Lambda function versioning and aliases
Lambda function versioning and aliases are essential features that contribute significantly to the security, manageability, and operational excellence of your serverless architecture. Understanding how to effectively use these features can help you maintain a robust security posture, simplify deployments, and facilitate rollbacks in case of issues.
The importance of versioning
Versioning in Lambda allows you to publish one or more versions of your Lambda function. As you make changes to your function, you can publish a new version, which becomes immutable. This immutability is a security feature as it ensures that a particular version of the function cannot be altered once it is published. This is crucial for auditing and compliance as it provides a clear history of what code was running at any given time. Therefore, it is a best practice to always publish a new version for production use, rather than relying on the mutable $LATEST version.
How versioning works
When you publish a new version of a Lambda function, AWS automatically assigns it a new version number. The latest version is always mutable and is referred to as $LATEST. However, once you publish a version, it becomes immutable. This means that the code, environment variables, and other settings are locked for that version. You can still execute it, but you can’t change it. This is particularly useful for maintaining a stable environment, especially when your Lambda functions are part of critical workflows. To ensure that only trusted individuals or systems can create, update, or delete versions, you should use IAM policies to restrict these permissions.
Aliases as pointers
Aliases in Lambda act like pointers to specific function versions. An alias enables you to redirect function traffic from one version to another without changing all the places where your function is invoked. This is particularly useful for implementing blue-green deployments, canary releases, or any other strategy that requires routing traffic to different versions of your function. Descriptive alias names such as production, staging, or testing make it clear what each alias is used for, aiding in both manageability and security.
Security benefits of aliases
Using aliases can enhance your security posture in several ways. For instance, you can have an alias that points to a version of the function that has undergone rigorous security testing. Before updating the alias so that it points to a new version, you can ensure that the new version meets all your security requirements. This makes it easier to manage security at scale as you don’t have to update every single function invocation – just the alias. Lambda supports weighted aliases, allowing you to route a percentage of your function invocation requests to one version and the rest to another, which is useful for gradually shifting traffic to new versions.
Rollback and audit trail
The immutability of versions and the flexibility of aliases make it easier to roll back to a previous version in case of a security incident or other issues. This is invaluable for incident response and forensic analysis. The ability to quickly switch back to a known, secure version of your function can be a lifesaver in emergencies. Additionally, the history of versions and aliases provides a clear audit trail, which is often required for compliance with various security standards. Monitoring both versions and aliases through CloudWatch and setting up alerts for unusual activity is also a key part of maintaining security.