monitoring and alerting tools are crucial. They ensure that any issues in production are immediately flagged for attention.
• Rollbacks: Even with the best testing processes, issues can sometimes arise in production. The ability to quickly roll back a release and revert to a previous state is a critical component of both CD methodologies.  

Process Background for Continuous Delivery

1. Automation: One of the cornerstones of CD is automation. From the moment code is checked into the repository until it is delivered to the user, every step, such as building, testing, and deployment, is automated.
2. Frequent Releases: Organizations can more frequently release small batches of changes to users by continuously delivering software updates. This helps get quicker feedback and ensures a reduced risk in each release.
3. Quality Assurance: CD relies heavily on a robust suite of tests. These tests ensure that new changes have not adversely affected the existing functionality. If the tests fail, the changes are not delivered, and the errors are returned to the developers.  

Process Background for Continuous Deployment

1. Immediate Feedback: With Continuous Deployment, developers receive immediate feedback on the production readiness of their changes. If something breaks due to a code change, it’s instantly visible, facilitating quicker fixes.
2. No Release Day: Since every change is automatically deployed to production, there isn’t a “release day” as such. Releases become a regular, everyday activity.
3. High Level of Confidence: Organizations that adopt Continuous Deployment have an extremely high level of confidence in their deployment process, often backed by a comprehensive suite of automated tests.  

Historical Context

Before the advent of Continuous Delivery and Continuous Deployment, the predominant model in software development was the Waterfall methodology.

This linear approach saw projects progress through a series of phases: requirements gathering, design, coding, testing, and, finally, deployment. Each phase was distinct, and there was minimal feedback between them.

Consequently, software releases were infrequent, sometimes taking months or years, and often accompanied by numerous bugs and issues because of the long feedback loop.  

Emergence of Agile and DevOps

The software industry began embracing Agile methodologies, which combine iterative development, regular feedback, and adaptability to address these challenges with the Waterfall approach.

As Agile practices gained traction, the need arose for better collaboration between development and operations teams. This led to the DevOps movement.

The essence of DevOps is to break down silos between developers and operations to accelerate software delivery and improve its quality.  

Rise of Automation Tools

The push for more frequent releases required robust tooling to automate the build, test, and deployment processes.

Tools like Jenkins, Travis CI, and CircleCI emerged as popular choices for automating these pipelines.

Configuration management tools like Ansible, Chef, and Puppet became crucial for managing infrastructure as code.  

Cloud Computing

Simultaneously, cloud computing platforms like Amazon Web Services (AWS), Google Cloud Platform, and Microsoft Azure began to rise in prominence.

These platforms offered Infrastructure as a Service (IaaS) and later Platform as a Service (PaaS) solutions, allowing organizations to deploy software faster, scale infrastructure on demand, and reduce the overhead of managing physical hardware.  

Organizational Adoption

Implementing Continuous Delivery and Continuous Deployment isn’t just about tooling and processes; it often requires a significant organizational cultural shift.

Teams must embrace collaboration, shared responsibility, and a “fail fast, recover quickly” mentality.

The old boundaries between developers, testers, and system administrators begin to blur, leading to the emergence of cross-functional teams.  

Challenges and Skepticism

Not all organizations or projects can seamlessly adopt Continuous Deployment, especially in highly regulated industries like finance or healthcare, where every software change might entail significant risks. Skepticism regarding the feasibility and advantages of these practices was, and in some cases still is, widespread.

Security, stability, and compliance concerns remain prevalent, requiring tailored strategies and tools to address them effectively.  

Conclusion

In sum, the journey to Continuous Delivery and Continuous Deployment has been shaped by technological advancements, evolving methodologies, and the industry’s continual push for efficiency and quality.

These practices are not just technical processes but represent a broader evolution in how we think about, develop, and deliver software. 

Continuous Delivery versus Continuous Deployment – 5 mins