initial commit

.gitignore

@@ -0,0 +1,5 @@
+.DS_Store
+.env
+.idea/
+bin/
+vendor/

Procfile

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+web: bin/web
+worker: bin/worker

README.md

@@ -0,0 +1,18 @@
+
+# ⏰ 🐕 . 📧
+
+## Watchdog.Email
+
+Full source code for http://watchdog.email
+
+Inspired by a lack of simple watchdog timers, I set out to see what makes them so difficult.
+
+Currently deployed to Heroku with the following Apps:
+- Heroku Redis
+- Heroku Scheduler
+- Papertrail
+- SendGrid
+
+2 Free Dynos are used to run the service:
+- web - handles frontend http requests
+- worker - runs on-schedule to send emails

app.json

@@ -0,0 +1,12 @@
+{
+  "name": "Watchdog.Email",
+  "description": "A Service That Sends You An Email In 25 Hours",
+  "keywords": [
+    "watchdog",
+    "timer",
+    "email",
+    "service"
+  ],
+  "website": "http://watchdog.email",
+  "repository": "http://github.com/jareklupinski/watchdog-email"
+}

go.mod

@@ -0,0 +1,16 @@
+module watchdog-email
+
+go 1.12
+
+require (
+	github.com/gin-gonic/gin v0.0.0-20150626140855-4cc2de6207f4
+	github.com/gomodule/redigo v1.8.3
+	github.com/heroku/x v0.0.0-20171004170240-705849e307dd
+	github.com/manucorporat/sse v0.0.0-20150604091100-c142f0f1baea // indirect
+	github.com/mattn/go-colorable v0.0.0-20150625154642-40e4aedc8fab // indirect
+	github.com/mattn/go-isatty v0.0.0-20150814002629-7fcbc72f853b // indirect
+	github.com/sendgrid/rest v2.6.2+incompatible // indirect
+	github.com/sendgrid/sendgrid-go v3.7.2+incompatible
+	golang.org/x/net v0.0.0-20150629084131-d9558e5c97f8 // indirect
+	gopkg.in/bluesuncorp/validator.v5 v5.9.1 // indirect
+)

