feat: add limiter service written in go

The limiter service is a reverse proxy written in go that
adds rate limiting functionality to make the vote process more fair.

This is to highlight that code synchronization works as well with
compiled languages like go as with dynamic languages like python.

.gitignore

@@ -68,3 +68,6 @@ typings/
 # IDEs
 .vscode
 .history
+
+# macOS
+.DS_Store

api/garden.yml

@@ -1,14 +1,14 @@
 ---
 kind: Build
 type: container
-name: api-build
+name: api
 description: The backend build for the voting UI
 
 ---
 kind: Deploy
 type: container
 name: api
-build: api-build
+build: api
 description: The backend deploy for the voting UI
 spec:
   args: [python, app.py]
@@ -25,7 +25,7 @@ spec:
   ingresses:
     - path: /
       port: http
-      hostname: api.${variables.base-hostname}
+      hostname: api-${variables.base-hostname}
   healthCheck:
     httpGet:
       path: /health
@@ -38,6 +38,6 @@ kind: Test
 type: container
 name: unit
 description: Unit test for backend API
-build: api-build
+build: api
 spec:
-  args: ["echo", "ok"]
+  args: ["echo", "ok"]

limiter/Dockerfile

@@ -0,0 +1,7 @@
+FROM golang:alpine as prod
+RUN mkdir /app
+ADD ./src /app/
+WORKDIR /app
+RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o main .
+CMD ["/app/main"]
+EXPOSE 8080

limiter/Dockerfile.syncmode

@@ -0,0 +1,8 @@
+FROM cosmtrek/air:latest as sync
+
+# We do not copy anything on purpose in sync mode.
+# Code will be copied using mutagen as part of Garden's code synchronization feature.
+RUN mkdir /app
+WORKDIR /app
+
+EXPOSE 8080

limiter/garden.yml

@@ -0,0 +1,54 @@
+# Production container to be used without sync mode.
+kind: Build
+type: container
+name: limiter-prod
+include:
+  - src
+  - Dockerfile
+exclude:
+  - src/tmp/*
+spec:
+  dockerfile: "Dockerfile"
+
+---
+
+# The sync container only provides the tools necessary for building the library
+# when using it during inner loop development together with Garden's sync mode.
+kind: Build
+type: container
+name: limiter-sync
+include:
+  - Dockerfile.syncmode
+spec:
+  dockerfile: "Dockerfile.syncmode"
+
+---
+
+kind: Deploy
+type: container
+name: limiter
+build:
+  $if: ${command.params contains 'sync' && (command.params.sync contains 'limiter' || isEmpty(command.params.sync))}
+  $then: limiter-sync
+  $else: limiter-prod
+include: []
+dependencies:
+  - deploy.api
+spec:
+  sync:
+    command: [air]
+    paths:
+      - target: /app
+        source: ./src
+        mode: one-way-replica
+        exclude: ["tmp/*/**"]
+  ports:
+    - name: http
+      containerPort: 8080
+      servicePort: 80
+  ingresses:
+    - path: /
+      port: http
+      hostname: limiter-${var.base-hostname}
+  env:
+    PROXY_URL: http://api

limiter/src/.air.toml

@@ -0,0 +1,44 @@
+root = "."
+testdata_dir = "testdata"
+tmp_dir = "tmp"
+
+[build]
+  args_bin = []
+  bin = "./tmp/main"
+  cmd = "go build -o ./tmp/main ."
+  delay = 0
+  exclude_dir = ["assets", "tmp", "vendor", "testdata"]
+  exclude_file = []
+  exclude_regex = ["_test.go"]
+  exclude_unchanged = false
+  follow_symlink = false
+  full_bin = ""
+  include_dir = []
+  include_ext = ["go", "tpl", "tmpl", "html"]
+  include_file = []
+  kill_delay = "0s"
+  log = "build-errors.log"
+  poll = false
+  poll_interval = 0
+  rerun = false
+  rerun_delay = 500
+  send_interrupt = false
+  stop_on_error = false
+
+[color]
+  app = ""
+  build = "yellow"
+  main = "magenta"
+  runner = "green"
+  watcher = "cyan"
+
+[log]
+  main_only = false
+  time = false
+
+[misc]
+  clean_on_exit = false
+
+[screen]
+  clear_on_rebuild = false
+  keep_scroll = true

limiter/src/.gitignore

@@ -0,0 +1 @@
+tmp

limiter/src/go.mod

@@ -0,0 +1,12 @@
+module example.garden.io/m
+
+go 1.20
+
+require github.com/didip/tollbooth/v7 v7.0.1
+
+require (
+	github.com/didip/tollbooth v4.0.2+incompatible // indirect
+	github.com/go-pkgz/expirable-cache v0.1.0 // indirect
+	github.com/patrickmn/go-cache v2.1.0+incompatible // indirect
+	golang.org/x/time v0.3.0 // indirect
+)

