Rolling deployment vs smoke test: Choosing a deployment strategy

Rolling deployment

Rolling deployment is a deployment strategy where the new version of an application is gradually rolled out to production servers. This method involves replacing instances of the old version with the new version one by one or in small batches. As each server or group of servers is updated, traffic is redirected accordingly.

This strategy provides a balance between deployment speed and risk management. It minimizes downtime since only a portion of servers are offline at any given time. However, during the transition period, different versions of the application coexist, which may lead to compatibility issues if not properly managed.

Smoke test

Smoke testing is a deployment strategy that focuses on verifying the basic functionality of a newly deployed application before making it fully available. A subset of critical tests is executed against the new deployment to ensure that core functionalities work as expected. If these tests pass, the deployment proceeds; if they fail, the deployment is rolled back.

This approach serves as an early warning system to detect major issues before they affect all users. Smoke tests are typically automated and designed to run quickly, checking only the most crucial aspects of the application. This strategy helps prevent catastrophic failures from reaching production environments by validating fundamental operations.

Comparison: Rolling deployment vs. smoke test

Risk management

• Rolling Deployment: Reduces risk by limiting potential issues to a subset of servers.

• Smoke Test: Identifies critical issues before full deployment, preventing widespread failures.

Deployment speed

• Rolling Deployment: Takes longer due to the gradual nature of the deployment process.

• Smoke Test: Can be faster overall but requires upfront time investment in test preparation.

Resource utilization

• Rolling Deployment: Requires additional resources to maintain both versions during transition.

• Smoke Test: Typically needs a separate test environment for verification before production.

Feedback loop

• Rolling Deployment: Provides real user feedback gradually as more servers receive the update.

• Smoke Test: Offers early technical feedback but limited real user feedback until full deployment.

Compatibility

• Rolling Deployment: Must handle multiple versions running simultaneously during deployment.

• Smoke Test: Doesn’t address version compatibility issues that may arise in production.

Feature flags with rolling deployments

Feature flags complement rolling deployments by adding another layer of control and safety. During a rolling deployment, new code is gradually released to servers, but feature flags can keep the new functionality hidden from users even though the code is present. This separation of deployment from release allows teams to deploy code frequently while controlling the visibility of features independently. Teams can then gradually expose new features to increasing percentages of users, monitoring for issues at each stage.

With rolling deployments, feature flags provide a safety mechanism if problems arise mid-deployment. Instead of rolling back the entire deployment—which can be complex when some servers have already been updated—teams can simply disable the problematic feature through the feature flag. This approach maintains system stability while allowing the deployment to continue, reducing the operational complexity and potential downtime associated with traditional rollbacks.

Feature flags with smoke testing

Feature flags enhance smoke testing by allowing testers to conditionally enable specific features during the testing phase. When combined with smoke tests, feature flags provide a way to test both the current production configuration and the new features that will eventually be released. This approach verifies that the core application functions properly with features both enabled and disabled, ensuring that the feature switching mechanism itself doesn’t introduce issues.

After successful smoke tests and deployment to production, feature flags continue to provide value by enabling controlled feature exposure. Teams can initially enable new features for internal users or a small percentage of customers to perform extended real-world testing. If issues are discovered after deployment that weren’t caught by smoke tests, the feature can be immediately disabled without requiring a new deployment. This provides an additional safety net beyond what smoke testing alone can offer.

Rolling deployments and smoke tests are both deployment strategies used to minimize risk when releasing new features or updates, but they serve different purposes and offer distinct advantages. Rolling deployments gradually replace instances of the previous version with the new version, often in batches or percentages, allowing for a controlled transition while maintaining system availability. This approach reduces downtime, enables easy rollback if issues arise, and requires less infrastructure than blue-green deployments. However, rolling deployments may introduce compatibility issues between old and new versions running simultaneously, can be slower than other deployment methods, and might require more complex orchestration to manage the transition effectively.

Smoke tests, on the other hand, are lightweight validation tests performed after deployment to verify that critical functionalities work as expected. These tests quickly check the basic functionality without extensive testing, serving as an early warning system for obvious issues. Smoke tests are ideal when you need rapid feedback about a deployment’s basic viability before proceeding with more comprehensive testing or exposing it to users. Choose rolling deployments when you need to minimize downtime while gradually shifting traffic in production environments, particularly for applications where users cannot tolerate disruption. Opt for smoke tests when you need quick verification of essential functionality regardless of your deployment method—they can complement rolling deployments or any other strategy as an initial validation step before proceeding with further testing or user exposure.

Frequently asked questions

What is rolling deployment according to the article?

Rolling deployment is a deployment strategy where a new version of an application is gradually rolled out to production servers. It involves replacing instances of the old version with the new version one by one or in small batches, with traffic being redirected accordingly. This approach balances deployment speed and risk management by minimizing downtime, as only a portion of servers are offline at any given time. However, it does present potential compatibility challenges during transition periods when different versions of the application coexist.

What is smoke testing in software deployment?

Smoke testing is a deployment strategy that verifies the basic functionality of a newly deployed application before making it fully available. It involves running a subset of critical tests against the new deployment to ensure core functionalities work as expected. If these tests pass, the deployment proceeds; if they fail, the deployment is rolled back. This serves as an early warning system to detect major issues before they affect all users, helping to prevent catastrophic failures from reaching production environments.

How do feature flags complement rolling deployments?

Feature flags add another layer of control and safety to rolling deployments by separating code deployment from feature release. During a rolling deployment, new code can be gradually released to servers while keeping the new functionality hidden from users. This allows teams to deploy code frequently while independently controlling feature visibility. If problems arise mid-deployment, teams can simply disable the problematic feature through the feature flag rather than rolling back the entire deployment, reducing operational complexity and potential downtime.

What are the key differences between rolling deployment and smoke testing?

Rolling deployment and smoke testing differ in several key aspects. For risk management, rolling deployment reduces risk by limiting potential issues to a subset of servers, while smoke testing identifies critical issues before full deployment. In terms of speed, rolling deployment takes longer due to its gradual nature, while smoke testing can be faster overall but requires upfront investment in test preparation. Rolling deployment requires additional resources to maintain both versions during transition, whereas smoke testing typically needs a separate test environment for verification. Additionally, rolling deployment must handle multiple versions running simultaneously, while smoke testing doesn’t address version compatibility issues that may arise in production.