Add Ruby/Rack application example with hot reload (#3515)

* Add Ruby/Rack application example with hot reload

* Optimize docker build with dependencies caching

* Change sync option to infer

* Comment typo

* Copy ruby example to examples/ruby folder

examples/ruby/README.md

@@ -0,0 +1,18 @@
+### Example: Ruby/Rack with hot-reload
+
+Simple example based on Ruby/Rack application demonstrating the file synchronization mode.
+
+#### Init
+
+```bash
+skaffold dev
+```
+
+#### Workflow
+
+* Make some changes to `app.rb`:
+    * The file will be synchronized to the cluster
+* Make some changes to `Gemfile`:
+    * The full build/push/deploy process will be triggered, fetching dependencies from `rubygems`
+
+

examples/ruby/backend/Dockerfile

@@ -0,0 +1,9 @@
+FROM ruby:2.7
+
+WORKDIR /app
+ADD Gemfile* ./
+RUN bundle install
+
+ADD . ./
+
+CMD ["bundle","exec","puma"]

examples/ruby/backend/Gemfile

@@ -0,0 +1,5 @@
+source 'https://rubygems.org'
+
+gem 'rack'
+gem 'rack-unreloader' # for dynamic reloading
+gem 'puma'

examples/ruby/backend/Gemfile.lock

@@ -0,0 +1,16 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    nio4r (2.5.2)
+    puma (4.3.1)
+      nio4r (~> 2.0)
+    rack (2.1.1)
+    rack-unreloader (1.7.0)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  puma
+  rack
+  rack-unreloader

examples/ruby/backend/app.rb

@@ -0,0 +1,5 @@
+class App
+  def self.call(env)
+    [ 200, {"Content-Type" => "text/html"}, ["Hello Skaffold!"]]
+  end
+end

examples/ruby/backend/config.ru

@@ -0,0 +1,7 @@
+require './app.rb'
+
+require 'rack/unreloader'
+Unreloader = Rack::Unreloader.new{App}
+
+Unreloader.require './*.rb'
+run Unreloader

examples/ruby/k8s/deployment.yaml

@@ -0,0 +1,33 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: ruby
+spec:
+  ports:
+  - port: 9292
+    targetPort: 9292
+  type: LoadBalancer
+  selector:
+    app: ruby
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: ruby
+spec:
+  selector:
+    matchLabels:
+      app: ruby
+  template:
+    metadata:
+      labels:
+        app: ruby
+    spec:
+      containers:
+      - name: ruby
+        image: ruby-example
+        ports:
+        - containerPort: 9292
+        env:
+          - name: RACK_ENV
+            value: "development"

examples/ruby/skaffold.yaml

@@ -0,0 +1,11 @@
+apiVersion: skaffold/v2alpha1
+kind: Config
+build:
+  artifacts:
+  - image: ruby-example
+    context: backend
+    sync:
+      # Sync app.rb file, being watch with rack-unreloader
+      # or add any other rb file to your application 
+      infer:
+      - '*.rb'

integration/examples/ruby/README.md

@@ -0,0 +1,18 @@
+### Example: Ruby/Rack with hot-reload
+
+Simple example based on Ruby/Rack application demonstrating the file synchronization mode.
+
+#### Init
+
+```bash
+skaffold dev
+```
+
+#### Workflow
+
+* Make some changes to `app.rb`:
+    * The file will be synchronized to the cluster
+* Make some changes to `Gemfile`:
+    * The full build/push/deploy process will be triggered, fetching dependencies from `rubygems`
+
+

integration/examples/ruby/backend/Dockerfile

@@ -0,0 +1,9 @@
+FROM ruby:2.7
+
+WORKDIR /app
+ADD Gemfile* ./
+RUN bundle install
+
+ADD . ./
+
+CMD ["bundle","exec","puma"]

integration/examples/ruby/backend/Gemfile

@@ -0,0 +1,5 @@
+source 'https://rubygems.org'
+
+gem 'rack'
+gem 'rack-unreloader' # for dynamic reloading
+gem 'puma'

integration/examples/ruby/backend/Gemfile.lock

@@ -0,0 +1,16 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    nio4r (2.5.2)
+    puma (4.3.1)
+      nio4r (~> 2.0)
+    rack (2.1.1)
+    rack-unreloader (1.7.0)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  puma
+  rack
+  rack-unreloader

integration/examples/ruby/backend/app.rb

@@ -0,0 +1,5 @@
+class App
+  def self.call(env)
+    [ 200, {"Content-Type" => "text/html"}, ["Hello Skaffold!"]]
+  end
+end

integration/examples/ruby/backend/config.ru

@@ -0,0 +1,7 @@
+require './app.rb'
+
+require 'rack/unreloader'
+Unreloader = Rack::Unreloader.new{App}
+
+Unreloader.require './*.rb'
+run Unreloader

integration/examples/ruby/k8s/deployment.yaml

@@ -0,0 +1,33 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: ruby
+spec:
+  ports:
+  - port: 9292
+    targetPort: 9292
+  type: LoadBalancer
+  selector:
+    app: ruby
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: ruby
+spec:
+  selector:
+    matchLabels:
+      app: ruby
+  template:
+    metadata:
+      labels:
+        app: ruby
+    spec:
+      containers:
+      - name: ruby
+        image: ruby-example
+        ports:
+        - containerPort: 9292
+        env:
+          - name: RACK_ENV
+            value: "development"

integration/examples/ruby/skaffold.yaml

@@ -0,0 +1,11 @@
+apiVersion: skaffold/v2alpha1
+kind: Config
+build:
+  artifacts:
+  - image: ruby-example
+    context: backend
+    sync:
+      # Sync app.rb file, being watch with rack-unreloader
+      # or add any other rb file to your application 
+      infer:
+      - '*.rb'