go.sum

@@ -0,0 +1,31 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/gin-gonic/gin v0.0.0-20150626140855-4cc2de6207f4 h1:ufr+93X0/9xTNvObfvbHsEkgCk8BrhmUH83Z8YIhzXE=
+github.com/gin-gonic/gin v0.0.0-20150626140855-4cc2de6207f4/go.mod h1:7cKuhb5qV2ggCFctp2fJQ+ErvciLZrIeoOSOm6mUr7Y=
+github.com/gomodule/redigo v1.8.3 h1:HR0kYDX2RJZvAup8CsiJwxB4dTCSC0AaUq6S4SiLwUc=
+github.com/gomodule/redigo v1.8.3/go.mod h1:P9dn9mFrCBvWhGE1wpxx6fgq7BAeLBk+UUUzlpkBYO0=
+github.com/heroku/x v0.0.0-20171004170240-705849e307dd h1:zn29UrzyUeQgqxBGXIwQqQJf75IiK4aeCtO5q1V2Vyo=
+github.com/heroku/x v0.0.0-20171004170240-705849e307dd/go.mod h1:opmAyjmIGn9/Y+9Nia6eIaktIXIoMhhFXEFbHLMsX3Y=
+github.com/manucorporat/sse v0.0.0-20150604091100-c142f0f1baea h1:3she1OMibtVtGiZSF65Cfi5ijRb+pAKXmstffNs5i+4=
+github.com/manucorporat/sse v0.0.0-20150604091100-c142f0f1baea/go.mod h1:zUx1mhth20V3VKgL5jbd1BSQcW4Fy6Qs4PZvQwRFwzM=
+github.com/mattn/go-colorable v0.0.0-20150625154642-40e4aedc8fab h1:3lgod/2wdM8WaJNBe16LkFmrz2XkXbH2YhbRWh38W9U=
+github.com/mattn/go-colorable v0.0.0-20150625154642-40e4aedc8fab/go.mod h1:9vuHe8Xs5qXnSaW/c/ABM9alt+Vo+STaOChaDxuIBZU=
+github.com/mattn/go-isatty v0.0.0-20150814002629-7fcbc72f853b h1:KOTLb2pwNaE8UOCVz1AgsFYzcswaNroRkBDIhblvUFk=
+github.com/mattn/go-isatty v0.0.0-20150814002629-7fcbc72f853b/go.mod h1:M+lRXTBqGeGNdLjl/ufCoiOlB5xdOkqRJdNxMWT7Zi4=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/sendgrid/rest v2.6.2+incompatible h1:zGMNhccsPkIc8SvU9x+qdDz2qhFoGUPGGC4mMvTondA=
+github.com/sendgrid/rest v2.6.2+incompatible/go.mod h1:kXX7q3jZtJXK5c5qK83bSGMdV6tsOE70KbHoqJls4lE=
+github.com/sendgrid/sendgrid-go v3.7.2+incompatible h1:ePQr9ns8so+28whk+gLKRYiyI5IiCESkDIqy7cjiwLg=
+github.com/sendgrid/sendgrid-go v3.7.2+incompatible/go.mod h1:QRQt+LX/NmgVEvmdRw0VT/QgUn499+iza2FnDca9fg8=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.5.1 h1:nOGnQDM7FYENwehXlg/kFVnos3rEvtKTjRvOWSzb6H4=
+github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
+golang.org/x/net v0.0.0-20150629084131-d9558e5c97f8 h1:NnqNZS6fS9JZOjzXyL3/g0j4bEm1B7HCkiVH9F5Zu8U=
+golang.org/x/net v0.0.0-20150629084131-d9558e5c97f8/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+gopkg.in/bluesuncorp/validator.v5 v5.9.1 h1:XEU2HtMj0Rki3kmHh+uilvENyWgDEaR5LDLtYsjiumM=
+gopkg.in/bluesuncorp/validator.v5 v5.9.1/go.mod h1:ScQmud/GM3iSR85jRE+8BI8E8oFv5oj4qyd5Xaw7hgE=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

static/main.css

@@ -0,0 +1,22 @@
+.jumbotron {
+  background: #532F8C;
+  color: white;
+  padding-bottom: 80px;
+}
+
+.jumbotron .btn {
+  background: #a49cb1;
+  color: white;
+  border-color: #845ac7;
+  margin-left: 0.75em;
+}
+
+.jumbotron .btn:hover {
+  background: #9580b7;
+}
+
+.jumbotron p {
+  color: #d9ccee;
+  max-width: 75%;
+  margin: 1em auto 2em;
+}

