In today's rapidly evolving software landscape, businesses need to deliver updates and new features to their customers quickly and efficiently. Progressive Delivery is an emerging DevOps practice that facilitates safe and controlled software releases. It allows organizations to test and roll out features incrementally, minimizing the risk of bugs and downtime.

Progressive Delivery Techniques

Progressive Delivery is built upon several techniques that help teams safely release and manage new software features. These include:

Feature flags

Also known as feature toggles, these allow teams to turn features on or off without deploying new code, providing granular control over feature rollout.

Recently I have used Unleash to manage feature flags. When working in Java, Spring Cloud Config was the feature flag platform of choice.

Canary releases

This approach involves releasing a new version of a service to a small subset of users, allowing teams to test and monitor the new version's performance before rolling it out to a larger audience.

For microservices running in Kubernetes, I have leveraged the routing capabilities of Istio to provide automated canary rollouts.

Blue-green deployments

This technique involves running two identical production environments (blue and green), with one hosting the new version of the software and the other hosting the current stable version. Traffic is gradually shifted from the old environment to the new one, allowing for safe deployment and rollback if needed.

A/B testing

A popular technique for measuring the impact of new features on user experience, A/B testing involves presenting different variations of the same feature to different user groups and analyzing the results.

Again, Istio has been my go-to when trying to set up a sucessful A/B test.

Microservices and Progressive Delivery

While Progressive Delivery offers significant benefits, implementing it in a microservices environment can present unique challenges. Microservices architectures consist of many independent services, often developed and deployed by different teams. Coordinating the rollout of new features across multiple services and ensuring consistency can be complex.

Service Dependencies

Microservices often have dependencies on other services in the system. When implementing Progressive Delivery techniques, it is crucial to ensure that new features and updates do not introduce breaking changes or negatively impact the performance of dependent services. To tackle this challenge, teams can adopt practices like contract testing, which verifies that a service's behavior remains consistent with the expectations of its consumers. Another approach is to use versioning to maintain compatibility between services during updates.

Managing Rollouts Across Services

Coordinating the rollout of new features across multiple services can be complex, particularly when different teams are responsible for various services. To ensure consistency and smooth transitions, organizations can adopt a shared set of Progressive Delivery tools and practices, such as standardized feature flags and centralized management for canary releases. This enables teams to have a unified approach to deploying and managing new features in a microservices environment.

Additionally, providing API version consistency will allow for microservices to continue to support dependent software while building out new functionality along an updated API version.

Ensuring Data Consistency

As microservices often rely on independent data stores, maintaining data consistency during Progressive Delivery rollouts can be challenging. Techniques like event-driven architectures and eventual consistency can help manage data across services. Additionally, feature flags can be used to control access to new data models or schemas, allowing teams to gradually transition to new data structures while ensuring consistency.

Monitoring and Observability

In a microservices environment, it can be difficult to monitor and observe the impact of new features on the entire system. To address this challenge, organizations should invest in comprehensive monitoring and observability tools that can aggregate data across all services. This enables teams to track the performance and behavior of individual services as well as the system as a whole, providing valuable insights for decision-making during Progressive Delivery rollouts.

Testing and Validation

Testing and validating new features and updates in a microservices environment can be complicated due to the distributed nature of the system. Adopting practices such as automated testing, integration testing, and end-to-end testing can help ensure the quality and stability of new features. Furthermore, monitoring user feedback and performance during canary releases or A/B tests can provide valuable insights for validating new features before wider deployment.

Case Studies

Many organizations have successfully implemented Progressive Delivery in their microservices environments, including leading technology companies like Netflix, Google, and Facebook. By learning from their experiences, you can adopt best practices to improve your own software release process.

For Netflix, you can refer to their Technology Blog: https://netflixtechblog.com/. Some of their articles related to Progressive Delivery techniques and their infrastructure are:

• The Netflix Simian Army: https://netflixtechblog.com/the-netflix-simian-army-16e57fbab116
• Global Continuous Delivery with Spinnaker: https://netflixtechblog.com/global-continuous-delivery-with-spinnaker-df1541e31c59

For Google, you can refer to their Engineering Blog: https://developers.googleblog.com/. Their blog covers a wide range of topics on software engineering, infrastructure, and practices.

For Facebook, you can refer to their Engineering Blog: https://engineering.fb.com/. Some articles related to Progressive Delivery techniques and their infrastructure are:

• Building and scaling the fast and reliable Facebook News Feed: https://engineering.fb.com/2021/09/21/core-data/news-feed/
• How Facebook does A/B testing: https://engineering.fb.com/2014/06/26/production-engineering/how-facebook-does-a-b-testing/

Progressive Delivery is an essential practice for modern software development, particularly in complex microservices environments. By adopting techniques like feature flags, canary releases, and blue-green deployments, you can reduce the risks associated with software releases and reap the benefits of safer, more controlled software deployments.