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Éloi Alain for Serverless By Theodo

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sls-mentor 1.0.0 available now! Your Free Open Source audit tool for AWS architectures!

Hi there! sls-mentor 1.0.0 is now available! 🚀


sls-mentor is a command line tool that produces a detailed report of the improvements you can make to your AWS architecture.

As a developer, I use sls-mentor to ensure that my project meets the highest quality standards

sls-mentor is the result of a two-year journey learning and improving AWS architectures.

  • sls-mentor covers a wide range of concerns: green IT, costs, security and more below),
  • sls-mentor has a thorough documentation of its checks to help your team understand the underlying issues,
  • sls-mentor suggests detailed actions to solve issues,
  • sls-mentor provides a clear API for the community to maintain and add new checks,
  • sls-mentor is framework agnostic.

The one liner of your dreams

npx sls-mentor
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npx sls-mentor

How does sls-mentor work?

Under the hood, sls-mentor uses the AWS SDK to check your provisioned resources against a set of rules. As a result, sls-mentor is compatible with all frameworks (Serverless, CDK, Terraform, CloudFormation, ...).

sls-mentor is designed for you

I know... You know the installation process

Of course you can install sls-mentor globally to use it across all your projects.

npm install -g sls-mentor
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Otherwise, you can add sls-mentor to your project's development dependencies.

npm install --save-dev sls-mentor
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To help you quickly understand the improvements you can bring your infrastructure, a bit at a time, sls-mentor comes with tons of options to reduce the scope of the analysis in a run.

Focus the analysis on a specific CloudFormation stack

Use the option -c to focus the analysis on specific CloudFormation stacks.

npx sls-mentor -c my-stack
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Focus the analysis on specific tags

Use the option -t to focus the analysis on specific tags.

npx sls-mentor -t Key=my-tag,Value=my-value
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Because AWS has quite restrictive rate limiting policy, it may be required to use at least one option if you have really big stacks.

sls-mentor is optimized to reduce its number of requests. For projects with a lot of resources, it will throttle requests to respect AWS quotas. This might cause a longer analysis time.

sls-mentor is best run in your CI

I recommend adding sls-mentor checks to a recurring job in your CI platform to get a periodic report of the improvements you can bring to your infrastructure. Depending on how often your infrastructure changes, you can run sls-mentor once a day, once a week or once a month.

By default, sls-mentor will exit with a non-zero code if it finds any issue. I recommend keeping this default setting and optionally use your CI provider option to allow this failing job. This way, you will be notified of any issue, and you will not block your deployment flow. Otherwise, you can use the option --noFail to always exit with a success code.

CI snippets

GitLab CI

This snippet will run sls-mentor after merge.

  image: node:16.17.0
    - post-deploy-test # the stage after your deployment
    - .setup-cli # setup AWS CLI (export environment variables)
    - install # the job that installs your dependencies
    - yarn sls-mentor -r eu-west-1 -c <stacks> # fill in the stacks you want to check
  allow_failure: true # allow the job to fail, when you want to run subsequent tests
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Circle CI

This snippet will run sls-mentor at 01:00 on Sundays.

      - image: cimg/node:16.17.0
      - checkout # checkout your code
      - setup-aws-cli # setup AWS CLI (export environment variables)
      - install # install your dependencies
      - run: yarn sls-mentor -p my-aws-profile -c my-stack-1 my-stack-2
      - schedule:
          cron: '0 1 * * 0' # run at 01:00 on Sundays
                - main
      - sls-mentor-checks
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⚠ You should be running at least Node v16 to get the appropriate return code.

Some issues are more important to you than others

That's why sls-mentor organizes the checks in 5 categories.

🌱 Green IT: this one is my favorite, it's about reducing your carbon footprint

💲 Costs: this one helps you reduce your AWS bill,

🔒 Security: you know, the thing that is important to you,

⚡ Speed: you know, the thing that is important to your users,

🧘 Stability: that's for your team.

To illustrate, let's consider the following two checks.

1. ARM – 🌱 + 💲 + ⚡

The default architecture for Lambdas functions is x86_64 but should be configure to arm64. Lambda functions that use arm64 architecture (AWS Graviton2 CPU) can achieve 34% better price performance than the equivalent function running on x86_64 architecture.

Full article on Lambda function architectures

2. S3 Intelligent Tiering – 💲

sls-mentor not only has checks for Lambda, but other AWS services as well. For example, the S3 Intelligent Tiering storage class is designed to optimize storage costs by automatically moving data to the most cost-effective access tier. For a small monthly charge, S3 Intelligent Tiering monitors access patterns and automatically moves objects that have not been accessed for a long time to lower-cost access tiers.

As I mentioned in the introduction, new checks are frequently added

We are currently working on a check to avoid infinite log retention in CloudWatch.

Starting from version 1.0.0, whenever a new rule is added, at least the minor version will be bumped.

⚠ If sls-mentor is configured to stop your deployment whenever a rule fails, do not to allow any minor version update (see semver), as the introduction of a new rule could suddenly stop your deployment.

sls-mentor: AWS Trusted Advisor's little brother?

On your path to a perfect AWS Cloud architecture, sls-mentor is a good first step before the advanced AWS Trusted Advisor.

sls-mentor's background is a different from AWS Trusted Advisor because rules are sourced from the community. Because sls-mentor uses the AWS SDK, power users can also add their own rules with maximum flexibility.

Solution Cost Source
sls-mentor Free Community
Trusted Advisor Start from $29 / month (depends on your plan and monthly AWS charges) AWS

In the end, both tools may be used together. ✨

About Kumo

This project was started at Kumo, a group of passionate developers highly experienced in Serverless architectures for the Web, to bring the highest quality solutions to our clients. sls-mentor has many valuable learnings of our team to help you learn faster.

Feel free to reach out to us on Twitter if you have any questions or feedback.

See also

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