Crab 🦀

Dynamic configuration file templating tool for kubernetes manifest or general configuration files

How to install

Download according to your computer architecture at release page go to release page

OS	Platform	Status
Ubuntu, Debian	amd64, arm64, 386	available
MacOS, Darwin	amd64, arm64, 386	available
Windows	amd64, arm64, 386	available

Extract using command like :

tar -xzf crab-cli-v0.1.0-darwin-amd64.tar.gz -C crab

Move to /usr/local/bin (Optional) :

cp crab/crab /usr/local/bin

Then check crab cli working properly :

Build From Source

• clone this repository
• make sure you have go version 18
• run make build

How to use

basic command fromat :

  crab -f <fileinputpath> -r <keyvalue> -o <outputfilepath>

Flags :

Flag	Description	Required	default
-f	file input path location eg. ./manifest/nginx.yaml (accept any config file ext, .env, json, yml, yaml etc.)	true	-
-o	write output file location eg. ./manifest/nginx-result.yaml	false	same as input file path (overwrite)
-r	key value replacable	true	-
-q	key value replacable with quotes	false	-
-v	verbose process	false	false

Case 1 Standart replace

First add {{replacableName}} to your file :

apiVersion: v1
kind: Service
metadata:
    name: nginx
    namespace: {{namespace}}
spec:
    ports:
      - targetPort: 80
        name: nginxhttp
        port: {{exposePort}}

crab cli will replace {{replacableName}} as the key, based on the example above :

• {{namespace}}
• {{exposePort}}

then run crab command :

  crab -f inputfile.yaml -r namespace=production -r exposePort=8081

yes you can override multiple key values ✔️

write output to another file add -o flag:

  crab -f inputfile.yaml -r namespace=production -r exposePort=8081 -o result.yaml

to make verbose add -v flag:

  crab -f inputfile.yaml -r namespace=production -r exposePort=8081 -o result.yaml -v

verbose output :

[REPLACED] from namespace to production
[REPLACED] from exposePort to 8081
[DONE] Crab output result at result.yaml

the result will be :

apiVersion: v1
kind: Service
metadata:
    name: nginx
    namespace: production
spec:
    ports:
      - targetPort: 80
        name: nginxhttp
        port: 8081

Click to watch the demo :

Youtube demo video :

• go to youtube

Case 2 Quotes replace

sometimes your config file needs string quotes, (like for env vars or connection string):

  namespace="production"

template file example :

apiVersion: v1
kind: Service
metadata:
    name: nginx
    namespace: {{namespace}}
spec:
    ports:
      - targetPort: 80
        name: nginxhttp
        port: {{exposePort}}

let's say we need a quote in the namespace :

  crab -f inputfile.yaml -q namespace=production -r exposePort=8081 -o result.yaml -v

yass you can simultaneously Replace multiple key values with quotes or not ✔️

result will be :

apiVersion: v1
kind: Service
metadata:
    name: nginx
    namespace: "production"
spec:
    ports:
      - targetPort: 80
        name: nginxhttp
        port: 8081

Sample Github Action

name: Demo deployment using crab

on:
  workflow_dispatch:

jobs:
  crab-manifest:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: mock job
        run: pwd

  deploy-test:
    runs-on: ubuntu-latest
    needs: crab-manifest
    steps:
      - uses: actions/checkout@v3
      - name: install crab cli
        run: wget -c https://github.com/alfiankan/crab-config-files-templating/releases/download/v1.0.5/crab-v1.0.5-linux-amd64.tar.gz -O - | tar -xz crab
      - name: recreate deployment manifest on test
        run: |
          ./crab -f example/manifest/nginx.yaml \
          -r namespace=test \
          -r publishPort=8000 \
          -q portName=test-server \
          -o nginx-test.yaml \
          -v
      - name: view manifest
        run: cat nginx-test.yaml
                    
  
  deploy-production:
    runs-on: ubuntu-latest
    needs: crab-manifest
    steps:
      - uses: actions/checkout@v3
      - name: install crab cli
        run: wget -c https://github.com/alfiankan/crab-config-files-templating/releases/download/v1.0.5/crab-v1.0.5-linux-amd64.tar.gz -O - | tar -xz crab
      - name: recreate deployment manifest on production
        run: |
          ./crab -f example/manifest/nginx.yaml \
          -r namespace=production \
          -r publishPort=80 \
          -q portName=prod-server \
          -o nginx-prod.yaml \
          -v
      - name: view manifest
        run: cat nginx-prod.yaml

Related article

• Replacing kubernetes manifest value dynamicly (coming soon on medium)