Kelbim
Classic ELBManage AWS Classic Load Balancers as code with Ruby
- Manages
- AWS Elastic Load Balancing (Classic Load Balancer)
- Language
- Ruby
- Package
- kelbim
- CLI
- kelbim
- Config file
- ELBfile
ec2 do
load_balancer "my-load-balancer" do
instances(
"cthulhu",
"nyar",
)
listeners do
listener [:http, 80] => [:http, 80]
end
health_check do
target "HTTP:80/index.html"
timeout 5
interval 30
healthy_threshold 10
unhealthy_threshold 2
end
end
endKelbim is a command-line tool that manages AWS Classic Load Balancers as code. You keep listeners, health checks, and policies in a Ruby file called an ELBfile, then apply it to update AWS. It supports the original Classic ELB only, not ALB or NLB.
What is Kelbim?
Kelbim manages AWS Classic Load Balancers as code. Each load balancer is described in a Ruby file called an ELBfile. The kelbim command compares the file to the live setup and applies only the difference.
Classic ELB settings are easy to get subtly wrong. A health check interval gets tweaked in the console. A listener is added during an incident and never written down. Kelbim moves these settings into version control, where each change is a diff you can review and dry-run first. This is the codenization approach.
An ELBfile can describe:
- Listeners, including SSL listeners with certificates
- Health checks, targets, and thresholds
- Attached instances, subnets, security groups, and policies
Kelbim covers Classic Load Balancers only. It predates ALB and NLB. So it mainly helps teams still running legacy ELBs, often beside Piculet for the security groups those balancers use.
- Manages Classic Load Balancers only, not ALB or NLB.
- Listeners, health checks, and policies all live in one ELBfile.
- Handles SSL listeners with certificates and load balancer policies.
- A built-in test mode reports mismatches between the file and live ELBs.
- Dry-runs double as drift detection for hand edits during incidents.
- The repo is archived since 2017, so plan an ALB or NLB migration.
Install and run Kelbim
Install
Install the kelbim gem (Ruby required).
$ gem install kelbimExport current state
Pull the live Classic ELB configuration into a ELBfile.
$ kelbim -e -o ELBfileDry-run, then apply
Preview the diff, then apply the change for real.
$ kelbim -a --dry-runKelbim uses a plain export, review, apply loop. Export the live setup with kelbim -e, or --split-more for one file per load balancer, and commit it to Git. That snapshot becomes the single source of truth for listeners, health checks, subnets, and policies. It fits the standard export, review, apply workflow.
Changes then happen in the file, not the console. Edit the ELBfile in a branch and run kelbim -a --dry-run to see what would be created, changed, or removed. Attach that output to the pull request. After review, kelbim -a applies it idempotently, so re-running makes no further changes. A periodic dry-run, or kelbim -t, catches listener or health check edits made by hand during an incident.
Use a Kelbim export as your migration map. It lists every listener mapping and policy in one place, which makes translating a Classic ELB into an ALB or NLB much easier.
What Kelbim can do
Export existing load balancers
kelbim -e writes current ELB config to an ELBfile. Use --split or --split-more for per-VPC or per-load-balancer files, which keeps diffs manageable.
Dry-run diffs
kelbim -a --dry-run previews every listener, instance, health check, and policy change. Nothing touches a production balancer unreviewed.
Listener and policy management
The DSL declares listener port mappings, including SSL listeners with certificates, plus load balancer policies. Use --without-deleting-policy to keep unmanaged policies.
Built-in inspection commands
--show-load-balancers and --show-policies dump the live state of your ELBs and policy types from the command line. No console needed.
Test mode
kelbim -t checks the real ELB config against your ELBfile and reports mismatches. It is a quick drift check for load balancer settings.
Scoped operations
-n or --elb-names limits work to specific balancers, and --ec2s restricts to certain VPCs. Both help in shared accounts.
| Feature | Supported? |
|---|---|
| Classic Load Balancer (ELB) | Yes |
| Application Load Balancer (ALB) | No |
| Network Load Balancer (NLB) | No |
| SSL listeners and certificates | Yes |
| Load balancer policies | Most types |
| ProxyProtocol, BackendServerAuth, PublicKey policies | Not supported |
When teams reach for Kelbim
Documenting legacy Classic ELBs
Many old accounts still run Classic balancers nobody dares touch. A Kelbim export turns them into readable code. You get an instant list of listeners, certificates, and health checks to review and audit.
Safe health check tuning
Changing thresholds on a production balancer is nerve-wracking. With Kelbim the change is a two-line diff. The dry-run confirms scope, and Git gives you an instant revert path if error rates move.
Preparing an ALB/NLB migration
Before leaving Classic ELB, you need a precise picture of current behavior. The ELBfile captures every listener mapping and policy in one place, so translating to ALB or NLB is far easier.