Kelda

Kelda creates easy to use development environments for microservices.

Setup

Kelda runs in a Kubernetes cluster. It does not create the cluster itself.

Kelda has two components:

• The Minion is a pod that runs in the cluster. It's responsible for creating and managing development namespaces.
• The CLI is how developers interact with their development namespace. It should be installed on the developer's laptop.

Minion

1. Deploy the Minion pod

   $ kelda setup-minion --license <path to license>
   

2. Check that it booted:

   $ kubectl logs -l service=kelda -n kelda
   

CLI

Install the CLI binary into your PATH

$ cp ./bin/kelda /usr/local/bin

Configuration Files

kubeconfig

Kelda uses the credentials stored in ~/.kube/config for communicating with the development cluster. The user is expected to setup their kubeconfig themselves.

User Configuration

The developer's laptop requires a configuration file in ~/.kelda.yaml.

# A unique namespace that will be used for the development namespace.
namespace: kevin

# The Kubernetes cluster to use for development. The name of the current
# cluster can be retrieved through `kubectl config current-context`.
context: dev-cluster

# The path to the configuration for deploying the application.
# More explanation on the workspace.yaml is below.
workspace: ~/kelda-workspace/workspace.yaml

To setup the user configuration:

1. Make sure the current Kubernetes context is set to the development cluster.
2. cd into the Kelda workspace directory.
3. Run kelda config.

Workspace Configuration

The workspace.yaml specifies what services and tunnels should be created in the development namespace.

tunnels:
  - serviceName: "gateway"
    remotePort: 80
    localPort: 8080

services:
  - name: "authorization-api"
  - name: "web-server"
  - name: "content-api"

The Kubernetes YAML for each service is stored in a directory with the same name. This YAML is deployed in each development namespace.

├── workspace.yaml
├── authorization-api
│   ├── deployment-authorization-api.yaml
│   └── service-authorization-api.yaml
├── content-api
│   ├── configmap-scss-compiler-config.yaml
│   ├── deployment-content-api.yaml
│   └── service-content-api.yaml
└── web-server
    ├── configmap-web-app-config.yaml
    ├── deployment-web.yaml
    └── service-web.yaml

Registry Credentials

The regcred secret in the kelda namespace is automatically copied to each development namespace. Kubernetes manifests can then reference this secret as an ImagePullSecret.

$ kubectl create secret docker-registry regcred -n kelda \
    --docker-server https://index.docker.io/v1/ \
    --docker-username=USERNAME \
    --docker-password=PASSWORD \
    --docker-email=EMAIL

Service Development Configuration

The directory from which kelda dev is run must have a configuration file named kelda.yaml that specifies how to run the service when in development mode.

# REQUIRED. Name of the service. Must match the name in workspace.yaml.
name: SERVICE_NAME

# REQUIRED. The files to sync from the local machine to the container.
sync:
- from: SRC_ON_LAPTOP
  to: DST_IN_CONTAINER
  except: ['.git']

# OPTIONAL. The image to run.
# If not set, Kelda uses the same image as when not developing.
image: DEV_IMAGE

# OPTIONAL. The command to run in the development container.
# If not set, Kelda uses the same command as when not developing.
command: DEV_COMMAND

File Sync Limitations

Kelda opens a file descriptor for each directory/subdirectory that's being synced, so the number of files that can be synced are limited by the system's maximum number of open files. If the limit is too low, kelda dev will error with "too many open files in system".

On OSX, the default maximum number of open files is 256. This can be increased by editing the limit.maxfiles: https://medium.com/mindful-technology/too-many-open-files-limit-ulimit-on-mac-os-x-add0f1bfddde.

Usage

kelda dev

kelda dev is the main process. It...

• Creates the development namespace.
• Is the main status view of the development namespace.
• Syncs local code changes to the development namespace.
• Keeps tunnels open for accessing the application.

Run it in the directory containing the kelda.yaml sync config.

Debugging

kelda ssh <SERVICE> creates a shell in SERVICE.

kelda logs <SERVICE> shows the logs of SERVICE.

Cleaning Up

kelda delete deletes the developer's namespace.

Upgrading

1. Download and install the latest version of the kelda CLI

2. Deploy the new version of the Kelda minion with

   $ kelda setup-minion --license <path to license>
   

3. Delete old development namespaces created by the previous version

   $ kelda delete
   

   Note This will only affect the current user's namespace. Each developer must run kelda delete.

4. Resume development

   $ kelda dev