limiter/src/go.sum

@@ -0,0 +1,16 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/didip/tollbooth v4.0.2+incompatible h1:fVSa33JzSz0hoh2NxpwZtksAzAgd7zjmGO20HCZtF4M=
+github.com/didip/tollbooth v4.0.2+incompatible/go.mod h1:A9b0665CE6l1KmzpDws2++elm/CsuWBMa5Jv4WY0PEY=
+github.com/didip/tollbooth/v7 v7.0.1 h1:TkT4sBKoQoHQFPf7blQ54iHrZiTDnr8TceU+MulVAog=
+github.com/didip/tollbooth/v7 v7.0.1/go.mod h1:VZhDSGl5bDSPj4wPsih3PFa4Uh9Ghv8hgacaTm5PRT4=
+github.com/go-pkgz/expirable-cache v0.1.0 h1:3bw0m8vlTK8qlwz5KXuygNBTkiKRTPrAGXU0Ej2AC1g=
+github.com/go-pkgz/expirable-cache v0.1.0/go.mod h1:GTrEl0X+q0mPNqN6dtcQXksACnzCBQ5k/k1SwXJsZKs=
+github.com/patrickmn/go-cache v2.1.0+incompatible h1:HRMgzkcYKYpi3C8ajMPV8OFXaaRUnok+kx1WdO15EQc=
+github.com/patrickmn/go-cache v2.1.0+incompatible/go.mod h1:3Qf8kWWT7OJRJbdiICTKqZju1ZixQ/KpMGzzAfe6+WQ=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+golang.org/x/time v0.3.0 h1:rg5rLMjNzMS1RkNLzCG38eapWhnYLFYXDXj2gOlr8j4=
+golang.org/x/time v0.3.0/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

limiter/src/main.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"log"
+	"net/http"
+	"net/http/httputil"
+	"net/url"
+	"os"
+
+	"github.com/didip/tollbooth"
+)
+
+func main() {
+	remote, err := url.Parse(os.Getenv("PROXY_URL"))
+	if err != nil {
+		panic(err)
+	}
+
+	// Rate limiter: Allow one vote per second.
+	// Suggestion: Try reducing this to 0.1 to allow one vote every 10 seconds.
+	// When using garden deploy --sync, the code change will be automatically synchronized
+	// See also https://docs.garden.io/guides/code-synchronization
+	limiter := tollbooth.NewLimiter(1, nil)
+	limiter.SetMessage("Please slow down.")
+	limiter.SetOnLimitReached(func(w http.ResponseWriter, r *http.Request) {
+		log.Printf("%s: Limiting: Too many requests", r.URL)
+	})
+
+	// Reverse proxy
+	handler := func(p *httputil.ReverseProxy) func(http.ResponseWriter, *http.Request) {
+		log.Println("Hello world!")
+
+		return func(w http.ResponseWriter, r *http.Request) {
+			log.Printf("%s: OK: Forwarding", r.URL)
+			r.Host = remote.Host
+			p.ServeHTTP(w, r)
+		}
+	}
+
+	proxy := httputil.NewSingleHostReverseProxy(remote)
+	http.Handle("/", tollbooth.LimitFuncHandler(limiter, handler(proxy)))
+	err = http.ListenAndServe(":8080", nil)
+	if err != nil {
+		panic(err)
+	}
+}

result/garden.yml

@@ -20,7 +20,7 @@ spec:
   ingresses:
     - path: /
       port: ui
-      hostname: result.${var.base-hostname}
+      hostname: result-${var.base-hostname}
   ports:
     - name: ui
       protocol: TCP

vote/garden.yml

@@ -27,12 +27,12 @@ spec:
   ingresses:
     - path: /
       port: http
-      hostname: vote.${var.base-hostname}
+      hostname: vote-${var.base-hostname}
   env:
-    HOSTNAME: vote.${var.base-hostname}
+    HOSTNAME: vote-${var.base-hostname}
     VUE_APP_USERNAME: ${local.username}
 dependencies:
-  - deploy.api
+  - deploy.limiter
   - deploy.result
 
 ---
@@ -55,7 +55,7 @@ type: container
 name: e2e-runner
 dependencies: [deploy.vote]
 spec:
-  image: ${actions.deploy.vote.outputs.deployedImageId}
+  image: ${actions.build.vote.outputs.deploymentImageId}
 
 ---
 kind: Test

vote/vue.config.js

@@ -5,7 +5,7 @@ module.exports = {
     progress: false,
     proxy: {
       '^/api': {
-        target: 'http://api',
+        target: `http://limiter`, // limiter is a rate limiting reverse proxy for the api
         changeOrigin: true,
         secure: false,
         logLevel: 'debug',