templates/index.html

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+<html lang="en">
+<head>
+  <title>Watchdog.Email</title>
+  <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
+  <script type="text/javascript" src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.4/js/bootstrap.min.js"></script>
+  <link rel="stylesheet" type="text/css" href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css"/>
+  <link rel="stylesheet" type="text/css" href="/static/main.css"/>
+</head>
+<body>
+<div class="jumbotron text-center">
+  <div class="container">
+    <h1>
+      ⏰ 🐕 . 📧
+    </h1>
+    <h2>
+      Watchdog.Email
+    </h2>
+    <p>
+      A Service That Sends You An Email In 25 Hours
+    </p>
+    <form class="form-inline" action="/" method="get">
+      <div class="form-group form-group-lg">
+        <label class="sr-only" for="email">Email address</label>
+        <input type="email" class="form-control form-control-lg" id="email" name="email" placeholder="Email">
+      </div>
+      <input type="submit" class="btn btn-lg btn-default" value="Start Watchdog">
+    </form>
+  </div>
+</div>
+<div class="container">
+  <div class="alert alert-info text-center">
+    Privacy Policy: We will only ever send you one email; when your Watchdog times out after 25 hours. After the email is sent, your address is wiped from our database.
+  </div>
+  <hr>
+  <div class="row">
+    <div class="col-md-6">
+      <h3>
+        <span class="glyphicon glyphicon-info-sign"></span>
+        How This Works
+      </h3>
+      <ul>
+        <li>
+          When you type in an email address and click Start Watchdog, a 25 Hour Watchdog Timer starts running on our servers.
+        </li>
+        <li>
+          After 25 hours have elapsed, Watchdog.Email sends an email to the address you specified notifying that the Watchdog Timer has run out.
+        </li>
+        <li>
+          If you want to delay the email from arriving for another 25 hours, type the same email address into the field again and click Start Watchdog to restart your Watchdog.
+        </li>
+        <li>
+          You can repeat this process as many times as you like; as long as you keep restarting your Watchdog within 25 hours, you will not receive an email.
+        </li>
+        <li>
+          You can also use this service programmatically by sending your Watchdog.Email request to <code>https://watchdog.email/?email=&lt;email_address&gt;</code>.
+        </li>
+      </ul>
+    </div>
+    <div class="col-md-6">
+      <h3>
+        <span class="glyphicon glyphicon-link"></span>
+        Further Reading
+      </h3>
+      <ul>
+        <li>
+          Wikipedia: A <a href="https://en.wikipedia.org/wiki/Watchdog_timer">watchdog timer</a> (sometimes called a
+          computer operating properly or COP timer, or simply a watchdog) is an electronic or software timer that is
+          used to detect and recover from computer malfunctions. During normal operation, the computer regularly resets
+          the watchdog timer to prevent it from elapsing, or "timing out". If, due to a hardware fault or program error,
+          the computer fails to reset the watchdog, the timer will elapse and generate a timeout signal. The timeout
+          signal is used to initiate corrective actions. The corrective actions typically include placing the computer
+          system in a safe state and restoring normal system operation.
+        </li>
+        <li>
+          Github: Full Source Code available at
+          <a href="https://github.com/jareklupinski/watchdog-email">https://github.com/jareklupinski/watchdog-email</a>
+        </li>
+      </ul>
+    </div>
+  </div>
+  <hr>
+  <div class="alert alert-info text-center">
+    We have no idea how to monetize this, and will continue to keep this running on a Heroku Free Tier until it begins accruing a billing rate above which we can spend.
+    If there is any danger to the service shutting down, we'll solicit some donations to keep the cost alive via Hackernews and Github.
+    If this still fails we will shutdown the incoming reset button and link for 25 hours by returning any calls to it with <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/402">a 402 error message</a>
+    to allow the last day's worth of watchdogs to elapse.
+  </div>
+</div>
+</body>
+</html>

util/email.go

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+package util
+
+import (
+	"github.com/sendgrid/sendgrid-go"
+	"github.com/sendgrid/sendgrid-go/helpers/mail"
+	"log"
+	"net"
+	"os"
+	"regexp"
+	"strings"
+)
+
+var emailRegex = regexp.MustCompile("^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$")
+
+func EmailIsValid(e string) bool {
+	if len(e) < 3 && len(e) > 254 {
+		return false
+	}
+	if !emailRegex.MatchString(e) {
+		return false
+	}
+	parts := strings.Split(e, "@")
+	mx, err := net.LookupMX(parts[1])
+	if err != nil || len(mx) == 0 {
+		return false
+	}
+	return true
+}
+
+func SendEmail(emailAddress string) {
+	from := mail.NewEmail("⏰🐕.📧", "[email protected]")
+	subject := "Your Watchdog.Email Timer has Fired!"
+	to := mail.NewEmail(emailAddress, emailAddress)
+	plainTextContent := "Reset your timer: http://watchdog.email/" + emailAddress
+	htmlContent := "Reset your timer: <a href=\"http://watchdog.email/" + emailAddress + "\">http://watchdog.email/" + emailAddress + "</a>"
+	message := mail.NewSingleEmail(from, subject, to, plainTextContent, htmlContent)
+	client := sendgrid.NewSendClient(os.Getenv("SENDGRID_API_KEY"))
+
+	response, err := client.Send(message)
+	if err != nil || response.StatusCode != 200 {
+		if response != nil {
+			log.Printf("Failed to send email to %s: %s, SendGrid Response %d: %s\n", emailAddress, err, response.StatusCode, response.Body)
+		} else {
+			log.Printf("Failed to send email to %s: %s, No SendGrid Response\n", emailAddress, err)
+		}
+	}
+}

