Mitigate Risk with Canary Deployments: Leveraging Azure DevOps and App Gateway

 

Deploying new application versions can introduce unexpected issues. This article explores implementing canary deployments with Azure DevOps and App Gateway. We'll guide you through configuring App Gateway routing rules, utilizing pipeline variables for controlled traffic routing, and automating rollbacks for identified problems in the canary environment.

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1. Understanding Canary Deployments: A Phased Rollout Strategy

• Canary Deployments: A technique for gradually rolling out a new application version to a small subset of users before exposing it to the entire user base.
• Benefits:
  • Reduced Risk: Allows early detection of issues in the new version before impacting all users.
  • Improved User Experience: Minimizes downtime and potential disruptions for the majority of users.

Why Azure DevOps and App Gateway?

• Azure DevOps: Provides a platform for managing your build and deployment pipelines.
• Azure Application Gateway: A layer-7 load balancer that routes traffic based on defined rules.
  • Benefits:
    • Flexible Routing: Enables routing traffic to specific versions of your application based on configuration.
    • Integration with DevOps: Seamlessly integrates with Azure DevOps pipelines for automated deployment and traffic management.

2. Configuring App Gateway: Setting Up Routing Rules

Prerequisites:

• An Azure subscription with an existing App Gateway resource.
• Two backend application pools (one for the current production version and one for the canary version).

Defining Routing Rules:

1. Navigate to your App Gateway resource within the Azure portal.
2. Click on "Routing rules" and choose "Add a rule."
3. Provide a descriptive name for the rule (e.g., "Canary Routing").
4. Configure the "Frontend listener" and "Backend pool" for the rule.
   • Frontend listener: The listener that receives incoming traffic.
   • Backend pool: The pool of application instances to route traffic to (choose the pool for the canary version).
5. Define a path-based condition (optional): Route traffic to the canary version based on a specific URL path (e.g., "/canary").

With routing rules established, App Gateway can now direct traffic to the desired backend pool based on your configuration.

3. Dynamic Routing with Variables: Controlling Canary Traffic Percentage

Leveraging Pipeline Variables:

• Azure DevOps pipelines allow defining variables that can be referenced within the pipeline tasks.

Implementing Dynamic Routing:

1. Within your Azure DevOps pipeline, create a variable representing the desired canary traffic percentage (e.g., "canaryTrafficPercentage").
2. Modify your App Gateway routing rule to use a conditional statement based on the pipeline variable.
   • Example: Route traffic to the canary pool only if a header value matches the $(canaryTrafficPercentage).

By referencing pipeline variables in your routing rule, you can dynamically control the percentage of traffic directed to the canary environment.

4. Automated Rollbacks: Mitigating Issues in Canary Deployments

Integrating Monitoring with Pipelines:

• Utilize Azure Monitor or other monitoring tools to track the health and performance of your canary environment.
• Configure alerts within your monitoring tool to trigger actions based on defined thresholds.

Implementing Automated Rollbacks:

1. Within your Azure DevOps pipeline, define a task that executes upon receiving an alert from your monitoring tool.
   • This task could involve disabling the canary routing rule or deploying the previous production version.

By integrating monitoring and automated rollbacks, you ensure a safety net that automatically reverts to the previous version if problems arise in the canary environment.

5. Benefits and Considerations

Benefits:

• Reduced Risk: Mitigate the impact of potential issues with new deployments.
• Improved Rollout Process: Controlled and gradual exposure of new versions to users.
• Automation: Automate traffic routing and rollbacks for a streamlined process.

Considerations:

• Monitoring: Implement robust monitoring to effectively detect issues in the canary environment.
• Rollback Strategy: Define a clear rollback strategy for reverting to the previous production version if necessary.
• Canary Size: Determine the appropriate size for your canary environment to balance risk mitigation with timely feedback.

By utilizing Azure DevOps and App Gateway for canary deployments, you establish a controlled and automated approach to introducing new application versions. This minimizes risk, improves your deployment process, and ensures a smooth user experience.