CI/CD Deployment Process: Build Once, Test Across Environments
Subbu Tech TutorialsIn modern DevOps practices, the goal is to deliver high-quality software rapidly, while maintaining consistency and minimizing risk. A key principle that enables this is the concept of "build once, deploy everywhere." This means that a single artifact (e.g., a Docker image, JAR file, or WAR file) is built once and then promoted across multiple environments (DEV → QA → STAGING → PROD) without being rebuilt. Let’s dive into how this works in real-world scenarios and why it’s a best practice in CI/CD pipelines.
1. Build Once, Promote Across Environments
The core idea is to build your application artifact once after code changes are pushed to the repository. This artifact (let’s say v1.0) is stored in a remote repository like Docker Hub, Nexus, or Artifactory. After the initial build, the same artifact is promoted through various environments:
DEV Environment:
This is the first stop, where developers deploy the artifact for initial testing and validation.
The goal here is to ensure the code behaves as expected in a controlled environment where developers can iterate quickly.
QA Environment:
Once the artifact passes the DEV environment, it is promoted to QA for more rigorous testing.
QA testers focus on catching bugs, running automated and manual tests, and validating the artifact under more real-world conditions. This is where edge cases and integration issues are often caught.
STAGING Environment:
STAGING closely mirrors the production environment.
The artifact undergoes final validation, and tests are done in production-like conditions. User acceptance testing (UAT) or performance testing is often performed here.
The goal is to ensure that the application behaves exactly as it should when it reaches production.
PROD Environment:
- Finally, the same artifact is deployed to production, where end-users interact with the software. The goal here is to ensure reliability, performance, and security.
2. What Happens When Bugs Are Found?
In an ideal world, no bugs would be found after deployment to QA or STAGING. However, in real-world scenarios, bugs often emerge during deeper testing. When a bug is identified:
Fixing the Bug:
- Developers make the necessary changes in the source code and commit the fixes.
New Artifact:
A new build is triggered, resulting in a new version of the artifact (e.g.,
v1.1).This new artifact now goes through the same cycle again (DEV → QA → STAGING → PROD) until it successfully passes through all environments.
This ensures that the final version of the artifact deployed in production is fully validated.
3. Why Use Multiple Environments?
Even when no bugs are found, you might wonder why organizations use multiple environments like DEV, QA, and STAGING. Here’s why:
Risk Mitigation: Each environment serves as a checkpoint. The deeper and more controlled testing environments like QA and STAGING help catch potential issues that might not surface in DEV. By promoting the same artifact through each environment, you ensure that the version deployed to production is stable and reliable.
Configuration Differences: Each environment has its own configurations (e.g., database connections, API keys). While the artifact stays the same, environment-specific configurations allow you to simulate real-world conditions. For instance, QA may use a separate database, and STAGING may have the same configuration as production to closely mirror live conditions.
Performance Testing: In environments like STAGING, the application can be tested under production-like load, ensuring it performs as expected before being exposed to real users in PROD.
Compliance and Approval: In industries like finance, healthcare, or e-commerce, compliance is critical. Regulatory requirements often mandate multiple testing phases and approvals before any code is promoted to production. Multiple environments ensure this process is followed thoroughly.
┌──────────────┐
│ Build Artifact │
└──────┬───────┘
│
┌───────▼────────┐
│ DEV Environment │
└────────────────┘
│
Deploy Artifact and Test
│
┌───────────────▼───────────────┐
│ │
┌──────▼─────┐ ┌──────▼─────┐
│ Success │ │ Fail │
└──────┬──────┘ └──────┬─────┘
│ │
Promote to QA Fix Code and
│ Rebuild Artifact
▼ │
┌───────────────┐ ┌─────▼─────┐
│ QA Environment │ │ DEV Again │
└───────────────┘ └───────────┘
│
Deploy Artifact and Test
│
┌──────▼─────┐ ┌──────▼─────┐
│ Success │ │ Fail │
└──────┬──────┘ └──────┬─────┘
│ │
Promote to Staging Fix Code and
│ Rebuild Artifact
▼ │
┌────────────────┐ ┌─────▼─────┐
│ Staging Environment │ │ DEV Again │
└────────────────┘ └───────────┘
│
Deploy Artifact and Test
│
┌──────▼─────┐ ┌──────▼─────┐
│ Success │ │ Fail │
└──────┬──────┘ └──────┬─────┘
│ │
Promote to PROD Fix Code and
│ Rebuild Artifact
▼ │
┌───────────────┐ ┌─────▼─────┐
│ PROD Environment │ │ DEV Again │
└───────────────┘ └───────────┘
│
Deploy Artifact and Monitor
│
┌──────▼─────┐
│ Success │
└─────────────┘
4. How It Works in Real Time
In real-world CI/CD pipelines, organizations follow the "build once, promote everywhere" principle to maintain consistency across environments. Here’s how it’s done:
Artifact Versioning: The artifact is versioned (e.g.,
v1.0,v1.1), and this version is used across all environments. This versioning ensures that what was tested in QA or STAGING is exactly what gets deployed to PROD.Environment-Specific Configurations: Configuration management tools like environment variables, Spring Profiles, Kubernetes ConfigMaps, or Secrets handle environment-specific differences. The artifact itself remains unchanged, but each environment has its own configurations (e.g., connecting to different databases or using different credentials).
Automation: Modern CI/CD pipelines are heavily automated, with tools like Jenkins, GitLab CI, CircleCI, or AWS CodePipeline handling the entire process from build to deployment. Automation ensures consistency and repeatability while reducing the chances of human error.
5. What If You Deploy Directly to Production?
Deploying directly from DEV to PROD without passing through QA and STAGING might seem tempting, especially if everything works in DEV. However, this introduces significant risks:
Uncaught Bugs: DEV environments often lack the real-world conditions or traffic loads seen in production. Bugs that don’t surface in DEV may appear in production and cause downtime or user frustration.
Lack of Validation: Without QA and STAGING, you miss the opportunity to run deep tests, performance checks, and validation under production-like conditions.
Compliance Risks: In regulated industries, skipping environments and processes can result in compliance violations, which may lead to legal and financial penalties.
6. Real-World Practices
Organizations like Facebook, Google, and Netflix follow similar principles but often extend them with techniques like canary releases (gradually releasing new code to a subset of users) or feature flags (enabling/disabling features without redeploying) to reduce risks further.
In most enterprises using tools like Jenkins, GitLab CI, or Kubernetes, this "build once, deploy everywhere" principle is standard practice. It ensures the highest level of quality control and minimizes the risk of deploying faulty artifacts to production.
7. Key Takeaways
Consistency: Using the same artifact across environments ensures that the version deployed in production is the same one that passed all tests.
Efficiency: The build is only repeated when necessary (e.g., after fixing a bug), reducing unnecessary rebuilds and speeding up the pipeline.
Risk Reduction: Every environment acts as a quality checkpoint, ensuring the artifact is thoroughly validated before reaching production.
"In learning you will teach, and in teaching you will learn." – Phil Collins
Thank you, Happy Learning!
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