improve memory footprint

CHANGELOG.md

@@ -6,6 +6,9 @@
 - Converted the entire app to a [Twelve-Factor App](https://12factor.net/).
   This has consequences in how you launch it, i.e. use environment variables
   instead of flags.
+- The interval between learning periods can be set at runtime now.
+- Unload mail content after classification and learning, should reduce memory
+  requirements.
 
 ## Fixed
 - Only permit unicode characters of bitsize larger than 2, this guarantees we

classify.go

@@ -178,7 +178,9 @@ func (m *Mail) Classify(db *bolt.DB, dir Maildir) (err error) {
 		}).Info("Moved to Junk folder")
 	}
 
-	return nil
+	err = m.Unload(dir)
+
+	return err
 }
 
 // Junk returns true if the wordlist is classified as a junk mail using Bayes'

learn.go

@@ -98,6 +98,11 @@ func (m *Mail) Learn(db *bolt.DB, dir Maildir) (err error) {
 
 	// Update the statistics counter
 	err = m.learnStatistics(db)
+	if err != nil {
+		return err
+	}
+
+	err = m.Unload(dir)
 
 	return err
 

mail.go

@@ -125,6 +125,15 @@ func (m *Mail) Load(dir Maildir) (err error) {
 	return nil
 }
 
+// Unload removes a mail's subject and body from the internal cache
+func (m *Mail) Unload(dir Maildir) (err error) {
+
+	m.Subject = nil
+	m.Body = nil
+
+	return nil
+}
+
 func trimStringFromBase64(s string) string {
 	if idx := strings.Index(s, "Content-Transfer-Encoding: base64"); idx != -1 {
 		return s[:idx-1]

mail_test.go

@@ -123,6 +123,28 @@ var _ = Describe("Mail", func() {
 					Junk:    true,
 				}))
 		})
+		It("Unload mail content from struct", func() {
+			m := s.Mail{
+				Key:     "1488226337.M327822P8269.mail.carlostrub.ch,S=3620,W=3730",
+				Subject: nil,
+				Body:    nil,
+				Junk:    true,
+			}
+
+			err := m.Load("test/Maildir")
+			Ω(err).ShouldNot(HaveOccurred())
+
+			err = m.Unload("test/Maildir")
+			Ω(err).ShouldNot(HaveOccurred())
+
+			Ω(m).Should(Equal(
+				s.Mail{
+					Key:     "1488226337.M327822P8269.mail.carlostrub.ch,S=3620,W=3730",
+					Subject: nil,
+					Body:    nil,
+					Junk:    true,
+				}))
+		})
 		It("Fail if Subject has already content", func() {
 			st := "test"
 			m := s.Mail{