util/redis.go

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+package util
+
+import (
+	"log"
+	"os"
+
+	"github.com/gomodule/redigo/redis"
+)
+
+type RedisController struct {
+	Conn redis.Conn
+}
+
+func NewRedisController() *RedisController {
+	redisURL := os.Getenv("REDIS_URL")
+	redisConnection, err := redis.DialURL(redisURL)
+	if err != nil {
+		log.Panicf("Failed to connect to $REDIS_URL %s\n", redisURL)
+	}
+	redisContext := RedisController{
+		Conn: redisConnection,
+	}
+	return &redisContext
+}
+
+func (r *RedisController) GetRedisConnection() redis.Conn {
+	rds := r.Conn
+	if rds == nil {
+		log.Panic("Redis Connection attempted before Redis Initialized!")
+	}
+	return rds
+}
+
+func (r *RedisController) CloseRedisController() {
+	err := r.Conn.Close()
+	if err != nil {
+		log.Panicf("Failed to close connection to redis %s\n", err)
+	}
+}

web/main.go

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+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"os/signal"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/gomodule/redigo/redis"
+	_ "github.com/heroku/x/hmetrics/onload"
+
+	"watchdog-email/util"
+)
+
+func startWatchdog(r *util.RedisController) gin.HandlerFunc {
+	fn := func(c *gin.Context) {
+		email := c.Query("email")
+		if email == "" {
+			c.HTML(http.StatusOK, "index.html", nil)
+			return
+		}
+		if !util.EmailIsValid(email) {
+			c.String(http.StatusBadRequest, "Cannot set Watchdog.Email timer for %s", email)
+			return
+		}
+		rds := r.GetRedisConnection()
+		now := time.Now().Unix()
+		alarm := now + 90000 // (60 seconds / minute) * (60 minutes / hour) * (25 hours / timeout)
+		rows, err := redis.Int(rds.Do("ZADD", "email", "CH", alarm, email))
+		if err != nil || rows < 1 {
+			log.Printf("Failed to set Watchdog.Email timer for %s: %s", email, err)
+			c.String(http.StatusInternalServerError, "Failed to set Watchdog.Email timer for %s", email)
+			return
+		}
+		c.String(http.StatusOK, "Watchdog.Email has been set at %d to send an email to %s at %d", now, email, alarm)
+	}
+	return fn
+}
+
+func main() {
+	log.Println("Watchdog.Email Server Starting")
+	redisContext := util.NewRedisController()
+
+	port := os.Getenv("PORT")
+	if port == "" {
+		log.Panic("$PORT must be set")
+	}
+
+	gin.SetMode(gin.ReleaseMode)
+	router := gin.New()
+	router.Use(gin.Logger())
+	router.LoadHTMLGlob("templates/*.html")
+	router.Static("/static", "static")
+	router.GET("/", startWatchdog(redisContext))
+	srv := &http.Server{
+		Addr:    fmt.Sprintf(":%s", port),
+		Handler: router,
+	}
+
+	go func() {
+		log.Println("Watchdog.Email Server Running")
+		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+			log.Panicf("Server Error: %s", err)
+		}
+	}()
+
+	quit := make(chan os.Signal)
+	signal.Notify(quit, os.Interrupt)
+	<-quit
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	if err := srv.Shutdown(ctx); err != nil {
+		log.Panicf("Server forced to shutdown: %s", err)
+	}
+	redisContext.CloseRedisController()
+	log.Println("Watchdog.Email Server Exiting")
+}