Add initial email handler logic.

joeybloggs · joeybloggs · commit f4dc6f06085c · 2016-06-03T15:07:17.000-04:00
diff --git a/handlers/email/email.go b/handlers/email/email.go
@@ -0,0 +1,260 @@
+package email
+
+import (
+	"bytes"
+	"html/template"
+	stdlog "log"
+	"os"
+	"time"
+
+	"gopkg.in/gomail.v2"
+
+	"github.com/go-playground/log"
+)
+
+// FormatFunc is the function that the workers use to create
+// a new Formatter per worker allowing reusable go routine safe
+// variable to be used within your Formatter function.
+type FormatFunc func() Formatter
+
+// Formatter is the function used to format the Email entry
+type Formatter func(e *log.Entry) *gomail.Message
+
+const (
+	space           = byte(' ')
+	equals          = byte('=')
+	colon           = byte(':')
+	base10          = 10
+	v               = "%v"
+	gopath          = "GOPATH"
+	contentType     = "text/html"
+	defaultTemplate = `<!DOCTYPE html>
+<html>
+    <body>
+        <h2>{{ .Message }}</h2>
+        {{ if ne .Line 0 }}
+            {{ display_file . }}:{{ .Line }}
+        {{ end }}
+        {{ range $f := .Fields }}
+            <p><b>{{ $f.Key }}</b>: {{ $f.Value }}</p>
+        {{ end }}
+    </body>
+</html>`
+)
+
+// Email is an instance of the email logger
+type Email struct {
+	buffer          uint // channel buffer
+	numWorkers      uint
+	formatFunc      FormatFunc
+	timestampFormat string
+	gopath          string
+	fileDisplay     log.FilenameDisplay
+	template        *template.Template
+	templateHTML    string
+	host            string
+	port            int
+	username        string
+	password        string
+	from            string
+	to              []string
+	keepalive       time.Duration
+}
+
+// New returns a new instance of the email logger
+func New(host string, port int, username string, password string, from string, to []string) *Email {
+
+	e := &Email{
+		buffer:          0,
+		numWorkers:      1,
+		timestampFormat: log.DefaultTimeFormat,
+		fileDisplay:     log.Lshortfile,
+		templateHTML:    defaultTemplate,
+		host:            host,
+		port:            port,
+		username:        username,
+		password:        password,
+		from:            from,
+		to:              to,
+		keepalive:       time.Second * 30,
+	}
+
+	e.formatFunc = e.defaultFormatFunc
+
+	return e
+}
+
+// SetKeepAliveTimout tells Email how long to keep the smtp connection
+// open when no messsages are being sent; it will automatically reconnect
+// on next message that is received.
+func (email *Email) SetKeepAliveTimout(keepAlive time.Duration) {
+	email.keepalive = keepAlive
+}
+
+// SetEmailTemplate sets Email's html tempalte to be used for email body
+func (email *Email) SetEmailTemplate(htmlTemplate string) {
+	email.templateHTML = htmlTemplate
+}
+
+// SetFilenameDisplay tells Email the filename, when present, how to display
+func (email *Email) SetFilenameDisplay(fd log.FilenameDisplay) {
+	email.fileDisplay = fd
+}
+
+// SetBuffersAndWorkers sets the channels buffer size and number of concurrent workers.
+// These settings should be thought about together, hence setting both in the same function.
+func (email *Email) SetBuffersAndWorkers(size uint, workers uint) {
+	email.buffer = size
+
+	if workers == 0 {
+		// just in case no log registered yet
+		stdlog.Println("Invalid number of workers specified, setting to 1")
+		log.Warn("Invalid number of workers specified, setting to 1")
+
+		workers = 1
+	}
+
+	email.numWorkers = workers
+}
+
+// SetTimestampFormat sets Email's timestamp output format
+// Default is : "2006-01-02T15:04:05.000000000Z07:00"
+func (email *Email) SetTimestampFormat(format string) {
+	email.timestampFormat = format
+}
+
+// SetFormatFunc sets FormatFunc each worker will call to get
+// a Formatter func
+func (email *Email) SetFormatFunc(fn FormatFunc) {
+	email.formatFunc = fn
+}
+
+// Run starts the logger consuming on the returned channed
+func (email *Email) Run() chan<- *log.Entry {
+
+	// pre-setup
+	if email.fileDisplay == log.Llongfile {
+		// gather $GOPATH for use in stripping off of full name
+		// if not found still ok as will be blank
+		email.gopath = os.Getenv(gopath)
+		if len(email.gopath) != 0 {
+			email.gopath += string(os.PathSeparator) + "src" + string(os.PathSeparator)
+		}
+	}
+
+	// parse email htmlTemplate, will panic if fails
+	email.template = template.Must(template.New("email").Funcs(
+		template.FuncMap{
+			"display_file": func(e *log.Entry) (file string) {
+				file = e.File
+
+				if email.fileDisplay == log.Lshortfile {
+
+					for i := len(file) - 1; i > 0; i-- {
+						if file[i] == '/' {
+							file = file[i+1:]
+							break
+						}
+					}
+				} else {
+					file = file[len(email.gopath):]
+				}
+				return
+			},
+		},
+	).Parse(email.templateHTML))
+
+	ch := make(chan *log.Entry, email.buffer)
+
+	for i := 0; i <= int(email.numWorkers); i++ {
+		go email.handleLog(ch)
+	}
+	return ch
+}
+
+func (email *Email) defaultFormatFunc() Formatter {
+	var err error
+	b := new(bytes.Buffer)
+	message := gomail.NewMessage()
+	message.SetHeader("From", email.from)
+	message.SetHeader("To", email.to...)
+
+	return func(e *log.Entry) *gomail.Message {
+		b.Reset()
+		if err = email.template.ExecuteTemplate(b, "email", e); err != nil {
+			log.WithFields(log.F("error", err)).Error("Error parsing Email handler template")
+		}
+
+		message.SetHeader("Subject", e.Message)
+		message.SetBody(contentType, b.String())
+
+		return message
+	}
+}
+
+func (email *Email) handleLog(entries <-chan *log.Entry) {
+	var e *log.Entry
+	var s gomail.SendCloser
+	var err error
+	var open bool
+	var message *gomail.Message
+	var count uint8
+
+	formatter := email.formatFunc()
+
+	d := gomail.NewDialer(email.host, email.port, email.username, email.password)
+
+	for {
+		select {
+		case e = <-entries:
+			count = 0
+			message = formatter(e)
+
+		REOPEN:
+			// check if smtp connection open
+			if !open {
+				count++
+				if s, err = d.Dial(); err != nil {
+					log.WithFields(log.F("error", err)).Warn("ERROR connection to smtp server")
+
+					if count == 3 {
+						// we tried to reconnect...
+						e.Consumed()
+						break
+					}
+
+					goto REOPEN
+				}
+				count = 0
+				open = true
+			}
+
+		RESEND:
+			count++
+			if err = gomail.Send(s, message); err != nil {
+				log.WithFields(log.F("error", err)).Warn("ERROR sending to smtp server, retrying")
+
+				if count == 3 {
+					// maybe we got disconnected...
+					open = false
+					s.Close()
+					goto REOPEN
+				} else if count > 3 {
+					// we reopened and tried 2 more times, can;t say we didn't try
+					log.WithFields(log.F("error", err)).Alert("ERROR sending log via EMAIL, RETRY and REOPEN failed")
+					e.Consumed()
+					break
+				}
+
+				goto RESEND
+			}
+			e.Consumed()
+
+		case <-time.After(email.keepalive):
+			if open {
+				s.Close()
+				open = false
+			}
+		}
+	}
+}
